Don:
We are looking into putting red oak floors throughout our home. We have pretty much narrowed down all of the details except for the size of planks we should use. Will there be any difference in the structural stability of a 4" plank vs. a 3 1/4" plank? We have heard that the wider the board, the more chance there is of some movement down the road. So, what size is your personal preference? Is there an industry standard?
One other question I have is regarding the natural ambering that occurs with red oak. Does using a Glitsa finish help reduce the amount of ambering that occurs?
Thank you so much for your time.
Plank Types, Sizes and Application
Unless your home is situated near a body of water, deep in the woods or somewhere else where significant shifts in internal moisture can be anticipated, the difference between 3- 1/4 and 4 inch plank will probably be negligible. Where issues or concerns exist regarding plank width or moisture migration, I generally recommend the use of a rift and/or quarter sawn cut. With the advent of high quality elastomeric mastics especially formulated for wood flooring, I often recommend the use of a full spread solid wood flooring mastic as well as nailing.
Four inch plank is probably still more standard than 3-1/4 inch plank but there are lots of new products being introduced these days (especially from other countries) utilizing the 3-1/4 inch profile.
Technically, wood flooring boards 3 inches or wider are considered plank flooring. In the past, domestic manufacturing of most plank wood flooring was fairly standardized with plank sizes graduated precisely at one inch increments from 3 to 12 or more but more commonly 3 to 8. Conifers and reclaimed materials varied from this somewhat informal flooring standard due, I believe, primarily to price and value. Half or quarter inch intervals were common, if not even more standard for these products.
Wood Flooring the Environmental Choice
While soft wood lumber intended for flooring competed head-to-head with that intended for the general building supply industry, hardwood lumber sold to the flooring industry was (and still is) a by product or “fall down” from the dimensional hardwood industry. Hardwood lumber graded as ‘gifted in character’ (that is abundant in knots, holes, wane, burls or other qualities generally perceived as “defects”) was sold to “fall down” manufacturers as a by product of the dimensional hardwood lumber manufacturing process.
Wood flooring manufactures are (for the most part) at the bottom of this list. Even pallet manufacturers need boards 4 inches or wider. Not wood flooring manufacturers. A pallet manufacturer also needs boards 3 to 3-1/2 feet or longer; but not a wood flooring manufacturer. So the hardwood lumber sold to most flooring mills is heavily picked over, and generally not as appealing to other manufacturers. That lumber, typically graded 2 Common, won’t sell at premium prices. That’s what’s sold to the wood flooring mills.
The flooring mills used to turn their “fall down” into firewood for their kiln furnaces or given to anyone willing to remove it from the premises at no charge. These days, firewood and sawdust are made into panels, wood pellets or sold as smoker fodder.
An Important Note: As of this writing, supplies of hardwood lumber have dwindled to their lowest level in many years due to the permanent closure of many hardwood lumber plants. All domestic species are in short supply, but White oak in particular. This does not mean there is a shortage in our hardwood tree population or that there has been an over demand for the product. Far to the contrary, our country’s hardwood tree population is at the highest level it has been in over 200 years. Since hardwood flooring is developed primarily as a by product from associated hardwood industries, the severely limited number of hardwood lumber companies currently has caused a temporary overtaxing of the entire supply system. Although the demand for hardwood flooring has dropped along with that for other hardwood products, it has not experienced the same level of diminished demand as have other hardwood industries. We have been told to expect hardwood flooring prices to continue to grow at unprecedented rates and to anticipate shortages for various hardwood flooring products for some time to come.
Antique and Reclaimed Flooring
Antique or reclaimed lumber normally requires re-sawing to make it more useable. Historically, its been marketed to by-product manufacturers, like the wood flooring industry, that could make better use of boards that were shorter and more narrow than that required by other hardwood or softwood manufacturers. Standard ‘commodity’ flooring mills never seriously attempted re-milling and selling antique or reclaimed lumber as flooring. That required far too much handling and care than they were willing or able to put forth. So, small “boutique” flooring mills began popping up in the late 70s and 80s as a “green” source for old growth lumber products. Initially, this was due to the limited price point that “old” lumber drew on the open market. These days the costs for old lumber have grown and its availability dwindled to the point that “antique” and “reclaimed” lumber now sells at premium prices.
Pretty much from day one, plank wood flooring milled from old beams, boards or reclaimed logs was milled utilizing the “live sawing” method. This is normally considered to be the most “green” milling process where the maximum possible yield from every piece of raw material is forthcoming. Then, a “mill run” or “wholesale” grading process is often implemented. This means basically that every single piece of material sawn from the log, board or beam is included in the flooring lot. So ¼, ½, and ¾ even 3/8, 5/8, and 7/8 intervals were often added to the normally even numbered plank widths with antique reclaimed flooring boards.
Variable vs. Random Width Plank
All those different widths with uneven intervals created math havoc with the resellers of antique reclaimed planking who wanted to sell the installers plank flooring in equal lineal feet. Their standardized tables that spelled out the precise square footage requirements of each width for a “variable” width plank floor didn’t allow for so many different and uneven combinations of widths. So they attempted to sell the plank flooring by the “random” width rather than the more classic “variable” width.
A “variable” width plank floor creates more of a standardized pattern to the floor installation’s appearance since it contains the same number of rows of each width. A “random” width plank floor’s installation must be completely arbitrary since the square footage and therefore lineal footage of each available width will vary. The appearance of a “random” width floor installation can be somewhat disordered to some people. It’s interesting to note that many plank installations dating back centuries contained “random” width planks. Since they utilized whatever was available to them at the time, their flooring rows represented such. On occasion, some rows were even begun with one width, then divided mid row into two planks of exactly ½ that width to finish the row.
To help mills and resellers sell their increasing cumbersome variable plank widths in the classic “variable” width format, I created a computer program called WIDTH to take care of all the math for them regardless of the number or sizes of widths. I have to confess that program is in dire need of a facelift. I wrote it in C and Assembler languages and it needs updating to run with all the bells and whistles on today’s super fast processors and GUI platforms. But for the guys willing to run it on a DOS platform, it still does a great job.
Some History of Floor Finishes
When Glitsa and Synteko (the two most domestically popular acid-curing floor finishes) were first introduced into this country, 40 years ago or more, they were highly touted as non-yellowing floor finishes. But that was in comparison to the major floor finishes on the market at the time...primarily oil-modified urethanes. When it was first introduced, oil-modified urethane was seen as a great advancement over the more commonly used floor finishing products at that time, varnishes, penetrating oils and waxes.
The oil-modified urethanes, of those days, yellowed considerably with age and sunlight as did virtually all the other oils, sealers, varnishes and waxes in use, but they could be counted upon to cure faster and provide a more durable surface film than their predecessors. Essentially, what an oil-modified urethane (or polyurethane as they were called in our industry) did for floor finish films was to provide polymers that would help the oils they were combined with cross link better for tougher finish films and do it much faster than the oils could alone.
State-of-the-Art Floor Finishes
Today’s state-of-the-art floor finishes are by and large waterborne products. The acid curing and moisture curing urethanes so popular for the past 25 or 30 years are being rapidly replaced by harder wearing, less toxic, waterborne coatings. Interestingly enough, many of the old style oils and waxes are enjoying renewed popularity. They offer a depth of color and ease of repair that none of the newer urethane products can boast. The hard wax oils, highly touted as more “green”, predominately from Europe, are variations of these penetrating oils with (in some cases) less toxic solvents. Keep in mind, just because it’s better for “the environment” doesn’t mean it is cleaner or less toxic for the user. A great example of this is Tung Oil. Tung Oil is considered food grade once it has dried, but it’s an accumulative toxin to the humans applying it in liquid form. I’ve had several good woodworking friends, bowl makers, turners, carvers and fine woodworking artists who’ve had to seek alternate trades after reaching toxic shock levels working with Tung Oil.
Most single component waterborne floor finishes are acrylics, urethanes or a combination of the two. Which is best depends on which manufacturer’s rep you happen to be speaking with at the time. The resins or binders utilized in all the various products are made by only a few different companies throughout the world. So except for the amount and type of resin, the end products don’t vary a great deal. Resins are almost always the most expensive part of a floor finish’s formula. So, the tougher, better resins and the percentage of same will cause the coating to cost more. Therefore, a good rule of thumb, is all things being equal, the more expensive the finish the better its quality.
Durability Rumors
You may have heard from some of the “Old Timers” that waterborne floor finishes are no good. Well, I’m an “Old Timer” and let me say this, the top-of-the-line coatings like Danish Finish and Danish ProSport have very little in common with the water-soluble coatings that came out 30 years or so ago. Those finishes were relatively expensive and difficult to use. Today’s water borne finishes are much easier to use and can be made relatively inexpensively. That makes them prime candidates for the DIY market. Go into virtually any hardware store, DIY center or box store and you’ll find a wide variety of inexpensive waterborne finishes lining the store shelves in the flooring department. Beware of the claims these products make. They have little in common with the top quality water borne floor finishes available to the professional, except that they are water soluble.
The really top-of-the-line wood floor finishes (the professional grade types of products) are NOT cheap...whether they’re waterborne or oil based. A good rule of thumb is, the cheaper the ingredients the cheaper the product. Professional grade, single component, Danish Finish and its two component industrial strength big brother, Danish ProSport, are significantly more expensive than their box store cousins. They are marketed to professional floor finishers and discerning do-it-yourselfers. These extremely high quality products have virtually no yellowing characteristics and contain exceptionally strong UV inhibitors to boot.
Where to Buy Top Quality Floor Finishes
It’s like what I told my son recently when he was in the market for a drill. He knew that I liked my Milwaukee drill, the one I’d owned for over 30 years. He said he could get a Milwaukee drill at his local box store for $20 to $30 but definitely for under $50. Why should he pay the $150 to $200 he was quoted for a Milwaukee drill at a construction supply house? My response to him was this. If you’re going to use the drill just once or twice a year and for short periods of time, buy a cheap one. You’ll go through a number of cheap drills over the years but you’ll probably come out even in the end. But, if you intend to use it regularly, want to keep it your whole life, or if you’ve got some serious work in mind for it, you’ll want to buy a professional grade drill motor and they don’t come on $20 or $30 drills.
It’s the same with most construction supplies or products. Professional grade items just don’t sell well in box stores. So if you want a good professional grade floor finish…one that will stand up to everyday wear and tear…you’ll need a top quality product. Whether you’re in the market for a good polyurethane, penetrating oil or water borne floor finish…expect to pay for quality. Professionals know that. Their reputations are on the line every time they put a product down on a client’s hardwood floor. Serious professional wood floor finishers insist on top-of-the line floor finishes…like the Danish Finish and Danish ProSport.
For professional grade polyurethanes and similar products we recommend and sell Lenmar Products. I have found them to be made of the finest quality ingredients and meet the exacting requirements of our demanding hardwood floor finishing clientele.
All acid-curing finishes (like Glitsa and Synteko) are considered professional grade. They contain so many toxic compounds and flammable solvents that the manufacturers generally restrict their sale to professionals only. That is how we enforce their sale in our wholesale supply division as well.
Comparisons of “Swedish” to Waterborne “Danish” Finishes
A one-on-one comparison of Glitsa or any other acid curing finish to a top-of-the-line waterborne product is not entirely feasible. There are a great many differences in addition to the obvious toxicity issue. Originally, acid curing products became popular not just because they didn’t yellow as much as their predecessors but also because they could be utilized as both sealer and finish. Many of the older floor and wood finishes needed a pore or grain filler along with a separate sealer in order to leave a consistent film face on the wood. Without this smooth film face, the surface would not look as beautiful and would wear prematurely.
Ironically, part of the acid curing floor finishes popularity came about because they left the floor’s surface less smooth. There were some who liked their hardwood floor’s surface finished without grain or pore filling and without staining. It was called a “Natural” finish. It required an extra coating (for a minimum of 3 total coats) of Swedish (acid curing) Finish to protect properly but was a look that could not be achieved in any other way.
To this day, that “Natural” look is still unique with hardwood flooring…particularly with red oak. The acid in the acid-curing finish reacts with the tannins in the oak (particularly “red oak”) causing it to turn a rather bold reddish brown when coated. Other solvent-based coatings will usually have a similar but somewhat more subdued effect on that wood. The same is true of American and Brazilian Cherries. These cherries will darken, intensifying their reddish hue over time, usually progressing to a brownish hue depending on the strength of sunlight striking them.
Appearance remains one of the single biggest differentiating factors between the “Natural” (no stain) finish application of a top quality product like Danish Finish or Danish ProSport water based finish and a Glitsa, Synteko or other acid-curing finish.
Still, in the final tally, waterborne coatings are gradually overcoming this last big hurdle. In high rise, multifamily homes or commercial venues with other tenants in place, a waterborne coating must usually be used due to toxins, odors, and flammability. Where durability is paramount, the Danish Finish or Danish ProSport can’t be bested. The difference between a top quality waterborne coating (particularly one like the Danish ProSport) and an acid curing finish like Glitsa or Synteko is like comparing apples to oranges. The waterbornes cure faster and will take so much abuse and still look beautiful, that there is really no comparison. The top-of-the-line waterbornes are more clear, have minimal if any yellowing and contain extremely strong UV inhibitors.
For a do-it-yourselfer, there is just no reason to settle for anything less than quality top-of-the-line waterbornes like the Danish Finish and Danish Prosport. The Danish Finishes, unlike most professional grade products, are extremely easy to apply. Getting a professional grade coating with either product has never been easier with any product, much less a professional one.
Stain Applications
If you plan to stain your floor, you'll probably end up utilizing a solvent-based product. In my opinion, there still is no substitute for solvent-based stains when doing wood floor finishing. This could change soon as many manufacturers are working hard to solve this problem.
In the mean time, if you planning to use an acid curing finish like Glitsa, Synteko or one of the other lesser known brands available, expect to see some slight yellowing of the stain color initially (particularly pastels) and even more over time. Part of this is due to the finish, part to the stain and part is due to the tannins, oils and resins in the wood.
In you plan to use an oil modified (polyurethane) finish, you should expect even more yellowing both initially and over time. One extra point regarding the use of polyurethanes. As a general rule, it will take 3 coats of acid cure or waterborne urethane to get the same film thickness build as two coats of polyurethane floor finish.
If you plan to use a waterborne urethane over a solvent-based stain, you’ll need to allow a little more dry time for your stain. This is especially true for highly pigmented stain colors, especially pastels or whites. But, expect to reap big dividends from the clarity of the finish film, its resistance to fading and color changes over time or with sunlight and loads of extra durability from foot traffic.
If you plan to use a penetrating oil (tinted or not) or one of the hard wax oils, espect considerably more dry time and curing time. I find lots of folks presold on these products from a environmental standpoint without realizing the whole story. When they find out that not only are these products not as “green” as the waterborne urethanes but also require substantially more TLC and maintenance, they hastily move away from them in favor of a more user friendly, environmentally friendly and user friendly choice.
Strictly speaking, the truest...clearest coating that you can apply to a floor is a top-of-the-line waterborne urethane...and...it is the toughest of the site-applied floor coatings available today.
In the end, there really is no WRONG choice…only one that is better for you and your application.
Hopefully this helps you. Please feel free to ask other questions.
Thanks,
Don
Don Bollinger don@woodfloorco.com Wood Floor Products, Inc. (206) 622-6996
Wednesday, July 28, 2010
Thursday, July 1, 2010
FAQ Installing Hardwood Flooring Over Radiant Tubes In Plywood Panels
Hi Don,
Thank you for your detailed and informative essay on installing wood
flooring over radiant systems. I enjoyed the read a lot.
I was wondering if you might be able to give me some advice concerning whether or not to seal all sides or at least back seal 4" rift & quartered white oak before installing over "warmboard?”
The heating system has been in place and running since December 09' and the AC has been running for 1 week. The white oak was delivered a few days ago and I was planning on giving it 2 weeks to acclimate. Most construction on the house is complete including Sheet rocking tile and paint. Most of the millwork installation remains. The
Project is a complete structural shell renovation of a 3500sf home in Queens New York. All floor, wall framing and windows are new. I have heard various opinions on back sealing and end grain sealing over radiant heat and I’m on the fence as to whether or not to do it or to skip it.
One last notable issue is that we would like to install some of the flooring parallel to the tubing which would place every 4th board directly on top of a line of pexal tubing. Warmboard recommends installing flooring perpendicular to the tubing but tell me that parallel can be done. Is it simply more difficult?
Sorry for sending you such a long email but hopefully you will have a few moments to give me your opinion.
Sincerely,
Max
New York, NY
Hi Max.
I hope you'll excuse my taking some extra time responding to your questions.
Radiant heating systems are near and dear to me. Many years ago before it became vogue to do so, I helped design and install geothermal heating and cooling systems. We used both the heat from the sun and the ground (and from lakes or ponds if they were handy) to warm homes in cool weather. In warm weather, we collected cool air from the ground or from lakes or ponds and pumped it into the homes. Warm air was taken off the outside shell of the homes and deposited back into the ground in place of the cooler air we’d collected. In the days before expensive energy, we cut heating/cooling costs by 90 to 95% with systems that are still running efficiently today.
The tenor and tone of your questions to me on wood flooring over radiant heat suggest a somewhat practiced understanding of their application. I applaud both your attitude and approach. So many architects these days seem in lockstep with the lemmings. Engineered wood flooring and plywood with plastic radiant tubes does indeed work, albeit the inverse of an efficient radiant heat transfer model.
For the peak performance, efficiency and appearance in wood flooring over radiant in-floor heating, quality conscious wood flooring installers around the globe continue to express their preference for solid wood flooring (preferably rift and/or quarter sawn material as you’ve specified) installed by gluing and nailing to a multi-layered plywood system that is set to “float” over a 1-1/2” or thicker cementitious mass. Such a system, when properly acclimated and installed, should perform exceptionally well with only a minimal amount of maintenance for many years.
The plywood panel systems were developed for retrofitting radiant systems into homes where the added weight of a more efficient system could not be supported. While variations of this method can perform adequately as a primary heating source, great care should be taken when comparing the efficiency these designs to those systems that enjoy significantly greater mass. As a rule, the greater the mass the more efficient the radiant system.
Systems operating on the fringes of radiant efficiency can be anticipated to function marginally, not just as heat transfer devices, but in other aspects as well. For example, noteworthy variances in conductivity within the hardwood flooring’s structure will translate to major variances in heat transfer and overall system efficiency. Minor glitches can become major anomalies in the workings of the entire mechanism. Minor to major appearance changes, such as color shades and gaping, are sometimes resultant within the wood flooring. On occasion these appearance changes are striking, depending on the floor-to-tube temperature and overall heat loss within the system.
Utilizing a plywood flooring system (i.e. an engineered wood flooring product) may serve to further stress an already strained radiant design. Many such systems result in a radiant design that employs an inordinately high floor temperature. Knowing this and knowing the results of a too high wood floor temperature, savvy hardwood flooring manufacturers are not guaranteeing their products installed over a radiant system that causes the surface wood flooring temperature to exceed 80 degrees Fahrenheit. Many such manufacturers are requiring temperature sensors be installed in their flooring systems in order to validate their warranties.
Leaving the wood flooring until all wet work is completed is always a good strategy. And, the two week scheduled acclimation period would normally be adequate in a standard scenario after stocking the material in a “dry” structure. Structures with radiant in-floor heating however should command a longer acclimation period. While time is important for acclimation, moisture content (MC) checks are mandatory.
Every good contractor, general or flooring, will own and use a moisture meter. The really good ones own several different types of meters. There are meters that measure concrete and cementitious materials and those that measure wood. There are pinned meters that leave holes in the materials being measured but they measure moisture at different depths. There are pin less meters that take only average overall readings of a material but do not leave holes in the material being measured. Regardless of the type meter the contractor uses, multiple moisture checks should be made of the subflooring, surrounding wood materials and the flooring to be installed.
Wainscoting, trim and base molding should also be measured and acclimated prior to installing on or near a radiant heated floor. These materials, along with the wood flooring, should be stickered in stacks no higher than two feet off the radiant floor with the heat on. Stacks should be arranged to accommodate a good air flow under, between and within the bundles of material. When the MC of the subflooring and the flooring to be installed is within 2% MC of each other, it’s time to install.
Sealing the backs and ends of the wood slats or planks as you propose can substantially reduce the ingress and egress of moisture within individual planks. For any questionable installation, I strongly recommend that a moisture resistant (but not moisture impervious) product be applied to backs (or bottoms) as well as to the ends if flooring is not to be glued to the substrate. There are even some hardwood flooring manufactures who use packaging tape applied to the bottoms of their planking to help resist a rapid ingress of moisture.
Our company began sealing the bottoms and ends of wood flooring boards years ago when we were required to install hardwood in homes or structures left unheated for months on end, or when we were required to install flooring on houseboats, cantilevered structures or buildings built on pier poles.
This extra sealing procedure is mostly redundant when gluing and nailing except for the board ends. As long as the sealant used is resistant and not impervious to moisture migration, it can’t hurt. Impervious sealants are perfect, right up to and until they fail. If boards expand and rupture the impervious seal, the impervious bond begins to work against rather than for protection of the wood. With today’s forest product colleges leaning toward “fast drying” procedures over previously recommended slow air drying prior to artificially drying in kilns, internal stresses can be built up within the wood’s structure causing “artificial” movement or movement without apparent significant changes in moisture content. But that’s another story.
Finally, I never recommend installing strip or plank flooring parallel to seams of any kind. At the very least, these seams can cause the flooring boards directly above them to move differently than those throughout the remainder of the structure. At worst, the boards directly above the seams can flex or move up and down with live loads. Gluing and nailing can help reduce these problems as well as improve the overall “feel” of wood flooring when installed over a radiant plywood panel system. Unfortunately, I’ve found that radiant plywood panel manufactures are somewhat divided on their allowance of glue-down flooring, let alone their allowance of gluing and nailing.
In conclusion, radiant systems are changing constantly, but the laws of physics remain the same. Like my old pappy used to say…you can teach an old dog new tricks but you’ll play hob teaching him to do tricks that don’t work.
I hope this all helps.
Don Bollinger
Thank you for your detailed and informative essay on installing wood
flooring over radiant systems. I enjoyed the read a lot.
I was wondering if you might be able to give me some advice concerning whether or not to seal all sides or at least back seal 4" rift & quartered white oak before installing over "warmboard?”
The heating system has been in place and running since December 09' and the AC has been running for 1 week. The white oak was delivered a few days ago and I was planning on giving it 2 weeks to acclimate. Most construction on the house is complete including Sheet rocking tile and paint. Most of the millwork installation remains. The
Project is a complete structural shell renovation of a 3500sf home in Queens New York. All floor, wall framing and windows are new. I have heard various opinions on back sealing and end grain sealing over radiant heat and I’m on the fence as to whether or not to do it or to skip it.
One last notable issue is that we would like to install some of the flooring parallel to the tubing which would place every 4th board directly on top of a line of pexal tubing. Warmboard recommends installing flooring perpendicular to the tubing but tell me that parallel can be done. Is it simply more difficult?
Sorry for sending you such a long email but hopefully you will have a few moments to give me your opinion.
Sincerely,
Max
New York, NY
Hi Max.
I hope you'll excuse my taking some extra time responding to your questions.
Radiant heating systems are near and dear to me. Many years ago before it became vogue to do so, I helped design and install geothermal heating and cooling systems. We used both the heat from the sun and the ground (and from lakes or ponds if they were handy) to warm homes in cool weather. In warm weather, we collected cool air from the ground or from lakes or ponds and pumped it into the homes. Warm air was taken off the outside shell of the homes and deposited back into the ground in place of the cooler air we’d collected. In the days before expensive energy, we cut heating/cooling costs by 90 to 95% with systems that are still running efficiently today.
The tenor and tone of your questions to me on wood flooring over radiant heat suggest a somewhat practiced understanding of their application. I applaud both your attitude and approach. So many architects these days seem in lockstep with the lemmings. Engineered wood flooring and plywood with plastic radiant tubes does indeed work, albeit the inverse of an efficient radiant heat transfer model.
For the peak performance, efficiency and appearance in wood flooring over radiant in-floor heating, quality conscious wood flooring installers around the globe continue to express their preference for solid wood flooring (preferably rift and/or quarter sawn material as you’ve specified) installed by gluing and nailing to a multi-layered plywood system that is set to “float” over a 1-1/2” or thicker cementitious mass. Such a system, when properly acclimated and installed, should perform exceptionally well with only a minimal amount of maintenance for many years.
The plywood panel systems were developed for retrofitting radiant systems into homes where the added weight of a more efficient system could not be supported. While variations of this method can perform adequately as a primary heating source, great care should be taken when comparing the efficiency these designs to those systems that enjoy significantly greater mass. As a rule, the greater the mass the more efficient the radiant system.
Systems operating on the fringes of radiant efficiency can be anticipated to function marginally, not just as heat transfer devices, but in other aspects as well. For example, noteworthy variances in conductivity within the hardwood flooring’s structure will translate to major variances in heat transfer and overall system efficiency. Minor glitches can become major anomalies in the workings of the entire mechanism. Minor to major appearance changes, such as color shades and gaping, are sometimes resultant within the wood flooring. On occasion these appearance changes are striking, depending on the floor-to-tube temperature and overall heat loss within the system.
Utilizing a plywood flooring system (i.e. an engineered wood flooring product) may serve to further stress an already strained radiant design. Many such systems result in a radiant design that employs an inordinately high floor temperature. Knowing this and knowing the results of a too high wood floor temperature, savvy hardwood flooring manufacturers are not guaranteeing their products installed over a radiant system that causes the surface wood flooring temperature to exceed 80 degrees Fahrenheit. Many such manufacturers are requiring temperature sensors be installed in their flooring systems in order to validate their warranties.
Leaving the wood flooring until all wet work is completed is always a good strategy. And, the two week scheduled acclimation period would normally be adequate in a standard scenario after stocking the material in a “dry” structure. Structures with radiant in-floor heating however should command a longer acclimation period. While time is important for acclimation, moisture content (MC) checks are mandatory.
Every good contractor, general or flooring, will own and use a moisture meter. The really good ones own several different types of meters. There are meters that measure concrete and cementitious materials and those that measure wood. There are pinned meters that leave holes in the materials being measured but they measure moisture at different depths. There are pin less meters that take only average overall readings of a material but do not leave holes in the material being measured. Regardless of the type meter the contractor uses, multiple moisture checks should be made of the subflooring, surrounding wood materials and the flooring to be installed.
Wainscoting, trim and base molding should also be measured and acclimated prior to installing on or near a radiant heated floor. These materials, along with the wood flooring, should be stickered in stacks no higher than two feet off the radiant floor with the heat on. Stacks should be arranged to accommodate a good air flow under, between and within the bundles of material. When the MC of the subflooring and the flooring to be installed is within 2% MC of each other, it’s time to install.
Sealing the backs and ends of the wood slats or planks as you propose can substantially reduce the ingress and egress of moisture within individual planks. For any questionable installation, I strongly recommend that a moisture resistant (but not moisture impervious) product be applied to backs (or bottoms) as well as to the ends if flooring is not to be glued to the substrate. There are even some hardwood flooring manufactures who use packaging tape applied to the bottoms of their planking to help resist a rapid ingress of moisture.
Our company began sealing the bottoms and ends of wood flooring boards years ago when we were required to install hardwood in homes or structures left unheated for months on end, or when we were required to install flooring on houseboats, cantilevered structures or buildings built on pier poles.
This extra sealing procedure is mostly redundant when gluing and nailing except for the board ends. As long as the sealant used is resistant and not impervious to moisture migration, it can’t hurt. Impervious sealants are perfect, right up to and until they fail. If boards expand and rupture the impervious seal, the impervious bond begins to work against rather than for protection of the wood. With today’s forest product colleges leaning toward “fast drying” procedures over previously recommended slow air drying prior to artificially drying in kilns, internal stresses can be built up within the wood’s structure causing “artificial” movement or movement without apparent significant changes in moisture content. But that’s another story.
Finally, I never recommend installing strip or plank flooring parallel to seams of any kind. At the very least, these seams can cause the flooring boards directly above them to move differently than those throughout the remainder of the structure. At worst, the boards directly above the seams can flex or move up and down with live loads. Gluing and nailing can help reduce these problems as well as improve the overall “feel” of wood flooring when installed over a radiant plywood panel system. Unfortunately, I’ve found that radiant plywood panel manufactures are somewhat divided on their allowance of glue-down flooring, let alone their allowance of gluing and nailing.
In conclusion, radiant systems are changing constantly, but the laws of physics remain the same. Like my old pappy used to say…you can teach an old dog new tricks but you’ll play hob teaching him to do tricks that don’t work.
I hope this all helps.
Don Bollinger
Thursday, January 21, 2010
FAQ Answer to Question on Grouting Compounds for Mixed Media Installations
Hi Don,
I read your webpage and I was wondering if you might be able to help me with a grout issue.
I am working with wood, glass, and marble in mosaics. The biggest issue I have is the natural expansion and contraction of the wood. Clear silicone is great for adhering glass, but I'd prefer not use that as a "grout" for the mosaics. Main reason is that it's toxic and will not be easy to clean off the glass or marble unless the installer enjoys very tedious work (I like tedious...mosaics obviously, but installers don't).
I've been in the mosaic field for 15 years and no one has been able to figure out a reasonable solution to this issue. Hence, no one is making wood, glass, and marble mosaics. I found a grout specific to wood, but it is not a good product...it stained black walnut to an ash grey and weeks later it was coming out of the joints.
I've attached a picture so you can get an idea of what I am dealing with.
If you have time and wouldn't mind helping me with this issue, I would much appreciate it. If not, no problem.
Thank you,
Katherine
Katherine, I’m sure you’re well aware yours is an age-old issue for artists, builders, architects and anyone who’s attempted to put two or more things together to form a whole for more years than history can record.
I’m a big believer in using the simplest method that will get the job done. I like “dry setting” stone for example because it’s the most forgiving (when done right) in all but the most troublesome situations. Still, it won’t work in every instance and is a difficult skill to master (at least for some).
It could work in your situation depending on the application. It would not work, of course, if the item were to get moved around a lot. I’ve utilized the dry set method on tables for example, with more than a modicum of success. The ancient stone setters used sand as a grout almost exclusively. When elastomeric properties are needed within the grout material itself, “bark” was often utilized. Probably the best known of which is cork. Finely ground bark or cork can be used in a loose mixture like silica sand or bound together to form sheets, strips or rolls to fill a variety of hole or gaps sizes.
The picture you sent me did not come through well, but of what I could tell, the gap you are attempting to fill is quite sizeable. Standard wood filling compounds will not work well in “large” gaps. They are made to take a stain and finish like raw wood and hopefully “disappear” or at least blend well with the piece or pieces they’re filling. Where you have large or expansive gaps to fill, the grout (if you must use one), can greatly benefit the overall system when made of a contrasting color, texture or pattern to what’s being filled.
We frequently use ground cork to make a flexible grout for wooden “rounds” or end grain block installations where the gaps are often quite large. Where wear is paramount and flexibility less so, we’ll resort to a highly plasticized mixture of cementitious grout and poly binder. We find such grouting materials can take foot traffic well and work better in many indoor installations where moisture can get trapped (such as entryways) and not easily pass through (as with most exterior applications).
Our company manufactures a variety of wood fillers, several of which are quite elastomeric. Two of our products, EZ Trowel FloorFill and Patch-It, contain 3 times or more resin than standard wood floor fillers. This greatly enhances their elastomeric properties. These products not only work well in standard wood flooring situations but also in highly resilient wood floors (e.g. sports floors) where standard wood floor fillers will simply pop out during active use.
There are occasions where we will mix wood, metal, stone and glass materials together to form a highly stylized or artistic floor. The grouting mixtures in these installations vary, but we often find a highly plasticized cementitious grouting compound the most advantageous all around.
Of course the tighter the pieces joined together, the less the issue of rejecting the grout (assuming a stable or immovable substrate). If pitch and yaw presents a significant problem with grout ejection (e.g. a yacht, houseboat, pier pole or similar construction), an elastomeric binder is a must. That’s one of the principle rationales behind dry setting and how exterior dry set systems have lasted for so many centuries. It facilitates the pass through of rainwater preventing (or at least reducing) freeze/thaw dilapidation and lends itself so readily to repair.
There are also many indoor wooden floors, as well as floors constructed of both wood and stone that rely on dry setting compounds which have endured exceptionally well for centuries. That’s my acid test for longevity…actual useful life.
Even dirt has been used with both stone and wood for countless centuries. I recently came across a near 200-year-old installation near my home of beautiful wooden marquetry set in bone dry dirt. I found no indication whatsoever of deterioration within the structure. Now that kind of fortitude truly impresses me.
Hope this helps,
Don Bollinger
I read your webpage and I was wondering if you might be able to help me with a grout issue.
I am working with wood, glass, and marble in mosaics. The biggest issue I have is the natural expansion and contraction of the wood. Clear silicone is great for adhering glass, but I'd prefer not use that as a "grout" for the mosaics. Main reason is that it's toxic and will not be easy to clean off the glass or marble unless the installer enjoys very tedious work (I like tedious...mosaics obviously, but installers don't).
I've been in the mosaic field for 15 years and no one has been able to figure out a reasonable solution to this issue. Hence, no one is making wood, glass, and marble mosaics. I found a grout specific to wood, but it is not a good product...it stained black walnut to an ash grey and weeks later it was coming out of the joints.
I've attached a picture so you can get an idea of what I am dealing with.
If you have time and wouldn't mind helping me with this issue, I would much appreciate it. If not, no problem.
Thank you,
Katherine
Katherine, I’m sure you’re well aware yours is an age-old issue for artists, builders, architects and anyone who’s attempted to put two or more things together to form a whole for more years than history can record.
I’m a big believer in using the simplest method that will get the job done. I like “dry setting” stone for example because it’s the most forgiving (when done right) in all but the most troublesome situations. Still, it won’t work in every instance and is a difficult skill to master (at least for some).
It could work in your situation depending on the application. It would not work, of course, if the item were to get moved around a lot. I’ve utilized the dry set method on tables for example, with more than a modicum of success. The ancient stone setters used sand as a grout almost exclusively. When elastomeric properties are needed within the grout material itself, “bark” was often utilized. Probably the best known of which is cork. Finely ground bark or cork can be used in a loose mixture like silica sand or bound together to form sheets, strips or rolls to fill a variety of hole or gaps sizes.
The picture you sent me did not come through well, but of what I could tell, the gap you are attempting to fill is quite sizeable. Standard wood filling compounds will not work well in “large” gaps. They are made to take a stain and finish like raw wood and hopefully “disappear” or at least blend well with the piece or pieces they’re filling. Where you have large or expansive gaps to fill, the grout (if you must use one), can greatly benefit the overall system when made of a contrasting color, texture or pattern to what’s being filled.
We frequently use ground cork to make a flexible grout for wooden “rounds” or end grain block installations where the gaps are often quite large. Where wear is paramount and flexibility less so, we’ll resort to a highly plasticized mixture of cementitious grout and poly binder. We find such grouting materials can take foot traffic well and work better in many indoor installations where moisture can get trapped (such as entryways) and not easily pass through (as with most exterior applications).
Our company manufactures a variety of wood fillers, several of which are quite elastomeric. Two of our products, EZ Trowel FloorFill and Patch-It, contain 3 times or more resin than standard wood floor fillers. This greatly enhances their elastomeric properties. These products not only work well in standard wood flooring situations but also in highly resilient wood floors (e.g. sports floors) where standard wood floor fillers will simply pop out during active use.
There are occasions where we will mix wood, metal, stone and glass materials together to form a highly stylized or artistic floor. The grouting mixtures in these installations vary, but we often find a highly plasticized cementitious grouting compound the most advantageous all around.
Of course the tighter the pieces joined together, the less the issue of rejecting the grout (assuming a stable or immovable substrate). If pitch and yaw presents a significant problem with grout ejection (e.g. a yacht, houseboat, pier pole or similar construction), an elastomeric binder is a must. That’s one of the principle rationales behind dry setting and how exterior dry set systems have lasted for so many centuries. It facilitates the pass through of rainwater preventing (or at least reducing) freeze/thaw dilapidation and lends itself so readily to repair.
There are also many indoor wooden floors, as well as floors constructed of both wood and stone that rely on dry setting compounds which have endured exceptionally well for centuries. That’s my acid test for longevity…actual useful life.
Even dirt has been used with both stone and wood for countless centuries. I recently came across a near 200-year-old installation near my home of beautiful wooden marquetry set in bone dry dirt. I found no indication whatsoever of deterioration within the structure. Now that kind of fortitude truly impresses me.
Hope this helps,
Don Bollinger
Monday, January 4, 2010
The What, When, Why, Where and How of Expansion for Wood Flooring… (FAQ) a very frequently asked question -- (January 2010)
Don,
I watched your video from 1990 where you put a hardwood floor in your house. I loved it. It was paced very well, detailed and informative yet not so slow moving that it put you to sleep like some how-to videos. I had to think just enough to stay into it.
My big question.....when do you cut wood to fit tight and when do you leave a gap? What is the point of a half inch gap on one side of the room when you have the boards on the other side jammed up tight against a fireplace? What about the ends of the boards? Is there a gap at the end of their length? It seems like you fit the board pretty tight lengthwise at the top of your stairs.
I have to install glue down engineered wood here in my house. It’s plywood with a veneer top. I just want some clear guidelines on how to deal with my fireplace and what to do when the boards run parallel to the track for my sliding closet door. I can't have a gap there. How can I leave a half inch? Am I retarded? Why does this seem contradictory? Leave a gap or not?
I know you are probably busy but if you have a sec to set me straight. I sure would appreciate it. That old husky dog sure was beautiful I'm sure he or she is gone by now. From the video, you seem like you might be laid back enough to answer this email.
Thanks for the great video.
Scott
Don,
I hope I'm not pushing my luck but to expand on the expansion gap question....
what if I change the flooring direction 90 degrees to set a dining area apart from a living room area? How will that effect the expansion gap placement? Is that even possible? Maybe I should call you. A three minute talk would probably eliminate a lot of typing.
Scott
You're right Scott, I’m just laid back enough to at least attempt to answer SOME of the many questions I get by email. I have always tried to be responsive to my readers and viewers over the years, particularly the last 20 since writing the Hardwood Floors book and doing those two videos/DVDs. Unfortunately, I may not be as quick to respond to some questions as some would like.
It’s especially rewarding for me to hear from folks who never knew a thing about wood floors, then through some assistance my book or videos/DVSs provided them, did their own floors and loved the way they turned out. I’m both surprised and delighted by the number of individuals from all over the world who’ve spoken to me at wood flooring conventions or schools I’ve helped teach and told me how I’ve helped them learn some portion of the trade. The best stories are the ones where learning the trade has made a huge difference in their lives. No amount of royalties could ever compare to such stories.
Many thanks to each and every one of you…thanks to all of you, I’ve both learned and taught countless facets of the hardwood flooring trade. A great master once told me, the best teachers always learn at least as much as they teach. I try to start each day with that emblazoned on my mind. Every one of us is both student and teacher. If we lose site of that, we’ve have surely lost our way.
Whenever I endeavor to write parts and pieces of what I’ve learned of my trade, I always paid solemn homage to the confidence placed in me by potential readers. Be assured, all facts, figures, descriptions and analysis will always be the absolute and honest truth as I know it to the best of my knowledge and abilities. Does this mean that I am always right? Of course not. But please know that I will always strive at all times to be as accurate as humanly possible. Upon discovery that I am wrong or as new information becomes available, I will immediately update my account with the most accurate version obtainable.
A lot of what you ask Scott is covered in FAQ on my two websites http:///www.theoakfloors and http://www.woodfloorco.com and on my blog on hardwood floors http://woodfloors-woodfloorpro.blogspot.com/.
For those who might be wondering, Kodiak, the Malamute you see in my two videos filmed in 1989 passed in 1999. Since his passing, he’s had two lines of successors. Currently we have both a male and female Malamute -- Kenai (female) and Aluke MacKenzie (male). Recent pictures of them can be found in my blogs.
I am putting together an interactive website http:///www.woodfloorpro.com for wood flooring professionals. It has been rough going trying to get all the stuff that needs doing in HTML code or whatever. Believe it or not, I learned computer programming and built my first computer in my early teens…when everything was done in binary code!
I’ve never tried to sell a program but have written several that hardwood flooring professionals use even today. The most popular program I’ve written for the hardwood flooring industry is the “Width Program”. That program calculates the number of square feet needed of each width for a variable width plank floor having the same number of rows in each width. It calculates waste et al. Problem is…I wrote it in C and C++ and have not updated it (yet) for today’s CPUs. I was developing sound routines (free lance) back then on several Beta formats for company’s no longer in business…like Wordperfect. So much has changed since I learned and worked in binary code, Pascal, C & C++. I guess I really am an old dinosaur…with computer programming anyway.
As many readers may know, I helped develop most of the hardwood flooring schools for the various wood flooring associations as well as many other groups. Like a number of other wood flooring contractors, I donated my time and expenses out of love for my trade and the pure enjoyment received from passing on what I knew. Alas, I’m no longer able to fly around the country as I once did. Severe health issues related to my Agent Orange exposure in Vietnam, coupled with depleted personal finances have at last taken their toll. Now I must be content with writing and sharing online what I hope is still of some use to those in the trade and those wanting to learn all or some part of it.
Now finally to your questions Scott…
Rather than repeat myself, I’ll attempt to address those issues not already covered in my other Q & A columns or in “Bollinger on Wood Floors” on my two websites.
There are several reasons for an expansion gap left around the room in any hardwood floor installation. The primary reason is to allow the floor to buckle in the event the floor is ever flooded. I explain more about the other reasons for an expansion space in “Expansion Space for a Hearth Border” in my Q&A or FAQ.
As I explained in my book, the rule of thumb for the expansion space with hardwood flooring is 1/16” of expansion space for every running foot across grain. Therefore a 16 X 20 foot room (assuming the flooring is running the long dimension of the room) would require a 1” expansion space. Since this can be divided in half, you can allow ½” at the walls lines. A ½” to ¾” expansion space is commonly called for with most residential installations but it is not uncommon to find 3 or 4 inch expansion gaps around a especially large solid wood flooring installations.
This expansion gap is especially important along the wall lines running the floor’s long dimension. NOTE: In most instances flooring joists will be installed running the “short” dimension and with a single layer ¾” thick for your subfloor and with 16” on center joists, the flooring should be run perpendicular to joists. In most instances, this will mean running the flooring down the longest room dimensions. Most flooring does not require an expansion space for the ends of boards since most wood species expand negligibly down their lengths.
When you have perimeters or intermediary walls or other solid intrusions into rooms, you must allow expansion space around them as well. When you have intrusions that are bordered or where flooring must be laid “flush” against them such as around hearths, perimeter borders or as you specified in your instance, at a closet door slider, you have to hope that you have allowed enough expansion space at adjacent wall lines or other intrusions opposite these. If this is not possible (e.g. a completely bordered room or where you have flush fit intrusions opposite one another, you must make other accommodations. This is important for the well being or appearance of your floor in these spots long term. This issue is often neglected or overlooked by novice installers and sometimes even practiced professionals. This can be helped by adding additional spacing between board rows and/or by using quarter sawn or a mix of rift cut and quarter sawn material.
A commonly utilized gap for expansion for wooden floors used to be between the sill plate and the terminal point at doorways. These were covered by raised thresholds to outside doors or those that straddled interior doors in the past. Now days, most construction does not accommodate raised interior thresholds and often does not allow for a gap a the terminal point of wooden floors as exterior doorways. In such cases, or around a hearth or border, a pliable or flexible seam can be installed as outlined in my FAQ section “Flexible Fillers for Expansion Gaps” in Bollinger on Wood Floors.
Solid tongued and grooved blind nailed wood flooring tends to move more in the direction of the tongues (if it is installed exclusively by blind nailing). This can allow the installer to make use of a double tongued board or “king board” in the center of the room or installation then lay the flooring in both directions away from this center board. This is commonly done in gymnasiums and other large wood flooring installations. Not only does this help with the expansion requirement but also keeps installation teams busy on both sides of the king board who frequently race with one another to expedite the work and reduce tedium with the work regimen. Even so, these large installations generally require planting “spacers” ever so often between rows to create gaps between boards. These spacers are removed shortly after installation so that the flooring can “settle-in” soon after it’s nailed into place.
I recall when I was teaching for the American Hardwood Export Council in Hong Kong some years ago. I had the opportunity of observing the practices of Chinese wood flooring installers in the “New Territories”. They were nailing down solid prefinished flooring that had not been fully acclimated to the high humidity of the area. They were putting “large” spacers between every row of 2-1/4” flooring. They removed these spacers within a few hours of them being placed. The next morning the “large” gaps between each row of flooring left by the spacers had been fully engulfed leaving a “tight looking” installation. Often, several days or weeks later this flooring was not only tight to the wall lines, having fully-filled the significant expansion space left at all wall lines and wall intrusions, but in many instances it had swollen so much the entire flooring system had cupped.
Again, the primary reason for the expansion gap is to allow enough space so that the flooring (if flooded) can expand into the expansion space sufficiently for it to buckle up off the substrate. In the event of a flood, if there is not enough room for buckling to occur, the flooring will push into the walls or whatever’s restraining it. I have seen exterior walls pushed off the rim joists causing irreparable damage to the structure (not just the flooring).
Engineered flooring (like plywood and other types of materials with the wood grain alternated or transposed) reduces the effect of expansion and contraction, effectively cutting it in half in many cases. Still, there remains a considerable requirement for an expansion allowance. Installing patterned flooring and/or running the flooring in opposing directions can significantly reduce the expansion requirement in certain installation – but not entirely, especially with “large” commercial or some residential installations as many so-called wood flooring “experts” oftentimes indicate.
I like using quarter sawn or a mix of rift cut and quarter sawn material for installations that need to help mitigate or ease this requirement for expansion space. Examples are bordered floors, floors over radiant heating systems, large installations or installations where large shifts in relative humidity are likely to persist. Another method for helping mitigate movement from moisture is by gluing as well as nailing boards to the substrate or underlayment. The right glue must be utilized, one that is meant for use with solid wood flooring. This glue then not only helps retain boards as moisture impregnates them, it helps prevent moisture from impregnating them in the first place by isolating their undersides from liquids or vapors.
So, in recapping our discussion of why and how to allow for expansion, let me reiterate. Leave gaps whenever and wherever possible. Historically, homes and other structures accommodated expansion spaces at all doors and walls in addition to the gap at wall lines. Generally, in the days of lath and plaster, the bottom of each wall line had a nailing board for trim and molding. This board was held up enough to allow the flooring to expand underneath it. In addition, the trim package in those days typically called for several pieces of floor molding (up to 1-1/4 to 1-1/2 inches in most cases). Use quarter sawn or rift cut flooring material when available. Change the flooring direction when you’re able to do so. Place spacers between flooring rows when the situation calls for it. Glue and nail if you’re concerned about migrating moisture.
Don Bollinger
I watched your video from 1990 where you put a hardwood floor in your house. I loved it. It was paced very well, detailed and informative yet not so slow moving that it put you to sleep like some how-to videos. I had to think just enough to stay into it.
My big question.....when do you cut wood to fit tight and when do you leave a gap? What is the point of a half inch gap on one side of the room when you have the boards on the other side jammed up tight against a fireplace? What about the ends of the boards? Is there a gap at the end of their length? It seems like you fit the board pretty tight lengthwise at the top of your stairs.
I have to install glue down engineered wood here in my house. It’s plywood with a veneer top. I just want some clear guidelines on how to deal with my fireplace and what to do when the boards run parallel to the track for my sliding closet door. I can't have a gap there. How can I leave a half inch? Am I retarded? Why does this seem contradictory? Leave a gap or not?
I know you are probably busy but if you have a sec to set me straight. I sure would appreciate it. That old husky dog sure was beautiful I'm sure he or she is gone by now. From the video, you seem like you might be laid back enough to answer this email.
Thanks for the great video.
Scott
Don,
I hope I'm not pushing my luck but to expand on the expansion gap question....
what if I change the flooring direction 90 degrees to set a dining area apart from a living room area? How will that effect the expansion gap placement? Is that even possible? Maybe I should call you. A three minute talk would probably eliminate a lot of typing.
Scott
You're right Scott, I’m just laid back enough to at least attempt to answer SOME of the many questions I get by email. I have always tried to be responsive to my readers and viewers over the years, particularly the last 20 since writing the Hardwood Floors book and doing those two videos/DVDs. Unfortunately, I may not be as quick to respond to some questions as some would like.
It’s especially rewarding for me to hear from folks who never knew a thing about wood floors, then through some assistance my book or videos/DVSs provided them, did their own floors and loved the way they turned out. I’m both surprised and delighted by the number of individuals from all over the world who’ve spoken to me at wood flooring conventions or schools I’ve helped teach and told me how I’ve helped them learn some portion of the trade. The best stories are the ones where learning the trade has made a huge difference in their lives. No amount of royalties could ever compare to such stories.
Many thanks to each and every one of you…thanks to all of you, I’ve both learned and taught countless facets of the hardwood flooring trade. A great master once told me, the best teachers always learn at least as much as they teach. I try to start each day with that emblazoned on my mind. Every one of us is both student and teacher. If we lose site of that, we’ve have surely lost our way.
Whenever I endeavor to write parts and pieces of what I’ve learned of my trade, I always paid solemn homage to the confidence placed in me by potential readers. Be assured, all facts, figures, descriptions and analysis will always be the absolute and honest truth as I know it to the best of my knowledge and abilities. Does this mean that I am always right? Of course not. But please know that I will always strive at all times to be as accurate as humanly possible. Upon discovery that I am wrong or as new information becomes available, I will immediately update my account with the most accurate version obtainable.
A lot of what you ask Scott is covered in FAQ on my two websites http:///www.theoakfloors and http://www.woodfloorco.com and on my blog on hardwood floors http://woodfloors-woodfloorpro.blogspot.com/.
For those who might be wondering, Kodiak, the Malamute you see in my two videos filmed in 1989 passed in 1999. Since his passing, he’s had two lines of successors. Currently we have both a male and female Malamute -- Kenai (female) and Aluke MacKenzie (male). Recent pictures of them can be found in my blogs.
I am putting together an interactive website http:///www.woodfloorpro.com for wood flooring professionals. It has been rough going trying to get all the stuff that needs doing in HTML code or whatever. Believe it or not, I learned computer programming and built my first computer in my early teens…when everything was done in binary code!
I’ve never tried to sell a program but have written several that hardwood flooring professionals use even today. The most popular program I’ve written for the hardwood flooring industry is the “Width Program”. That program calculates the number of square feet needed of each width for a variable width plank floor having the same number of rows in each width. It calculates waste et al. Problem is…I wrote it in C and C++ and have not updated it (yet) for today’s CPUs. I was developing sound routines (free lance) back then on several Beta formats for company’s no longer in business…like Wordperfect. So much has changed since I learned and worked in binary code, Pascal, C & C++. I guess I really am an old dinosaur…with computer programming anyway.
As many readers may know, I helped develop most of the hardwood flooring schools for the various wood flooring associations as well as many other groups. Like a number of other wood flooring contractors, I donated my time and expenses out of love for my trade and the pure enjoyment received from passing on what I knew. Alas, I’m no longer able to fly around the country as I once did. Severe health issues related to my Agent Orange exposure in Vietnam, coupled with depleted personal finances have at last taken their toll. Now I must be content with writing and sharing online what I hope is still of some use to those in the trade and those wanting to learn all or some part of it.
Now finally to your questions Scott…
Rather than repeat myself, I’ll attempt to address those issues not already covered in my other Q & A columns or in “Bollinger on Wood Floors” on my two websites.
There are several reasons for an expansion gap left around the room in any hardwood floor installation. The primary reason is to allow the floor to buckle in the event the floor is ever flooded. I explain more about the other reasons for an expansion space in “Expansion Space for a Hearth Border” in my Q&A or FAQ.
As I explained in my book, the rule of thumb for the expansion space with hardwood flooring is 1/16” of expansion space for every running foot across grain. Therefore a 16 X 20 foot room (assuming the flooring is running the long dimension of the room) would require a 1” expansion space. Since this can be divided in half, you can allow ½” at the walls lines. A ½” to ¾” expansion space is commonly called for with most residential installations but it is not uncommon to find 3 or 4 inch expansion gaps around a especially large solid wood flooring installations.
This expansion gap is especially important along the wall lines running the floor’s long dimension. NOTE: In most instances flooring joists will be installed running the “short” dimension and with a single layer ¾” thick for your subfloor and with 16” on center joists, the flooring should be run perpendicular to joists. In most instances, this will mean running the flooring down the longest room dimensions. Most flooring does not require an expansion space for the ends of boards since most wood species expand negligibly down their lengths.
When you have perimeters or intermediary walls or other solid intrusions into rooms, you must allow expansion space around them as well. When you have intrusions that are bordered or where flooring must be laid “flush” against them such as around hearths, perimeter borders or as you specified in your instance, at a closet door slider, you have to hope that you have allowed enough expansion space at adjacent wall lines or other intrusions opposite these. If this is not possible (e.g. a completely bordered room or where you have flush fit intrusions opposite one another, you must make other accommodations. This is important for the well being or appearance of your floor in these spots long term. This issue is often neglected or overlooked by novice installers and sometimes even practiced professionals. This can be helped by adding additional spacing between board rows and/or by using quarter sawn or a mix of rift cut and quarter sawn material.
A commonly utilized gap for expansion for wooden floors used to be between the sill plate and the terminal point at doorways. These were covered by raised thresholds to outside doors or those that straddled interior doors in the past. Now days, most construction does not accommodate raised interior thresholds and often does not allow for a gap a the terminal point of wooden floors as exterior doorways. In such cases, or around a hearth or border, a pliable or flexible seam can be installed as outlined in my FAQ section “Flexible Fillers for Expansion Gaps” in Bollinger on Wood Floors.
Solid tongued and grooved blind nailed wood flooring tends to move more in the direction of the tongues (if it is installed exclusively by blind nailing). This can allow the installer to make use of a double tongued board or “king board” in the center of the room or installation then lay the flooring in both directions away from this center board. This is commonly done in gymnasiums and other large wood flooring installations. Not only does this help with the expansion requirement but also keeps installation teams busy on both sides of the king board who frequently race with one another to expedite the work and reduce tedium with the work regimen. Even so, these large installations generally require planting “spacers” ever so often between rows to create gaps between boards. These spacers are removed shortly after installation so that the flooring can “settle-in” soon after it’s nailed into place.
I recall when I was teaching for the American Hardwood Export Council in Hong Kong some years ago. I had the opportunity of observing the practices of Chinese wood flooring installers in the “New Territories”. They were nailing down solid prefinished flooring that had not been fully acclimated to the high humidity of the area. They were putting “large” spacers between every row of 2-1/4” flooring. They removed these spacers within a few hours of them being placed. The next morning the “large” gaps between each row of flooring left by the spacers had been fully engulfed leaving a “tight looking” installation. Often, several days or weeks later this flooring was not only tight to the wall lines, having fully-filled the significant expansion space left at all wall lines and wall intrusions, but in many instances it had swollen so much the entire flooring system had cupped.
Again, the primary reason for the expansion gap is to allow enough space so that the flooring (if flooded) can expand into the expansion space sufficiently for it to buckle up off the substrate. In the event of a flood, if there is not enough room for buckling to occur, the flooring will push into the walls or whatever’s restraining it. I have seen exterior walls pushed off the rim joists causing irreparable damage to the structure (not just the flooring).
Engineered flooring (like plywood and other types of materials with the wood grain alternated or transposed) reduces the effect of expansion and contraction, effectively cutting it in half in many cases. Still, there remains a considerable requirement for an expansion allowance. Installing patterned flooring and/or running the flooring in opposing directions can significantly reduce the expansion requirement in certain installation – but not entirely, especially with “large” commercial or some residential installations as many so-called wood flooring “experts” oftentimes indicate.
I like using quarter sawn or a mix of rift cut and quarter sawn material for installations that need to help mitigate or ease this requirement for expansion space. Examples are bordered floors, floors over radiant heating systems, large installations or installations where large shifts in relative humidity are likely to persist. Another method for helping mitigate movement from moisture is by gluing as well as nailing boards to the substrate or underlayment. The right glue must be utilized, one that is meant for use with solid wood flooring. This glue then not only helps retain boards as moisture impregnates them, it helps prevent moisture from impregnating them in the first place by isolating their undersides from liquids or vapors.
So, in recapping our discussion of why and how to allow for expansion, let me reiterate. Leave gaps whenever and wherever possible. Historically, homes and other structures accommodated expansion spaces at all doors and walls in addition to the gap at wall lines. Generally, in the days of lath and plaster, the bottom of each wall line had a nailing board for trim and molding. This board was held up enough to allow the flooring to expand underneath it. In addition, the trim package in those days typically called for several pieces of floor molding (up to 1-1/4 to 1-1/2 inches in most cases). Use quarter sawn or rift cut flooring material when available. Change the flooring direction when you’re able to do so. Place spacers between flooring rows when the situation calls for it. Glue and nail if you’re concerned about migrating moisture.
Don Bollinger
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