Plank Flooring and Wood Floor Finishes

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

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