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

8 comments:

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