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I am planning to install prefinished solid 3 1/4" wide by 3/4" thick ash hardwood in my home using 2" cleats. I live in Canada, so the average indoor humidity difference between winter and summer is quite high, maybe 50%. I don't use air-con in the summer. It is early December now, so I expect each board to expand in width by approximately .01" between now and summer.

Is there any reason why I should not put small gaps of .01" between each board (using a removable shim) as I nail them down? I still plan to leave a 1/2" gap around the entire room, just in case.

I ask this because I don't understand how a tightly-fitted floor is supposed to expand at all. What happens to the nails around the periphery if the whole floor moves by a good fraction of an inch? Are they simply ripped or bent out of place? By 1/2 an inch?? Or does the 45 degree angle of the nails force each board (and progressively the whole floor) to rise up by the same amount as the expansion? And when they shrink back down what pulls them back into place? People walking on the floor?

In removing my old maple floors I saw no such evidence of major movement. So I ask, quite literally, what gives?

jLegris
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Do NOT install expansion spaces between each board. You want a very tight fit between each board and then leave an expansion space around the perimeter of each room.

First you’ll need to acclimate the wood to your house. This may vary by location and season, but generally the manufacturers recommend about 10 days.

Second, seal the floor (again, according to the manufacturer’s recommendation).

Third, lay the “sleepers” out according to the size of your flooring and the allowable span. Sleepers are NOT fastened to the floor. They are designed to “float” or slide depending on expansion of the flooring.

Next lay out the flooring (loosely). This will give you an idea of color, etc., but will also help acclimate the finish flooring. Gaps at the perimeter is based on the size of the room. When we do gymnasiums, we leave a 2” gap and cover with an appropriate base. In homes, we generally leave a 1” gap.

See MFMA recommendations for acclimation and installation: https://www.maplefloor.org/ForArchitects/Installation.aspx

Btw, to test your finish flooring, hold a piece vertically and insert another piece into the T&G edge. If it fits tight, it’s okay. If not, you’ll have problems with the T&G edges when you walk on them. They’ll snap and pop and drive you nuts. If it’s not tight (and supports the other piece of wood when held vertically,) then I’d send it back. (See MFMA guidelines.) https://www.maplefloor.org/Home.aspx

Btw, yes, I know it’s the Maple FlooringManufacturing Association, but is consistent with ash, etc. too.

Lee Sam
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Wood gives, and takes....

In my opinion, wood will compress when needed. Picture a hammer striking a board and leaving a mark, it compresses. This is quite the exaggeration, but for a point. The wood in the center of your floor, held in place by all the other nails surrounding it will compress. Although I do not know how much area is "held tight" by this theory, but it will negate the need to consider how much of the floor will actually move.

If you leave the standard 1/2" from the drywall so a 3/4" base will cover it, that will suffice very nicely. If you have a gap at the drywall/plaster to allow the floor to have more room to move, you can use the exposed plate under the edge of the drywall to start your gap, therefore you can use a thinner base without resorting to shoe mold.

Another point to consider is the "cut"or "saw" of the flooring. Quarter sawn, rift cut and plain sliced, factors in on the movement of the floor. That topic alone can be looked up as to how it affects wood movement. The terms I used may be different in different regions, but the nature of the wood when cut is the same.

Jack
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