Expansion gap for hardwood

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Old 03-25-15, 08:02 PM
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Expansion gap for hardwood

So, I've been getting ready to install some hardwood flooring and doing some research about expansion gaps. I found some information that said with solid hardwood, the flooring will expand mostly in the direction of the tongue/groove - at leastthat was my understanding of it. Did I misinterpret and/or is that accurate? Is most of the expansion in that one direction? I would still leave a gap in the other direction, but if that information is true, it would save me a lot of time undercutting plaster walls to make room.
 
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Old 03-26-15, 03:41 AM
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There are tongues and grooves in both directions. Wood normally swells and contracts in the opposite direction of the grain. IF it is properly acclimated (72 hours) you should need no spacing for expansion. If the run is over 30', then it is sometimes accepted to use fender washers in the middle run, but I have only seen that on basketball courts and commercial applications. In a residence you should not need it.

You will leave 1/4" around the perimeter regardless. Your baseboard/shoe molding will cover the gap.
 
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Old 03-26-15, 04:48 AM
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Thanks for the info. The room is about 30' x 14' at the widest points and the flooring will have acclimated a week or two before I start putting the flooring in, so it sounds like the 1/4" gap will be fine. I never heard of the thing about putting washers in the middle. What is that about?
 
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Old 03-26-15, 06:37 AM
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Which direction does the floor joist system run? You are going to have to lay the flooring perpendicular to the floor joists. If that results in a run that has the widths orientated to the 30' length you may have to start in the middle of the room and work in both directions using a spline to change directions. If the widths orient to the 14' direction, you probably will not have much of an issue with expansion.
 
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Old 03-26-15, 02:11 PM
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The joists run in the 14' direction, and I have an old house with plank subfloors, so I will end up having to install the hardwood perpendicular to the planks, making it parallel to the joists.

Do you forsee expansion problems in that scenario?

I'm thinking I may tear up the existing flooring early and take an undercut saw to the plaster and make room for expansion just to be safe... It's more work, but less worry in the long run.
 
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Old 03-26-15, 02:44 PM
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I would seriously consider removing the planks altogether and putting 3/4" Advantech down in its place. Hardwood fighting hardwood that will both expand and contract differently.

You also will end up with a floor that "does the wave" as it dips slightly between the joists if you go parallel to the direction of the joists.

Advantech is a premium subfloor and is considered an industry standard now. 3/4" minimum for OAB type products for hold power on the cleats.
 
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