Flooring Puzzle

[Warren Wilson]

I am replacing the flooring in a bedroom and using a composite "wooden" product. The salesman recommends gluing. So far so good. I imagine the coefficient of expansion of the composite is similar to that of plywood.

But he also recommends leaving 1/2" around the edges (at the walls) for expansion/contraction. This part puzzles me -- how is the flooring material going to move in relation to the subfloor (plywood) if it is glued to it?

This in turn made me reflect that I have installed sold wood (3/4") in the past using a regular flooring nail gun, which would also -- you would think -- create a "crossgrain" issue between the oak flooring (subject to seasonal humidity change) and the plywood subfloor (not so much affected). I left room for expansion/contraction, but it has not been an issue. And in any case, the two products are securely nailed together so where can the expansion/contraction take place?

What am I missing here?

[Wayne Lomman]

Warren, building a house has lots of allowances like this in case something happens, not necessarily because it will happen. A house moves in myriad ways and gaps like you are talking about protect the floor from wall movement as well as vice versa. If you have a flood the damage is less for example. A house is built on a long standing accumulation of knowledge and this is an example of this. Cheers

[Cameron Hood]

Are you sure that the salesman wasn't suggesting that you just glue the pieces to each other rather than gluing them to the floor? If the pieces were glued to each other, then basically you have a floating floor and the space around the edges makes sense.

[Sam Beagle]

It's always a good idea to leave the gap. It's not gonna hurt anything anyway. It's a protective measure. You can make it 1/4" if you would rather. A gap alone is the key.

[Sean Troy]

When I did mine, it was glued to each other, not the floor. A rosen type paper went down and then 1/4 cork. Wood floated on that. 3/8 around the edges and then trim.

[Karl Andersson]

The floor may not expand; the wall studs and plate, if wood, will expand and contract - best not to have them butted up against the floor -although 1/2 in may be a bit more than you need. I've never used that floor product, so don't know about the glue though.

[Warren Wilson]

Thanks -- the notion of gluing the pieces to each other makes sense. Perhaps that is just what he meant.

Having built several houses from lot layout right to finish carpentry (the general contractor always seemed to need one extra guy), I understand the other comments about how the components of a house interact. What puzzled me was the notion that laminating two laminates would result in one part moving in relation to the other.

It all makes sense, though, if the flooring is only edge glued and remains a floating floor.

[Shawn Pixley]

I am replacing the flooring in a bedroom and using a composite "wooden" product. The salesman recommends gluing. So far so good. I imagine the coefficient of expansion of the composite is similar to that of plywood.

But he also recommends leaving 1/2" around the edges (at the walls) for expansion/contraction. This part puzzles me -- how is the flooring material going to move in relation to the subfloor (plywood) if it is glued to it?

This in turn made me reflect that I have installed sold wood (3/4") in the past using a regular flooring nail gun, which would also -- you would think -- create a "crossgrain" issue between the oak flooring (subject to seasonal humidity change) and the plywood subfloor (not so much affected). I left room for expansion/contraction, but it has not been an issue. And in any case, the two products are securely nailed together so where can the expansion/contraction take place?

What am I missing here?

Having done this a couple of times, here are my thoughts. In our bedroom, I nailed a composite Bamboo floor down over the plywood and joists. I did a border in the carmelized bamboo. I wouldn't glue down. I left a 1/4" at the drywall. The layout and calculations are a bit complicated as you can imagine.

In LOML's studio, we were on the concrete slab. I didn't glue this down either, but let it float. This was cork flooring. Again, I left 1/4" at the walls.

I suspect that you will find that the walls are not perfectly straight nor parallel to each other. Trying to scribe an entire room would be very challenging. Especially given the T&G flloring and trying to get the last piece fitted and then layed down tighly to the wall. Most of the house has no baseboards. The house originally had the flooring layed down before the drywall was hung. I recommend accepting a gap and covering with with your baseboard. Personally, I wouldn't glue if you don't have to (despite the salesman's recommendation). If it can be nailed down, I would. My personal opinion only. You should do what you think is best.

[John TenEyck]

My friend put down a floating composite wood floor and it buckled like a giant whale when he left for a few months in the Summer with the AC off, even though he had left 1/4"+ around the edges. His problem was he never opened the boxes prior to install. They had been in his garage for 2+ years, sealed in their boxes and plastic and he, incorrectly, assumed it would be OK. Big mistake.

Even with the recommended gap, composite floors can expand a lot.

John

[Jeff Duncan]

I don't think the floor is going to move, though as has been mentioned maybe it's good to leave a gap anyway. I've installed solid 3/8" parquet flooring glued down to ply underlayment and left a 1/8" gap around most of the perimeter. A couple spots where it met up with a top stair tread it was flushed right to the wood. It's been about a decade and still looks a good as when it was first finished. The glue dries and stays flexible so there is some give if needed. Your using composite which in theory should move even less than the solid....I think your fine if you want to go a bit tighter.

good luck,
JeffD

[Jim Breen (NY)]

When I did commercial wood floors, we would cork the borders on some floors but those were the sizes of basketball courts. In residential installs, the gap under the baseboards was usually left open and if there were room transitions, the wood would float under any thresholds/saddles.