How much expansion space is need for solid oak flooring?

Question

I have purchased Bruce 3/4" solid oak flooring and I am looking for some guidance with respect to expansion space. This is standard tongue and groove flooring that will be nailed down. This is also an above grade installation, on a wooden subfloor, in the Saint Louis Missouri region.

Unfortunately, the manufacturers website does not have an installation guide for my product. (I submitted a question asking for one, but who knows if/when they will respond.) And the recommendations for their other products vary greatly, and are not very specific for the ones that appear to be similar. So am asking for some general "rule of thumb" guidance.

Going with the boards, I could have runs up to 48' long. There is one doorway where we could add a T-molding as we transition between rooms, but that only takes about 10' off the total length.

Across the board, my longest run is about 24', with ~half of it being in a hallway where board lengths will be shorter.

The packaging has one reference to standoff distance on the starting run, which indicates they want a 3/4" expansion gap at the walls.

My core question is whether I need to try to add some additional expansion gap, either at the wall or in the run, to account for the dimensions I am working with and local climate?

Answer 1

3/4" gap all around has been the norm that I have seen on old house installs. If the drywall is high enough to make that gap to the framing all the better. That way the gap could be bigger and the base will still cover if you choose to not have shoe mold as many new installs nowadays go that way.

The biggest issue for solid wood floors over a large area is getting the wood acclimated. This usually means leaving the flooring in the environment in which it will be laid for 2 weeks. In the get it done now mentality of today, that never happens. then it is a matter of making sure the wood is within an acceptable range of moisture content that is compatible with the subfloor. If you can get or have a moisture meter, that will tell you what you need.

If you are coming out of a heating season, you home will be really dry, somewhere as low as 2-4% Moisture content (MC) Material as it comes from the suppliers, as long as it has not set in a warehouse for a long time, is supposed to be about 6% MC. This is not a bad difference. Usually if the floor is within 2% of the subfloor, there will be no issue. During the summertime the humidity will increase the MC to perhaps as much as 10%. Still the wood flooring needs to match this closely or it will try to swell rapidly to match the MC of the subfloor. Buckling may occur.

If it all goes in at the same MC or close it will all move together and have minimal issue. If the wood does swell up too much, that is what the gap on the long edges are all about, insurance. The ends to not need the same concern, then length of the floor only changes ever so slightly as the MC changes. In my experience ther has been no other need to make any other accomodation for expansion than the gap at the walls, no "T" strips needed.