so i picked up a hydrometer to measure the humidity in the home. up here(buffalo) the winters are dry inside. although i have a furnace humidifier i can only maintain about 35 to 40% relative humidity in the winter and i think it will rise to at least 50 in the summer (just a guess). Im installing bruce solid 3/4" maple (second floor), you guys think i should i leave a gap between each row of wood maybe half the thickness of a credit card to allow expansion for the summer mnonths? Do any pros do this when installing in winter? thanks in advance.

That's how it was done in the old days. Everything was calculated and the humidity at the time of install, determined the space used.

I think every row is a bit much, maybee every 3-4 feet is more the standard. What size plank are you going to put down also will add to the equation and the width of the room will as well. Maple will move faster than many others out there and yes some pro's will space a floor if they feel that it needs to have a little space for the summer months if you expect the humidity to get back up in your home.

the boards are 3.5" and the first room is about 10x12.

i will be moving slow on this job (its my first floor) which is not a problem because i play poker for a living and therefore create my own hours.

there is about another 1200 ft to go after this room. the wood won't be coming for another two months so i expect to do the tail end of the job in the spring when humidity is higher.

can you tell me how many thousandths i should space between boards now? (when humidity is 38% probably 10% lower than it will be come spring and summer)

btw, thanks for the replies you guys are invaluable.

In a room that size I dont think you are going to have that much of an issue with movement but if you feel better about it put a space about every 4 ft that equals the thickness of two or three of those poker cards.

does it make any difference that im doing the whole upstairs without any transitions (this room will attach to the halway which inturn leads to two other bedrooms).

Man, you want me to work and use my brain, on off hours!!


I have the charts to figure exactly how much each board is going to swell with a gain of 10% humidity added in the room. I'm just not near them right now.

You should be able to find species swell charts.

Mine is for 2¼ Oak, and i would have to do a lot of math to come up with 3½ Maple.

If the floor goes around walls thats where your expansion is going to be, in acuality the 3" doorway is probally the only place where it continues thru with no breaks.

well floorguy and others i found this site that maybe can help me approximate the change, what do you guys think?

http://www.spmesquite.com/articles/defa ... ntentID=33

that meant you to Kevin and thanks again for all the info, i'm good with renovations and mechanics, but im nervous about putting in someone elses floor for my first install

geez according to the stability chart: hard maple = .00353 x 3.5 (inches wide) x 10 (% humidity change) = about .125 or 1/8 of an inch! thats per board, seems very excessive to me

Yep, quite excessive. Think how much that floor is going to grow in just 8 boards wide....

You can equate out the gap needed exactly, so the floor doesn't buckle, when it gains back some moisture.

on this site it says this chart applies to tangential shrinkage, which way is that?

acccording to those calculations i will be gaining about 4 inches of swell in a 10 foot room (about 35-40 boards across)