I'd like to understand why wood movement in a floor necessitates large expansion gaps around the outside of the room. I'm not asking why wood as a material undergoes changes due to moisture - I'm interested in how the floor system as a whole actually behaves once installed.

Take for example common wood-strip flooring such as 3/4 oak. Here's a diagram showing a typical recommended installation along a wall parallel to the floorboards:

enter image description here

How is it possible that the entire floor could ever move by approx 3/4" at the walls without being totally destroyed? Nails would be torn out, boards split, etc. if the floor moved that much, no? So is the gap really useful?


(What I would have thought was: given the way boards like this are nailed, the tongues would remain in place relative to the floor, the grooves would slide around, and the floor as a whole would not move at all. Gaps would just open and close between individual strips.)

  • Floating floors move as a whole system, if boards throughout are nailed down then the floor can't move as a single unit (which can lead to a host of problems if the ideal range of in-service conditions are exceeded).
    – Graphus
    Nov 25, 2018 at 19:17

1 Answer 1


You're correct that the 3/4" gap isn't going to be entirely closed and then open again seasonally.

Part of that big a gap is convenience... you can have the baseboard installed and still pull a floorboard out. It's easier to lay a floor with loose gaps. (And given the wows and flutters in long walls, the gap will be wide in places and narrower in others and you can still have a straight run.)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.