I am putting in an engineered wood floor on half of my basement (length ways): landscape fabric, dmx underlayment, 1/4 inch plywood, then engineered floor. Three sides of the floor will be against walls, but one side will be "open" My question is when I walk on the floor close to the open side, will it sag? Should I go up to 1/2 inch ply. (Height in the basement is scarce).
I could put a strip of something under the open end (adjacent to the DMX but under the ply) to hold the floor up (something that is 8 mm thick, because that is the thickness of the DMX), but I am concerned that this will defeat my attempts to help air flow under there? Or should I not worry about airflow and just depend on the dmx to trap the moisture under there?
If I should use something, what would you recommend?
Putting aside the sag issue, are there other good reasons for me to move from 1/4 inch to 1/2 in ply? Thanks.