I have installed hydronic radiant heat pipes under the subfloor; used aluminum plates for spreading the heat from pex pipes. The house is old, I think the original subfloor is 5/8 Douglas fir. Up to this point, everything was fine, the flow was not making any noise, for several seasons. Later, we decided to renovate upstairs, and decided to add a layer of 1/2" plywood to the existing subfloor, since we want to run engineered hardwood planks in parallel to joists.
We used just regular, 1/2" 4-ply plywood, attached using 1 1/8" regular wood screws, no glue. Now, here is the issue. Whenever heating starts, I hear the floor "talking" - ie expanding, and making a little crackling noise. If at this time, I walk across the room, there is a wave of that "adjustment" happening, which would be fine, if it would be silent, but it's not. Once you walk, or the floor settles changing the temperature, the crackling is gone, and after it's quiet. When cooling-off starts, the floor goes through the same process.
So, anyone had experience with this, and solved this issue in the past?
I can tell it's not pex moving in aluminum tracks, nor aluminum radiators canning/shifting/etc effect, because other rooms that do not have additional layer of 1/2" plywood don't do that. Besides, the issue appeared only after I have installed that additional layer of plywood.
- 1/2 plywood is cheap, ie not good quality, and makes the noise on its own. I could unscrew several plywood sheets, and see whether they will make any noise afterward.
- Since the glue wasn't used, and those plywood sheets are from different wood, they expand at different speed, thus rubbing surfaces, thus making the noise. Course of action: use glue (the question would be: pl400: rubbery vs mapei wpa:acrylic vs mapei 975:polyurethane)