Screwing plywood subfloor to concrete slab

[joeka101]

Hi,

I've read similar posts but seems a little different. Would appreciate thoughts.

5.5x3.5m extension. Solid floor. Subfloor and engineered wood floor covering will be continuous with existing suspended timber floor of main house

Structure (bottom to top):
150mm hardcore / sand blinding / DPM / 120mm celotex / VCL / 100mm concrete with self levelling compound. The concrete is ABOVE the insulation / VCL / DPM.

I don't like glued floating floors as they never feel quite "solid" in my experience. Not keen on adhesives if possible. Generally prefer removable fixings in case of revisions / repairs.

Id like to screw a 18mm plywood subfloor in to the concrete so I can use hidden tongue and groove screws for the engineered wood floor.

As the concrete slab is WITHIN the thermal /VCL envelope, I assume this would be fine.

Sense check?

Cheers,
Joe

 

[muh3]

I hope you don't run any underfloor heating in the concrete

Only issue you have is expansion, I would just leave a small 2-3mm gap between the ply sheets, also the 18mm ply will not give you much hold for the hidden screws. Do you get screws small enought for this?

 

[joeka101]

Cheers mate. Yeah, no UFH! Small hidden screws (tongue tite).

I just dislike the slight give in a floating floor.