Engineered flooring over 2 different substrate

Discussion in 'Builders' Talk' started by MrTopOut, Nov 7, 2023.

  1. MrTopOut

    MrTopOut New Member


    Hoping someone maybe able to provide some advice with regards to installing wood floor over two different substrates (Concrete and Timber Floor Boards).

    I have relatively large room with a subfloor make up of a concrete oversite slab, abutting a suspended floor. We are wanting to install an engineered parquet flooring. However am concerned with the different substrates and potential for movement.

    Most of the floors we have looked at are a glued down solution, and was wondering how this can be achieved with the existing construction. could I simply run a 5mm ply board over the full floor area?

    Any help or advise is greatly appreciated
  2. Mark DM

    Mark DM Screwfix Select

    You could ply over everything although I would go WBP 9mm rather than 6mm if you can. another option would be self level the concrete slab and ply over the suspended floor. Either way, put plenty of screws in.(time consuming) Grid pattern. I go at 125mm centers max. ( I vac the holes to remove dust build up from drilling then fix) Also, an expansion margin say 7-10mm around the perimeter if skirting will cover is worthwhile. I'm sure there is an adhesive alternative to bond the ply but I prefer mechanical fixing. Note... Concrete slab needs to be completely dry before covering.
  3. MrTopOut

    MrTopOut New Member

    Thanks Mark, think I’d prefer to mechanically fix, the first option of 9mm ply feel like it’s the way to go, and provides some continuity over both the concrete and suspended floor

    I’m pretty sure the movement between the concrete and timber would be neglible, however don’t want to risk it
  4. MrTopOut

    MrTopOut New Member

    Would you just use a counter sink concrete screw to fix the the ply down
  5. Mark DM

    Mark DM Screwfix Select

    I like and use torx head and generally use size 3.5 x 25 or 30 depending on floorboard thickness so as not to risk any pipe or cable issues. Obviously fine on the concrete. I use red plugs. It's all a little time consuming but once pilot drilled a good masonry drill bit goes straight through. I vacuum the holes to clear the dust, tap the plugs in, set all the screws, tap them to send the plug down and then work round with a screw gun. Heads are big enough to hold and countersink down. into floorboards, a pilot drill and screw straight in. I work in rows starting at the end across the sheet to ensure it lays as flat as possible .

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