Floating floor over tamped concrete garage floor

[mac1231]

Hi

I want to create a floating floor as follows

18mm P5 T&G
25mm PIR
1200 gauge DPM
Original garage floor

Challenge is, the existing floor is tamped so not even. I’m assuming I would need to level it with self levelling compound before I start or would the PIR absorb any bumps in the concrete?

also, would you put the floating floor down first and build the studs (boarding the walls) off this or build the wall studs first?

thanks

 

[Deleted member 174758]

I don't think the PIR would have problems with the rough tamped surface, but I'd say that it will probably conform too readily to any crowning or dipping in the sub-floor, so without actually seeing the floor first hand I'd probably opt to level the sub-floor first. An uneven PIR surface might give you some problems getting tight glued joints in the P5 chipboard

I'd opt to build the studwork off the original sub-floor after levelling and laying the DPM because the concrete will give you something substantial to anchor the sole plates to. Better installed after the DPM has gone in to minimise any tendency for the timber to wick up moisture from the sub-floor. Also means that if you subsequently hang something heavy on the walls, such as book shelves, etc the load will transfer into the floor