Floor construction for Garage conversion (Ed.)

[Kieran102]

Hi guys.
I’m doing a garage conversion in my house and on my plans it says to use 150mm timbers for the floor joists. The problem is with 150mm the joists will sit directly on to the current concrete garage floor. I’ve read some where there should be a space of 150mm below the joists for damp raising. Can I use a vapour barrier between the concrete and bottom of joist or will that cause other issues.

 

[thomp1983]

Vapour barrier such as visqueen all the way across the floor and then lapped up the sides of the walls would be my way of doing it.

Are you sure you need the joists, I converted half my garage into a bedroom joining it to the existing bedroom and I just used celotex with t+g chipboard on top to create a floating floor, I had 120mm ish difference between the two floor levels.