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chashyde · Joined: 06 Jun 2003 Posts: 36

I have a large integral garage that I am converting into part of the living accomodation. The problem is the garage floor, which is about 175mm lower than the rest of the house. That in itself is not a problem, a step would be OK.
The garage floor is concrete with a DPM, but no insulation. The rest of the ground floor has wooden flooring attached to 50mm square battens, and, as far as I can see, no ventilation bricks are in situ to allow air circulation under the wooden floor.
The garage floor slopes, as per the building regs at the time, 70mm in 7.2m, which is about 1 in 100, so slight to be unnoticeable.
My question is, can I lay insulation (50mm Kingspan) then put 50mm square battens on top of that, and then wooden flooring, to match the rest of the ground floor?
I don't really want to go to the expense and hassle of laying a new concrete floor on top of the old one, which is perfectly serviceable.

Any advice as to the best course of action would be gratefully received.

thescruff · Moderator Joined: 03 May 2003 Posts: 4314 Location: Bath

I would put the joists down first and get the levels right with packing etc, then cut the kingspan or similar between the joists.

Check with your local builders merchant, there is a Kingspan substitute which is considerably cheaper.

chashyde · Joined: 06 Jun 2003 Posts: 36

Thanks for that scruff, that was the original plan, but then I thought I might have to ventilate it. What are the depth of the joists when it needs to be ventilated, as opposed to the depth when it doesn't ?

thescruff · Moderator Joined: 03 May 2003 Posts: 4314 Location: Bath

If the sub floor is dry I wouldn't worry too much, just a couple of small vents below the insulation, which I would fix to the top edge of the joist.

chashyde · Joined: 06 Jun 2003 Posts: 36

Could I have a little extra help here, do you mean that the vents would be into the room(s), or to the fresh air outside ?

thescruff · Moderator Joined: 03 May 2003 Posts: 4314 Location: Bath

To outside.