How to raise a garage floor

[carlasaurus80]

Hi all,

I am currently in the planning stage of converting part of my integral garage in to a utiltiy and downstairs toilet. Approx 2m by 2.5m.

I have spoken with the builing office and they are happy with my insualtion plans for the internal walls and loft space. However a question I have is how best to raise the floor level in the garage.

The floor is concrete and is level, but of a rough finish, no signs of damp so it seems to have a DPC, certainly all the surrounding garage walls do.
I need to raise the floor about 150mm (including floor finishes). I have seen the option of DPM, then rigid insulation boards with T&G boards on top, but not sure hopw sturdy this would be.

Is there an alternative, say by fixing timber joists to the concrete floor and then insualting between and how would this work?

I am scratching my head slightly with this one as there are so many different examples online, just want some ideas from people who know really! Buidling regs are happy with insualion and then floor finish over the top, but I'd like an alterantive if there is one!

Any suggestions would be much appreciated.

Cheers

 

[^woody^]

Span joists across off hangers

 

[carlasaurus80]

problem is from what I've read is that any joists must have a 150mm air gap under them, so the floor would end up being too high.

 

[freddiemercurystwin]

The space between the concrete and the underside of the boards just needs to be full filled with insul.

 

[ColJack]

75mm of foam insulation, then 75mm of screed... nice floor to tile onto for the bathroom and utility..

 

[^woody^]

problem is from what I've read is that any joists must have a 150mm air gap under them.

Well stop reading that nonsense then

No air gaps = no condensation, so lay the membrane and fill the voids completely with insulation. Use treated timber though