detatched garage conversion

[spanner202]

I have a detached brick built garage set back 1m from the rear of my 1930 semi. It's got a flat concrete roof and no dpc. I am planning to convert it to an office/playroom. Planning don't seem to be interested and the local building control think it's exempt from building regs (class 6 exempt i.e. detached outbuilding less than 30m sq, brick built and not to be used for sleeping). So it sounds like I can do what I want internally.

My initial plan was to construct a inner block work room and fill the cavity with rockwool but I have just found the metal studwall/partition wall system at wickes. It looks very quick but I'm after some advice on the dpc and where to insulate the stud wall? And any general advice?

For the dpc I though of using a plastic sheet laid on top of the current concrete floor, all in one piece and then turned up at the walls about half a metre (will it be ok to leave the outerwall without any dpc??). I then thought of building the metal stud wall on top of the dpc. I can fix the top of the partition wall to the underside of the concrete roof but if I fix the bottom it will go through the dpc sheet! Any ideas?

The new floor would be 50mm polystyrene sheet with chipboard on top sat on the dpc plastic sheet. How does this all sound?

 

[Chukka63]

as a DIY job and not a professional job i would do what youre suggesting.id also run some dpc between the roof and stud head.leave a 50mm air gap between new wall and old.i have no qualms about fixing through the dpc for studwork.im sure others will prefer some belt and braces alternative.some roof insulation would be a good idea too.

 

[spanner202]

as a DIY job and not a professional job i would do what youre suggesting.id also run some dpc between the roof and stud head.leave a 50mm air gap between new wall and old.i have no qualms about fixing through the dpc for studwork.im sure others will prefer some belt and braces alternative.some roof insulation would be a good idea too.

Thanks that's a good tip about the roof because it's concrete and feels a bit on the damp side. On closer inspection there does appear to be a dpc in the single skin but I have a feeling the outside level is a above it. You mention DIY versus professional. What would be the professional approach? I want it to last!

Thanks again.

Simon

 

[Chukka63]

things like celotex or similar rather than jablite (polystyrene).you would want some air floor above the roof insulation,below the roof.