Garage conversion questions

[Rob.S]

My house is on the market but I don’t see it selling any time soon. As I need some more space I am contemplating converting my detached garage to an office at minimal cost and as temporary as possible in case a buyer wants to convert it back. I also want to partition off the rear of the garage with a stud wall so it can be used as a store room.

I believe my house was built in about 1982 and used as the show house, the detached garage was the sales office. It is brick built and has a pitched roof. Inside it has a painted celling and some walls are plastered and wallpapered so I’m hoping a conversion back to an office could be done fairly easily.

My question is the damp course seems to run above the floor level inside, is this bad news? Around the edge of the door I can see polythene beneath the cement floor. When it was built as an office in 82 by Wimpey homes would building regs mean they'd have done a half decent job and is there anything else I should check for?

Thanks

 

[noseall]

i would not be too concerned about the dpm, at least there is one present! most dpc's occur at floor level - where's yours in relation to the ffl?

my main concerns would be insulation and how i was going to heat the space.

inadequate insulation is likely to lead to condensation and ultimately fungus or rot. this can be countered with plenty of ventilation but will be rather uncomfortable in cold winter periods.

 

[Rob.S]

I've done some more research (since my original post in October!) into insulation and thinking of laying a floor over 75mm kingspan board (75 is about the most I can do with the current ceiling), then insulating the walls with 100mm of the same, plasterboarding etc.

Would it be reasonable to block off the up-and-over door off with the following layers - bearing in mind I don't want to make it too hard to return it to a garage.

1 up-and-over door as is
2 damp proofing membrane
3 18mm OSB
4 stud wall with 100mm kingspan
5 plasterboard

Heating wise I'm just thinking a small electric heater. Would this be sufficient?

 

[mikric]

sorry didnt spot it was detached garage post edited as lots of what I replied with was not relevant

 

[Rob.S]

Here is a Google Sketchup of what I'm trying to achieve:



Would I need to be concerned with condensation in the store room area at the back?

 

[noseall]

your solutions are good. put the damp membrane directly behind the plasterboard on the warm side. fix a breather membrane on the cold side.

 

[Rob.S]

your solutions are good. put the damp membrane directly behind the plasterboard on the warm side. fix a breather membrane on the cold side.

Will do, thanks Noseall!

 

[Rob.S]

Managed to pick up a load of loft insulation from the B&Q deal (£3 for 5.4m2) last week. Is it possible to use this fibre glass in the stud walling of my garage or do I need wall specific stuff?

 

[noseall]

fibre glass (per thickness) does not offer the same thermal protection as say celotex or kingsapan foam board insulation and/or rockwool combined with foam board.

no doubt it will be better than nowt but you will need about 270mm thickness to achieve a worry free, condensation free wall.

 

[Rob.S]

As it was £3 for a pack I got nearly 60m2 of it for £33! Its 200mm deep so perhaps I can double it up?

 

[noseall]

doubling up to 400mm will only be effective if you have 400mm space in which to put it.

compressing it down effectively reduces the efficiency of the fibreglass. it works by trapping air.

 

[Rob.S]

Ah ok makes sense. 400mm walls might not leave me with much space!