New French Doors on old garage (convert)

2 Apr 2024
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United Kingdom
Hi All, I have a single Skin Brick Garage at the bottom of my garden with a flat roof, there is no damp course the the base appears to be a massive slab of concrete. The Flat roof is a 200mm Cavity and then plaster board ceiling.

Id love some critique on the below.

> Take down existing ceiling plasterboard, re felt roof and replace OSB if needed.
> Fill with some Rockwall insulation and reapply new moisture resistant board (any advise on the rockwall / Kanuf) ?
> Liquid DPM The Floor and Walls
> Self leveling compound for the floor
> Clotex insulation on the floor (what would be the min I can get away with) I'm a little restricted with height and budget > Then Chipboard then hard wood / laminate
> The single skin walls I plan to batten, 50mm rockwall/Kanuf, plaster board then have the lot skimmed.

There will be some oil filled rads in there for winter.

How does all this sound?

The other issue I have is the entrance. I have attached an image of the current state and what I hope to achieve. I want the narrower French doors, I then plan to frame out either side then OSB, external membrane and clad with composite or equivalent.

I don't know what to do with the base though? So if the doors come with a 80mm deep ceil for example can I screw this directly into the existing concrete base or should I run a horizontal layer of bricks along along the base first then sit the doors and frame on that ? Then paint the liquid DMP up the first Corse of bricks?


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Wow, that's some garage.:LOL:

Have you anymore phots? is it damp inside?

There's lots of threads on here about ventilation needed for flat roofs. (cold roof).
See you might be looking at cladding when finished?

For the roof, you could look at removing the felt, and externally insulating, boarding then re-covering (warm roof).
Walls, you could externally insulate, hold on with battens and then clad in rough sawn wood/composite, alternatively just bond insulation to the inside or hold in place with battens and then board.

DPC and Insulation on the floor and float your floor covering.

If you can raise the new door, yes, sit on engineering bricks, no need to screw down, just screw it into the side studs you'll be building.

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