Garage conversion, help needed

[higgster]

hi guys,

I am converting my semi integral garage.

Had the building control guy round yesterday to find out what they expect/require.

I have a few questions with ref to the damp proofing, searched all over the net but can't seem to find specifics.

It is a single skin wall, has a damp proof course 20mm up from garage floor, he said the best way is to build a 100mm stud wall on top of a course of bricks, infill with 100mm celotex, I understand this but oviously I need to lay the bricks on a dpc, I have to put in a dpm, do I lap this under the dpm, (wont be any return up the brick)
Also he mentioned a breather membrane between the stud wall and external wall, might be tricky to fit this once stud wall built??
also he said that I need a cavity tray and weep holes between the stud wall and external wall, I understand the need for weep holes but a cavity tray all around?? due to the floor height there is only 20mm between heights.
What do I do with the top of the cavity between, external and stud wall?? does it get left open to the roof or do you need to cap it off??

hope that makes some sort of sense,

any help greatly appreciated.

 

[^woody^]

I would fit a big sheet of polythene to the wall top to bottom. Then lay a polythene DPM on the floor, and turn it up the wall 300mm and tape it - this turn up must be on the room-side of the vertical one.

This gives you a complete barrier to any moisture ingress.

If the BCO insists on weep holes, drill some in the wall at the level of the existing concrete slab

No need for a tray

Then presumably you will be having a new floor, so form this in timber joists to the required height, and have this new floor right up the external wall so that you can build your stud frame off it

Build the frame up against the wall, use 100mm Kingspan/Celotex between the timbers, tape all joints and then you can just plasterboard and skim it

 

[higgster]

Woody, thanks for the reply,

I understand all of what you have said, doing it that way will eliminate having a cavity.
As the garage is semi-integral part of the outside wall is cavity, then goes on to single skin, it is approx 190mm deep, so is it ok to build the stud work off the floor as you suggested but bringing it out 90mm, but then that would leave an air gap, so do I just fill it all with celotex? So approx 200mm overall.
Sounds the easiest solution!

Thanks once again

Matt