timber frame infill to cavity wall garage coversion

[capital1965]

I am converting my 1960s bungalow garage to a habitable space. I plan to build a timber frame infill wall to replace the door. I have removed wooden panels that were at either side of the opening to reveal a cavity wall with a 50mm, uninsulated cavity. The inside leaf is block and the outside leaf is block faced with stone, not sure what the technical term is. The DPC is higher by about 30mm at one side of the opening. The plan was to build a plinth wall 2 courses high, to sit the sole plate on. I had wrongly assumed it was a solid wall.

I am looking for the simplest solution to building my infill wall.

I chose the timber frame method because it didn't involve digging a trench for the BCO and I am I could do it myself, hence save money.

My dilemma is that for a timber frame with upvc cladding (with no external masonry leaf) infill to work I would need to lay the plinth brick course in the middle of the cavity, thus bridging it, unless I can use a vertical DPC too along with a cavity closer. If I did this I would have to tie in the new brick leaf diagonally from the inner and outer existing leaves at each end.

If I continue the inner and out leaves I would have to step the outer leaf in by 10mm to allow for batten and cladding so it overhangs slightly which reduces the cavity by the same amount. I still need to address the DPC not matching. Can I just lap it up and past the existing at one end and seal with mastic?

Any other solutions gladly accepted!

Alternatively, I could pay a brickie to solve my problems and do it the traditional way; more costly and less satisfying though.

 

[^woody^]

You put a vertical DPC where the frame meets the wall, and the DPM deals with the out of level existing damp course.

 

[capital1965]

Thanks Woody. Which of my two proposed solutions would you recommend? One leaf of bricks down the middle of the two existing leaves to rest the sole plate on or two leaves with an extra wide sole plate that rests on both? It is the outer leaf where the DPC doesn't match in height. There are actually 2 DPCs on the right as you look at the garage, one at a block higher than the first which continues around the return (which is a party wall).

 

[^woody^]

A picture of the existing would help

 

[capital1965]

http://s349.photobucket.com/user/abbo27/media/IMG_0603_zps0pcdbwoj.jpg.html?sort=3&o=0
http://s349.photobucket.com/user/abbo27/media/IMG_0602_zpsee4fiazi.jpg.html?sort=3&o=1
http://s349.photobucket.com/user/abbo27/media/IMG_0600_zpsyk1ebghp.jpg.html?sort=3&o=3

I hope these appear, I have not posted pics before.

 

[^woody^]

I'd work out how far back the two course of brickwork needs to be to allow for the cladding to be flush with the face of the external wall, and set the brickwork and frame there.

Presumably, you want the inside wall flush, so you may end up having a 215mm wall up to floor level and a similar thickness frame.

The only potential issue there is that it appears that your drive concrete slab will go under the proposed wall. Some BCO's wont like this and would like it cut to prevent movement of or future replacement of the drive concrete affecting the wall. Otherwise, you can just rely on the frame being well made and well fixed to the walls, so that it self supports.

Don't worry about DPC levels, as thats just about detailing the new DPC and DPM so that it all joins and forms a barrier

 

[capital1965]

Thanks. That sounds like a plan. Would there be any problem using 2 courses of blocks on their sides rather than bricks as it gives me the 215mm and would be quicker? The new floor height will be 70mm to match the adjoining room so the new wall will finish above floor level. At the party wall side the existing DPC is also considerably above the proposed floor height. I guess I just lap the DPM above that as it will be behind the new stud and insuation.

The BCO has seen the site and did not raise the issue of the drive slab going under the wall so hopefully, this won't be an issue.

 

[^woody^]

You can use the very dense concrete blocks, if you like the appearance.

 

[capital1965]

It will be painted black and there will only a bit showing so unless someone looks closely they won't notice. Thanks for the advice. I spoke to BC today and they gave me a verbal OK on that method. As luck would have it my BCO is on holiday until Monday so I will crack on; worse case I have to take down two courses of blocks.