Timber Frame Detail Question

So, I'm going to attempt to convert my garage on a shoestring. Step 1 is replacing the garage door with a door, window & timber frame wall. The wall will be stud frame with OSB either side (plus DPC, breather membrane, ventilation gap & cladding) sitting on a block wall (which I did a while back) 6 inches wide (really 135mm) & 150mm off the ground on which will sit the DPC.

My first question is, should the OSB on the outside overhang the block, or should it be in line with the block? (This will determine whether I use 100mm wide studs, or 125mm wide studs for the wall).

My second question is (if the OSB is overhanging the block on the outside) should the 150mm DPC also overhang the block to protect against splashes hitting the underneath of the OSB?

Third question is should the breather membrane extend lower than the OSB?

Below (hopefully) a couple of rough sketches to illustrate my project & wall detail with & without OSB overhang on the outside.

Thanks.

JonathanAl

Q 1 in line with block, not overhung

Q 3 if it extends a bit lower it doesn't really matter. Use treated sole plate. Normally you could put insulated plasterboard on inside instead of osb, then decorate as desired.

Thanks.

C. Eastwood

https://www.boards.ie/discussion/2058257825/timber-frame-detail-question

The timber should not pass below the DPC. See Photo.

C6EFB67C-C2B3-48E2-807F-B5B31DBC553C.jpeg

You must fit a vapour permeable Breather Membrane on the cavity face (Cold face) of the Timberframe.

See photo.

41B8F98C-CFA1-4892-833A-9258594BF1F8.jpeg

I would not fit plasterboard slabs in a domestic garage. Only fit OSB.

If you want to insulate, fit 100 mm fibreglass insulation between the studs.

The cavity MUST be Ventilated by fitting vents top and bottom in the outer block wall, to prevent Dry Rot in the timber frame.