Opinions on Wall Specification

Squall Leonhart

An uncle of my wife's is getting some drawings done up for a house extension he's looking to build.

His architect/drafter has the following specification on the wall. Can I get some opinions on same?

12.5mm plasterboard with skim finish on
Vapour barrier on
150x44mm timber @ 300 c/c stud partition filled with cellulose insulation with
150 x 44mm sole plate strapped and fixed to foundation wall
150 x 44mm header under roof joists
1200x600x150mm Kore platinum insulation
fixed to OSB with foam adhesive and 200mm mushroom fittings
Greentherm fix premium basecoat trowelled to insulation
Greentherm premium reinforcing mesh laid into basecoat
Greentherm acrylic 1.5mm grit, colour to match existing
Aluminium window cills.

BryanF

I went with 225 head/sole, with 2no. 4’’ Studs staggered (connected with ply plates) and 50 service cavity. Outside cross battened before cement fibre. The insulated Kore passive foundation system worked well for me.

Squall Leonhart

BryanF wrote:

I went with 225 head/sole, with 2no. 4’’ Studs staggered (connected with ply plates) and 50 service cavity. Outside cross battened before cement fibre. The insulated Kore passive foundation system worked well for me.

Thanks Bryan,

Cross battening was for ventilation purposes?

Any chance of a quick sketch or any photos you may have from time of construction?

I work in design, but residential is something I've not drawn since maybe 2007 and I'm very much out of the loop on it.

Dudda

If it’s a small extension with only 150mm deep of void to fill then use fibreglass / frametherm instead of the cellulose as it will be cheaper. Cellulose gets cheaper and more efficient on larger areas and will deeper voids to fill as you’ve a truck to come and set up. I’ve no idea how big the extension is so you’ll have to get quotes and work out if it’s worth the additional cost.

I’d have a service cavity internally to avoid puncturing the vapour barrier. 25mm is enough if you’re worried about space.

BryanF’s option of staggered joints would be better but more expensive.

Would you look at woodfibre insulation instead of the Kore platinum insulation as it would allow the timber structure to breath more.

BryanF

Big fan of cellouse as it has decrement delay properties and it’s a low embodied energy material.

Squall Leonhart

BryanF wrote:

I went with 225 head/sole, with 2no. 4’’ Studs staggered (connected with ply plates) and 50 service cavity. Outside cross battened before cement fibre. The insulated Kore passive foundation system worked well for me.

Dudda wrote:

BryanF’s option of staggered joints would be better but more expensive.

Could anybody hazard a fag packet sketch of this, I'm having trouble visualising.

Dudda

Looking only at the timber structure part you have regular studs like in this image.



BryanF is on about two layers of studs like in the below image (his maybe staggered and not opposite each other)



Got the images from this page which kinda explain them and another option which are JJI studs.
http://www.llstructures.ie/timber-frame-and-passive-house-build

Squall Leonhart

Did a quick sketch on cad, see attached.

Does this look correct-ish?

I've shown 12.5mm plasterboard fixed to 50mm horizontal battens which are fixed at every 600mm to a 100x44 mm stud. vapour control layer is shown in dashed red. Studs are staggered. Cellulose insulation pumped. OSB board fixed at 600mm centres to outside. 150mm Kore platinum insulation fixed, then finished with an external render.

BryanF mentioned ply plates to connect the studs. I'm not sure how this works?