Brick&Block, SIPS & Brick, Brick&PIR?

[JP_]

Still thinking about a rear extension (see other thread/s).
The last one I did was very old-school - brick, rockwall, blocks, dot&dab plasterboard, plastered.
This created a wall about 30cm thick, which is 60cm off the width of the room.

So looking at alternatives - SIP and brick shell seems much thinner, but people say expensive. But, why not brick with, say, 75mm PIR between battons (or whatever they are called) and all overlain with 25mm PIR board, to reduce leaks, and a good plasterboard screwed on top of that?

Then do something similar for the roof - large sloping roof with total of 100mm PIR boards.

Is that doable on a largish single story extension. e.g. 6.5m wide and 5m deep?

 

[tomfe]

If you have 2.4m ceilings you can use 6" block, you might do it on 4" if you had an SE and used some steel, then either internally or externally insulate.

 

[JP_]

I didn't quite understand that - too many terms to look up!
I'd still need bricks on the outside though?

 

[jeds]

As above, you probably couldn't justify (structurally that is!) a 2400 high solid wall, with roof loading, in 102mm. When I have done solid walling they normally come out at 140mm minimum. That's not to say it wouldn't work in practice - but if you need building regs you'd need calculations to prove it.

 

[RonnyRaygun]

As above, you probably couldn't justify (structurally that is!) a 2400 high solid wall, with roof loading, in 102mm. When I have done solid walling they normally come out at 140mm minimum. That's not to say it wouldn't work in practice - but if you need building regs you'd need calculations to prove it.

Thinner walls would probably require wind posts to break up the spans.

Out of interest, would there be any issue with penetrating damp if the wall was 140mm or thereabouts? Or would there have to be some kind of internal tanking?

 

[tony1851]

Doubtful Building Regs would allow you to do a single-skin wall 5/6.5m long and 2.5m(?) high without some stiffening pier in the middle.
Is it worth all the downsides to gain an extra 200mm on the width?