Fitting new *upstairs* window - how to Acro prop?

[Lobster]

I want to install a window (almost 1m wide) in a cavity wall. However, it's on the first floor; and on the inside it's actually above the stairway - this will be partly boxed over as the idea is to reclaim the large volume of currently dead space above it (it goes right up to 1st floor ceiling level) and incorporate it into a new bedroom.

If this were a downstairs window I'd just wack in a Strongboy and crank it up with an Acro prop in order to insert a lintel, but how on earth do I prop the wall in this case? I'd need an Acro prop about 4m tall on the outside, or about 3m on the inside (and anyway, that would have to stand on the stairs.)

FYI there are about 4 courses of brick between the lintel position and the soffits, and there are rafters sitting on top of the wall - so plenty of weight up there, I presume!

Thanks David

[Gav]

i remember, some years ago, we took the whole back of a 3 storey house down, we used acro's spaced about two feet apart parralell to the wall we were taking down on each floor with double scaffy boards between them and the floor/ceiling. made it look spookily roman/greek

none on the outside tho!

everything stayed secure all the way to completion of job

hope this helps

[daddyfreddy]

There is a prop you can hire which sits in the wall just below the opening you want to make, just like the strongboy at the top. Can't remember if it's just 2 strongboys with a prop inbetween or specially made. Can't seem to find it on google right now either.

[Lobster]

Oh I see what you mean - that makes perfect sense. I suppose an upside-down strongboy at the bottom, with a prop between the two, ought to work, though I'd be a little nervous at going ahead just on that basis!

Me neither. Has anybody else come across this technique, or better yet, a purpose-made prop for this task? (or what it's called!?)

Thanks David

[Rob Morley]

How about aproaching it from the other direction and using something in the roof space to support the joists and rafters, spreading the load to their neighbours? Then you'd only have to worry about a few bricks.

[Lobster]

That sounds like a good one. Actually today I had a builder mate round to ask him what he thought, and he reckoned I should just go for it with no propping at all!

Logic being that the front leaf, over which the rafters protrude, doesn't bear any weight of the roof at all; the front leaf was built after the rafters were put in place, with the bricks built up around them. That I can see does make perfect logic. Thus the only risk is that the 4 courses above the window drop out and need replacing after the lintel has been positioned.

Regarding the inner leaf, which takes the load of the rafters - the load is actually taken by the timber wall plate on top of the wall, and matey reckons that the wall plate will be happy to take this load temporarily while the lintel is fitted. Being a naturally cautious type, I remain unconvinced; however, the guy is a very experienced builder; and having just seen Rob' suggestion above, I could do that too, as a belt'n braces approach?

Comments welcome!

David

[Stuart Noble]

That's how every builder I've had dealings with has done it too.

[Lobster]

But with good or bad results?!!

David