New Window in Gable end

[Aml999]

I am converting the loft of an old single story building 30ft x 20 ft. I have PP and I have been allowed to fit a window in each gable end. With a 650mm window I need a 950mm lintel. There are only 12 courses of bricks above the new lintel but the brickwork may support some roof weight as there is a small beam under the ridge that sits on the apex of the gable.
Can anyone tell me if I will need to use acrow?. Is it possible to use 1 acrow in the middle of the span and use a Strongboy top and bottom of the acrow. My problem is I have no joists in yet and the ceiling below is held up just by some old 3 x 2s- so no where to brace the acrow.

Thanks for any assistance

 

[^woody^]

Generally you can get away without an acrow for smallish windows in a wall with a lot of brickwork around/above it, as the wall has an ability to self support.

In this case, the small triangle of bricks at the apex has no support from the side and so is likely to drop.

Rather than mess about, its probably easier to remove the brickwork, install the lintel and rebuild it

 

[noseall]

agree with woody. an old gable end is likely to be unstable at best.

you may be able to install the widow and lintel with propping, but it may even further disturb an already weak structure.

by the way, the ridge beam should be self supporting, but you wrote of a beam beneath the ridge? or did you mean beneath the ridge tiles?

 

[Aml999]

Thanks for your comments noseall and woody.

The whole building is grade 2 listed and was a 1950s brick/brick addition to a 1880s stone house.
The exterior has a cement screed to simulate the stone of the older part
and I dont want to disturb this more than I have to.
The beam under the ridge may well not originally have been load bearing, but as it is 30ft long and there are only 2 A frames it may have 'assumed' some load with settlement etc.
I have had a structural engineer redesign these A frames to allow dooways to be installed and he has told me to use 30kg/m steels to support the new joists, I have a hiab to lift these in with. So perhaps I could hold off on the windows untill I have joist for the acrows (if I need acrows), but I was hoping to use the new window openings right from the start to give access for equipment and materials.

 

[Shytalkz]

I sincerely hope that you've got listed building consent for all of this work...

 

[Shytalkz]

...I have had a structural engineer redesign these A frames to allow dooways to be installed and he has told me to use 30kg/m steels to support the new joists...

Presumably a 152UC section. I can't believe that the conservation officer would be at all happy with that proposal in a listed building.

 

[Aml999]

Hi, yes I have got listed building planning consent for all the works

 

[Shytalkz]

Blimey, more easy-going lot than over here then. Steel in a timber frame is a definite no-no in their eyes, regardless of the engineering merits.

 

[Aml999]

great.. thats got the listed buildings bit out of the way.........

now does anyone have any advice on the topic

 

[^woody^]

now does anyone have any advice on the topic

Yeah, the advice is to read the previous replies!