New window opening in stone wall

Mizydoscape

We have a box room in our house with a borrowed light window in it. I want to investigate the cost to have a new external window put into the wall. Added complications are that the wall in question is approx 2 ft thick granite stone and is also curved. It is on the first floor.

Does anyone have an estimate of what kind of cost I should be expecting? Would it be thousands? Would we need planning/structural engineer/building regs? What kind of contractor would we need to quote? I assumed a builder/stonemason but maybe wrong! We are in the South West if that makes any difference. Thank you.

Robin9

Doesn't sound like a job for the standard builder.  I would talk to an architect who specialises in old buildings.

Is the building listed ?

FreeBear

You may need planning, you will certainly need building regs approval - They may require a structural report.

If the building is listed, you will also require Listed Building Consent.

As to how much it will cost, I really wouldn't like to guess. With a 2ft thick stone wall, You don't want the average jobbing builder. Someone with a good knowledge of old properties is essential, and that isn't going to come cheap.

Mizydoscape

It's not listed no

stuart45

How wide is the window going to be. It does add to cost as it's not on the ground floor. In the South West a lot of the builders are familiar with that type of construction. It does take a bit more work to support the wall properly. 

Apodemus

One of the problems is that the individual stones might not align in the way that you need them to.  I know of one house where a simple kitchen-to-dining room hatch turned out to be half-way along a really huge granite block and they ended up taking down and rebuilding far more of the wall than they ever envisaged, just trying to find the ends of the block.

Mizydoscape

I did wonder about that Apodemus. I've attached a picture of next door who have exposed the stone over their fireplace. The house is the same construction as mine as it was originally all one building.

A 600mm square window would be sufficient. 

Permitted development suggests that if the window is obscured glass and the same as other windows in the house then we don't need planning.

stuart45

Is it rendered on the exterior? If so it makes the job easier, as the jambs can be built back up in brickwork bonded to the stonework.

Mizydoscape

Yes it is rendered externally 

weeg

Actually, it's a fairly simple (which is not the same as easy) answer, especially if it's rendered.
You cut a slot and remove the stonework half way through the depth of the wall and put in precast lintels, ramming in drypack mortar at the bearings as you come back out. Wait for it to go off, and then go around the other side of the wall and repeat. Then cut out the hole for the window under your new lintels. Lintels are 100mm wide as standard, so you'll need 5-6 of them to fill the whole wall width. Because you are never entirely cutting through the whole depth of the wall, you don't need to worry about propping it.

You will however need permission from building standards, as it's a loadbearing wall. And I live in scotland, so the whole permissions system in England is foreign and confusing to me!

stuart45

Is that definately  Granite and not Chert? If I was doing the job(although I've not seen it) I would normally prop the roof plate, and then remove the stonework up to the plate. If it's a timber frame would build it in with brickwork, lintels on top and then brickwork up to the plate. 
Cost wise you are looking at 4 figures.