Attempting a new window opening in old stone house.

[ESquared]

I am comtemplating a DIY project of an opening of 1250mm x 1500mm to install a window in a 700mm thick 400 year old stone wall. There will be about 750 mm of stone remaining above the new opening. The wall is an exterior bearing wall, above which is an attic and a 16/12 pitch tile roof. Access to the interior is okay, but the exterior would require scaffolding as it is on the second floor and over a small shed extention.
My plan would be lay out the lintel location, and then to saw 1/3 of the way through, from the interior, and only remove enough stone to allow me to slide in a prescast lintel or pour a concrete lintel in situ. I would then do the same on the exterior, but most likely would do an in situ pour due to the weight of the lintel, and the difficulty dragging it up 3m to the platform. Once the lintels reached sufficient hardness, I would remove the stone below the two lintels to create the full 1250 x 1500 opening. Once exposed I would remove the remaining stone in between the two new lintels and remove the remaining stone between the two lintels and the install the center lintel, either using a precast, or steel I Beam. I don't think that I can inject a concrete slurry that would dry to sufficient hardness, if I tried to do an in situ center lintel.
Am I totally crazy doing it this way? Any opinions or suggestions to help me (A) Not kill myself. (B) Not have the wall collapse on me (C) Make it easier.

 

[mointainwalker]

Basically sounds ok to me. I did something similar last year but used a number of 150 x 150 timbers ( 4) as the lintel, because that was what there was elsewhere in my barn above openings. Wall above lintel was also 0,7/0,8.

Why are you thinkimg of sawing the stone rather than using an SDS with chisel to take it out ?

 

[themiddleagedun]

If I were to do this I'd take the wall down from the top. It's not worth trying to save 750mm of wall?

Take it down to cill height, build up the sides to the required height, fit your lintel and rebuild the top section.

Stone walls are very "loose" and full of rubble inside. I think if you fit your lintels first you'll end up undermining them. Good luck.

 

[ESquared]

mountainwalker:
At this point I think I would start with sawing, with the hope of getting a nice straight edge to minimize finish work. I can imagine reverting to an SDS and chisel for the center lintel.
the middleagedun:
I appreciate the advice and I wrestled with doing this. In fact I still am. If the wall wasn't 700 thick, I might have considered it. That's a lot of stone to replace. Also both surfaces have been cleaned and rejointed with the last few years, so the only lose rubble will be in the center, and if I have the outer lintels in place by then, disruption should be minimized. If the stone above the lintel cut decides to come down when I cut out the lintel, that will obviously tell me that I shold have taken the stone down first.
This is how my thinking is going, but all of my decisions are cast in putty. This is why I'm throwing the issue out to opinions and help.

 

[mointainwalker]

If you are talking about interior finish, does this mean no internal insulation ? Whereabouts are you ?

 

[ESquared]

Wrong term. I meant to minimize packing out after the lintel is placed.
I'll also run the saw edge on the verticals to cut out the opening after the lintels are in place.
I'm in the Dordogne.

 

[mointainwalker]

What sized saw are you going to use ? I ask because i can't see how you can do it on a wall this thick without a huge saw-blade.

 

[ESquared]

The short answer is I haven't got that detailed in my planning yet,but I think I will use the largest hand held stone saw available from our local tool rental place. The goal is to just get a straight exposed cut and then remove the inner layers of stone with chisels so size isn't the only criteria - manageability is a key factor so as to not cut off any vital parts of my anatomy.

 

[mointainwalker]

Think you may possibly have a problem with that plan.

Largest device you can normally handle is the 230 mm angle-grinder which gives you max 100 mm cutting depth.

After that you move up to thelarger motor-driven water-cooled machines you see cutting paving-slabs and kerbstones. i think because of safety and their weight these are always operated on the ground.

I just had a look at my local hire-company website and they advertise a motor-driven chainsaw with a diamond-chain ( really) for E 120/day, cutting-depth 385 mm.

i'd be interested in what you finally do, so please tell us what happens.

 

[RedHerring2]

I don't know if you've seen this post, ESquared.

Similar job but on the ground floor.

//www.diynot.com/forums/viewtopic.php?t=210516&start=0&postdays=0&postorder=asc&highlight=

We rebuilt the inner skins in blockwork. Stone for the outer skin and a semi-dry concrete mix between the two skins.
As the old fella said, it doesn't take long to rebuilt the bit above the window and, also, as he said, the middle is almost loose rubble.

You can also get a 'Chainage' block, which is a typical concrete block but with a vacant 'U' section along the top middle into which goes a triangular reinforcement and concrete. You can build a ring beam with it if you want, and tie it into the 'cadt-in-situ' lintel.

 

[ESquared]

mountainwalker:
Thanks for the info on the diamond chained, chain saw. That sounds like it would do the trick. When it gets closer to go time, I'll see if our local place has one.
We/I won't be starting until I get the approval from the Batiment de France which can take up to three months - but no longer. Application went in on August 10th. I'll let you know how we make out.
RedHerring2:
I just came back from our local Pointe P and showed them pictures and discussed the project with them. They recommended the exact same thing as the chainage block, except it is in terracotta. it's called monomur. Lay it in place with steel in the center and fill it with concrete. I would need two for my 700 mm wall as they are 300 mm wide. Exterior of monomur would be faced in stone. Best part is that they are light, easy to install and fairly inexpensive for France 1400 long for 34€. Tax included. Can't beat that with a stick.