Broken stone lintel in chimney breast - how to fix?

[goosebump]

Hello,
In a fit of excitement we removed the plaster from the (suspiciously large) chimney breast in the living room and were pleased to discover a great big fireplace, with stone lintel. Sadly the lintel has broken, with an obvious crack in the middle.
The original fireplace had been bricked up to fit a "standard" firebox (hope Ive used the right term). The bricks remain in place until we have worked out how to safely proceed....

We would like to re-instate the original opening, in order that we can fit a stove.
Is it possible to fix stone lintels whilst they are in situ (I imagine not)? The stone itself has only one vaguely flat-ish face and isnt dressed, so a "rustic" finish would be fine.
Is there a sneaky way of fitting a hidden lintel behind the broken one?
If we have to remove the broken lintel, how do we support the chimney breast (its stone built with lime mortar and with rubble fill)?

The chimney breast only exists in the ground floor room, the flue is within the stone wall in the floor above. Sizes as follow: Chimney breast/lintel width 70 inches. Gap below is 40 inches wide.

Any advice really appreciated, thanks!

 

[cmother1]

You seem to have stumped everyone with this one Goosebump. You don't say what the cross section of the lintel is, but it could weigh up to half a ton so you'd need good access for the lifting gear to get the broken one out and the new one in, while still supporting the masonry above. Hmm.. bit of a poser that one.
Some friends of mine in Derbyshire had a fireplace just like yours, complete with cracked lintel. It didn't seem to be a problem and could have been there for centuries. Yours might be equally stable.
Any chance you could drill a a hole through it end to end and fit a chunky tie- bar? Just a thought...it would save a lot of aggro.

 

[goosebump]

Thanks for the reply and sorry for the delay in getting back - IT issues.

As a guestimate the lintel is 70 inches across, about 8 inches tall and at least 6 inches deep (one end seems to taper a bit). Its rough and ready though, and I imagine depth varies along the length. Ive not removed any of the bricks below it for fear of disturbing it, so cant be sure.

I like the tie-bar idea - hadnt occurred to me. But how do you drill a 70 inch, straight hole? And would it then just be a case of sliding a steel rod down the middle and tightening up the ends in nut and (very long) bolt fashion? And if that is how it works, how do you decide the diameter of the steel rod needed?

Cheers!

 

[cmother1]

That's a tiddler compared to some. 8" doesn't really seem deep enough for that width - hence the crack, perhaps. Given the small cross section I should think drilling would be pretty tricky too.
Anyone else got any thoughts?

 

[amwc]

when designing modern stone 'lintels' two steel lintels are used one above the stone lintel as a relieving lintel to take the load from the brickwork etc and another lintel to take the load from the stone. you can do this quite easily by having the lintels supported on the cheeks of the fireplace if there is no room directly behind the stone. these would need designing but a phone call to IG or catnic would get a basic design. the other option may be to use a channel section to wrap around the back of the stone lintel?

 

[goosebump]

Been working away from home for a couple of days, but am going to measure the lintel properly once back, and maybe take a brick out from below so i can have a poke about and better gauge its size. Will post the dimensions once I know....the tie-bar idea still seems to be the most likely/easiest fix. In the meantime Ive worked out how to upload pictures, so here it is:
View media item 15333

 

[cmother1]

Good luck with the measuring. As a rule of (squashed) thumb reckon on 130 to 150lbs per cubic foot. If you know exactly what stone it is you should be able to get a more accurate estimate. If you live in a mining or quarrying area you should be able to find men with big drills, but as I said earlier the small section could mean the whole thing might fall to bits when you start putting it under pressure. If you could find someone who knows the local material their input would be invaluable.
AMWC's idea of a channel round the back is appealing. You might even be able to get away with a heavy "L" section angle iron which would be even less invasive.

 

[goosebump]

The house is in north Wales - built for the quarries in the first place. Rough hewn slate is my guess at the stone and Im hopeful there are big drills nearby. Thanks for the weight guesstimate info!

 

[cmother1]

In that case up the estimate to 160 to 170lbs per cuft. Dense stuff these metamorphic rocks!

 

[rosslovatt]

Hey goosebump, I'm in prety much the same boat, just wondering how your getting on ? I've got a third stone mason coming around this week, the first two we just a bit to "cow-boy" like for me. If the third one is any better I will post his thoughts up here.
To replace, to strengthen, to brace or to leave well enough alone ???

 

[rosslovatt]

Have been pondering over putting a couple of these into the lintel and leaving it at that.
see video on this page. One marked "wall reinforcement"
Bit of a risk going in with the angle grinder, but if done where the lintel is nice and thick !!!??? What do we all think of this idea ???

 

[goosebump]

Ok,
Update is as follows - we had a builder take a look (whilst pricing up other stuff) and he said we are fine to remove the bricks below the lintel, the chimney breast wont collapse. My understanding of physics isnt great, but that seemed a bit counter intuitive! He explained that the weight of stones above the lintel (specifically, above the ends of the lintel), will prevent it from falling.
Hmmmmm. I wasnt convinced, but could see his point.
In the interests of house preservation I also asked the structural engineer (who came to do do some calcs for a bit of steel work needed elsewhere). He said the same as the builder. However, he added it would probably settle a bit, and in the long term some bracing might be an idea, if only to make it look less like its all about to give way. He suggested bolting bit of steel to the back, or somehow fitting a skinny steel lintel below the existing one.
So there you have it. Im not sure if this is the same for all lintels everywhere, but it seems that so long as enough of the lintel ends are "held", it can survive an unsupported crack in the middle.
We are still yet to unbrick the fireplace...but I will let you know what happens!

 

[goosebump]

Sucess.
We have removed about half a skip worth of brick and soot and the chimney breast remains in place. The broken lintel still looks less than inspiring, but hasnt shifted.