Stone lintel join - what the?

[Schmikester]

Hi,

I'm currently refurbishing a cottage and have found a bricked up stone fireplace under layers of plasterwork on the chimney. So far so good. I'm planning to remove the bricks, however the lintel seems to be in two pieces with a zig zag 'l' shape join at the centre. Clearly this is a planned join and not a later crack. Can anyone tell my what this type of lintel is called and how it stays up, I'm struggling to understand how it supports the chimney before I have the confidence to remove the brickwork. Perhaps a timber lintel was used below this which now needs replacing, and it is simply decorative stonework instead?

Any help gratefully received,
Mike

 

[stuart45]

Looks like they used a halving joint, more common with timber. They might have put some dowels in it. Could be they didn't have a long enough piece of stone. Never seen it done like this before, but it probably will hold. I did a job last year putting concrete lintels above a frame in a solid stone wall that had none, and although the wall had cracks and dropped a bit 2 large stones had wedged together and formed a kind of lintel.
The main problem would be if the jambs moved out a bit which could cause the centre to drop a bit if it wasn't doweled.

 

[Ian H]

Is it stone? It looks like concrete on my screen.

 

[tony1851]

Are you sure it's not just render, as it seems continuous with the strips down the side?
They wouldn't have designed a concrete lintel like that - still less a stone one.
Could it be render which was applied before fixing an older (original) larger fire surround?
(nice -'50s fire surround, btw).

 

[Schmikester]

Thanks for your replies. Yep, its definitely limestone having sanded it a bit to check - pics below show better the centre join and dowels, and the join between sides and top of the stone. Its in a 17th century cottage so goodness knows how long its been there, I assume its been like that for quite a long time. I guess the concern is when it was bricked up whether they also did something to weaken it at the same time like removing dowels etc. My plan going forward is to acro prop both 'sides' of the joint while removing the bricks and then slowly ease them off to see if there is any drop/sag.

 

[vinn]

OP,
Hack off all the plaster below and above the lintel to expose the brickwork.
Then remove the, as noted above, typical 50's fire surround, & all the rubble.
Post a pic.

The plugged fixing holes you see were probably for fixing the mantel.

Depending on what you expose, & depending on how you want the finished chimney breast face to look - you could fix Strong Boys a few courses above the stone lintel, and then insert a modern lintel below the Strong Boys.
But first, insert a shorter Strong Boy just below the centre of the stone lintel to keep things propped while working above.

Like others, I've never seen that kind of joint before - usually it might have a joggle and/or a keystone?
Perhaps there is a joggle on the back side?

 

[Schmikester]

We started to remove the bricks today, current state shown below. There is no joggle visible on the back side so far, so I think it is genuinely an unsupported two-part stone lintel. The plan is to install an oak lintel underneath the stone, currently underpinned by props although the structure does still seem to be self-supporting at the moment as you can see in the photo!

 

[Schmikester]

Finally cleared the fireplace today. For info, on the inside of the chimney above the join is an unloaded 'gap' (pic below, you can just make out the join below the gap). The weight is being distributed in a triangle towards the edges above the 'lintel' so that almost no weight is actually placed on it, loading the sides of the chimney breast instead. Has anyone else seen a design like this?

Nonetheless we've put in a wooden support structure for the moment (pic below) until something more permanent can be done, probably involving an oak railway sleeper cut into the sides.

 

[vinn]

Thanks for the new info & pics.
Presumably you've read up on the similar threads on here ref. building opening dimensions etc?
What is your final intention for this fireplace?