Widening Fireplace: Corbelling

[dawz84]

how did it go with the corbelled bricks in the flue? did many courses come away or were the ones higher up holding ok?

Here's a image to show you. On the right you can see 3 bricks floating from before I knocked them out, with all the loose bricks behind. On the left you can see the diagonal colour change where I broke them off. In fact every one was tied into the party wall on review.

On the far left the dark patch you can see where I took all the lose bricks then mortared them back in. I mortared all the lose bricks behind as well to add strength.

 

[dawz84]

New issue, the floor inside the fireplace is lower than the main floor, which we had tiled with some luxury laminate, few months back. From the Deepest point to the edge of the level floor there's a difference of 1 Inch.

I've manage to source one piece of slate which is well over the 12mm guide. The question is how do I lay it. Should I use some self levelling compound to bring the floor level up? Or can I get away with a cement mix in the fire and sit the slate directly in it?

 

[jacko555]

Cement

 

[blup]

As you say, a useful guide for others. By how much does/did the corbelling extended from the rear of the flue which originally looks about a brick length deep? On the pic with the green circle it is difficult to make out where they have been cut/chopped. I'm interested in understanding it as I have a similar project in mind on a 1930's fireplace with a similar arrangement.

Blup

 

[dawz84]

As you say, a useful guide for others. By how much does/did the corbelling extended from the rear of the flue which originally looks about a brick length deep? On the pic with the green circle it is difficult to make out where they have been cut/chopped. I'm interested in understanding it as I have a similar project in mind on a 1930's fireplace with a similar arrangement.

Blup

I misunderstood what you put originally and prepared an image. Since I went to the trouble of preparing it I'll share it anyway

The black arrows are every brick I had to chop on the left side. As you can see when it reached the corbelling every brick was tied into the wall. Wasn't the same on the right side, it was every other brick but it was supporting much less. The right side image shows how it looks further up the chimney above the arrows.

Now to answer your question. It was about a bricks length. But half of one brick was in the Party wall at the rear and and another brick in the chimney breast. The middle joined by mortar.

 

[blup]

Got it thanks, but isn't the structural integrity influenced by the loss of support from cutting back the left hand jamb which presumably took some of the load from transferred down by the flue?

Blup

 

[dawz84]

Got it thanks, but isn't the structural integrity influenced by the loss of support from cutting back the left hand jamb which presumably took some of the load from transferred down by the flue?

Blup

1. Well I'm no expert, but the HETA's Engineer said it was no problem when he inspected and told me what to do.

2. I actually had a structural engineer back in May. Kitchen & diner was knocked through. I had the fireplace opened up to have a Kitchen hob put inside it with a extractor system. I hadn't thought about it till now but was widened in a very similar fashion. The fireplace was almost identical. The instruction was for nothing but a single lintel.

Cant argue with that... calculations from a structural engineer.

3.I just also had a thought that if you go in your loft you can see the chimney flue just floating on the wall as they don't bother encasing it in a chimney breast. Obviously it has to be toothed into the wall self supporting. The corbelling is very extreme from the front and back of the house to the chimney at the apex.

 

[blup]

Guess it must be belt and braces, thanks.

Blup

 

[jacko555]

@blup I had a very similar job done (widened kitchen fireplace, and opened vertically) to fit rangemaster and inline extractor.

SE was fine with the corbelling removal / support and lintel approach.

 

[dawz84]

Sourced a piece of slate 20mm thick from a reclamation yard, £80. Was 130cm by 65cm. Next problem was how I was going to cut it. Looked up Dimond edged blades (£20-30) I could put in a angle grinder but didn't want to ruin the slate. Phoned round some kitchen places that wanted £25 per cut!

Finally I phoned a local shop that makes headstones. £30, they cut it, rounded off the edges then oiled the sides with something that made it black instead of the grey in turns.

Will cement it in later. I just got to work out what im going to do with the sides. I'm torn. I really like the look of these hexagon boards but my opening is 1070mm and all the boards I can find come in 1000mm. I'm not sure how i would hide the gap?

The alternative is to use some sort of render on the sides and keep the bare brick at the back. I'm going to try clean up the bricks and see how they look. The side sides will need covering because of the non facing bricks on display stacking vertically.

 

[dawz84]

Next stage done, vermiculite board, plastered and mantel.

 

[blup]

Looks good

Blup