Widening Fireplace: Corbelling

[dawz84]

Hi,

I see lots of threads on widening a fireplace for a wood burner but it all gets a bit hazy around what you do on the inside of the chimney.

I have a 1940-50's house. Was originally an open fire that was converted to Gas. I've had it capped off, gas fire removed and opened up the chimney as far as the current lintel will allow. (See image Below)

The current width is only 22' (560mm). I realise I can get a wood burner to fit the space but feel it would look more aesthetically pleasing wider and I assume more efficient.

So the answers to fit a new lintel which leaves 220mm (a bricks length) on the outside edge of the chimney breast which also gives me slightly more height (image below).

So my question is what do you do with the inner wall of the fireplace cavity? I assume you simply take it down and rebuild it at the new width... but what about the chimney flue? It appears to corbel out which they've smothered over with mortar that appears to be resting on the wall I want to remove if that makes sense? (Image below)

I've done a quick drawing to illustrate it. If I remove the bricks from the left hand side what then supports the left hand side of the chimney flue?

I've noticed between the left hand side of the fireplace and the back wall that every other brick seems to be toothed in. Will that be the same with the corbell up the flue, in which case its self supporting, allowing me to widen without worrying about it dropping down?

Thanks for the help.

 

[Koolpc]

If it were me, i would leave as is and fit a nice fire in there. Less hassle for the sake of a few inches either side.

 

[dawz84]

That was my first instinct and I'm tempted too leave it, but if the flues are toothed into the party walls, there no issue, hack away.

It would make sense why no one mentions it with all these widening threads. Seems a shame when I've already gone to so much effort to just shoe horn something in.

 

[tomg86]

facing a similar issue myself https://www.diynot.com/diy/threads/advice-on-fireplace.596926/#post-5327042, was wondering if angled steel from front to back might work...

 

[dawz84]

So... I decided to just do it.

started by knocking out the tops, which revealed the corbell. To my horror the bricks behind on the left were just lose, in filled.

As we were told and thought roughly every other brick was toothed into the party wall. So you could take a few out that would almost drop, then the next few set half way in the wall supporting the load on top.

Quite pleased, never used mortar before. Ready for next phase.

 

[blup]

I thought the flue or gather should be left as it is structural but I suppose you are doing that by leaving the toothed brick in situ.

Would be really interesting to see pics as you progress.

Blup

 

[stuart45]

Rule of thumb for chimneys is to not rely on someone else's tying in.
Catnic CN 102.

 

[dawz84]

Sorry, I just realised although I uploaded it I hadn't attached the Final image from Friday. See below

I'll continue to upload, as it progresses. Maybe a handy guide for someone. I'll attach some prices.

 

[Koolpc]

Looks good. Hope its strong and all solid.

 

[dawz84]

Looks good. Hope its strong and all solid.

I hope so too. The bit on the left I was worried about, after I took out some of the lose bricks I realised that they had toothed in some bricks higher up to hold them. I rebuilt in some of the lose bricks and mortared it all up, figured it would sure it all up and take weight off the corbelling.

 

[dawz84]

Anyone know if you can get some sort of pre finished/paintable fire board? Something I can use to tidy up the brick?

 

[tomg86]

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

 

[blup]

Rule of thumb for chimneys is to not rely on someone else's tying in.
Catnic CN 102.

Is this what you mean? (Post 12, pic 3)

opening the chimney breast up

Hi, Ive a chimney I want to open up to take a wood burner, only the current and i think original opening is only 20" across , the lintel being only 1/2 a brick wider than this either side, the chimney is 48" wide. I'd like to put in a new lintel and widen the cheeks out by at least 8"...

www.diynot.com

Blup

 

[stuart45]

Yes, that helps hold up brickwork if it's not tied in properly.

 

[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?

As we expected the Corbelled bricks were tied into the back wall. It wasn't quick and a challenge to remove them. You have to snap them halfway into the wall and clean up the edge, I just used a DSD Drill which did the job. I Had to remove 3 or 4. A brick or 2 around would drop, most of the time it was some effort to get them out. All the mortar held them in. If you look close enough you can visibly see which way they laid the brick and if it tied into the party wall.

As Luck would have it when I started to take bricks out a guy across the road was have a flue liner fitted by a HETAS Engineer. Ran over and grabbed him as he was coming down the ladder to give me a quote etc. He came over and gave me some pointers.

He said for a start my proposed opening was too small, basically saying the higher it is the more efficient it is. He marked on the wall where I should go at a minimum. Ended up being 43 Inch from bottom of Lintel.

I asked about the corbelling and he looked and basically told me not to worry about it. He said there tied into the wall all the way up and pointed it out to me how to check. He basically said if it wasn't built like this its not safe as all the weight of the whole chimney stack in on a few bricks. They spread the loads by toothing it into the back wall.