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DIY Tutorials

Fitting a Lintel in a Chimney

fitting a chimney lintel

On our mission to get the dining room chimney log-burner ready, I recently shared how we removed the old back boiler and uncovered a slightly questionable chimney opening. The original victorian supporting arch had been removed (I'm so damn angry at the 70s!) and instead some brick 'pillars' had been erected either side of the opening to "support" the chimney. Worse than this though, was that these pillars seemed to have either been built out of plaster or the worst crumbly mortar ever. Needless to say, some seriously dodgy building work had occurred inside this chimney at some point and as a result, the chimney had not been supported properly supported for the last 40-odd years and we now had to fix it.

Sadly when these cowboy builders of the 70s removed the original arch, (which if they had not had done, would have meant this opening wouldn't even need any new supports and they wouldn't have had to have built the dodgy brick supporting pillars - grr!) their re-bricking of the chimney where the arch had been, made absolutely no sense at all. Some bricks had been put it on their side which skewed the entire formation of bricks and absolutely none of the bricks were in line with one another. Obviously none of the bricks had been supported in the middle of the chimney either, which meant everything was a little sunken and loose above. Considering just how long the chimney had been like this, I was pretty surprised that it wasn't much much worse actually. But, we knew we had to rectify this before we could go any further with our log burner installation. As a reminder, here's what it looked like just after we removed the old boiler..

how to open up a chimney

We removed a good amount of plaster and decided on a height for the lintel. This will also be the end height for the opening inside the chimney, so it needed to be big enough to comfortably fit our log burner and some flue. We were happy with the existing width of the opening, so we wont be removing any bricks sideways, other than the ridiculous 'pillars'. A lintel in a chimney needs to have an overhang of between 12-15cm either side, which luckily for us was an entire half brick, so we used a SDS drill with a chisel drill bit to pop half a brick out either side of the opening for the lintel to sit onto. You don't need acrowprops for an opening under 1m and in our case we had the dodgy brick pillars for a little bit of support anyway (not that they were doing much really - but we kept them in place anyway).

installing a lintel in a chimney
DIY fitting a lintel
removing bricks for a lintel

Once the bricks were chopped out, we then needed to cut the lintel to size. A re-inforced concrete lintel is perfectly suitable for this job and can be cut with just an angle grinder. We borrowed a very low spec one from Grants parents which took FOREVER to cut through, but it did the job.

We fitted the lintel into beds of mortar either side, making sure it was completely level. Because the brickwork above the lintel was so loose we had to remove almost all the bricks that had been re-bricked in the 70s and fit them again properly. I did this one layer at a time, so not to create one giant hole and freak the hell out. I'm sure it wouldn't have made any difference if I had removed all the bricks at once, but it's one of those perception things. One giant hole makes me much more nervous and anxious than just a few bricks at one time.

concrete lintel in chimney
how to re-brick a chimney

I'd done a bit of bricklaying in the garden recently (posts on that coming soon!) so I'm not a complete stranger to laying some bricks and I think my recent garden project prepared me greatly for this. I used bagged mortar which just needs mixing with water and re-bricking around 15 bricks took up almost a whole bag(!). I didn't have to cut any bricks to size either as we still have a whole garden filled with bricks from removing internal walls - so this part was pretty simple.

re-brickng above a lintel
fixing sunken brickwork in a chimney
chimney without a lintel

Once it'd been re-bricked properly we could begin removing the dodgy brick pillars, remaining pipes from the boiler and finally open the hole up properly. It was very messy work, with a lot of soot dust falling down the chimney (luckily no dead birds!), but eventually we were left with one beautifully square opening ready for a log burner! We also removed the rest of the plasterwork around the chimney too - it'll be easier to replaster the whole thing this way than patch-plastering.

opening a chimney for a log burner
removing plaster around chimney
chimney opening progress for log burner
how to open a chimney
opened chimney ready for log burner

I always find the idea of structural work more scary than it actually is. Making a giant hole in a chimney sounds like precarious stuff, but actually bricks are tough stuff and the Victorians knew how to build resilient houses. Fitting a lintel really isn't as complex as it sounds, so this is definitely a DIY job I recommend giving a go! After all, it's saved us bags of cash on paying a builder!

Have you any experiences with fitting lintels/opening chimneys? 


New Tools Purchased:
None (although we did borrow an angle grinder!)

Materials Used:
Lintel £14
Blades for Angle Grinder £7
Mortar £5
Bricks - free from removing internal walls

Total: £26

How to fit a lintel in a chimney


1 comment

  1. I've been putting off a job because I too had a nervous aversion to anything 'structural'. But after reading your post I finally faced my fear and knocked out a row of bricks from an internal wall and installed a lintel, ready to create a doorway. Dunno what all my fuss was about!


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