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Preparing a Chimney Opening for Log Burner

Getting the Chimney Log Burner Ready!

September 6, 2016 - No Comments - 5 min read

If you’ve been following the blog for a while, you’ll know we’ve been making progress in the dining room towards fitting a log burner! I’m beyond excited, not just because log burners are damn cool, but because this will be the first time we’ll have a proper way of making heat in this house. So far we’ve already removed the old back boiler, installed a lintel and we’re finally down to the finishes with the next job on the to do list being all the internal works. This means boarding the opening to make it fireproof and fitting a hearth.

Lining the Fireplace

There are building regs in place regarding chimney openings where a solid fuel appliance is being used. These ensure the area is safe and free from combustible materials so that there’s no chance of anything setting fire. Bricks are obviously non-combustible anyway, so you can  have the opening of your chimney with its original exposed brickwork for a more rustic/natural look to your fire, but for us the bricks weren’t in the greatest condition and we even had some missing where the pipework for the old back boiler had been. Instead we’ll be boarding the inside of the fireplace with a fireproof board which will be painted and will give a more sleek and modern look, although I have to admit – I am slightly jealous of all the exposed brick chimney openings!

When boarding a chimney for any multi-fuel appliance, you must use a fire retardant materials and methods. I did heaps of research on deciding what method would be best and decided a fireproof board was the best option. Simply plastering over the bricks will more than likely cause the plaster to crack and fall off over time and I’m really not keen on the idea of rendering either. The board we’re using is a hardiebacker baord which you can pick up from B&Q. It’s smooth in its finish which makes it perfect for painting straight onto.
The first job was to replace any missing bricks that had been removed in the past to accommodate pipes for the back boiler. We still have plenty of bricks lying around from removing internal walls so I simply popped a brick back in and mortar’d it up.

replacing bricks in a chimney
replacing bricks in a chimney

To fit the fireproof boards, we cut them to size using a jigsaw making sure that they protrude out of the chimney opening by around 12mm. This is so that when we fit plasterboard to the outside of the chimney it matches up against one another.

how to cut hardiebacker board
how to line a fireplace for a wood burner

We’re having to use four separate cuts of board, ideally we wanted to use just three (one for each side with no obvious joins) but the boards weren’t both wide and tall enough to accommodate the back section so we’ve used a smaller length of board along the very top. To ensure the join wont be visible after painting, I will be using some flexible caulk and a bit of polyfiller over the top. Flexible caulk is obviously far less prone to cracking then filler, so we’ll also be using it along the corners as well where the baords butt up against one another, just to make sure there’s no small gaps and so that it looks completely finished.

To affix the boards we used plasterboard adhesive and fitted them just like plasterboard, using dot and dab. We always PVA walls prior to adhesive (50% PVA, 50% water) this improves adhesion and also ensures there’s no lose dust that might inhibit sticking. Fitting these boards was actually really easy to do – there were no awkward cuts and as long as you measure everything correctly, you can’t really go too wrong.

lining a chimney opening
dot and dab inside a chimney
fitting fireproof board in a chimney opening

Fitting the Hearth

Next up was the hearth. Regulations for the decorative hearth are dependant on the stove you’ve purchased. Any kind of non-combustible material is perfectly adequate for use as a hearth but the thickness of the hearth is where the regulations come in – you will need to check the requirements specific to your burner. The size of the hearth must also cover the floor space where the door opens, this ensures that no hot ash can fall onto combustible flooring. Underneath the decorative hearth there must be a constructional hearth too. This is usually made from concrete and unless a previous owner took a sledge hammer to it, there should be one in most Victorian Fireplaces. Our stove needed to be fitted on a 12mm thick hearth, but we’re using limestone which is 20mm thick anyway.

I love the rustic look of limestone and this grey one was an absolute bargain from eBay at just £20/square metre! We cut the limestone using a wet tile saw, which was slow and slightly awkward considering just how big these slabs of limestone are! But, it did the job. I always recommend using some kind of tape along the edge that you’re cutting, this makes the cut a lot less rough.

how to fit a limestone hearth
cutting limestone for a hearth

To fit the tiles I used a suitable limestone adhesive that’s also flexible as obviously the tiles are going to be getting a lot of heat on top of them, there needs to be accommodation for movement and expansion. I didn’t take any photos of this part as we were on a super strict late deadline and I was in ‘must get job done!’ mode. Sorry about that! I’ve never installed limestone tiles before, but they’re exactly the same as tiling any other material… just a little harder to move around!

After fitting, I treated the tiles with a limestone sealer which I did before grouting to ensure the grout doesn’t end up staining the tiles.

sealing limestone in a chimney opening

Since we’re using limestone, I’ve gone for quite a thick grout line so used an appropriate thick-gap grout with it. I also used a grout bag to apply it, which I think it helps push the grout right into the gap a lot better and it also creates a whole lot less mess to clean up later. I’m really pleased with the finish!

thick grout line on limestone tiles

A quick coat of paint on the boards and we’re now completely ready for our log burner. The colour I’ve gone for is ‘Downpipe’ by Farrow and Ball which will eventually cover the entire chimney and back wall. You can also see how the boards match up to an off-cut of plasterboard in the photo below too..

cathedral grey limestone hearth
DIY fitting a hearth

The old flue that’s currently in the chimney will be removed and replaced with a newer flue, but we’ll be having all that done during the log burner installation day. We wont be fitting the log burner ourselves and I’ll explain why in my next post, but we’ve saved ourselves bags of cash doing everything ourselves up till now. Everything we’ve done hasn’t been too difficult (even installing the lintel was much easier than we anticipated!) and I definitely think these are jobs worth tackling yourselves, if you feel you can.

You can find thorough in-depth how-to articles regarding all aspects of fitting a log burner on the stovefittersmanual.co.uk which was a great help to us and I seriously recommended!

Have you done any work to your fireplace/chimney ready for a burning stove?

Costs:

(rounded to the nearest pound)

New Tools Purchased:
None

Materials Used:
Mortar – free from previous projects
Hardiebacker x3 £48
Plasterboard adhesive – free from previous projects
PVA – free from previous projects
Limestone £56
Tile Adhesive £21
Grout £12
Sealer £20
Paint £44

Total: £201

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Kezzabeth

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Hi - I'm Kezzabeth! Self-taught DIYer, Renovator and Blogger on a mission to turn our house into a home. Seven years ago I was clueless and skill-less, but since then I've learnt how to build, tile, plumb and more. This is my little place on the web where I share everything I've learnt so you can learn too. Read More

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Disclaimer

DIY Content: We’re not builders or experts in the trade industry, so please take any information on this blog as a rough guide and just our own experiences. This blog relates to our home only and you should always consult a professional in you’re in any doubt of work. Please also be aware Building Regulations change often, so always do your own research as well.
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