Fireplace questions (Photos included)

[benraz69]

Evening all! First post, so go easy

I've just moved into an Edwardian property which has a working clay back fireplace & have removed the surrounding out-of-keeping 1970s blockwork. The main issue is I've only been left with 170mm depth of fireplace. The original grate which sits on top is 280mm deep. Is the remaining overlap of grate just meant to sit on the (granite) hearth as pictured below?

I was planning to dot & dab the granite hearth down onto the constuctional hearth below using drywall adhesive. I was then planning to render the existing brickwork & tile over. Finally, I was planning to fit a large wooden surround. Does all of that sound feasible?

• Also, is fire cement an appropriate product to use for rendering?
• Will regular tiles, adhesive & grout suffice? Or are there specialist fire resistant products I should be using?
• Any other recommendations?

In case it helps, below is how it currently looks. Thanks in advance, Ben

 

[Richard C]

Evening all! First post, so go easy

Why do people say that, it’s a sure fire way of getting kicked by the resident trolls.

I've just moved into an Edwardian property which has a working clay back fireplace & have removed the surrounding out-of-keeping 1970s blockwork. The main issue is I've only been left with 170mm depth of fireplace. The original grate which sits on top is 280mm deep. Is the remaining overlap of grate just meant to sit on the (granite) hearth as pictured below?

Can you explain a little more about your intentions, are you planning to keep this as an open fire or install some kind of stove?

Are those floor boards I can see? If so it may not comply with current regulations, some dimensions are needed.

I was planning to dot & dab the granite hearth down onto the constuctional hearth below using drywall adhesive.

Don’t do that; drywall is completely unsuitable, will almost certainly not withstand the heat & will fail. Your constructional hearth may not be large enough, see above comment.

I was then planning to render the existing brickwork & tile over.

Depends on proximity to the fire but you will probably need a specialist heat proof render or use a lime render mix; you will also need to use a quality cement based tile adhesive.

Finally, I was planning to fit a large wooden surround. Does all of that sound feasible?

That depends on the proximity to the fire which is governed by regulation.

• Also, is fire cement an appropriate product to use for rendering?

Not really

• Will regular tiles, adhesive & grout suffice? Or are there specialist fire resistant products I should be using?

Ceramic/porcelain/stone tiles are usually OK but it depends, it’s the adhesive & grout which needs special consideration.

• Any other recommendations?

Give some more detail.

 

[benraz69]

Hi Richard, thanks for the quick response

Can you explain a little more about your intentions, are you planning to keep this as an open fire or install some kind of stove?

Yes, I was just planning on keeping it as an open fire.

Are those floor boards I can see? If so it may not comply with current regulations, some dimensions are needed.

Yes, they are floorboards. The constuctional hearth is 820 x 385mm.

Don’t do that; drywall is completely unsuitable, will almost certainly not withstand the heat & will fail.

Bearing in mind the granite's nearly 40mm thick, I'm surprised there'd be enough heat transfer to do any damage. Can you suggest an alternative method?

Depends on proximity to the fire but you will probably need a specialist heat proof render or use a lime render mix; you will also need to use a quality cement based tile adhesive.

I was planning to render/tile to the outer edge of the clay back & brickwork above it. The end result being you can see the left & right sides of the clay back (blackened in picture), but no brickwork.

Are most tile adhesives cement based, or is it a specialist product?

That depends on the proximity to the fire which is governed by regulation.

If it helps, the dimensions are as follows (W x H):

• Clay back 500 x 570mm
• Actual opening 500 x 780mm
• ID of wooden surround 870 x 910mm

Thanks again

 

[Symptoms]

ben - I'd be suprised if your clay fire back & grate was older than the 'out-of-keeping 1970s blockwork' you whipped out earlier ... they were probably put in together ... (actually they look in too good a condition to be much older). Judging from the footprint of your constructional hearth and the height of the opening I reckon there may have been a cast-iron chimney piece in there from when the house was built and possibly a tiled hearth; hundreds of thousands of these beauties were ripped-out back in the day by brain dead Philistines.

Consider removing the clay fire back and source a cast-iron piece (salvage or repro) and re-tile the hearth (again salvage or repro); finish off with a period fender (salvage or repro).

 

[Richard C]

Yes, they are floorboards. The constuctional hearth is 820 x 385mm.

To comply with current regulations, the constructional hearth must extend 300mm to the front & 150mm each side of the fire; there should be no combustible material (floorboards) within this area.

Bearing in mind the granite's nearly 40mm thick, I'm surprised there'd be enough heat transfer to do any damage. Can you suggest an alternative method?

Believe me, it will get very hot; this link gives details of current regulations for constructional & decorative hearths; http://www.stovesonline.co.uk/stove_building_regulations.html
Also see Part J Building Regs which contains more detailed information; http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADJ_2010.pdf

I usually bed on mortar but have used silicone. I can see some problems with your hearth; was it sold to you as suitable for solid fuel? Solid fuel hearths are usually made in 3 sections with further smaller sections immediately in front of the fire/ash pan. This immediate area of the hearth gets very hot relative the outer perimeter & will expand at a much higher rate. The sectional hearth construction allows this differential expansion, without it the hearth will most likely crack. Also the grate is directly over the granite; again very high temperatures are involved, I cannot see the granite hearth surviving.

I was planning to render/tile to the outer edge of the clay back & brickwork above it. The end result being you can see the left & right sides of the clay back (blackened in picture), but no brickwork.

For the render you need to use either something like Vitcas heat proof render or a sand/cement/lime render; apply in two coats 5:1:1 - 6:1:1 to avoid cracks & the render blowing. Only use heat proof plaster (Vitcas or similar) 300mm either side or 800mm above the fire opening; Gypsum plaster will only stand 49 degrees & will fail very quickly.

Are most tile adhesives cement based, or is it a specialist product?

No so much specialist but you need a quality trade product; I use BAL Rapidset which will withstand up to 150 degrees. Avoid cheap own brand & DIY products, they are mostly crap. I like to use 600 x 300 granite tiles to construct surrounds; I space them ½ mm apart & silicone the joints rather than grout which tends to fail due to expansion & contraction.


Some good tips from Smptoms

 

[benraz69]

ben - I'd be suprised if your clay fire back & grate was older than the 'out-of-keeping 1970s blockwork' you whipped out earlier ... they were probably put in together ... (actually they look in too good a condition to be much older). Judging from the footprint of your constructional hearth and the height of the opening I reckon there may have been a cast-iron chimney piece in there from when the house was built and possibly a tiled hearth; hundreds of thousands of these beauties were ripped-out back in the day by brain dead Philistines.

Consider removing the clay fire back and source a cast-iron piece (salvage or repro) and re-tile the hearth (again salvage or repro); finish off with a period fender (salvage or repro).

Hi Symptoms, I won't let my wife read your post (She wants to go down the same route ). I looked into it, but started seeing pound signs rolling before my eyes! I also assumed fitting a new fire would have to be done by an approved (HETAS-?) installer anyway.

To comply with current regulations, the constructional hearth must extend 300mm to the front & 150mm each side of the fire; there should be no combustible material (floorboards) within this area.

Well that should be okay, as mine is 385mm deep & extends 160mm over each side of the fire.

I can see some problems with your hearth; was it sold to you as suitable for solid fuel?

We inhereted it from a friend of ours. It was removed from an open fire, though it wasn't currently in use. There seem to be plenty here though, for example.

Solid fuel hearths are usually made in 3 sections with further smaller sections immediately in front of the fire/ash pan. This immediate area of the hearth gets very hot relative the outer perimeter & will expand at a much higher rate. The sectional hearth construction allows this differential expansion, without it the hearth will most likely crack. Also the grate is directly over the granite; again very high temperatures are involved, I cannot see the granite hearth surviving.

Bearing that in mind, where the grate overlaps the hearth - could I cut a shallow U-shaped section out of the back of the granite? I could then bed the hearth down & level/fill the cut out with the same fire resistant cement/concrete that remains behind it (in the back hearth). This would mean that the grate isn't sitting on the granite.

I've contacted a local worktop firm who are able to cut a section out of the granite for around £85, which I didn't think was unreasonable-?

For the render you need to use either something like Vitcas heat proof render or a sand/cement/lime render; apply in two coats 5:1:1 - 6:1:1 to avoid cracks & the render blowing. Only use heat proof plaster (Vitcas or similar) 300mm either side or 800mm above the fire opening; Gypsum plaster will only stand 49 degrees & will fail very quickly.

Thanks Richard, some excellent advice there. The Vitcas products look good & it'll make life easier ordering from one place.

No so much specialist but you need a quality trade product; I use BAL Rapidset which will withstand up to 150 degrees. Avoid cheap own brand & DIY products, they are mostly crap.

Understood. I've used BAL products before & there are a few tile merchants around this way, so not a problem.

 

[Richard C]

We inhereted it from a friend of ours. It was removed from an open fire, though it wasn't currently in use. There seem to be plenty here though, for example.

If you look carefully you will see that solid fuel hearths are made in sections, one piece granite hearths will crack if exposed to excessive heat.

Bearing that in mind, where the grate overlaps the hearth - could I cut a shallow U-shaped section out of the back of the granite? I could then bed the hearth down & level/fill the cut out with the same fire resistant cement/concrete that remains behind it (in the back hearth). This would mean that the grate isn't sitting on the granite.

Even so, heat from the fire will still transfer into the hearth.

I've contacted a local worktop firm who are able to cut a section out of the granite for around £85, which I didn't think was unreasonable-?

For another 40 quid or so you can get a new solid fuel hearth already cut to you’re your requirements;

View media item 39112
Personally I think you would do far better to go that route & stick the one piece decorative hearth on Ebay; it’ll be junk when it cracks!

Understood. I've used BAL products before & there are a few tile merchants around this way, so not a problem.

 

[benraz69]

Personally I think you would do far better to go that route & stick the one piece decorative hearth on Ebay; it’ll be junk when it cracks!

Duly noted. On eBay she goes

If we're not using the granite hearth, the missus would prefer a tiled hearth using the same tiles we're getting for the fireplace - which is fine by me. However, to get the tiles level with the back hearth, I need to build the hearth up by at approx 65mm before tiling. What's the best way of doing this?

Also, when building it, can I keep the same footprint as the constructional hearth?

Finally, the missus is looking at mosaics (including glass). Asides from being fiddly, any problems with these?

Thanks again

 

[Richard C]

If we're not using the granite hearth, the missus would prefer a tiled hearth using the same tiles we're getting for the fireplace - which is fine by me. However, to get the tiles level with the back hearth, I need to build the hearth up by at approx 65mm before tiling. What's the best way of doing this?

At that depth you’re probably best to shutter it out & use a 1:2:4 concrete mix. But what will you do about the raw hearth edge, tile it? It depends what look you want but, IMO, it’s going to look very 1970’s, especially with the mosaics. Along with York stone fire surrounds & mantles, it’s the sort of thing I normally get asked to replace!

Also, when building it, can I keep the same footprint as the constructional hearth?

As long as the constructional hearth compiles with the minimum sizes in B Regs then yes.

Finally, the missus is looking at mosaics (including glass). Asides from being fiddly, any problems with these?

As above, it depends what sort of look you’re after I suppose but, personally, I don’t think mosaics will look good around a fire, very 1970’s; & it may complicate matters somewhat.

You should really use mosaic adhesive but the BAL product I use specifies a maximum temperature 100 degrees. I’ve measured temperatures in the wall around log/multi fuel stoves &, based on these, 100 degrees is not going to be enough; Rapidset is good for 150 degrees. Similarly some grouting products are only specified up to 100 degrees. I don’t grout anyway as the continual expansion/contraction around the fire tends to make it crack & fall out.

Having personally had a failure with my own fire surround around 3 years ago (caused by Gypsum plaster in my case), I spec check all the materials I use & keep it simple with what I now know works. As I said, I only use pre-constructed solid fuel hearths & I’ve never attempted to construct my own, too fiddly & time consuming. I use large format granite or stone tiles to form fire surrounds, leaving a ½ mm gap which I fill with clear silicone.

 

[benraz69]

At that depth you’re probably best to shutter it out & use a 1:2:4 concrete mix. But what will you do about the raw hearth edge, tile it? It depends what look you want but, IMO, it’s going to look very 1970’s, especially with the mosaics.

Thanks Richard, that should help me talk the wife out of going for mosaics

Yes, I was planning to tile the edge. An alternative would be to fit some kind of skirt/scotia round it & then mitre it into the skirting board along the front of the chimney breast.

Right, time to get cracking. What, if anything, should I do to prepare the constuctional hearth before laying the concrete over it? (Same for the brickwork before rendering it).

 

[Richard C]

Yes just give it a good damp down.

 

[Symptoms]

ben wrote: "....but started seeing pound signs rolling before my eyes!" but by the time you've gathered all the building materials for the job and invested the time with the construction I bet the pound sign will almost be equal to the purchase price of one of these repro jobbies:
http://www.periodhousestore.co.uk/prods/cast-iron-fireplaces-combinations.html

Now I'm not suggesting for one minute that you should get the tackle from these people but I'll bet a beautiful combination unit would be the dog's boll.....s over most other installations; and Mrsben would love you forever (also just imagine the scene ... ben & Mrsben cuddled-up on the mat infront of a blazing fire in a cast iron combo jobbie, Oh, and the dog would love it too)

 

[Richard C]

Listen to Symptoms wise words