Hairyloon
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Finishing a fireplace.So, I can slap plaster about to a standard that I find acceptable, but I believe that plaster is inappropriate for the inside of a fireplace, and I have not yet quite got rendering up to the required spec (and I'm still not certain what the correct mix is).
So do I keep practising, or is there something I can use to smooth it off?
Also, the floor of the fireplace, underneath whatever I decide on for a hearth stone, is that just plain ordinary concrete?
Mine is recessed and needs filling back up.
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ksia
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When we had our chimney put back in, when we lived in the UK, the structure was simply breeze-block (spelling?). We thought it had to be lined and stuff but the builder assured us 'no' and it did work fine. This was only the bottom half of the chimney - the rest was still there in the room above and roof. (Goodness know what the previous owners were thinking.)
The floor of the fireplace was just concrete (as far as we could tell) and stayed that way.
This was a small, coal, fireplace.
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vegplot
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Lime based renders offer a softer finish. Heat tolerant as well.
You can sit hearth on top of compacted hardcore followed by a layer of sand, perhaps in a weak cement or lime (you'll have some left over from the render won't you) mix.
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Nicky cigreen
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we made the hearth of our fireplace with reclaimed granite paving slabs (ironically you cant buy new Dartmoor granite anymore, so although i live in a largely granite house.. on Dartmoor, I would have to have imported granite from India! FFS....). We found the slabs (paivng slabs from a nearby town) at a very good price in a reclaim yard, and lime mortared them. We have a woodburner on this though, not a direct fire.
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Treacodactyl
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I thought fireplaces, hearths etc these days are covered by buildings regulations? If that's the case I'd confirm the hearth infill with them.
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vegplot
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| Treacodactyl wrote: | | I thought fireplaces, hearths etc these days are covered by buildings regulations? If that's the case I'd confirm the hearth infill with them. |
In summary (for stoves):
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Hearth Requirements
A hearth is constructed of non-combustible material and is used to protect nearby combustible material from the heat of the stove and from hot fuel that could potentially fall from the stove.
A stove must stand on a non-combustible plinth extending a minimum of 300mm in front & 150mm out from the stove at the sides. The edges of the hearth should be clearly marked e.g. a change in level.
Hearth Thickness: Models that have been designed and tested to have a hearth temperature not exceeding 100° centigrade, may use a 12mm hearth. Untested stoves must either use a 125mm thick hearth with a 50mm air gap underneath or a solid 250mm thick hearth. The later two measurements can include a Constructional Hearth which is unseen and built below floor level, finished with a Superimposed Hearth which is the finished material on which a stove will sit.
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Hairyloon
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| vegplot wrote: | Lime based renders offer a softer finish. Heat tolerant as well.
You can sit hearth on top of compacted hardcore followed by a layer of sand, perhaps in a weak cement or lime (you'll have some left over from the render won't you) mix. |
Except that I have already done most of it in a normal mortar. 
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James
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I built a hearth for our woodstove (NOT open fire) thus:
- rubble base.
- concrete to roughly level off the rubble.
- Self leveling screed to form a perfect level
- Fireboard
- flexible (latex) cement (to absorb expansion/ contraction between the hot surface and the cold underneath)
- Hearth surface (we used thick terracotta tiles grouted with flexible grout to allow expansion/ contraction)
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Hairyloon
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| James wrote: | | I built a hearth for our woodstove (NOT open fire) thus: |
Sorry, yes mine is for a stove.
| Quote: | - rubble base.
- concrete to roughly level off the rubble.
- Self leveling screed to form a perfect level |
Was my plan also, slight concern whether the self levelling stuff is OK with heat.
Though I don't really see the floor getting particularly hot (I never set fire to my caravan for example, and I'd expect the new stove to have better legs).
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James
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| Hairyloon wrote: | | slight concern whether the self levelling stuff is OK with heat. ). |
It should be. But I wasn't too sure either, hence the fire board (its a grey cementitious fibre board with a proportion glass fibre incorporated).
| Hairyloon wrote: | | Though I don't really see the floor getting particularly hot . |
It doesnt. After all that work of making sure the floor is properly constructed for temperature fluctuations, the tiles under the woodstove hardly get any hotter than just above body temperature (slightly warm to touch). I'd say that within an inch or so of the surface, the temperature will be normal.
But if I did it again, I'd do it exactly the same, just to be on the safe side. Then you know everything's going to be OK (and it'll last without cracking).
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