Bricked up fireplace -- maybe reinstate?

[fernicarry]

Another day, another horror story...

Starting point, external wall that's been lined in plasterboard with quite a generous gypsum skim. We don't use this room and its not heated so unsurprisingly its quite foosty. There was a small plastic grill to vent the fire opening but PO had stuffed that full of bubble wrap...




Plasterboard was very soft and crumbled to dust with little persuasion. Debris lying between the plasterboard and the wall up to a height of about 12" so no chance of air circulation in the void. Back of plasterboard covered in black mould.




Lots of debris inside the fire opening, pretty much up to the level of the vent. Given that the vent was chain drilled after the fact and we can see the blown back of the brick on top of the debris pile this is obviously a later attempt to address a developing "problem".



The debris was mostly sand, a bit of soot and a few small stones. The deeper down I got the colder the sand felt although it wasn't exactly wet. The bricks and cement mortar were hard as a very hard thing but eventually got them out. Seems to be a slate hearth laid to the bottom of the opening. Quite a lot of efforvescence in the bottom left on the stone and bricks and the slate was damp on the left side but now dried out. I guess a small amount of water comes down the chimney and gets trapped so the bottom of the wall just got wetter and wetter over time.





In terms of putting it all back together again, the internal wall has now been parged with Thermaplasta thermal to fill gaps and level it out somewhat. Next I'll insert IndiNature hemp batts between and behind the studs, then wood wool boards and a finishing coat of Breathaplasta universal and fine. The wall should end up well and truly breathable (on this side at least) and I'll have a bit of thermal improvement on that side of the room.

We are considering reinstating a fireplace with a tiled insert and a small stove like a Hobbit. Having a functioning fire flue on this side of the building would be beneficial in keeping the external wall dry but losing the wall space on what is a very small room isn't ideal.

The opening is 3' wide and the flue continues up at about the same width. What I'm most unsure about is how to reduce the size of the recess to match the insert? I want to do this myself before an installer rocks up and insists in doing it in cement. And should I remove that piece of slate?

 

[Cubist]

Depending on the final dimensions of the opening you want to leave for the insert I'm thinking that bricks may be your best option and could be used to provide some additional support to the 'flying' bricks already in situ that form the crude arch of the chimney breast. This approach may also help to avoid any further disturbance of the what appear to be rubble stone built surrounding walls?

 

[fernicarry]

Thanks. There is a really substantial stone lintel above those bricks so no danger of movement. I'll knock out the rest of them once I psych myself up for the level of violence needed.

So should I build a brick "chamber" about the size of the opening in the insert for the stove to sit in? How about the void space either side? Fill with vermiculite or similar?

I don't have any other original fireplaces here to compare with hence what might be silly questions.

 

[paulc]

If you are putting a free standing stove in like the Hobbit, I'd not bother making the opening any smaller. If nothing else, it gives you somewhere to put an ash can and perhaps even stack a couple of logs.

 

[Cubist]

I'll knock out the rest of them once I psych myself up for the level of violence needed.

Pent up rage issues among Period Home Owners is not uncommon and as rule its usually directed toward the Home Improvement Bandits employed by previous owners... and of course the Conservation Officer. Imagining one such villain may give you the spur needed to get the job done but... but often when I've tried this tactic I've found my thumb in the way of the hammer!

Pauls idea sounds good but in the event it doesn't appeal to your good self I'm not sure how much benefit filling the void with vermiculite may be.

 

[LadyArowana]

Aren’t there “rules” about how far away some stuff like the side of a stove has to be from the other stuff like the wall beside it? We don’t have any stoves at all, just ornamental non functional grates, which no doubt cover a multitude of sins, so zero direct experience. There seem to be rules about everything nowadays, frankly I’m waiting to be issued official guidance on which leg I should put into my tights first!

 

[fernicarry]

If you are putting a free standing stove in like the Hobbit, I'd not bother making the opening any smaller. If nothing else, it gives you somewhere to put an ash can and perhaps even stack a couple of logs.

Thats a good idea, the big stove in the living room has quite a lot of stove-related paraphernalia stacked around it.

I do quite fancy having a nice tiled cast iron insert though so that I'll have at least one fire place that looks somewhat period-correct as sadly all have been removed or replaced with something "modern".

However a related problem is that the insert I have my eye on is only 30" wide rather than the more standard 36" but even so most fire surrounds seem to have an opening of more like 39 or 40"... How does that work? Maybe ebay is an unrepresentative sample of what is available.

 

[fernicarry]

Aren’t there “rules” about how far away some stuff like the side of a stove has to be from the other stuff like the wall beside it?

Yes indeed. Each stove has a specified distance to combustible materials that should be observed. Its usually around 200 or 300mm.

Our big stove has an unusually short distance, maybe because its a boiler stove so the outside stays a bit cooler. The new chimney sweep was all set to send me to Chimney Jail last year for flagrantly piling up the kindling within what she considered to be the danger zone.

The irony is that when we took out the open fire to fit that stove we discovered that the laths just above it were quite charred.

 

[Cubist]

There seem to be rules about everything nowadays, frankly I’m waiting to be issued official guidance on which leg I should put into my tights first!

The First Lady informs me that 'its both'. Another puzzle for me, but just another of the myriad mysteries she brought with her into my life - obviously I'm doomed to wear this baffled expression to the end it seems.

 

[paulc]

I do quite fancy having a nice tiled cast iron insert though so that I'll have at least one fire place that looks somewhat period-correct as sadly all have been removed or replaced with something "modern".

However a related problem is that the insert I have my eye on is only 30" wide rather than the more standard 36" but even so most fire surrounds seem to have an opening of more like 39 or 40"... How does that work? Maybe ebay is an unrepresentative sample of what is available.

When I installed my stove (an inset cassette), I padded out the space a bit with breeze block. The remaining space was filled with vermiculite mixed with a bit of cement and a dash of water - The cement will hopefully bind the vermiculite together and stop it falling out should I ever need to pull the stove out.
The space around the original open fire back had been infilled with random bits of rubble and mortar - Took several wheelbarrow loads to get it all out of the house. If i were to put a fireplace inset back in, I'd probably fill the void with vermiculite mixed with a binder. Easier to shovel in and fill the gap without leaving huge voids.

 

[fernicarry]

State of play at the moment. Wall parged with Breathaplasta Thermal to fill gaps and get it level. 50mm Indinature hemp insulation between the studs with offcuts filling the gap behind the studs. Wood wool boards attached and edges tied into existing plaster with haired lime. The picture rail should hide the worst of the join. About as far as I can go until I make a decision about the fire opening.

Stove installer coming to take a look sometime this week.

 

[a twig]

Wow great progress!

 

[fernicarry]

So, after several promises and no-shows the stove installer finally came to take a look. I explained I wanted a Hobbit stove fitted inside a reclaimed cast iron insert, I'd actually already been through this on the phone with him so it should hardly have been a surprise. "We don't do that one". " We usually just leave it open and put a beam above it for a mantel". "I'll send you something".

More radio silence and a week later than promised he sent a short email suggesting two stoves, both much too wide to fit into an insert... And he wants five and a half grand for the privilege of not doing anything remotely similar to what I asked for. Business must be good if he can *iss all over potential customers like this.

There's a Salamander dealer about an hour's drive away, so I'll pay them a visit tomorrow.

 

[paulc]

When I had my stove installed, I went out and bought the model I wanted at a price i was willing to pay. I just paid the fitter to drop a suitable liner down the chimney, hook up the stove, and complete the paperwork for building regs compliance. All the finishing work, including the final coat of plaster, I did myself.

 

[a twig]

Another vote for paulc’s approach, get the fitter to do the minimum they legally “have” to do and do the rest yourself. I got a £3000 quote down to £1200 that way - and for the stove I picked up a refurbed Morsoe for £400 from a local place rather than the >£1000 the fitter would have charged me for a new one

 

[fernicarry]

Thanks. Looks like I’ll be doing the donkey work and just get a fitter to the liner.

One bit of progress, we found an insert we both like and that really suits the space. So now I can start figuring out how to fix it into position.



Should it sit on top of the hearth? Or is the hearth templated around it? I can see little tabs at the bottom of the legs, presumably they would fit into slots to keep it in position?



The constructional hearth is still below the floorboards but with a gap of about 4” and there are a couple of small joists supporting the boards that covers where the hearth used to be. Could I just lay a new slab on the same joists? I’d like to avoid having a cold bridge onto the constructional hearth. The gas pipe in the picture will be removed.

 

[paulc]

The constructional hearth is still below the floorboards but with a gap of about 4” and there are a couple of small joists supporting the boards that covers where the hearth used to be. Could I just lay a new slab on the same joists? I’d like to avoid having a cold bridge onto the constructional hearth.

You need a 5" (125mm) thick slab of noncombustible material under the fireplace and extending out the full width & depth of the hearth. Either concrete or limecrete will do the job. See picture below which was extracted from Part J Building Regulations.

 

[fernicarry]

I thought for a 12mm rated stove I could just lay the hearth straight onto the floor timbers, but having googled that a bit now there is also the 840mm radius thing which would come too far into the room.

So seems like I'll have to build up the constructional hearth again. Could I put an inch or so of A1 rated insulating plaster under the decorative hearth to stop cold bridging or would that not have enough compressive strength?

 

[paulc]

So seems like I'll have to build up the constructional hearth again. Could I put an inch or so of A1 rated insulating plaster under the decorative hearth to stop cold bridging or would that not have enough compressive strength?

If the A1 rated plaster is rated as non-combustible, you should get away with it. Any compressive loads would be spread across the whole area, and you won't be building a supporting wall on top. Your supplier should be able to advise on the suitability.

 

[fernicarry]

A1 rating is "no contribution to fire". Same as concrete, brick, stone etc. So I think from a combustibility pov I'm good. Intention is also to line the back and sides of the fire chamber with the same insulating plaster.

I dug out the Scottish regs (here). Section 3.45 talks about separate constructional and superimposed hearths. The constructional hearth only need extend 150mm in front of the stove. The superimposed hearth should extend out to the full 300mm distance in front of the stove, and 500mm out from the wall but has to be 50mm thick.

So potentially a bit less building up so long as I can make up a superimposed hearth that is 50mm thick. 30mm slate sitting on cement board should work for that.

I wonder just how closely the stove fitter will pay attention to all this.