Fireplace wall render/plaster


V

VisionSet

I'm renovating a traditional fireplace and have discovered the render to be
sand/cement which I'm pretty certain isn't original.
Question is, what was there previously in a 1930's semi and what should I
put back there? Would browning & finish be okay, or should it be
sand/cement?
In my reading I haven't seen this mentioned.
Fireplace will be used with 10kw input living flame gas fire.

TIA
 
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A

Andrew Gabriel

I'm renovating a traditional fireplace and have discovered the render to be
sand/cement which I'm pretty certain isn't original.
Question is, what was there previously in a 1930's semi and what should I
put back there? Would browning & finish be okay, or should it be
sand/cement?
Sand/cement/waterproofer may have been used because the brickwork
behind is too damp for gypsom plaster directly. This can happen
because of lack of damp proof course in the rubble/soil used to
form the base of the fireplace and hearth, which breaches the
damp proof course in the brickwork. This didn't matter when the
houses were built as a regular fire kept it dry, but becomes a
problem when the fireplace is no longer regularly used (and I
doubt your living flame fire will send enough heat into the floor
to keep it dry).
 
V

VisionSet

Sand/cement/waterproofer may have been used because the brickwork
behind is too damp for gypsom plaster directly. This can happen
because of lack of damp proof course in the rubble/soil used to
form the base of the fireplace and hearth, which breaches the
damp proof course in the brickwork. This didn't matter when the
houses were built as a regular fire kept it dry, but becomes a
problem when the fireplace is no longer regularly used (and I
doubt your living flame fire will send enough heat into the floor
to keep it dry).
A-ha I've replaced the constructional hearth with a new DPM'd version.
So, so long as the heat isn't going to affect the plaster, I'll plaster it.

Thanks,
Mike W
 
A

Andrew Gabriel

A-ha I've replaced the constructional hearth with a new DPM'd version.
So, so long as the heat isn't going to affect the plaster, I'll plaster it.
What about the floor inside the fireplace?

I have done a couple where I have removed the hearth (taken it
down well below floor level), floor-boarded across the top, and
then built a new hearth on the floor. For the fireplace base, I
dug out down to the level of the damp-proof slate in the brickwork,
lined the hole with DPM, filled bottom half with vermaculite, and
the top with sand and cement. I'm not actually using this as a
fireplace, but it could be in the future.

Plaster is remarkably heat resistant (I've had it glowing red hot
from a blowlamp without apparent ill effect), but I wouldn't use
it _inside_ a working fireplace. Should be no problem on the chimney
breast though. I still used a sand/cement/lime/waterproofer scratch
coat though for the bottom metre of wall, as in my case the outside
ground level is a bit high, and I'm not going to do anything about
that.
 
V

VisionSet

it.

What about the floor inside the fireplace?
You mean the back hearth?
The constructional hearth is all one piece with DPM overlapping a good bit
above the DPC. I shall bonding & finish it like elsewhere.
Fire & hotbox came yesterday. Vermiculite tomorrow. Cast iron combo &
hearth on Saturday, ooh exciting.
Thanks,
Mike
 
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Be aware of the regulations regarding heat, and materials, and therefore the restrictions on the type of fire/stove that one may use, especially when building on top of a wooden substructure. Also patching over/around lime with cement/gypsum is a terrible can of worms to prise open. Although I'm rooted in conservation, a thirties building may not be bothered by a new cement render. Never plaster inside the fireplace, it's asking for trouble - unless it's an ornamental installation.
 
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