Repair to red sandstone fireplace

[Makingtime]

I have uncovered a large red sandstone fireplace (about 2 meters wide and a meter deep). It had been infilled with a large amount of bricks and cement. The stones at the back of the hearth are in very poor condition and in places have brushed away completely, exposing the concrete harl on the outside of the house.

We are working with lime, as concrete will do more damage in the long run. I would like to build up the back of the hearth. I am looking for the best way to add strength. We have been advised lime mortar with small slate pieces can be applied to build the wall up. I would like to know if pouring a lime mortar and aggregate mix into shuttering would be an option?

 

[endecotp]

Are you worried about the structural integrity of the wall and chimney?
Do you hope ever to use it as a fireplace?

 

[vinn]

OP,
Do you have a stone walled house?
Do you have a solid walled house ie no cavity?
Is the floor in the "fireplace" room a suspended floor?

Perhaps post pics of the fireplace wall inside the room, and the fireplace itself, & pics of the exterior of the chimney breast.

 

[Makingtime]

Hello

It is a solid sandstone wall. The walls are around 2 foot thick but the back of the fireplace seems to reduce to about 6". I have attached a photo of the fireplace and a close up of the back of the hearth - the green plastic appears to be sheeting applied to the wall on the outside under the concrete harling.

Although we have supported the arch while we are pointing and reinforcing, mainly for piece of mind we are not too concerned about structural integrity of the chimney breast. It is the back of the hearth that concerns slightly, especially as ultimately we would like to remove the harling from the outside - so reinforcing there is a concern.

The room has a (more recent) concrete floor, but the wall appears to be built straight onto the ground. The fireplace floor is partly concrete (in the centre where the most recent open fire was), around this we have filled with mortar to provide a base for building up the back of fireplace wall.

We are planning to fit a wood burning stove in the recess - before opening up the hearth there was a working open fire installed.

 

[Makingtime]

Photo

• Makingtime
• 27 Mar 2017

Photo (1)

• Makingtime
• 27 Mar 2017

Back of hearth showing sandstone deterioration to point that backing of external concrete...

 

[vinn]

I dont think that the timber propping arrangement is necessary - although its difficult to see clearly.
With respect: for pics, could you remove all chattels and get a clear focus?
Still no pic of the exterior - a pic would help?

Until you have a dimensioned overall proposal for the existing fireplace opening its not worthwhile to advise you further on re-building.

The green plastic sheeting:
How come, if there was an active fire in place, the plastic didn't melt?
If plastic was used as a "tanking" behind the render then unless metal lath was used the render could not be applied?
Is it possibly the flopped up edge of a DPM from below the concrete floor?

As for your proposals: why not read my recent posts advising on doing exactly what you propose?

 

[Makingtime]

Thank you for your replies.

Yes, probably unnecessary but better safe than sorry - as we cleaned the wall down it wasn't clear whether large spaces between stones where mortar had disappeared were new or not.

I will post some better pics as soon as possible.

The sheeting is visible in a number of places so does appear to be tanking - the wall is not accessible from the outside as we still have to fight our way through the neighbour's overgrown garden. The lack of melting will be down to the foot or so of wet stone and sand that was between the fireplace and the back wall. The build is around 250 years (we think) so the concrete floor cannot relate to the plastic on the outside.

I haven't been able to track down similar post, can you point in the right direction?

Ian

 

[endecotp]

we are not too concerned about structural integrity of the chimney breast. It is the back of the hearth that concerns slightly

You've managed to break through the entire wall just by "brushing" the stone; I would be more than slightly concerned about the structural integrity of what's left.

Is it a listed building?

 

[Makingtime]

We have exposed a fair amount of other wall which is far thicker and in reasonable condition, so the rot does appear limited to the back of the hearth. That said, we also been advised to remove the concrete harling from the outside to prevent further damage to the sandstone - this is something of a dilemma as the 2 inches plus of concrete undoubtedly add strength (hence wanting to built up the back of the fireplace).

No, it is not listed, but we are in a conservation area.

 

[vinn]

Until you can come thro the garden and clear away all brush to ground level and then pic the result there's not much more to say.

Refs:
opening fireplace 9 dec 16
enlarging fireplace 14 feb 17
removing fireplace 17 mar 17
damp chimney 26 feb17