Damp proofing a stone garden wall

seannash

Hi,
Currently my garden has an old stone wall thats about a 12 inches thick around it.

We are going to be extending and would like to have the stone wall left exposed in the kitchen.
I'm trying to figure out if we can avoid damp in this instance. We wont be plastering the front facing side of the wall either and the wall extends past our garden also.

BryanF

Don’t

If you real want the stone wall look internally rebuild it afterwards

seannash

BryanF wrote: »

Don’t

If you real want the stone wall look internally rebuild it afterwards

Cant unfortunately, If I knock it Ill lose the look on the outside also. I want to keep both.
Is it feasable

mickdw

Ownership wise, do you own the entire width of the wall?
If so, what you need to do is take it down, get proper foundations in, a property wall system for the extension, then put the stone back to both inner and outer surfaces.

Calahonda52

How do you know the wall will take the load of the extension?
Why no plastering outside face?
whats the weatherproofing going to be?

TheBoyConor

Is it going to be an internal wall? Both sides exposed internally when finished?

It'll be a massive cold bridge.
It'll bring dampness up through it from below. There is no reliable way of preventing this.
It'll provide a path for radon to enter the building.

If you really want to keep it, then dismantle it and rebuild it inside on the floor. which should be locally thickened or reinforced to support it.

If you want the wall rebuilt identically then you'll have to get a suitably trained and experienced mason to number the stones in the wall and photograph it before dismantling and then they will rebuild it in the same pattern inside. That will cost €€€.

Edit: if it is a perimeter wall that will be supporting the structure then there is absolutely no way you should do what you are proposing. The wall would have to be taken down and a proper foundation put in. Then the wall should be rebuilt in a proper fashion that an engineer is prepared to put their name to it's ability to carry any loads. That alone will cost serious €€€. Then it's construction would have to satisfy Part L U value requirements etc which would not be very feasible with a plain stone wall.

In that instance your best bet would be to demolish and build a regular cavity wall and then clad on both sides with the stone from the old wall.

seannash

mickdw wrote: »

Ownership wise, do you own the entire width of the wall?
If so, what you need to do is take it down, get proper foundations in, a property wall system for the extension, then put the stone back to both inner and outer surfaces.

I have permission to remove the wall if I want but I'd like to retain it. The wall is absolutely ancient and Id prefer to not take it down to rebuild it as it just wouldn't be the same.

seannash

Calahonda52 wrote: »

How do you know the wall will take the load of the extension?
Why no plastering outside face?
whats the weatherproofing going to be?

So the wall wont take any load, it'll all be rsj's.
I don't want to plaster the outside face as its a beautiful old wall which I don't want to cover.
In terms of weatherproofing, I guess that's why I'm here

Metric Tensor

To answer your question by a slightly circuitous route:

Is it possible: Anything is possible but you will spend a LOT of money to get a substandard end result.

Is it feasible: Not really.

Is it a good idea: Definitely not.


You cannot rely on either the strength of the wall or it being waterproof either from outside or below so the only way to incorporate it into the house is make it completely internal or make it completely external and have a glass panel adjacent to it.

seannash

TheBoyConor wrote: »

Is it going to be an internal wall? Both sides exposed internally when finished?

It'll be a massive cold bridge.
It'll bring dampness up through it from below. There is no reliable way of preventing this.
It'll provide a path for radon to enter the building.

If you really want to keep it, then dismantle it and rebuild it inside on the floor. which should be locally thickened or reinforced to support it.

If you want the wall rebuilt identically then you'll have to get a suitably trained and experienced mason to number the stones in the wall and photograph it before dismantling and then they will rebuild it in the same pattern inside. That will cost €€€.

One side will face the outside and one will be internal.
I might have to face the fact I gotta line the inside which is a shame.

TheBoyConor

is it a supporting wall.

I like the suggestion above of leaving the wall in situ externally and placing a glass curtain wall along that area so it is visible inside.

But you will have to leave sufficient provision to maintain and access the area in between.
Also, construction that close to an old wall like that will require inspection and temporary works to the old wall to make sure it is not going to collapse or subside during construction. That too is going to cost a fair deal of money.

The smartest option is to demolish, build a new cavity wall and clad with stone taken from the old wall.

Your initial proposal is a complete non runner. Not impossible technically, but it would be a nonsensical cost for what it is.

seannash

TheBoyConor wrote: »

is it a supporting wall.

I like the suggestion above of leaving the wall in situ externally and placing a glass curtain wall along that area so it is visible inside.

But you will have to leave sufficient provision to maintain and access the area in between.
Also, construction that close to an old wall like that will require inspection and temporary works to the old wall to make sure it is not going to collapse or subside during construction.

It wont be a supporting wall. It'll be left untouched. My concern is damp.
Is there no pumped damp course that could go into the mortar that would work?

TheBoyConor

seannash wrote: »

It wont be a supporting wall. It'll be left untouched. My concern is damp.
Is there no pumped damp course that could go into the mortar that would work?

There is but it is moreso for brick. And anything I've ever heard about it was that it was no use most of the time and was often a failure. It's not a reliable solution.

So if it is not supporting, then how is the top of the wall closed off from the roof?
What detail are you using to ensure that no loading from any part of the building will act on it?

Also note that this wall most likely has little or no foundation - stone walls rarely do ime.
When you excavate for the floor or indeed for any external groundworks and drainage, this could compromise the stability of the wall. You need to be sure that the wall is stable during construction and in the finished structure.

And anyway, if it is an external wall sure it will not have a snowballs chance in hell of satisfying minimum U-value requirements. That alone makes it a non-runner besides everything else. Furthermore, you'd have condensation issues with that cold wall.

mickdw

Is it forming part of the Proposed external wall or forming a feature within the new extension.

TheBoyConor

Op if you want to keep the stone effect the best way is to demolish, build a cavity wall and clad it with the stone from the old wall. If you really really want the wall to be visually identical, or close to identical, then you can catalogue the masonry and reconstruct in the same pattern. The former will require deep pockets, the latter will require even deeper pockets.

Your proposal as it stands is a non-runner from an engineering perspective. No-one will sign off on that.

I'll also add that if the wall is a boundary wall and you are removing the wall and reconstructing as above, then beware that you will have additional costs from ancillary works on the far side of the wall such as:
- any landscaping and repairs to the garden or hardstanding areas in the other property.
- dealing with any clashes with the new foundation and any existing services such as water, elec and sewer pipes or any ducting present.

seannash

TheBoyConor wrote: »

There is but it is moreso for brick. And anything I've ever heard about it was that it was no use most of the time and was often a failure. It's not a reliable solution.

So if it is not supporting, then how is the top of the wall closed off from the roof?
What detail are you using to ensure that no loading from any part of the building will act on it?

Also note that this wall most likely has little or no foundation - stone walls rarely do ime.
When you excavate for the floor or indeed for any external groundworks and drainage, this could compromise the stability of the wall. You need to be sure that the wall is stable during construction and in the finished structure.

And anyway, if it is an external wall sure it will not have a snowballs chance in hell of satisfying minimum U-value requirements. That alone makes it a non-runner besides everything else. Furthermore, you'd have condensation issues with that cold wall.

I'll try to explain, we are digging 4 holes and setting 4 concrete plinths which will support steel beams, all tied back into the original building.
This is a 2 storey extension with a flat roof on top. The joists will overrun the steel and float just above the top of the old wall.

In terms of passing code, the building is listed so I think its exempt (Open to correction)

TheBoyConor

Well if it is a PS then you may well be Part L exempt.

If it is a protected structure then that puts a whole different spin on it.
Have you planning permission?
Have you an engineer and architect overseeing things?

Still whatever you do you need to be aware of the effect excavation for the floor, pad foundations and any other work will have on the walls stability and put in appropriate measures to ensure it is safe and stable. You don't want to be screwing around with this in an amateur fashion.

seannash

TheBoyConor wrote: »

Well if it is a PS then you may well be Part L exempt.

If it is a protected structure then that puts a whole different spin on it.
Have you planning permission?
Have you an engineer and architect overseeing things?

Still whatever you do you need to be aware of the effect excavation for the floor, pad foundations and any other work will have on the walls stability and put in appropriate measures to ensure it is safe and stable. You don't want to be screwing around with this in an amateur fashion.

Thanks, yes I have an engineer and a conservation architect involved. I have permission to demolish the wall but I want to keep it. The house is from 1820 but the wall is much older.

TheBoyConor

Right.
Then follow the advice of your engineer and architect.

Over and out.

seannash

TheBoyConor wrote: »

Right.
Then follow the advice of your engineer and architect.

Over and out.

I know thats what should be the approach but the architect is of the opinion that whilst its possible it will lead to issues with damp. I'm trying to see if there's a way to avoid the damp issue.

Thanks for the responses though.

TheBoyConor

There really isn't a reliable means of ruling out damp.

If you're dead set on it, the demolish rebuild and clad way is the only sure fire way to get what you're looking for.

seannash

TheBoyConor wrote: »

There really isn't a reliable means of ruling out damp.

If you're dead set on it, the demolish rebuild and clad way is the only sure fire way to get what you're looking for.

Thanks. I guess I'll concede defeat on this one No harm in asking I suppose

BryanF

seannash wrote: »

One side will face the outside and one will be internal.
I might have to face the fact I gotta line the inside which is a shame.

Just don’t do it. Thermally/air-tightness/weathering/structurally et al

Metric Tensor

seannash wrote: »

Is there no pumped damp course that could go into the mortar that would work?

There are products advertised to stop rising damp in such a manner but there effectiveness is ... how do I put it politely ... questioned in some quarters!


And they are definitely not a "whole wall" solution.


As pointed out above - even if you did make it water tight you would still have to insulate it somehow.

TheBoyConor

You'd also have big problems with damp on the wall arising from condensation on the inside face.

Metric Tensor

TheBoyConor wrote: »

You'd also have big problems with damp on the wall arising from condensation on the inside face.

Huge!