Re pointing

[AlexG]

Hi all, we about to renovate our house. It’s a Methodist chapel, originally built in the 1870’s of Bath stone, and converted to a house in the 1970’s. The walls are round 40 cm thick. I’ve been told that we can probably help the walls breath better if we repoint the them with lime. See images. There is some spalling and what appears to be cement repairs. It appears to be a real mix of pointing materials done over the years… some of it is very dark and almost looks like mastic, some is light grey and some darker with light and dark specs in.

Any advise would be welcome on:
- what the current pointing is; cement or lime?
- is the repointing something that could be tackled by a complete novice (trying to save money)
- is there any general advise on how deep to go when removing the current pointing? Eg should I keep digging out the pointing until I see a change in material, or stop after a certain distance? Obviously I don’t want to cause the stone to become unstable.

Many thanks
Alex

 

[aockenden]

All those pics appear to be cement pointing. Yes it can be done by a novice with some basic information and the right attitude. When scraping out the existing, you definitely want to get all the modern cement out of the joint (otherwise, what's the point of the whole exercise), and probably want to get back to the original bedding mortar. Hopefully it'll be a few CM deep of cement with the original bedding mortar (typically lime or clay) directly behind. I wouldn't repoint a joint much less than 1 inch deep.

 

[Stevers]

That's quite a patchwork quilt of repairs, most of it very neatly done in very fine joints on stone that looks to be in excellent condition. There's lots of scope for damage to that lovely stone trying to get it out, so if there isn't a problem I'd just keep an eye on it, or perhaps concentrate your money and time on what you consider to be the most unsightly bits. In the early days here I used a cement lime mortar for patch repointing near Oolite quoins (Doulting rather than Bath Stone), and there's no sign that's it been any sort of problem to those after twenty years.

 

[eon]

Hi all, we about to renovate our house. It’s a Methodist chapel, originally built in the 1870’s of Bath stone, and converted to a house in the 1970’s. The walls are round 40 cm thick. I’ve been told that we can probably help the walls breath better if we repoint the them with lime. See images. There is some spalling and what appears to be cement repairs. It appears to be a real mix of pointing materials done over the years… some of it is very dark and almost looks like mastic, some is light grey and some darker with light and dark specs in.

Any advise would be welcome on:
- what the current pointing is; cement or lime?
- is the repointing something that could be tackled by a complete novice (trying to save money)
- is there any general advise on how deep to go when removing the current pointing? Eg should I keep digging out the pointing until I see a change in material, or stop after a certain distance? Obviously I don’t want to cause the stone to become unstable.

Many thanks
Alex

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Pointing is very novice friendly. But you do need to take the time and care to ensure that the lime doesn’t cure too quickly. Keeping it damp and draping hessian over it for 5-10 days depending on conditions is advisable. It takes a bit of planning but absolutely worth it. Time of year is a consideration too, avoid frost, it’s recommended to only work when temperatures are above 5 degrees.

As for removing the existing cement mortar a plugging chisel is really useful for this. Once you have removed a small section work back towards that void so the mortar has somewhere to break away to. I wouldn’t be tempted to use a grinder as you could really damage that lovely stonework.

Also your choice of sand is important, washed sharp sand is better than your typical plastering sand.

I’ve being doing lots of pointing and rebedding of damaged bricks all over our house, inside and out. It’s very methodical and rewarding work! Good luck

 

[eon]

That's quite a patchwork quilt of repairs, most of it very neatly done in very fine joints on stone that looks to be in excellent condition. There's lots of scope for damage to that lovely stone trying to get it out, so if there isn't a problem I'd just keep an eye on it, or perhaps concentrate your money and time on what you consider to be the most unsightly bits. In the early days here I used a cement lime mortar for patch repointing near Oolite quoins (Doulting rather than Bath Stone), and there's no sign that's it been any sort of problem to those after twenty years.

Yes I was going to say this too, some of the above looks really good. So unless it’s causing serious damp issues I would be inclined to leave any that is sound and just make repairs in lime where needed.

 

[AlexG]

Thanks for all of the replies. Very helpful. A stone mason and an independent building heating / ventilation consultant said that the current pointing will be contributing to the issues we are having with mold.