Advice Needed on Repointing Stone Work

[Jake215]

Hi Everyone,

I'm seeking some advice on what to do after knocking off the cement render on the side return of my house.

The wall was originally rendered with cement, like the other houses in my row. However, most of the renders are in poor condition, and mine was by far the worst.

I really like the stonework underneath the render and would love to have it repointed. Here is my plan:

1. Finish knocking off the remaining cement render.
2. Rake out the old mortar.
3. Either sandblast or power wash the stonework.
4. Repoint the stonework.

This is where I start feeling unsure about the process.

• Can I simply repoint the stonework, or does it need to be rendered again?
• If repointing is the way to go, should I be using lime mortar? I prefer to use lime, but the inside of the house has insulating plasterboards dot and dabbed onto a scratch coat with multi-finish. I’m concerned whether using lime on the outside will be effective given the interior condition.

Additionally, if I decide to point with lime, can I use a pre-mixed hydraulic lime mortar like the EcoRight Pre-Mixed Hydraulic Lime Mortars, or should I opt for a more traditional mix like the one from Heritage Cob and Lime?

Thanks in advance for your advice!

Jake

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[malcolm]

Using lime for repointing would be a very good idea if the interior isn't breathable. Water is always going to get in and it's a good idea to let it out again before the wall gets damp. Cleaning the stones probably won't be necessary - even with bits of cement still stuck to them they'll look fine when repointed. If you do clean do it before digging out loose mortar.

The stonework looks a little untidy so it was probably originally rendered but there is no need to render if you prefer the look of the stone.

For the mix I tend to mix my own so don't know much about the pre-mixes. I use sharp sand mixed 50:50 with builders sand and NHL 3.5 from the local builders merchant. For soft stones like limestone lime putty would be better than NHL 3.5. Local sand often has the advantage of matching the colour of whet was used originally. They don't transport sand very far so it ought to be local sand you are buying.

 

[Jake215]

Using lime for repointing would be a very good idea if the interior isn't breathable. Water is always going to get in and it's a good idea to let it out again before the wall gets damp. Cleaning the stones probably won't be necessary - even with bits of cement still stuck to them they'll look fine when repointed. If you do clean do it before digging out loose mortar.

The stonework looks a little untidy so it was probably originally rendered but there is no need to render if you prefer the look of the stone.

For the mix I tend to mix my own so don't know much about the pre-mixes. I use sharp sand mixed 50:50 with builders sand and NHL 3.5 from the local builders merchant. For soft stones like limestone lime putty would be better than NHL 3.5. Local sand often has the advantage of matching the colour of whet was used originally. They don't transport sand very far so it ought to be local sand you are buying.

Amazing, thanks Malcom. Really helpful advice, thanks for taking the time.