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Welcome to the Bunnings Workshop community @jasp. It's terrific to have you join us, and many thanks for your question about repointing a stone wall.
To repoint your stone wall, start by raking or chiselling out the loose and crumbling mortar to a decent depth, usually around 15–25mm, so the new mortar has a solid surface to grip into. Clean out any dust or debris with a stiff brush, and lightly dampen the joints before applying fresh mortar. If any stones are loose, bed them back securely in mortar before repointing around them.
A good general-purpose option is a mortar made from 1 part cement, 1 part hydrated lime, and 6 parts sharp or “brickies” sand. Bagged Mortar mixes make this simple. Once the mortar is packed firmly into the joints, smooth it off neatly and allow it to cure slowly, keeping it damp and protected from strong sun or wind so it doesn’t crack. Excess mortar can be brushed off the stone surface once it begins to dry.
For materials, I'd grab a couple of bags of mortar mix, which can be coloured with oxide, and you’ll also want basic masonry tools like a pointing trowel, plasterers hawk, and stiff brush to get the job done.
Please let me know if you have any questions.
Mitchell
Hi @jasp,
Concrete and mortar are closely related but behave differently, so it’s a good question.
Concrete contains coarse aggregate (small stones or gravel), which makes it strong in bulk applications like slabs or footings, but it’s not ideal for repointing because the larger aggregate makes it difficult to pack tightly into narrow joints and doesn’t bond as well to stone.
Mortar, on the other hand, is formulated specifically for bedding and pointing masonry. It uses sand (without large stones) and lime for flexibility and adhesion, allowing it to be worked neatly into joints, grip the sides well, and permit the wall to move slightly without cracking.
So while concrete would “work” in the sense that it will set, it’s not the right choice for repointing stonework. I’d recommend swapping it for a bagged mortar mix. You’ll find the job easier, the finish neater, and the repair more durable in the long run.
Mitchell
