In short: use lime mortar on older, solid-wall properties (roughly pre-1919) with soft handmade bricks or stone, because it is soft and lets the wall breathe. Use a cement-based mortar on modern cavity-wall houses with hard machine-made bricks. Putting hard cement on a soft old wall traps moisture and cracks the brick faces — the single most common repointing mistake.
When people ask whether to repoint in lime or cement, they usually expect it to be about the finish or the colour. It is not — it is about how the wall handles moisture. Get the mortar type wrong and you can do more harm than good, so it is worth understanding which your house actually needs before any raking out starts.
Why the mortar type matters more than the finish
Mortar is meant to be the sacrificial part of a wall. It should be slightly softer than the brick or stone, so that when moisture and weathering take their toll it is the joint that erodes — not the masonry. When the mortar is harder than the surrounding brick, that logic reverses: the brick becomes the weak point, and the faces start to crumble instead.
Lime and cement behave very differently here. Cement sets hard within hours and is largely waterproof. Lime is softer and porous: it lets moisture move through the joint and evaporate, and it slowly hardens over weeks by absorbing carbon dioxide from the air. On the right building, each is the correct choice. On the wrong one, cement in particular causes trouble.
How to tell which your house needs
A few quick checks point you in the right direction:
- Age: built before roughly 1919? Assume lime unless proven otherwise. Built from the 1930s on with cavity walls? Usually cement.
- Wall construction: solid walls (one thick leaf, headers and stretchers on show) lean lime; cavity walls lean cement.
- Brick or stone type: soft, handmade or stock bricks and natural stone want lime; hard, uniform machine-made bricks are fine with cement.
- The existing mortar: pale, sandy and easily scratched suggests lime; very hard and grey suggests cement — though cement may have been wrongly added to an older wall.
If those signals disagree with each other, that is exactly when it is worth having someone look before committing.
When lime mortar is the right choice
Lime is the correct mortar for most period and traditionally built properties. It keeps the wall breathable, it flexes with slight movement instead of cracking, and it is soft enough to protect old bricks and stone. On listed buildings and in conservation areas it is often a requirement, not just a preference. Lime comes in different forms — hydraulic lime (NHL) and lime putty — and the right one depends on exposure and the original build, which is a detail worth getting specified correctly.
When cement mortar is the right choice
For most houses built from the 1930s onward — cavity walls, harder machine-made bricks — a cement-based mortar is appropriate and is what the wall was built with. It is stronger, sets quickly and stands up well to exposure. The key is matching the mix and colour to the existing joints so a repointed patch does not stand out against the rest of the wall.
What goes wrong when cement is used on an old wall
This is the mistake that costs owners of older homes the most. Hard cement pointing seals the joints, so moisture that used to escape through the mortar is driven into the brick instead. Through winter freeze-thaw cycles the brick faces blow and flake — spalling — and damp can show up inside. Because the damage is to the bricks rather than the joints, putting it right means far more than a repoint. Using the correct soft mortar from the start avoids the whole problem.
Can you tell from the look?
Often, yes. A correct lime joint tends to be slightly recessed and textured, sitting just back from the brick face. Hard, smooth, raised “ribbon” pointing proud of the brick is a classic sign of cement applied over an older wall. The finish is also part of matching the work to the rest of the house — see our guide on matching brickwork, and the difference between pointing and repointing.
The cost difference
Lime repointing usually costs a little more than cement — roughly £10–£20 per square metre more — because the materials cost more and the work is more specialist. For full figures see our guides on lime mortar repointing cost and general repointing costs. Spending a bit more on the correct mortar is almost always cheaper than repairing spalled brickwork later.
This guide is general advice for UK homeowners; the right mortar for your wall depends on its age, construction and condition, which are best confirmed on site.
Getting it checked
If you are not sure which mortar your brickwork needs, we can tell you quickly. If your property is in Hampshire, Berkshire or Surrey, send us the details — the age of the house and a photo of the joints — and we will come and look before any work is priced.
Frequently asked questions
Should I use lime or cement mortar for repointing?
It depends on the age and construction of the wall. Older, solid-wall properties (roughly pre-1919) with soft handmade bricks or stone should be repointed in lime mortar, which is soft and breathable. Modern cavity-wall houses with hard machine-made bricks are usually repointed in a cement-based mortar. Matching the original mortar is the safe rule.
How do I know if my house has lime mortar?
Lime mortar tends to be softer, paler and slightly sandy, and you can often scratch it with a coin or a screwdriver. It is usual on properties built before about 1919, on solid (non-cavity) walls, and under soft or handmade bricks and stone. If the existing joints are very hard and grey, that is more likely a cement mortar, which may itself have been added later.
What happens if you use cement mortar on an old house?
Cement mortar is harder and less breathable than the soft brick or stone around it. Moisture that would once have evaporated through the joints is instead pushed into the masonry, and as it freezes and thaws the brick faces can crack and flake away, which is called spalling. On a period property, hard cement pointing can quietly cause damage that is expensive to put right.
Can you repoint over cement with lime?
You should not simply point lime over existing cement. If a period wall was wrongly pointed in cement, the cement is normally raked out carefully first and the joints repointed in a suitable lime mortar. Raking out hard cement without damaging soft old bricks is skilled work and is best assessed on site.
Is lime mortar more expensive than cement?
Usually yes. Lime mortar materials cost more and the work needs specialist skill and care, so lime repointing typically costs around 10 to 20 pounds per square metre more than cement. It is a false economy to use cement on a period wall to save money, because the repair bill later is far higher.
What age house needs lime mortar?
As a rule of thumb, properties built before about 1919, and many up to the 1930s, were built with lime mortar and solid walls, and should be repointed in lime. Houses built from the 1930s onwards with cavity walls and harder bricks are generally fine with a cement-based mortar. Age is a guide, not a guarantee, so the brick and existing mortar should be checked too.