If your house was built before about 1919, its walls were almost certainly laid and pointed in lime mortar, and repointing them in hard cement mortar is one of the most common ways older brick and stone gets damaged. The rule conservation bodies agree on is simple: the mortar should be slightly weaker and more permeable than the brick or stone around it. This guide explains why, how to tell what you have, and how repointing brick and stone should actually be done.
What is pointing, and why does it matter?
Pointing is the outer face of the mortar in the joints between bricks or stones. Behind it is the bedding mortar the wall was built with. Pointing keeps the worst of the weather out of the joints, but in an older solid wall it has a second job that is easy to miss: it is meant to be the sacrificial part of the wall.
Older solid walls have no cavity. Rain soaks into the outer face and dries out again, mostly through the joints. Lime mortar is soft and porous, so moisture, salts and frost do their damage in the mortar rather than in the brick or stone. Every few decades the joints weather back, you rake them out and repoint, and the masonry itself survives. The Society for the Protection of Ancient Buildings (SPAB) describes exactly this: lime pointing erodes in preference to the masonry and so protects it.
Lime mortar vs cement mortar: what’s the difference?
| Lime mortar | Cement mortar | |
|---|---|---|
| Hardness | Softer than most old brick and stone | Often harder than the masonry |
| Permeability | Lets moisture move and evaporate | Much less permeable |
| Flexibility | Tolerates slight movement; fine cracks can self-heal | Rigid; cracks along the joint edge |
| What fails first | The mortar (cheap to renew) | The brick or stone face (expensive, often irreversible) |
Modern cavity walls are designed around cement mortar and hard, dense bricks, so cement is the right choice there. The problem only arises when cement goes into a wall that was built to work with lime.
Why cement pointing damages older brick and stone
When a soft, porous wall is repointed in hard, dense cement, the roles reverse. The mortar is no longer the weakest, most porous part of the wall, so:
- Moisture dries out through the masonry instead of the joints. Water and dissolved salts are drawn to the edges of each brick or stone.
- Frost and salts attack the face of the masonry. The outer skin of the brick or stone flakes or crumbles (called spalling), often leaving the cement standing proud like a grid of ridges.
- The joint cracks at the edges. Rigid cement can’t move with the wall, so hairline gaps open between mortar and masonry. Rain gets in but can’t dry out quickly, which feeds penetrating damp inside.
Historic England’s repointing guidance identifies unsuitable repointing as among the most frequent causes of damage to the character and fabric of historic buildings. SPAB’s guidance on inappropriate cement pointing makes the same point about pre-1919 walls.
The Yorkshire stone terrace angle
Across West Yorkshire and the Pennine towns, a huge proportion of older housing is solid sandstone and gritstone: stone terraces, back-to-backs, weavers’ cottages and farmhouses. Many have been repointed in cement at some point in the last fifty years, sometimes in thick ribbon or strap pointing that stands out from the face of the stone.
Combine that with Pennine rain driven against exposed elevations and you get a familiar pattern: decaying stone faces, damp patches on the inside of the worst-exposed wall, and owners told they need a damp-proof course when the real problem is the wall’s ability to dry out. Our guide to telling rising, penetrating and condensation damp apart explains why that diagnosis matters.
Not every sandstone suits every lime. Conservation guidance notes that some sandstones respond better to a mildly hydraulic lime than to a pure, non-hydraulic one, which is one reason repointing stone isn’t a one-recipe job.
How to tell whether your pointing is lime or cement
You can usually get a good idea without testing:
- Colour. Lime mortar tends to be off-white, cream or buff, often with small white lumps of lime. Cement mortar is typically mid to dark grey.
- Hardness. Lime mortar can usually be scratched with a key or a nail. Cement mortar can’t, or only with effort.
- Profile. Cement repointing is often smeared over the stone edges, or raised in a ridge (strap pointing). Original lime pointing is normally flush or slightly recessed.
- What’s failing. If the masonry is crumbling around sound, hard mortar, the mortar is too strong. If the mortar has eroded back but the brick or stone is sound, the wall is behaving as it should.
Where it matters, for example on a listed building or a large project, a mortar sample can be analysed to match the original mix.
When does a wall actually need repointing?
Less often than many people are told. SPAB’s advice is that repointing is premature until the mortar has weathered back to a depth roughly equal to the joint width, or is genuinely loose. Patchy erosion on one exposed elevation doesn’t mean the whole house needs doing.
Signs that repointing (or putting right previous repointing) is needed:
- mortar recessed deeper than the joint is wide, or crumbling out when touched;
- open joints letting rain in, especially on chimneys, gables and parapets;
- cement pointing with cracks along its edges, or masonry spalling around it;
- damp patches on the inside face of solid walls after wet weather, with no plumbing cause.
Our damp checker can help you think through what a damp patch on a solid wall is likely to mean.
How repointing should be done
Good repointing is slow, careful work. The key points from Historic England and SPAB guidance:
- Rake out by hand, not with an angle grinder. Grinders widen the joints and chip the arrises (edges) of brick and stone. Joints are usually raked to around twice their width in depth.
- Remove cement carefully, or not at all. Hard cement can be hard to remove without damaging soft masonry. Sometimes the least harmful option is to leave sound cement and deal with it later.
- Choose a lime mortar matched to the masonry and exposure. That might be a non-hydraulic lime for soft brick in sheltered spots, or a natural hydraulic lime (graded NHL 2, 3.5 or 5) for more exposed work. The sand should match the original in colour and texture.
- Damp the joints first so the wall doesn’t suck the water out of the new mortar.
- Finish flush or slightly recessed. Not ribbon, strap or heavily struck joints.
- Protect the work. Lime needs protection from frost, rain and fast drying from sun and wind. SPAB notes that many failures happen because the weather was ignored; avoiding winter repointing is wise.
Ask any contractor what lime they intend to use, how they will rake out, and how they will protect the work. A vague answer is a warning sign.
What does repointing cost?
We don’t publish figures for contractors’ work, because the price depends on things that vary hugely from house to house:
- Access (scaffold is often the biggest single cost on a terrace or gable);
- how much cement has to come out, and how carefully;
- joint width and stone type, since wide joints in rubble stone take far more mortar and time than fine brick joints;
- the area involved, and whether only the worst elevations need doing;
- listed building or conservation area requirements.
Getting the diagnosis right first usually saves money. Repointing a whole house when one elevation and a chimney need attention is a common waste.
Is cement pointing on a house I’m buying a problem?
Usually it’s a maintenance issue rather than a reason to walk away. But it’s worth knowing about, because the fix (careful removal and lime repointing) costs more than a standard repoint, and any damp it has caused needs sorting at the source. On older solid-walled houses we normally recommend a Home Survey Level 3, which looks closely at walls, pointing and damp and explains the likely causes. If the property is listed, see our guide to surveying a listed building, since repointing a listed building in the wrong material can be unauthorised work.
Getting independent advice
If you own an older house and have been told it needs repointing, a damp-proof course or both, an independent view is worth having before you commit. Our building advice service looks at what the wall actually needs. We sell no repairs or treatments, so the advice is only about the building. Get in touch with the address and a few photos of the walls.
Sources and further reading
- Repointing Brick and Stone Walls: Guidelines for Best Practice — Historic England
- Repointing — Society for the Protection of Ancient Buildings
- Inappropriate cement pointing — Society for the Protection of Ancient Buildings
- Pointing with lime — Building Conservation Directory
- Damp in historic buildings — Historic England