Can I just point over the old mortar?
The short answer is no, and the reason why explains most of what goes wrong with domestic repointing — including why overband pointing is worse than doing nothing.
- Difficulty
- beginner
- Time
- 10 min
- Read
- 4 min
- Safety
- caution
Short answer
No. New mortar smeared over sound or decayed old mortar has no depth and nothing to grip, so it shrinks off and drops out within a year or two. Worse, mortar smeared across the brick faces — overband or ribbon pointing — seals the face, traps water behind it, and blows the brick faces off. Rake out to at least twice the joint width.
Every year people repoint a wall by buttering new mortar over the existing joints, and every year it comes off. The diagram shows why in cross-section: a two- or three-millimetre skim has nothing behind it, no mechanical key and no thickness to resist shrinkage. And the version of this that spreads out across the brick faces does not just fail, it damages the wall.
Safety
Step by step
- Understand what depth does.Mortar packed into a recess at least twice as deep as the joint is wide has a mechanical key on three sides, enough thickness that shrinkage does not break the bond, and enough cover to weather. A skim over an old surface has none of those.
- Recognise overband or ribbon pointing.Mortar spread across the face of the bricks above and below the joint, so the joint lines look wide, raised and slightly wavy, and the bricks look recessed. Frequently found on Victorian terraces where somebody was paid by the day.
- Understand why overband is actively harmful.It creates a hard, wide, impermeable band across the wall face. Water still gets in behind it through the untouched decayed joint and then cannot evaporate out, so it sits against the brick. Frost then blows the brick faces off, and the damage is permanent.
- Check what you actually have before deciding to redo anything.Pointing that is merely weathered and slightly recessed does not need doing at all. Run a key along it — if it resists, leave it alone. Repointing sound joints is expensive, unnecessary and, done badly, harmful.
- Rake out properly where it does need doing.At least twice the joint width, square, with clean vertical faces against the brick and sound mortar at the back. Take out all the loose and decayed material, not just what falls out on its own.
- Use hand tools by preference.A plugging chisel and a lump hammer. Slower than a grinder and far less likely to cut into the bricks. The characteristic damage from grinder repointing is a wall where every joint has a saw cut into the brick above and below it, and it is permanent.
- Control the dust if you must use power.On long runs of hard cement mortar a raking disc may be the only realistic option. Use water suppression or on-tool extraction, an FFP3 mask, and keep away from the arrises.
- Remove existing overband carefully.It is worth taking off, but the removal is where brick faces get damaged. Work with hand tools, take it off in small areas, accept that some faces underneath will already be spalled, and consider getting a specialist in on a whole elevation.
- Brush, dampen, fill in layers and tool.Brush the joints out, wet the brickwork and let the surface water go, fill in two or three compressed layers, and tool at thumbprint firmness to the profile the rest of the wall has.
- Do not repoint the whole house because one elevation has failed.Pointing weathers unevenly, and the weather elevation usually goes first by decades. Repoint what needs it, and leave sound joints alone.
Questions people ask
Is it ever acceptable to point over old mortar?
Not on a wall you want to last. There is no depth for the new material to grip, and it fails. If the existing joints are sound, the correct action is to leave them alone rather than to skim them.
How deep should I rake out?
At least twice the joint width, so a 10mm joint is cut back at least 20mm, and further where the mortar behind is still soft. Square, not tapered.
Should I remove overband pointing that is already there?
Generally yes, because it traps water and damages the brick faces, but do it carefully and by hand. On a whole elevation of hard cement overband on soft brick, get a quote from someone who does this work regularly.
Can I use an angle grinder to rake out?
It is what a lot of people do and it is how a lot of walls are damaged. The disc cuts brick as readily as mortar, and a moment's slip leaves a permanent cut in the face. Hand tools are the default, and any power cutting needs water or extraction.