Repointing looks simple: rake out the old mortar, push in some new. Plenty of London homeowners have a go, and on a small garden wall it can be a perfectly sensible weekend job. On a Victorian terrace facade, though, the wrong mortar or a careless grinder can cause damage that costs far more to put right than the repointing would have.
Repointing means removing the outer 20 to 30mm of failed mortar from the joints, brushing and dampening them, then refilling with fresh mortar and finishing the joint to match the original profile. Done properly, it should last 40 to 60 years. The raking out is the slow, unglamorous part and it is where most DIY jobs go wrong, because the temptation is to speed things up with an angle grinder.
A grinder in inexperienced hands will nick the brick faces, widen the joints and permanently change the look of the wall. On the narrow joints typical of older London stock brick, often under 10mm, there is very little margin for error. Hand raking with a plugging chisel or a mortar rake is slower but far safer for the bricks.
Most homes in North London built before the 1930s were pointed with lime mortar, which is softer than the bricks and lets moisture escape through the joints. Bagged cement mortar from a DIY shed is much harder and effectively waterproof. Use it on old brickwork and moisture gets trapped behind it, then in winter the freeze and thaw cycle blows the faces off the bricks. Spalled brick faces cannot be repaired, only cut out and replaced.
If your house is Victorian or Edwardian, you almost certainly need a lime-based mix, typically an NHL 3.5 hydraulic lime with well-graded sharp sand at around 1:2.5 to 1:3. Post-war and modern brickwork usually suits a cement and lime mix instead. Matching the colour and joint style, whether flush, weather struck or bucket handle, matters just as much if you do not want the repair to stand out.
There is a genuine middle ground here. A low garden wall, a few metres of failed joints you can reach from the ground, a shed or outbuilding: these are realistic DIY projects if you are patient and willing to practise your joint finish on an inconspicuous spot first. Expect to manage roughly 1 to 2 square metres a day working carefully by hand, so budget your time honestly.
The jobs to leave to a professional are anything at height needing scaffolding, whole elevations, chimney stacks, anything on a listed building or in a conservation area, and any wall showing stepped cracking, bulging or damp inside. Those symptoms often point to movement or a failed damp course rather than simple mortar erosion, and repointing over them just hides the problem. Scaffolding alone for a terrace front elevation typically runs to several hundred pounds, which changes the economics of doing the rest yourself.
As a rough guide, professional repointing in London tends to fall between £60 and £120 per square metre, with lime work at the upper end because it is slower and needs protection while it cures. A typical terrace front elevation might come in somewhere between £1,500 and £4,000 depending on access, joint depth and mortar type. These are ballpark figures, not quotes; the state of the existing joints and whether any bricks need replacing make a real difference.
Timing matters too. Lime mortar should not go in when frost is expected or in baking direct sun, so spring and autumn are the best seasons for this work in the UK. If you do tackle a small area yourself, work in the shade where possible and keep the new joints damp for a few days so the mortar cures rather than dries.
Run a key along a joint: if mortar crumbles out easily, has eroded back more than about 10mm, or has visible gaps and plant growth, it is due. Isolated soft patches can often wait; widespread erosion lets water in and should not be left through another winter.
No. New mortar smeared over old joints, sometimes called bagging or buttering, has nothing to key into and will fall out within a couple of years. Joints need raking out to a depth of at least twice their width, usually 20 to 30mm, before repointing.
Usually not for ordinary repointing, but listed buildings need listed building consent for works affecting character, and some conservation areas have Article 4 directions covering front elevations. A quick call to your borough's conservation officer before starting can save serious trouble.
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