Signs Your Brickwork Needs Repointing: A London Guide

The obvious signs: crumbling, cracked or missing mortar

The simplest test costs nothing. Run a key or flathead screwdriver along a mortar joint at chest height on a sheltered wall, then compare it with a joint low down on a wall that takes the weather, typically the south or west face. If the mortar scratches out easily as dust or sand, it has lost its binder and is no longer doing its job.

Look also for joints that have visibly receded. On older North London terraces, original lime mortar often erodes back 10 to 15mm from the brick face over decades. Once the joint sits that far back, rainwater pools on the exposed brick edge instead of shedding off, and frost damage follows.

• Mortar that crumbles or powders when scraped with a key
• Joints recessed more than about 10mm from the brick face
• Hairline cracks running along the joints, especially around windows and doors
• Whole sections of mortar missing, often near the damp course or below window sills

Damp patches inside are often a pointing problem

A surprising number of internal damp complaints trace back to failed pointing rather than a leaking roof or rising damp. When joints are open, wind-driven rain gets pulled into the wall and shows up inside as damp patches, peeling wallpaper or black mould, usually on the wall that faces the prevailing weather.

If the damp patch appears or worsens after heavy rain and sits at random heights on an external wall, suspect the pointing before paying for a damp survey. Rising damp, by contrast, tends to show as a tide mark within a metre or so of the floor. It is worth ruling out the cheaper fix first.

Spalling bricks: the sign you have left it too long

Spalling is when the face of the brick blows off, leaving a crumbly, pitted surface. It happens because water trapped behind hard or failed mortar freezes and expands inside the brick. London stock bricks, common across Victorian and Edwardian terraces, are soft and particularly prone to this.

Once bricks spall, repointing alone will not fix them. Individual bricks can be cut out and replaced, but matching weathered yellow stocks is fiddly and adds cost. This is why the standard advice is to repoint when the mortar fails, not when the bricks start failing too. A handful of spalled faces near the ground is a warning; whole patches of blown brickwork means the wall has been drinking water for years.

White staining and previous bad repairs

Efflorescence, the white powdery bloom on brick faces, is salt carried out of the wall by moisture. A little on new brickwork is normal and washes off. Persistent or spreading efflorescence on an older wall tells you water is moving through the masonry, and open joints are the usual entry point.

Also look for earlier repairs done in hard cement mortar, which often show as grey, proud, slightly shiny joints on an otherwise lime-built wall. Cement pointing on soft brick traps moisture and forces it out through the brick face, accelerating spalling. If a previous owner has patched a Victorian wall with cement, that pointing may need raking out and redoing in a lime mix even if it looks intact.

What repointing involves and roughly what it costs

Proper repointing means raking or grinding the old mortar out to a depth of at least twice the joint width, usually 15 to 20mm, then refilling with a mortar matched to the age and softness of the brick. For most pre-1930s London housing that means a lime-based mix, not a modern cement mortar. Anyone quoting to simply smear new mortar over the old joints is offering a cosmetic job that will fail within a few years.

Costs vary with access and condition, but as a rough guide expect somewhere in the region of £40 to £75 per square metre in London, with scaffolding extra if the work goes above the first floor. A single elevation on a typical terrace might run from £1,500 to £4,000 or more depending on height, joint condition and mortar type. Small isolated patches can often be done for a few hundred pounds, which is exactly why acting on early signs pays off.