How to Tell If Your Brickwork Needs Repointing

Run the simple checks first

You do not need scaffolding or special tools to make a first assessment. Pick a dry day and walk around the house, paying particular attention to the walls that face the prevailing weather, which in the Cynon Valley usually means the south and west sides. Chimneys, parapets and anything above gutter level tend to fail first because they get soaked from more than one direction.

Take a key or a flat head screwdriver and gently drag it along a few mortar joints at different heights. Sound mortar will resist and leave barely a mark. If it crumbles into sand, flakes away or the tool sinks in more than a couple of millimetres without effort, that section is failing.

• Mortar that rubs away as loose sand or dust under your finger
• Gaps, cracks or missing chunks between bricks, especially under window sills
• Joints that have eroded back more than about 5 to 10 millimetres from the brick face
• Green algae or dark staining tracking along the joints, a sign they are holding water
• Damp patches or peeling paint on inside walls that match up with worn joints outside

Why valley weather is hard on mortar

Aberdare and the surrounding valleys see well over 1,300 millimetres of rain in a typical year, roughly double what parts of eastern England get, and much of it arrives as driving rain against exposed gable ends. Once mortar starts to open up, water gets into the joint, then winter frost freezes and expands it. Each freeze and thaw cycle pushes the joint apart a little more, which is why deterioration often speeds up once it starts.

There is also the age of the housing stock to consider. A lot of terraced homes around here were built between the 1880s and 1930s using lime mortar, which is softer and more breathable than modern cement. If a previous repair used a hard cement mix on old lime built walls, the mortar can trap moisture and force the brick faces to blow off instead, which is called spalling. If you can see bricks with their faces flaking away, that is worth a professional look rather than another quick patch.

Failing pointing or something more serious?

Not every crack means repointing. Fine, crumbling joints with the bricks themselves sound and square is the classic repointing job. But cracks that run through the bricks as well as the joints, stepped cracking that follows the mortar lines diagonally up a wall, or walls that bulge or lean can point to movement in the structure, and repointing alone will not fix those. In that situation get a builder or surveyor to look before any cosmetic work is done.

A quick interior check helps too. Musty smells, damp plaster or black mould concentrated on an external wall, particularly a chimney breast, often traces back to saturated joints outside. Repointing will stop more water getting in, but soaked masonry can take months to dry out fully afterwards, so the sooner it is caught the better.

What good repointing involves and rough costs

Proper repointing means raking or grinding the old mortar out to a depth of around 15 to 20 millimetres, cleaning the joint, then packing in new mortar matched to the original in strength, colour and finish. On older valley terraces that usually means a lime based mix. The shortcut to avoid is smearing new mortar over the top of failed joints, sometimes called buttering. It looks tidy for a year or two, then falls off.

Costs depend heavily on access, wall condition and mortar type, so treat any figure as a guide only. Small patch repairs might start from a few hundred pounds, a single elevation of a typical terraced house often lands somewhere in the range of 1,000 to 2,500 pounds, and a whole detached house or work needing scaffolding will be more. Chimneys cost proportionally more because of the access involved. A written quotation after someone has actually inspected the wall is worth far more than any online estimate.