How to repoint old brickwork

Video by Skill Builder. This walk-through is based on the video "Repointing Old Brickwork - Best Mix & Tools" by Roger Bisby of Skill Builder. Roger covers the mortar mix question in detail and demonstrates his technique for getting a clean, weathered finish. The discussion on why hard cement damages soft Victorian bricks is the most useful part if you have a period property.

1. Assess the joints and decide how much needs doing

Work around the wall in good daylight and probe the mortar joints with a screwdriver or pointing key. Anywhere the mortar crumbles out without much pressure, or where you can push the tool in more than about 5 mm, needs repointing. Note any areas where the mortar has dropped out entirely or where damp staining follows a joint line — those are priority sections.

It is common to find that the worst damage is at lower levels where rain splash and ground moisture are highest, and around window sills and cills where water sits. In East Kent, the coastal and estuarine air is harder on older mortar than inland areas, so do not be surprised if the joints on exposed elevations are worse than sheltered sides.

2. Rake out the old mortar to the correct depth

Use a plugging chisel and hammer, a mortar raking tool, or an angle grinder with a raking disc to remove the old mortar to a minimum depth of around 15–20 mm. Do not just scratch the surface — if the new mortar is too shallow it will not bond properly and will crack out again within a couple of years.

Work carefully near the brick faces. The bricks themselves should not be touched. If you are using a power tool, keep the disc centred in the joint and move steadily along — do not let it wander onto the brick edge. Afterwards, brush the joints out thoroughly with a stiff brush to remove dust and loose debris, then dampen the wall lightly with clean water. Dry joints will pull moisture out of the fresh mortar too fast and weaken it.

3. Choose the right mortar mix for the age of your wall

This is where most people make the mistake that causes long-term damage. For Victorian and Edwardian brickwork — which covers a large proportion of homes in Sandwich and the surrounding villages — the original mortar was lime-based. The bricks are relatively soft, and a modern OPC cement mortar is harder and less flexible than the bricks themselves. That means any movement in the wall gets absorbed by cracking through the brick face rather than through the joint, which is expensive to fix.

For pre-1920s brickwork, use a hydraulic lime mortar or a lime-sand mix. A typical mix is 1 part NHL 3.5 hydraulic lime to 2.5 parts sharp sand. For post-war brickwork with harder, more dense bricks, a 1:1:6 cement–lime–sand or 1:4 cement–sand mix is fine. If in any doubt, go softer rather than harder — you can always repoint again later, but you cannot uncrack a brick.

4. Mix the mortar and test the consistency

Mix small batches — enough for 20 to 30 minutes of work. Mortar that sits too long in the bucket starts to stiffen and loses workability. Add water gradually until the mix is stiff enough to hold its shape when you press a trowel into it, but still slides cleanly off the blade without crumbling. It should look and feel like stiff mashed potato.

Match the colour to the existing mortar as closely as you can. Most builder's merchants stock bagged lime mortars in buff, grey, and near-white tones. Hold a small sample against the wall when dry before committing to a full mix — mortar dries lighter than it looks when wet. A patchwork of obviously new pointing looks worse than the original crumbling joints.

5. Apply the mortar and work it into the joints

Load a small amount of mortar onto a pointing hawk and work it into the joints using a pointing trowel or a bucket trowel for the wider bed joints. Press the mortar firmly in to eliminate air pockets. Start with the vertical perpend joints, then do the horizontal bed joints. Work from the top of the area downward so that any dropped mortar falls onto unpointed wall, not fresh work.

Do not overfill the joints. The mortar should sit flush with the face of the brick or very slightly recessed — not built up proud. On exposed walls a slightly recessed or weather-struck profile sheds water better. On sheltered walls a flat flush finish is traditional and looks neat.

6. Finish and clean up while the mortar is still green

After about 30 to 45 minutes — when the mortar has firmed up but not fully hardened — go back over it with a jointing tool or the edge of a trowel to compact and smooth the surface. Then brush the joints lightly with a soft brush to close up the surface texture and remove any nibs of mortar. This is what gives pointing a proper, weatherproof finish.

Clean any mortar smears off the brick faces while they are still fresh — a damp sponge and gentle scrub works well at this stage. Once mortar has fully hardened, removing smears is much harder and may need an acid cleaner. Keep the new pointing damp for the first few days if the weather is dry and hot, and protect it from frost for at least a week. Mind you, in Kent in spring or autumn, a bit of light rain after completion is no bad thing — it slows the cure and helps the mortar strengthen.

When to call a handyman

Call Richard if the wall needs scaffolding to reach, if large areas of the house need repointing and you want it tackled properly in one visit, or if you are not sure whether the existing mortar is lime or cement. Using the wrong mix on an old property is genuinely damaging, and it is worth getting a second opinion before you start. He covers property maintenance work across Sandwich, Deal, Folkestone, and the wider East Kent area. Get in touch to discuss.