How to repoint crumbling brick mortar on your house

Crumbling joints can make an otherwise sound brick wall look neglected, but deteriorated mortar can also allow wind-driven rain into the masonry. Repointing replaces the failed outer mortar without rebuilding the entire wall. Done carefully, it improves weather resistance and helps prevent loose bricks, damp patches and frost-like surface damage caused by trapped moisture.

The job is manageable for a careful homeowner when the damage is shallow and limited to individual joints. Australian houses, however, use several brick and mortar systems, from older solid masonry in Adelaide and Melbourne to modern brick veneer across new suburbs. Before reaching for a grinder, identify the mortar, check the wall’s condition and make sure the repair will not trap water behind the bricks.

Check whether repointing is suitable

Inspect the wall on a dry day. Sound mortar should be firm when scratched with a screwdriver, while failed mortar may be powdery, cracked, recessed or soft enough to remove by hand. Look for loose bricks, stepped cracks that run through several courses, bulging walls, rust stains above openings and dampness inside the house. These signs can indicate movement, failing lintels or water entry beyond a simple joint repair.

A small test area is worthwhile. Remove mortar from a short horizontal and vertical joint, preferably in an inconspicuous spot, and examine its colour, texture and hardness. If the surrounding brick faces crumble, the wall leans, or cracks are wider at one end, stop and contact a qualified bricklayer or structural engineer. In a heritage-listed terrace or cottage, check with the local council before altering the façade; some councils require approval for work that changes historic masonry.

Choose a compatible mortar mix

The new mortar should be slightly softer and more permeable than the brick. That allows the joint to absorb small movements and release moisture rather than forcing water through the brick face. Very hard cement-rich mortar can damage older, softer bricks, particularly in heritage homes around inner Melbourne, Hobart or Adelaide. Lime mortar may be appropriate for old solid masonry, while many post-war homes use a cement-lime-sand blend.

Do not guess by colour alone. Take a small sample to a specialist masonry supplier, and match the aggregate size as well as the shade. Products sold through Australian hardware chains such as Bunnings can be convenient, but a premixed repair mortar is not automatically suitable for every wall. Read the manufacturer’s instructions, follow the specified water ratio and avoid adding extra cement simply to make the mix seem stronger.

Prepare the joints and work area

Protect windows, garden beds, paving and nearby paintwork with drop sheets. Wear safety glasses, gloves and a properly fitted P2 respirator, especially if using power tools on old mortar. Remove wall-mounted fittings where practical, and check that electrical cables, plumbing and gas lines are not hidden in the work zone. A small pointing chisel and club hammer give better control than a large demolition tool.

Rake out loose mortar to a depth of about two to two and a half times the joint’s height, commonly around 20 to 25 millimetres. Work from the top down and avoid striking the brick arrises, which are the exposed corners of each brick. A grinder with a narrow diamond blade can speed up extensive work, but it produces dust and can widen joints quickly. For a small patch, hand tools are usually safer.

Brush the joint clean and rinse away dust with a gentle stream of water. Do not leave the cavity flooded. The bricks should be damp but not dripping when fresh mortar is applied. This pre-wetting prevents dry masonry from pulling water out of the mix too rapidly, a useful precaution during hot Queensland weather or a dry, windy summer in Western Australia.

Pack and finish the replacement mortar

Mix only an amount that can be used before it begins to stiffen. Press the mortar firmly into the back of the joint with a pointing trowel, filling deep areas in layers rather than creating a hollow skin over the surface. Complete the vertical joints first and then the horizontals, or work in small manageable sections. Keep the mortar off the brick face because staining becomes harder to remove as it cures.

When the mortar is thumbprint firm, tool it to match the existing profile. A flush finish suits some modern brickwork, while a slightly recessed or weather-struck profile may be appropriate elsewhere. The joint should shed water without forming a ledge that holds it. Brush away crumbs gently once the mortar has tightened, and do not smear wet mortar across the brick faces.

Protect new work from strong sun, rain and overnight cold for several days. Lightly misting the joints can slow drying, but avoid washing them out. In much of Australia, intense ultraviolet exposure and sudden temperature changes can dry a repair too quickly, while coastal areas add salt-laden air that can accelerate surface deterioration. Follow the mortar manufacturer’s curing guidance rather than relying on a generic timetable.

Deal with moisture before sealing the wall

Repointing will not solve a leaking gutter, blocked downpipe, failed flashing or rising damp. Check roof drainage, window sills, weep holes and the ground level beside the wall first. Keep soil, mulch and paving below the damp-proof course, and never cover weep holes in brick veneer. Where moisture has already entered a room, dry the area thoroughly and address the source before closing the joints; guidance on preventing mould growth is also useful after a serious water event.

Avoid painting or applying a waterproof coating to sound, breathable brickwork simply because the joints look tired. Film-forming sealers can trap moisture, causing blistering, salt deposits and spalling bricks. If a specialist recommends a treatment, ask whether it is vapour permeable, compatible with the masonry and reversible. A brick wall needs a clear path for moisture to escape.

Know when a bigger repair is needed

A few isolated joints can be repaired over a weekend, but widespread failure requires a methodical assessment. If mortar is missing across several elevations, bricks are loose, or water appears around windows after rain, have a bricklayer inspect the wall. A professional can identify movement, replace damaged bricks, repair lintels and match a traditional mortar more accurately than a general patching product.

Vegetation can contribute to masonry problems when roots disturb footings or dense growth keeps walls damp. Before planting a large tree near the house, check its mature height and root spread, and consider local service clearances. Advice on planting near power lines is particularly relevant in Australian suburbs, where overhead wires remain common and council or utility restrictions may apply.

After the repair, inspect the joints every year, especially after intense storms, prolonged wet seasons or nearby building work. Take photographs of suspicious cracks so you can track whether they are changing. Australian homeowners can also use broader home maintenance guidance to connect masonry checks with gutter cleaning, pest prevention and other seasonal tasks.

A sound repointing repair is built on restraint: remove only failed mortar, use a compatible mix, keep the brick faces intact and let the wall breathe. For a small patch, clean the joints, dampen the masonry, pack the mortar firmly and cure it slowly; for movement, dampness or extensive damage, arrange a qualified inspection before the problem spreads.