Damaged bricks are one of the most common external maintenance issues in UK housing, particularly in Victorian and Edwardian stock. The repair approach depends entirely on what has caused the damage: surface spalling can often be addressed with repointing or a brick slip, while structural cracking needs professional assessment before any physical work begins.
Most cosmetic brick repairs are within reach of a competent DIYer. Structural repairs, or any work on a listed building, must involve qualified tradespeople and, in some cases, statutory consent.
What Causes Brick Damage?
Understanding the cause is essential before choosing a repair method — fixing the symptom without addressing the root cause will mean the problem returns.
Spalling is the most common form of brick deterioration in the UK. The face of the brick flakes or crumbles away, typically caused by water penetrating the brick and freezing in cold weather. The freeze-thaw cycle expands the water and forces the surface apart. Spalling is particularly common on softer, more porous Victorian bricks, especially on north-facing or exposed elevations.
Sulphate attack occurs when soluble sulphates in the mortar or the bricks themselves react with moisture over time. The mortar expands, causing the horizontal (bed) joints to crack and the brickwork to bow outward. It is most commonly seen in chimneys and older gable walls.
Impact damage — from vehicle strikes, scaffolding poles, or accidental knocks — produces localised cracking or chipping. The brick structure is usually sound; only the affected units need replacing.
Structural movement causes stepped diagonal cracking through mortar joints (usually settlement) or horizontal cracking at lintel level (often lintel failure). These patterns differ significantly from surface weathering and always require investigation by a structural engineer before any cosmetic repair is attempted. Filling structural cracks with mortar without addressing the cause is a waste of time and money.
Diagnosing the Problem: Repoint or Replace?
A quick assessment will help you decide which repair method is appropriate.
Run a screwdriver blade along the mortar joints. If the mortar crumbles away easily, repointing is the primary repair. If the mortar is sound but individual bricks are flaking, spalled, or broken, the bricks themselves need attention. If cracks follow a stepped or diagonal pattern across multiple courses, stop and consult a structural engineer.
Check the depth of any spalling. If the brick face has only lost a few millimetres, a protective consolidant or masonry paint may be sufficient. If the face has lost more than a third of its depth, or if the brick is structurally compromised, replacement is the right course.
Repair Methods Compared
| Method | Best For | 2026 Cost (Labour + Materials) | DIY Feasibility |
|---|---|---|---|
| Repointing | Decayed or cracked mortar joints, sound bricks | £15–£25 per m² | Yes, with care |
| Brick slip | Surface spalling, cosmetic face loss | £30–£70 per brick | Possible but fiddly |
| Isolated brick replacement | Broken, badly spalled, or impact-damaged bricks | £25–£60 per brick | Yes for 1–2 bricks |
| Section rebuild | Extensive structural damage, multiple failed courses | £150–£350 per m² | No — trade only |
How to Repoint Brickwork
Repointing replaces deteriorated mortar in the joints without disturbing the bricks themselves. It is the most common brickwork repair and is suitable for DIY on small areas.
Tools and materials needed:
- Cold chisel and club hammer (or an angle grinder with a mortar raking disc for larger areas)
- Pointing trowel and a brick jointer
- Stiff brush
- Mortar (see note on specification below)
- Safety glasses and gloves
- Dust mask (essential if using power tools)
Step by step:
- Rake out the old mortar to a depth of at least 15mm. Shallow repointing will not bond properly and will fail quickly. Remove loose material with a brush.
- Dampen the joint with a water spray. Dry masonry will absorb moisture from the new mortar too quickly, causing it to crack before it sets.
- Mix the mortar to a stiff but workable consistency. Press it firmly into the joint in layers if the depth is more than 20mm, allowing each layer to firm up before adding the next.
- Finish the joint to match the existing profile. The most common profiles in UK brickwork are weather-struck (angled to shed water) and flush (for softer historic bricks). Avoid ironing or over-compressing the joint surface, which can cause water to track along the face.
- Keep the repair damp for 48–72 hours in warm weather to allow proper curing. Avoid working in frost or when temperatures are forecast to drop below 5°C.
Mortar Specification: Lime vs Cement
Getting the mortar mix right is critical. Using too strong a mortar in older brickwork is a common and damaging mistake.
- Pre-1919 buildings should almost always be repointed with a lime mortar (typically NHL 2 or NHL 3.5 hydraulic lime with well-graded sand). Cement mortars are harder than the surrounding masonry and cause the bricks — not the joints — to bear the stress of movement, leading to further spalling.
- Post-1945 brickwork is typically built with cement mortar and can be repointed with a cement:sand mix of 1:4 or 1:5.
- When in doubt, take a sample of original mortar to a specialist supplier for matching.
If the property is listed, using an inappropriate mortar specification may constitute unauthorised works. Listed Building Consent must be sought for any repairs that alter the character of the building, including changes to mortar colour or profile.
How to Replace an Individual Brick
Isolated brick replacement is achievable as a DIY task for one or two bricks but becomes a trade job once multiple adjacent bricks are involved.
- Rake out the mortar from all four joints surrounding the damaged brick to a depth that allows you to extract it cleanly. An angle grinder is quicker than a cold chisel for this stage.
- Remove the brick by working from the centre outward. Avoid excessive force on surrounding bricks — if the brick is very firmly bedded, the mortar can be drilled out further to loosen it.
- Source a matching replacement. Brick matching is one of the most time-consuming parts of the job. Take the old brick to a reclamation yard and match as closely as possible for size, colour, texture, and porosity. London stock, Staffordshire blue, and common reds are all widely available second-hand.
- Prepare the recess by cleaning out all old mortar and dampening the surrounding brickwork.
- Bed the new brick on a fresh mortar mix, checking it is level and flush with the surrounding face.
- Fill the remaining joints and finish to match the existing profile.
Structural Brick Repairs
Any cracking that is wide (more than 2–3mm), actively growing, or following a stepped or diagonal pattern across multiple courses requires assessment by a structural engineer before repair work begins. This includes:
- Lintel failure (horizontal cracking above openings)
- Subsidence (diagonal cracking, typically stepped)
- Expansion or thermal movement in longer wall runs
- Roof spread pushing on gable walls
A structural engineer will identify the cause of movement, confirm whether it has stabilised, and specify an appropriate repair. Attempting cosmetic brickwork repairs over active structural movement is both ineffective and potentially dangerous.
For sections of brickwork that require rebuilding — typically following structural failure or significant spalling over a wide area — expect to pay £150–£350 per m² for a qualified bricklayer working in 2026, depending on the complexity of the bond pattern, the need for scaffolding, and access.
[!warning] Listed Buildings Any repair or alteration to the external fabric of a listed building, including repointing and brick replacement, may require Listed Building Consent from the local planning authority. Working without consent is a criminal offence. Always contact your local conservation officer before starting work on a listed structure.
When to Call a Professional
- Structural cracking of any kind — always get a structural engineer’s opinion first
- More than a few square metres of repointing — scaffolding and professional equipment will give a better result
- Matching bricks in a heritage building where colour and texture matter
- Any work on a listed building
- Chimney stack repairs above roof level — working at height without appropriate equipment is a significant safety risk
