How do i repair cracked or crumbling mortar repointing? (2026)
Quick Answer
To repair cracked or crumbling mortar, remove the loose or failed mortar from the joint, clean out dust, lightly dampen the masonry, then pack in a suitable new mortar and finish the joint to match the existing work. The key is using a compatible mortar and avoiding damage to the bricks or stones, because mortar should usually be softer and more breathable than the masonry around it.
Overview
Repointing repairs the outer part of masonry joints where mortar has cracked, fallen out or turned powdery. Done properly, it helps keep out water, reduces draughts and protects the wall from further deterioration. The basic process is simple: rake out unsound mortar, clean the joints thoroughly, dampen the area, press in fresh mortar in layers if needed, then finish and cure it carefully. What matters most is compatibility. Mortar that is too hard, too dense or unsuitable for the wall can trap moisture and cause bricks or stone to crack or spall, especially on older buildings. This is a realistic DIY job for small, non-structural areas where the masonry units themselves are sound and access is safe. It is not just a matter of filling gaps with any cement mix. Older walls often need a more breathable mortar, and modern hard cement mortars can be harmful in some cases. Good preparation is what makes the repair last: remove enough failed mortar, keep joints clean, and avoid smearing mortar across the face of the masonry. You should also only repoint when the wall is dry enough to work on and weather conditions are suitable, following the mortar manufacturer’s instructions for mixing, application and curing.
Who this is for
Homeowners tackling small areas of worn mortar on brick or stone walls, garden walls, chimneys at safe low level, or similar masonry where the damage is limited to the joints rather than the structure.
What you’ll need
- Safety glasses, gloves and a dust mask or respirator suitable for masonry dust
- Joint raker, plugging chisel or mortar rake
- Hammer
- Stiff brush and/or vacuum
- Water spray bottle or fine mist sprayer
- Pointing trowel or small margin trowel
- Hawk or mortar board
- Suitable replacement mortar or ingredients recommended for the wall type
- Joint finishing tool or a rounded/flat tool to match the existing profile
- Protective sheeting if needed
Before you start
Check whether the problem is only failed pointing or something more serious. If bricks or stones are loose, bulging, deeply cracked, moving, damp for an ongoing reason, or the wall is part of a structural or heritage building, get expert advice before starting. Identify the existing mortar as far as you can and choose a compatible replacement; for older brick or stonework this often means avoiding an overly hard cement-rich mix. Also check the weather and the mortar product instructions, because very wet, very hot, frosty or rapidly drying conditions can spoil the repair.
Step-by-step
- 1
Assess the wall and mark the repair area
Inspect the joints and the masonry units around them. Scrape lightly at suspect joints to find where mortar is actually loose, hollow, powdery or detached. Mark the area to be repaired and check whether cracks continue through the bricks or stones themselves.
Why: This helps you distinguish cosmetic pointing failure from structural movement or masonry damage. Repointing failed joints will not fix a moving or unstable wall.
- 2
Remove the failed mortar carefully
Rake or chisel out the damaged mortar from the joints, working slowly to avoid chipping the edges of the bricks or stone. Remove all loose material until you reach sound mortar. Hand tools are usually safest for small jobs and older masonry. If you use power tools, do so with great care and only where appropriate for the masonry and your skill level.
Why: New mortar needs a clean, solid backing and enough depth to bond properly. Leaving weak material behind is a common reason repairs fail early.
- 3
Clean out the joints thoroughly
Brush out all dust, grit and fragments from the joints. Vacuuming can help on small jobs. The joint faces should be free of loose debris, salts, plant growth and anything that would stop the new mortar adhering.
Why: Dust acts as a bond breaker. Clean joints help the fresh mortar grip the sides of the masonry rather than just sitting loosely in the gap.
- 4
Lightly dampen the masonry
Mist the joints and surrounding masonry so they are slightly damp but not running wet. Follow the mortar manufacturer’s guidance. Very porous masonry may need more than one light misting before pointing.
Why: Dry masonry can suck moisture out of fresh mortar too quickly, leading to weak curing, shrinkage cracking and poor bond.
- 5
Mix or prepare a compatible mortar
Use a mortar suitable for the type and age of the wall, and follow the product label or manufacturer instructions exactly for mixing and working time. Mix only as much as you can place before it starts to stiffen. If you are unsure what mortar is appropriate, especially for an older property, check manufacturer guidance or seek specialist advice.
Why: Mortar compatibility affects strength, breathability, movement and moisture behaviour. Using the wrong mortar can damage the wall over time.
- 6
Pack the mortar into the joints
Press the mortar firmly into the back of the joint with a pointing trowel, filling it fully rather than smearing it over the surface. For deeper joints, build it up in layers as recommended by the product guidance, allowing each layer to firm up as needed before adding more. Keep the mortar off the masonry face as much as possible.
Why: Fully compacted mortar is stronger, sheds water better and is less likely to crack or fall out. Layering deep fills reduces shrinkage and voids.
- 7
Finish the joint to match the existing profile
When the mortar has started to firm up but is not fully hard, tool the joint to match the original finish as closely as possible, such as flush, slightly recessed or bucket-handle style if appropriate for the wall. Brush off crumbs gently once the surface is ready, without dragging mortar out of the joint.
Why: Joint shape affects both appearance and weather resistance. Finishing at the right stage compacts the surface and improves durability.
- 8
Protect and cure the repair
Protect the fresh work from rapid drying, heavy rain, frost and accidental disturbance. Follow the product instructions for curing and aftercare. If cleaning is needed, do it gently and only when the mortar has firmed sufficiently, avoiding aggressive methods that can stain or damage the wall.
Why: Most repointing failures happen after application, when mortar dries too quickly, gets washed out or is exposed to unsuitable conditions before it gains strength.
Why this works
Repointing works by replacing deteriorated mortar at the exposed face of the joints so the wall can again resist rain penetration and minor movement. Mortar is intended to be the sacrificial element in many masonry walls: it should weather before the brick or stone does, making it easier and safer to renew than the masonry itself.
Common mistakes to avoid
- Using a mortar that is harder or less breathable than the existing wall requires
- Only filling the visible surface crack instead of removing all loose mortar first
- Damaging brick or stone edges while raking out joints
- Repointing onto dusty, dirty or bone-dry joints
- Smearing mortar across the face of bricks or stone and leaving hard-to-remove staining
- Working in unsuitable weather or ignoring the product’s curing instructions
Troubleshooting
New mortar cracks soon after application
The joint may have been too dry, too deep for a single fill, or the mortar may have dried too fast. Remove failed material, re-clean the joint, dampen appropriately, refill properly and protect it during curing.
Mortar falls out or feels hollow
This often means the old mortar was not removed deeply enough, the joint was dusty, or the mortar was not packed firmly into the back of the joint. Rake out and redo the area properly.
Repair looks a different colour
Some colour difference is normal at first and may reduce as the mortar cures and weathers. For important visible areas, test a small patch first and use the same product and mixing method consistently.
White deposits appear on the surface
This can be efflorescence from salts moving through damp masonry. Let the wall dry and brush deposits off dry if appropriate. If dampness is persistent, address the source of water rather than repeatedly cleaning the surface.
Bricks or stones start flaking near repaired joints
This may indicate moisture problems or mortar that is too hard for the masonry. Stop repointing and get specialist advice, especially on older or soft masonry.
Compare your options
Ready-mixed repointing mortar
Best for: Small repairs where convenience and consistency matter
Pros: Simple to use, manufacturer guidance is clear, less mixing guesswork
Cons: May not suit all older or specialist masonry, colour and compatibility still need checking
Site-mixed mortar to a suitable specification
Best for: Repairs where close material matching is important
Pros: Can be better tailored to the wall, useful for traditional masonry when correctly specified
Cons: Requires more knowledge, easier to get wrong, consistency can vary between batches
Spot repointing only damaged joints
Best for: Localised failure
Pros: Less disruptive, lower material use, preserves more original fabric
Cons: Patch repairs may be visually obvious and nearby joints may fail later
Repointing a whole elevation
Best for: Widespread mortar failure
Pros: More consistent appearance and performance across the wall
Cons: Larger job, more costly, greater risk of damage if done poorly
| Option | Best for | Pros | Cons |
|---|---|---|---|
| Ready-mixed repointing mortar | Small repairs where convenience and consistency matter | Simple to use, manufacturer guidance is clear, less mixing guesswork | May not suit all older or specialist masonry, colour and compatibility still need checking |
| Site-mixed mortar to a suitable specification | Repairs where close material matching is important | Can be better tailored to the wall, useful for traditional masonry when correctly specified | Requires more knowledge, easier to get wrong, consistency can vary between batches |
| Spot repointing only damaged joints | Localised failure | Less disruptive, lower material use, preserves more original fabric | Patch repairs may be visually obvious and nearby joints may fail later |
| Repointing a whole elevation | Widespread mortar failure | More consistent appearance and performance across the wall | Larger job, more costly, greater risk of damage if done poorly |
Alternatives
- For hairline cracks in otherwise sound interior decorative mortar joints, cosmetic filling may be possible, but it is not a substitute for proper external repointing.
- If only a few bricks are loose or damaged, replacing those units as well as repointing may be the better repair.
Pro tips
- Test your mortar choice and joint finish on a small inconspicuous area first.
- Match the joint profile to the existing wall so water sheds properly and the repair blends in.
- Work methodically in small sections so you can finish the joints at the right stage.
- Keep tools and the masonry face clean as you go; dried smears are much harder to remove later.
Safety notes
- Mortar removal creates silica-containing dust; wear suitable respiratory protection and control dust where possible.
- Wear eye protection when chiselling or raking out joints.
- Be cautious with ladders and do not attempt high-level or chimney work without proper access equipment and training.
- Wet mortar and lime-based materials can irritate or burn skin; use gloves and wash off splashes promptly.
- Do not use power tools on old or fragile masonry unless you are confident they are appropriate and you can control them safely.
Legal & regulatory notes
Listed, heritage or protected buildings may require specialist methods or formal approval before repointing, and inappropriate mortar can damage historic fabric. Local building rules and body corporate or strata rules may also affect exterior work. Check local requirements before starting.
What this guide does not cover: This guide covers small-scale repointing of cracked or crumbling mortar only. It does not cover structural wall repair, chimney rebuilding, scaffold safety, retaining wall engineering, exact mortar specification for heritage conservation, or diagnosing all causes of damp.
Cost considerations
Costs vary mainly with access, wall height, extent of failed joints, mortar type, and whether matching traditional materials is needed. Small ground-level patch repairs are often manageable as DIY, but widespread or high-level repointing usually becomes more expensive because preparation, safe access and skilled finishing matter more than the mortar itself.
Prefer to hire a professional?
If this job is beyond a confident DIY — or the work needs to be done by a licensed professional — you can find a verified qualified local tradesperson through these directories of real, verified trade businesses. Compare local tradespeople, read their details and request quotes before you commit.
Frequently asked questions
Can I just fill cracks in the mortar without removing the old joint?+
Usually no. If the mortar is loose or crumbling, a surface fill will not bond well or last. Proper repointing means removing failed mortar back to sound material first.
How do I know if I need lime mortar or cement mortar?+
It depends on the wall age, masonry type and existing mortar. Older solid-wall brick and stone buildings often need a more breathable mortar. Check manufacturer guidance, conservation advice for historic buildings, or ask a specialist if unsure.
Can repointing stop damp?+
It can help reduce rain penetration through open joints, but it will not solve damp caused by leaks, failed flashing, rising damp, blocked drainage, bridging, or condensation. The source of moisture still needs addressing.
Should I repoint in winter or very hot weather?+
Avoid unsuitable conditions. Frost, heavy rain, strong sun and rapid drying can all spoil fresh mortar. Follow the mortar manufacturer’s instructions and choose stable weather if possible.
When is mortar damage too serious for DIY?+
If the wall is bulging, moving, shedding bricks, cracked through the masonry units, or if the damage affects a chimney, retaining wall, heritage building or anything high level, it is best assessed by a professional.
Sources & references
Guidance on this page is traced to documented sources. Last checked 25 September 2026.
- NHBC Standards · industry
Supports general good practice on masonry durability, weather resistance and workmanship, though exact project requirements should be checked in the relevant standard or product guidance.
Basic repointing practice changes slowly, but exact product instructions and local heritage or building requirements can vary.