Cracked or crumbling mortar joints are one of the most common maintenance issues facing NZ homeowners with brick or concrete block walls. Left untreated, deteriorating mortar allows moisture to penetrate — a serious concern in our often wet and windy climate — leading to water damage, efflorescence, and even structural problems over time. The good news is that repointing (also called pointing or tuck-pointing) is a manageable DIY job for small areas, provided you use the right materials and technique.
What Is Repointing and Why Does Mortar Fail?
Repointing is the process of removing damaged mortar from the joints between bricks or blocks and replacing it with fresh mortar. Mortar is softer than brick by design — it acts as a sacrificial layer, absorbing movement and moisture so the bricks themselves don't crack. Over time, UV exposure, freeze-thaw cycles (common in southern and elevated parts of NZ), and general weathering cause mortar to shrink, crack, and crumble. Poor original mix ratios or the use of an overly hard mortar can also accelerate deterioration.
Assessing the Damage First
Before you reach for a chisel, take a good look at the wall:
- Minor cracking or surface erosion — ideal for DIY repointing.
- Deep cracks running through bricks (not just joints) — may indicate structural movement; get a professional assessment.
- Widespread crumbling across a large area — consider hiring a qualified bricklayer for efficiency and consistency.
- Damp patches or staining inside the home — investigate the moisture pathway before repointing.
If you're unsure whether cracking is cosmetic or structural, BRANZ has useful guidance on diagnosing wall defects.
Tools and Materials You'll Need
| Item | Purpose |
|---|---|
| Cold chisel or plugging chisel | Raking out old mortar |
| Club hammer | Driving the chisel |
| Angle grinder with mortar rake disc | Faster removal on large areas |
| Stiff brush | Cleaning out dust and debris |
| Pointing trowel | Applying new mortar |
| Bucket and mixing paddle | Mixing mortar |
| Safety glasses and dust mask (P2) | Personal protection |
| Pre-mixed repointing mortar or bagged sand/cement | The repair material |
For most NZ homeowners, a pre-mixed repointing mortar (available at Bunnings or Mitre 10) is the easiest option. If you're mixing from scratch, a common general-purpose ratio for repointing is 1 part cement to 4–5 parts bricklaying sand, with a small amount of lime to improve workability. Crucially, do not use a stronger mix than the original mortar — a mix that is too hard will cause the bricks themselves to crack as the wall moves.
Step-by-Step Repointing Process
1. Rake Out the Old Mortar
Using a plugging chisel and club hammer (or an angle grinder with a mortar raking disc for speed), remove the old mortar to a depth of at least 15–20 mm. Shallow repairs won't bond properly and will fail quickly. Work carefully to avoid chipping the brick faces.
2. Clean the Joints
Brush out all loose dust, debris, and old mortar fragments with a stiff brush. For best adhesion, dampen the joints with clean water — dry brick will suck moisture out of the fresh mortar too quickly, weakening the bond.
3. Mix Your Mortar
Mix to a firm but workable consistency — it should hold its shape when squeezed but not be crumbly or sloppy. Mix only as much as you can use in about 30–45 minutes, especially on a warm NZ summer day.
4. Apply the New Mortar
Using a pointing trowel, press mortar firmly into the joint, working it in layers if the joint is deep. Overfill slightly, then finish flush with the brick face (or match the original profile — weatherstruck, flush, or recessed joints all have different drainage characteristics).
5. Finish and Cure
Once the mortar has begun to stiffen (but before it fully sets), tool the joint to match the surrounding profile. Keep the repair damp for a day or two by misting with water — this slows curing and produces stronger mortar. Avoid repointing in direct hot sun or when frost is forecast.
Choosing the Right Mortar Profile
The joint profile affects both appearance and weather resistance. A weatherstruck joint (angled to shed water) suits exposed NZ conditions well. Avoid deeply recessed joints on exterior walls as they can trap water — particularly important in high-rainfall regions.
Safety Considerations
Mortar dust contains silica, which is hazardous to lungs with repeated exposure. Always wear a P2 dust mask and safety glasses when raking out joints, especially if using an angle grinder. WorkSafe NZ provides guidance on working safely with silica-containing materials. Work gloves are also recommended as fresh mortar is alkaline and can irritate skin.
When to Call a Professional
Repointing a small section of garden wall or a few joints near a window is well within DIY reach. However, you should engage a qualified bricklayer when:
- The affected area is large (a full wall face or more).
- Cracks run diagonally or through the bricks themselves, suggesting foundation or structural movement.
- The wall is part of a loadbearing structure — under the NZ Building Code, significant structural repairs may require a building consent and the involvement of a Licensed Building Practitioner (LBP).
- The brickwork is heritage or decorative and requires colour-matched mortar.
- You're working at height above a single storey — scaffolding and fall protection become important safety considerations.
A skilled bricklayer will also ensure the mortar mix is correctly matched to your existing wall, preventing future damage. You can find qualified local bricklayers on tradedirectory.co.nz.