Tying new brickwork into an existing brick wall is one of those jobs that looks straightforward but has several details that can make or break the result — literally. Done correctly, the junction will be structurally sound, weathertight, and nearly invisible. Done poorly, you risk cracking, water ingress, and a wall that moves independently of the structure it's meant to connect to. Here's what you need to know before you start.
Understand What You're Connecting To
Before picking up a trowel, assess the existing wall carefully. Key questions include:
- What bond pattern is used? Common patterns in NZ include stretcher bond, English bond, and Flemish bond. Your new work should continue the same pattern where possible.
- What's the mortar type? Older NZ homes (pre-1970s) often used lime-based mortars, which are softer and more flexible than modern cement mortars. Using a hard cement mortar against a soft lime mortar can cause cracking as the two move differently.
- Is the existing wall structural or a veneer? Many NZ homes use brick veneer (a single skin of brick tied to a timber frame), while others have solid double-brick construction. The connection method differs between the two.
- Is there any existing damage or movement? Cracks, spalling, or efflorescence should be investigated and repaired before you add new brickwork.
If you're unsure about the structural role of the wall, consult a licensed building practitioner before proceeding. You can find qualified tradespeople at tradedirectory.co.nz.
Two Main Methods: Toothing vs. Wall Ties
Toothing (Raking Out)
Toothing is the traditional method and gives the strongest mechanical bond. It involves cutting or raking out alternate courses of the existing wall in a stepped pattern so the new bricks can interlock directly with the old ones.
- Use an angle grinder with a diamond blade or a cold chisel and club hammer to carefully remove every second brick end (or half-brick) at the junction.
- The resulting stepped profile — the "tooth" — allows new bricks to slot in and bond across the joint.
- This method is best when the bricks and bond pattern match closely and the existing wall is in good condition.
- Take care not to damage surrounding brickwork. Wear eye protection and a dust mask; older mortar and brick dust can contain silica, which is a serious respiratory hazard. Check WorkSafe NZ guidance on working with silica dust.
Wall Ties and Stitching
Where toothing isn't practical — for example, when the new wall runs parallel to the existing one, or when you can't disturb the existing structure — stainless steel wall ties or helical stitching bars are used.
- Drill into the existing wall at every second or third course (typically every 450 mm vertically) using a hammer drill.
- Insert stainless steel ties or helical bars into the drilled holes, bedding them in with a suitable epoxy or cementitious anchor (products from Sika or Ardex are commonly used in NZ).
- Embed the protruding end of the tie into the mortar bed of the new brickwork as you lay each course.
- Use stainless steel ties only — galvanised ties can corrode over time, especially in NZ's coastal or high-humidity environments, causing rust staining and eventual failure.
Matching Mortar: A Critical Step
Mismatched mortar is one of the most common mistakes in brick repair and extension work. The general rule is: new mortar should be no stronger than the existing mortar or the bricks themselves.
| Situation | Recommended mortar mix (by volume) |
|---|---|
| Modern cement bricks, post-1980s | 1 part cement : 5–6 parts sand |
| Older clay bricks, mid-century | 1 part cement : 1 part lime : 6 parts sand |
| Heritage lime mortar walls | Hydraulic lime mortar — seek specialist advice |
Always test a small sample area and allow it to cure before committing to the full junction. Colour-matching is also important for visual results; take a sample of the existing mortar to your supplier at Mitre 10 or PlaceMakers to find the closest sand and cement blend.
Preparing the Junction Surface
- Clean the existing wall face thoroughly. Remove loose mortar, dirt, paint, and any efflorescence. A stiff brush and water are usually sufficient; avoid high-pressure washing directly into the joint.
- Dampen the existing brickwork before laying new mortar against it. Dry bricks will suck moisture out of fresh mortar too quickly, weakening the bond.
- Rake out the existing mortar joints at the junction to a depth of at least 15 mm to give the new mortar a proper key.
NZ Building Code Considerations
Depending on the scope of work, your project may require a building consent. Under Schedule 1 of the Building Act, some minor repair and maintenance work is exempt, but adding a new wall or structural element generally is not. Always check with your local council before starting — rules vary by region and by the nature of the work. MBIE Building Performance has clear guidance on what requires consent.
For brick veneer construction specifically, the connection to the timber framing must comply with NZS 3604 (Timber-framed buildings) and the NZ Building Code clause E2 (External moisture). Getting this wrong can lead to water ingress behind the veneer — a costly problem in NZ's variable climate.
When to Call a Professional
While an experienced DIYer can handle small toothing or tie-in jobs, you should engage a licensed bricklayer if:
- The wall is structural or load-bearing.
- The project requires a building consent.
- You're working on a heritage or character property where mortar matching is critical.
- The existing wall shows signs of significant movement, cracking, or moisture damage.
- You're unsure of the wall's construction type or condition.
A qualified bricklayer will also ensure the work meets BRANZ best-practice guidelines and the NZ Building Code. Find a trusted local bricklayer on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
