Corbelling is a traditional bricklaying technique where successive courses of bricks are stepped outward to create a decorative projection — think of the classic capping detail on a garden wall or a decorative band beneath a coping. Done correctly, it's a satisfying DIY project for a competent homeowner; done incorrectly, it can lead to cracking or collapse. Here's how to get it right.
What Is Corbelling and Where Can You Use It?
A corbel is a brick (or series of bricks) that projects beyond the face of the course below it. On a garden wall, corbelling is most commonly used to:
- Create a decorative string course (a horizontal band partway up the wall)
- Form a capping or coping detail at the top of the wall
- Add a pillar cap or decorative crown to a pier
For a freestanding garden wall, corbelling is largely decorative and structural loads are modest — making it one of the more approachable bricklaying projects for a capable DIYer.
Key Rule: The Projection Limit
The most important technical rule in corbelling is how far each course can safely project. As a general guide used in standard trade practice:
- Each course should project no more than one-third of the brick's depth (roughly 25–30 mm for a standard NZ brick)
- The total corbel projection should not exceed the thickness of the wall itself
- Each course must be fully bedded in mortar with no voids
Exceeding these limits risks the corbelled section tipping or cracking under its own weight, especially if the wall is exposed to wind or frost. If you're unsure whether your design is within safe limits, consult a licensed bricklayer — you can find one on tradedirectory.co.nz.
Tools and Materials You'll Need
- Standard NZ clay or concrete bricks (matching your existing wall)
- Mortar mix — a 1:1:6 cement:lime:sand mix is typical for garden walls
- Brick trowel, jointing iron or bucket handle
- Spirit level and line pins with string line
- Tape measure and pencil
- Rubber mallet
- Pointing trowel
- Stiff brush for cleaning
For mortar, a pre-mixed bagged mortar is convenient and consistent. Products are available from Bunnings or Mitre 10. Always check the manufacturer's mix ratio on the bag.
Step-by-Step: Laying a Corbelled Detail
1. Plan Your Courses on Paper First
Sketch out your wall profile showing each corbelled course. Decide:
- How many courses will corbel out (typically 2–4 for a capping detail)
- The projection per course (e.g. 25 mm per course)
- Whether you want a single corbel (one course projecting) or a stepped corbel (multiple courses each stepping out)
2. Prepare the Base Course
Ensure the last standard course of brickwork is level, clean, and fully cured before you begin corbelling. Scrape off any mortar drips and check with a spirit level across the full length.
3. Set Your String Line
Set a string line at the height of the first corbelled course, offset outward by your planned projection. This gives you a consistent reference for the front face of each corbelled brick.
4. Lay the First Corbelled Course
- Apply a full bed of mortar to the top of the base course — don't skimp, as voids weaken the joint
- Place each brick so it projects the planned amount (e.g. 25 mm) beyond the course below
- Check each brick is level side-to-side and front-to-back with your spirit level
- Tap gently with a rubber mallet to seat the brick; avoid knocking it out of position
- Maintain consistent perpend joints (vertical joints) — stagger them as you would in standard brickwork
5. Repeat for Each Subsequent Corbelled Course
Allow each course to firm up for at least 30–60 minutes before laying the next, especially in warm or windy weather. This prevents the fresh mortar from being squeezed out under the weight of the next course.
6. Finish With a Coping or Cap
The top course is typically a coping brick laid flat or on edge to shed water. Ensure it overhangs slightly on both sides (at least 25–30 mm) to direct water away from the wall face. A good coping is one of the best ways to extend the life of a garden wall in NZ's variable climate.
7. Point the Joints
Once the mortar is thumb-print firm (not wet, not rock hard), use a jointing iron or bucket handle to finish the joints. A weathered or recessed joint sheds water well and suits most NZ garden wall styles. Brush off crumbs with a stiff brush once fully set.
Mortar and Weather Considerations
NZ weather can be unpredictable. Avoid laying brickwork:
- In temperatures below 5°C (mortar won't cure properly)
- In direct hot sun or strong wind without shading/misting (mortar dries too fast and weakens)
- When rain is forecast within 24 hours of laying
For guidance on durable external masonry construction, BRANZ publishes excellent technical resources relevant to NZ conditions.
Building Consent Considerations
Most low garden walls are exempt from building consent under Schedule 1 of the Building Act, but height thresholds and conditions vary — always confirm with your local council, but always confirm with your local council before starting — rules vary by region and site. The MBIE Building Performance website has clear guidance on consent exemptions.
When to Call a Professional
Consider hiring a qualified bricklayer if:
- Your wall is over 1 m high or structurally significant
- The corbelling is load-bearing (e.g. supporting a beam or roof element)
- You're unsure about projection limits or structural stability
- The wall is retaining soil (retaining walls have specific engineering requirements)
- You want a complex multi-course corbel or decorative arch detail
A licensed bricklayer will ensure the work is structurally sound and looks professional. Find a local bricklayer on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
