Use Case | Haunch Needed? | Notes |
---|---|---|
Block paving driveway | ✅ Yes | Prevents edge shift from vehicle loads and daily traffic |
Garden patio with slab edges | ✅ Often | Helps hold edge slabs firm and finishes the job neatly |
Footpaths or stepping stone runs | ⚠️ Sometimes | Useful where soil is loose, or edging needs restraint |
Concrete slab base (no edging) | ❌ No | Not required unless laying decorative edging around it |
Before laying the haunch, make sure your edging blocks or final course of slabs are securely in place and properly aligned. Clear a trench or space along the outer edge of the paving where the haunch will go — typically 100–150mm wide and deep enough to contain the haunch without it spilling into your sub-base or surface. The ground underneath should be compacted and firm to give the haunch support. If you're retrofitting, remove any loose soil or debris that could interfere with the concrete setting cleanly against the edge blocks.
A typical haunch uses a semi-dry concrete mix at a ratio of about 1 part cement to 4 parts sharp sand (or all-in ballast). You want the mix to be just wet enough to hold its shape when compacted by hand. If you're working on a tight edge or need a smoother finish, a slightly wetter mix can help with shaping. Avoid overly sloppy concrete — it won’t support the edges properly and may slump as it cures. Mix only what you can lay in 15–20 minutes, especially in warmer weather where drying time is shorter.
Place the concrete firmly against the base of the edge restraint or slab, packing it tightly in place. Use a bricklaying trowel to form a haunch angle of roughly 45° — this shape adds strength and allows rain to run off. The top of the haunch should sit just below the slab edge so it's either hidden or flush. Compact it as you go to eliminate voids and air pockets. For long runs, work in manageable sections to keep the concrete workable while you're shaping. Neatness counts — this edge finish protects your paving and improves the final look.
Once the haunch is laid and shaped, let it cure undisturbed. It needs at least 24 hours before you backfill or apply any pressure — longer if conditions are wet or cold. Don’t allow soil, gravel, or foot traffic to press against it while it's still green. If needed, lightly cover the haunch with plastic sheeting to stop it drying too fast in direct sun. Proper curing ensures the haunch reaches full strength and forms a long-lasting restraint. Once set, it’ll be strong enough to support edging against traffic, weather, and soil pressure for years to come.