What Is a Concrete Haunch? And Do You Really Need One?

Contact

What a Concrete Haunch Actually Does

  • ✔ Locks paving edges in place

    A haunch keeps block paving or patio edges from moving outward over time, especially under load or weather pressure.
  • ✔ Acts as edge support for paving slabs and bricks

    It braces the outer course of blocks or slabs, giving them something to lean against and preventing lateral shift.
  • ✔ Prevents spreading under vehicle loads

    On driveways or paths, a haunch stops the outer edges from pushing out when cars or foot traffic apply pressure.
  • ✔ Helps control water movement

    It keeps the structure tight and intact even during heavy rain or washout conditions, preventing erosion at the edges.
  • ✔ Provides a tidy, finished edge

    Whether visible or hidden just below the surface, a haunch gives your paving job a clean and professional edge detail.

When Do You Actually Need a Concrete Haunch?

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

Using a Concrete Haunch

  • Secures paving edges and prevents movement over time.
  • Essential for load-bearing projects like driveways.
  • Helps the base resist erosion from rain or pressure washing.
  • Gives a more professional and finished look.

Using a Concrete Haunch

  • Adds a bit more labour and material cost to the job.
  • Can be messy if not trowelled neatly — needs a clean finish.
  • Must be allowed to set fully before backfilling or loading.

Skipping the Haunch

  • Speeds up install time and lowers upfront material cost.
  • May be fine for small, decorative patios or tight border work.
  • Useful when laying slabs flush with existing hard edges.

Skipping the Haunch

  • Increases risk of edge blocks drifting or working loose.
  • Can lead to spreading and joint failure in block paving.
  • Less resistant to erosion, root pressure, or subsidence.

✔ How to Install a Concrete Haunch Properly

  1. 1

    Prepare the Edges of Your Paving Area

    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.

  2. 2

    Mix a Semi-Dry or Wet Concrete Mix

    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.

  3. 3

    Lay and Trowel the Haunch Against the Edges

    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.

  4. 4

    Let the Haunch Set Before Backfilling

    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.

🔹 What is a concrete haunch used for?
A concrete haunch is used to support and lock in the edges of paving — especially block paving and patios. It braces the outer edge and prevents movement or spreading over time, particularly under pressure from vehicles, weather, or foot traffic. It also gives the edge a clean, solid finish and helps protect the structural integrity of the paving layout.
🔹 Do I need a haunch for a patio?
Most patios benefit from a concrete haunch, especially if the outer slabs or edging blocks aren’t naturally restrained. It’s not always essential, but it does help keep everything in place over time. For patios with curves, raised edges, or high foot traffic, a haunch is a simple addition that adds long-term stability and keeps the surface looking sharp.
🔹 Can you hide a concrete haunch below the surface?
Yes — many installers shape the haunch so it sits below ground level, hidden by soil, gravel, or lawn. As long as it's trowelled neatly and allowed to cure, the haunch doesn’t need to be visible to do its job. Just make sure it still supports the paving edge fully and isn't too shallow to resist lateral movement.
🔹 What mix should I use for a haunch?
A typical haunch mix is 1 part cement to 4 parts sharp sand or ballast. You want a semi-dry consistency that holds shape when pressed — not too wet, or it’ll slump before setting. For visible edges or tighter shaping, a slightly wetter mix can help. The goal is strength and stability once cured, not flow like with poured slabs.
🔹 What happens if I skip the haunch?
Without a haunch, paving edges can shift outward over time — especially under pressure or in wet ground. This leads to loose joints, gaps, and a weakened overall structure. In high-traffic areas like driveways, skipping the haunch almost always results in edge failure. It’s a small detail that makes a big difference in how well your paving holds up.