Discover the benefits of haunched manhole design with in-situ formwork solutions from Manhole Form Hire
At Manhole Form Hire, we pride ourselves on helping contractors go beyond standard construction solutions — and our latest project with Chadoak Pty Ltd shows exactly how adaptable our heavy-duty pit boxes can be.
In this first for our business, we supported the construction of a haunched pit — a 9x9 manhole that reduces to 9x6 at the top— using our in-situ formwork system. This project proved not only that it can be done, but that it can be done safely, efficiently, and with precision.
🔍 What is a Haunched Pit?
A haunched pit is designed with a narrower upper section that increases down to a wider base, typically where large diameter pipes enter the structure. This "haunch" provides additional strength and support at the entry point of the pipe, helping distribute loads more evenly and protect against damage or movement over time.
✅ Why Use a Haunched Pit?
Haunched pits are commonly used in infrastructure and drainage projects where extra support is required — especially in areas with large pipes or heavy surface loads.
✔️ Key Benefits of Haunched Pit Construction:
- Increased Pipe Support
The haunched design creates a wider bedding area for the pipe, reducing stress and preventing movement or damage, particularly important for large diameter pipes. - Reduced Inlet Size at Ground Level
By narrowing the top of the pit, smaller grates or covers can be used — which improves both aesthetics and pedestrian safety. - Improved Structural Stability
The shape, combined with proper bedding material, helps the pit resist soil movement and external pressures — especially beneficial in high-traffic areas like roadways or industrial sites.
🧰 The Role of In-Situ Formwork and Pit Boxes
Constructing a haunched pit traditionally requires custom or pre-cast forms, but using in-situ formwork systems like our heavy-duty pit boxes gives contractors greater flexibility and control on-site.
With in-situ construction:
- You can adapt quickly to site conditions
- Avoid long lead times for custom concrete products
- Make on-the-fly adjustments for complex installations
- Save costs while still achieving compliance and structural integrity
For this project with Chadoak, we worked closely with their team to configure a formwork setup using our standard heavy-duty box system — showing that you don’t always need a custom product to achieve a complex design.
🏗 Our Experience: From Concept to Completion
This haunched pit — reducing from 9x9 to 9x6 — is something we’d been asked about before, but hadn’t yet seen through. Partnering with Mick from Chadoak, we helped bring it to life.
There was careful planning involved, but now that we've mapped out the approach and confirmed it works, we can confidently offer guidance to future clients considering similar builds.
This project proves our formwork system is more than capable of handling non-standard configurations.
💬 Thinking Beyond the Standard Pit?
If your next job involves:
- Large diameter pipes
- High load environments
- Tight site conditions
- Custom pit transitions
…then a haunched pit with in-situ formwork might be the solution — and Manhole Form Hire has the gear and know-how to help make it happen.
👷 Work Smarter with Manhole Form Hire
Our heavy-duty pit boxes offer the strength, flexibility, and ease of use that modern sites need — and now we’ve proven they can be used to construct complex haunched pits too.
