Anti-Settlement Cast Iron Manhole Covers
A cover is only as good as its frame. Our anti-settlement range uses a height-adjustable frame, so the cover can be re-levelled to the road after asphalt is laid, settled or milled off.
The Problem
Why Covers Sink — and Why Bolts Fix It
A conventional cover sits on a frame bedded in mortar. When the surrounding asphalt is compacted or re-laid, the frame stays where it was and the road surface rises or falls around it — the classic 10–20 mm lip that catches tyres and holds water.
An adjustable frame is anchored into the structure, and the frame ring is raised or lowered by bolts to meet the finished road level. The cover is then re-seated on the corrected ring — no breaking out, no new mortar bed.
- Adjustment range [±30] mm on site
- Re-levelling without removing the frame
- Backing ring takes the load, not the asphalt
- Works with new-build and resurfacing
Installation
Five Steps on Site
Set the baseAnchor the backing plate to the chamber or concrete collar.
Set the ringAdjust bolts to the binder course level.
PaveLay asphalt around the frame, compact normally.
Re-levelAdjust bolts to the final surface after rolling.
Seat the coverFit the cover, check it is flush and non-rocking.
After resurfacing: loosen the bolts, re-level and re-seat — the frame does not have to be cut out.
FAQ
Anti-Settlement Questions
1.Is “anti-settlement” the same as “self-levelling”?
In practice, yes. Both describe a frame that can be adjusted to the finished road level. “Self-levelling” is the term used when the cover follows the surrounding surface automatically; ours is bolt-adjusted, which is more controlled on site.
2.How much height adjustment do I need?
For a single asphalt overlay, [20]–[30] mm is typical. For deeper reconstruction, tell us the layer thicknesses and we will size the frame.
3.Can the frame be re-used if the road is rebuilt?
The cover and ring can usually be re-used; the backing plate and bolts are replaced if corroded. Ask for a spare bolt set with the order.
4.Does the adjustable frame reduce the load rating?
No — the test load is carried by the backing ring, which is bolted to the structure, not by the adjustment bolts. The assembly is tested as a complete unit to D400 or E600.
