Manhole Adjustment Rings: Raising Covers for an Overlay
Manhole adjustment rings are the spacers that set a manhole frame at the right height. When a road is overlaid, the pavement rises and the old covers end up in a hole. Adding or changing rings brings the frame back level with the new surface so it does not become a pothole or a plow catcher.
Asphalt tonnage calculator →Types of rings
| Type | Notes |
|---|---|
| --- | --- |
| Precast concrete grade rings | Traditional; common in 2 to 6 inch thicknesses; set in mortar |
| HDPE plastic rings | Light, watertight; often in thin increments, including sloped rings |
| Rubber rings | Recycled rubber; flexible, absorb some impact |
| Expanded polypropylene | Very light, sealed with adhesive or sealant |
| Steel paving risers | Fit inside the existing frame for a quick raise on overlays |
Steel risers for overlays
A steel riser ring drops into the existing frame and lifts the cover by the overlay depth, for example 1.5 or 2 inches. No digging or rebuilding is needed. Risers must match the frame size closely and are usually secured with set screws or clamps.
Full frame adjustment
When the frame is cracked, loose or far off grade:
- Saw cut and remove pavement around the frame.
- Remove the frame and old rings or mortar.
- Set new rings to the needed height, sealing each joint.
- Reset the frame, aligned with the road's slope and crown.
- Backfill and compact around it, then patch with asphalt or concrete.
Sloped rings help match the frame to a road with a strong cross slope.
Timing with paving
- Before milling: mark structures so the milling machine avoids them.
- After milling, before paving: lower or protect frames so the paver passes over.
- After paving: core around frames and raise them to grade, or install risers.
See mill and overlay for the overall process.
Common problems
- Frames left low: they collect water and break the pavement edge; see asphalt patch sits too low.
- Frames left high: a bump that catches plows.
- Too many rings: tall stacks crack and settle; agencies often cap total height.
- Poor sealing: groundwater gets into the sewer.
Catch basins have similar grade issues; see catch basin repair.
Quantity example (made-up numbers)
A 2-inch overlay on a parking lot of 30,000 square feet with 6 manholes is about 3,333 square yards. At about 110 lb per square yard per inch, that is about 367 tons. Order 6 risers or plan 6 frame adjustments at 2 inches. Use the asphalt tonnage calculator and see asphalt overlay cost.
Questions people ask
What are manhole adjustment rings?
Rings stacked between the top of a manhole structure and the cast iron frame to bring the frame up to the finished pavement grade.
What are manhole grade rings made of?
Precast concrete is traditional. Newer options include high-density polyethylene, recycled rubber and expanded polypropylene. Steel risers that sit inside the existing frame are also used for overlays.
How thick are manhole adjustment rings?
Concrete rings commonly come in thicknesses of about 2 to 6 inches. Plastic and rubber rings are available in thinner increments and sometimes in sloped versions.
What is a manhole riser ring for paving?
A steel ring that drops into the existing frame to raise the cover by the overlay thickness, so the frame does not have to be dug out.
Is there a limit to how many rings can be stacked?
Many agencies limit total adjustment height, often around 12 inches or less, and the number of rings. Check local standards.
Who is responsible for raising manholes during paving?
Usually the paving contractor under the road agency's contract, coordinated with the sewer or utility owner. On private lots, the owner or their contractor handles it.
Related guides
- Catch basin repair
- Mill and overlay
- Asphalt overlay cost
- Asphalt patch sits too low
- Road milling machine
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