Cast Iron Manhole Risers and Extension Rings

Amercast manufactures and supplies cast iron manhole risers, extension rings, and adjustable riser systems designed to raise existing manhole frames and covers to finished grade. These products provide a cost-effective solution for roadway resurfacing, pavement rehabilitation, utility adjustments, and municipal infrastructure upgrades without requiring complete frame replacement.

Cast iron manhole risers are commonly installed when roads are repaved, resurfaced, or reconstructed. By placing a riser ring between the existing frame and cover assembly, municipalities and contractors can quickly restore proper elevation while reducing labor costs, traffic disruptions, and excavation requirements. Adjustable risers and extension rings are widely used throughout sanitary sewer systems, stormwater infrastructure, utility vaults, and roadway drainage systems.

What Is a Manhole Riser?

A manhole riser is a cast iron or steel extension ring installed beneath an existing manhole cover to increase the elevation of the frame and cover assembly. Manhole risers are commonly used during asphalt overlays and roadway rehabilitation projects where pavement elevations have increased.

Rather than removing and replacing an entire frame and cover assembly, contractors can install a riser ring to bring the casting back to grade quickly and economically. This significantly reduces installation time and project costs while maintaining the integrity of the existing structure.

Common Applications

Amercast cast iron risers are commonly used for:

• Sanitary Sewer Manholes
• Storm Drain Structures
• Catch Basins
• Utility Vaults
• Telecommunications Structures
• Water Distribution Systems
• Roadway Rehabilitation Projects
• Pavement Overlay Programs
• Municipal Infrastructure Improvements

Available Riser Types

Solid Cast Iron Riser Rings

Solid cast iron risers provide a durable and economical solution for raising existing manhole castings. These rings are manufactured to fit standard municipal frame and cover assemblies and provide long-term structural performance under traffic loading.

Adjustable Manhole Risers

Adjustable risers allow field adjustment to accommodate varying frame dimensions and grade requirements. These systems are commonly specified when exact elevations are unknown before installation.

Extension Rings

Extension rings are installed during resurfacing projects to raise existing manhole covers without disturbing the original frame. They provide a fast, durable, and cost-effective method of restoring access structures to grade.

Common Sizes

Amercast can supply risers to meet numerous municipal standards and casting configurations.

Standard Diameter Sizes

Common Heights

Cast iron riser rings are commonly stocked in 2″, 3″, 4″, and 6″ heights depending on municipality specifications and paving requirements.

Material Specifications

Municipal-grade cast iron risers are commonly manufactured from ASTM A48 gray iron and can be supplied for H-20 traffic-rated applications when properly installed within reinforced roadway structures.

Benefits of Cast Iron Manhole Risers

Reduce Construction Costs

Risers eliminate the need for complete frame replacement, reducing labor, material, and traffic control expenses.

Fast Installation

Many riser systems can be installed in minutes, minimizing roadway disruptions and lane closures.

Durable Performance

Cast iron risers are designed to withstand repeated traffic loading, freeze-thaw cycles, and harsh environmental conditions.

Compatible With Existing Infrastructure

Risers can be manufactured to fit existing municipal castings and utility standards, simplifying maintenance and rehabilitation projects.

Custom Municipal Castings

Amercast specializes in custom municipal castings and can manufacture:

• Custom Diameter Riser Rings
• Custom Height Extension Rings
• Adjustable Riser Systems
• Sewer Castings
• Water Utility Castings
• Storm Drain Castings
• Utility Access Frames
• Traffic-Rated Castings
• Municipality-Specific Designs

We routinely manufacture products to match city, county, DOT, utility authority, and engineering specifications.

Related Products

• Manhole Frames and Covers
• Adjustable Manhole Risers
• Manhole Risers and Extension Rings
• 27″ Manhole Riser
• Catch Basin Grates
• Municipal Castings

Performance Characteristics

Why Choose Amercast?

Amercast supplies municipal-grade cast iron manhole risers and extension rings engineered for roadway rehabilitation, utility infrastructure, and municipal construction projects. Available in standard and custom sizes, our risers provide a proven solution for restoring manhole elevations quickly, safely, and cost-effectively.

Contact Amercast today for pricing, municipal specifications, custom sizing, and engineering assistance.

Manhole Risers are used when regrading roads and repaving surfaces. Manhole risers and extension rings are a cost effective way to bring existing manhole frame covers and manhole frames and grates to grade. Manhole risers are made in cast iron, mild steel and can be also come furnished in adjustable patterns. We carry various different municipal standards and size specifications. Manhole riser installation is fast, quick and relatively easier opposed to installing a brand new manhole cover.

Manhole Extension Rings are for use on resurfacing projects to raise the elevation of the existing manhole without changing the frame. Extension Rings are easy to install, cost effective and are durable.

Adjustable Risers Specifications

1. All material for risers (excluding adjustment device) shall be A.S.T.M. A-36 Steel, meeting 575MQ (HS-20).
2. Steel material for lower riser shall be 3/4” minimum thickness.
3. Material for upper riser shall be 3/8” minimum thickness.
4. On 3 piece riser, material joining upper & lower riser shall be a minimum of 16 gauge A-36 steel, a maximum of 12 gauge, and must be continuous (no “tab joining” allowed) with no exceptions.
5. All upper and lower sections of riser bars must be continuously welded with a minimum of 1/8” weld. On 3-piece riser, a 1/8” continuous weld is required along the top, joining the 12 or 16 gauge material. Stitch welded sections are not permitted.
6. Adjustment device shall be a minimum 3⁄4” 13 U.N.C. solid 304 Stainless Steel bolt, 4” maximum length. Plated bolts are not acceptable. Adjustment nuts shall be C1020 cold rolled steel, minimum outside diameter shall be 1”, minimum length shall be 1 5/8”, maximum length shall be 1 3⁄4”.
7. Adjustment of riser shall be 0” + or – 1⁄2” diameter.
8. Risers shall be fabricated to the top of the manhole cover diameter given in a “closed” position.
9. All risers shall be coated with black asphalt paint.