Stack of manhole cover lids for drainage inspection chambers
Bulb Help & Advice

Manhole Covers & Frames Explained

How to measure and choose the size you need and choose the right loading class for your project.

Manhole Cover Size

Manhole covers come in a variety of different sizes depending on the requirements of the buildings project. Typically, manhole cover sizes will range from 300mm x 300mm to 1200mm x 1200mm and be either square, rectangular or round in shape. The size of a manhole will need to be large enough to suit the maximum pipe size and are typically at least 1 metre deep.

The size listed is usually the size of the clear opening of the manhole. For example, a manhole cover listed as 600 x 450mm will probably have a larger dimension including the frame.

A diagram demonstrating manhole size vs manhole cover size.

What Size Manhole Cover Do I Need?

Tempting though it may be to use a cover far larger than the hole, it is best practice to source a cover that is a good size match. A manhole cover that’s too small could fall in.

What Types Of Manhole Covers Are There?

There are 3 main types of manhole cover; ductile iron, recessed/screed and solid top. Each has their own features and benefits, which we've outlined below:

Ductile iron

Solid and reliable, ductile iron will not corrode as quickly as cast iron, nor is it as brittle. Ductile iron is stronger than cast iron too. The loading classes for ductile iron manhole covers are subject to BS EN 124:2015 regulations.

Recessed/screed

These covers have recessed areas suitable for laying block paving or a layer of screed – great for decorative finishes in driveways. The loading classes for recessed covers are rated to FACTA loading specifications.

Solid top

Lighter galvanised steel manholes, often fitting flush at ground level and have inset grab handles. Usually for lighter use. Weight classes for solid top covers are subject to BS EN 124:2015 regulations.

Manhole cover weight classes

Covers subject to BS EN 124:2015 regulations are rated A15 to F900.

The numbers in the load class code denote ‘kiloNewtons’ that the cover is capable of withstanding i.e. C250 is capable of withstanding a 250kN load test.

Weight classifications for manholes are as follows:

A15 – Pedestrian and cyclist use only.

A15

Pedestrian and cyclist use only

B125 – Driveway duty and occasional light traffic such as access only routes.

B125

Driveway duty and occasional light traffic such as access only routes

C250 – slow moving cars and vans such as in car parks.

C250

Slow moving cars and vans such as in car parks

D400 – Fast moving heavy traffic such as on main roads.

D400

Fast moving heavy traffic such as on main roads

E600 – Heavy, moving plant and plant with solid tyres such as forklifts in heavy duty areas like warehouses, docks etc.

E600

Heavy, moving plant and plant with solid tyres such as forklifts in heavy duty areas like warehouses, docks etc.

F900 – Particularly high wheel loads such as airports.

F900

Particularly high wheel loads such as airports

Covers rated by FACTA are listed from FACTA A to FACTA F

All FACTA wheel loads are for moving pneumatic-tyred vehicles. Please check before ordering that you have the correct load class.

FACTA A

Pedestrian use and up to 5kN wheel loads

FACTA AA

Small vehicles up to 15kN wheel loads

FACTA AAA

Cars up to 25kN wheel loads

FACTA B

Cars and vans up to 50kN wheel loads

FACTA C

Trucks up to 65kN wheel loads

FACTA D

Articulated lorries up to 108kN wheel loads

FACTA E

Heavy, moving plant up to 158kN wheel loads

FACTA F

Aircraft and heavy plant up to 237kN wheel loads

Types of manhole seals

Single seal

Most standard manhole covers have a single seal which is applied to the cover and frame. This seal can be sealant or neoprene strips. This type of seal is usually sufficient to create an airtight seal.

Double seal

This is, in effect, a doubling of the seals above, but forms a comprehensive airtight seal, so long as that seal isn’t under any pressure. This sort of seal is best suited to internal sewage manholes.

No seal

Some covers have no airtight seals but slot into place. These are often called “plain seated”. Perfect for access to cables and utilities and where smells are not going to be an issue. These types also tend to be more cost effective.

Types of locks and badges

Need your manhole locked? As an extra security measure, you have the ability to have a locking mechanism installed into the cover. Ask at the time of ordering if you need locks for your manhole covers.

What Is Manhole Badging?

Badging your manhole can be a convenient way of telling workers what’s accessible within the manhole without the need to open it. Having “gas” or “FW” (foul water) clearly visible on a manhole can save valuable time and effort in the future. If you need your manhole covers badged, please ask at the time of ordering.

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