How do I measure a manhole cover?

How to measure for a new manhole cover?

If you need to replace an old manhole cover just check out this handy blog.

Firstly check out what type of manhole cover you have and what area it is in; then consider if the areas usage will change e.g. an outdoor manhole cover being integrated into a household extension. This will change the regulations regarding the manhole/access cover and a different cover will be needed to replace it.

Can you lift the manhole?

Be careful make sure you do it carefully if you do not have the keys. hints and tips for this supplied in another blog just click the link.

With the cover removed you can see what the cover accesses and how deep it is. It will also allow you to measure correctly.

Please be careful around an open manhole!



Manhole terms

Clear Opening size/aperture – This is the size that all manhole covers are sold. Please no don’t confuse it with the next dimension.

Overall size/with frame – This is the measurements of the whole manhole cover including the frame.

In tray Depth – This is the depth from the top of the tray to bottom of the tray.

Overall depth – this is the depth from the top of the tray to the base of the cover including the frame.

You can see an example of a popular outdoor aluminium recessed manhole cover  with all its sizes explained. 

DS-60-3030 Double Sealed Cover & Frame
Clear Opening: 300mm x 300mm x 48mm
External Dimensions: 360mm x 360mm x 60mm
In-tray Depth: 48mm | Overall Depth: 60mm

The main issue with manhole covers is in measuring sizes. Switching old with new can throw up some different size issues. But the most common issue is a mistake made in the part of the cover measured before ordering. The explained item is not 30x30cm in overall size the 30x30m is the opening/aperture size.

What do I measure?

All manhole covers are sold on clear opening size, this is the aperture size once the cover has been removed from the frame.

To get this measurement from a circular cover removes the cover and measure from the inside walls of the frame from one side to the other across the opening.

A square or rectangular cover measurement is again after the cover has been removed from the frame. Measure the width and the length from the inside walls of the frame and also the height of the frame.

These will both give you an accurate size for the clear opening of the new cover you need.

Please note – Overall size of the frame does not automatically mean that the clear opening size will be the same as you currently have.

Measure the opening size to determine your requirements!

We are always on hand to help with any measuring queries before purchase. Call or email our helpful team can always give you their helpful advice.

Get in touch for any manhole size queries at or call us on 0105 515 1415

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