DETERMINING THE CORRECT SIZE MANHOLE COVER
When purchasing a manhole cover online, it's important to ensure that the size of the cover you are buying will match the size of the drainage opening in your property. Here are a few steps you can take to determine the size of the manhole cover you need:
• Measure the size of the clear opening: Use a tape measure to determine the length and width of the drainage opening in your property, this is the inside dimension of the chamber. It's also important to note the thickness of the walls surrounding the opening.
• Check the dimensions of the manhole cover: Online retailers will typically provide the dimensions of the manhole cover in the product listing, the size you will see eg. 600mm x 450mm is the clear opening size and not the overall size of the cover and frame. Compare these dimensions to the size of the drainage opening in your property to ensure that the cover will fit properly. If your access opening is 600mm x 450mm then a 600mm x 450mm cover is required, double check the external dimensions in the product listing to ensure there is room to sit the entire cover and frame.
• Consider the load-bearing capacity: Make sure that the manhole cover you are purchasing has the appropriate load-bearing capacity for the intended use. For example, if the cover will be used on a driveway, you will need a cover with a higher load-bearing capacity than if it will be used on a walkway. A comparison of weight ratings can be found further down this article.
• Check the material of the manhole cover: Manhole covers can be made of different materials such as cast iron, galvanised steel and plastic. Consider which material is best for your needs, and check that the cover you are purchasing is made of the desired material. Some manhole covers are recessed, meaning they can sit a multitude of substrates or tiles, the thickness dimension will determine what you can fit inside, roughly 50mm thickness for a tile or 80mm thickness for a slab or paving block.
When replacing a manhole cover, what other products will I need that can be purchased from the same merchant?
When replacing a manhole cover, there are a few additional products that you may need to purchase from a builders merchant in order to properly install the new cover. Here is a list of some common products you may need:
• Lifting keys or tools: Manhole covers can be heavy and difficult to remove, so you may need special tools or lifting keys to help remove the old cover and install the new one.
• Security bolts: In some cases, security bolts or locking systems may be necessary to prevent unauthorized access to the drainage system. Generally found in commercial settings these may be purchased separately, though in a residential setting, bolts are usually provided on certain manhole covers as standard. Get in touch with the UK Build Supplies team if you would like us to suggest a lockable cover for your property.
• Paint or coating: If the existing frame is rusty or corroded, it's recommended to paint or coat it before installing the new cover. Cast manhole covers from new can sometimes show early stages of rusting, this is due to the minimal amount of bitumen applied at the factory. This is completely normal and will not affect the integrity of the cover, the oxidization will wear away with normal traffic, though if deemed unsightly a coating of bitumen paint can be applied for improved aesthetics.
• Concrete or asphalt: If the existing frame needs to be leveled, you may need to purchase asphalt or concrete to level the surface before installing the new cover.
It's always recommended to consult with a professional engineer or builders merchant to ensure that you have all the necessary products and tools to properly replace the manhole cover.
Comparison of BS EN 124 Classification and suitable load bearings:
BS EN 124 classification is a European standard that classifies manhole covers and gully gratings based on their load-bearing capacity and durability. The standard includes six classes of covers, each with different specifications for load-bearing capacity and traffic use. Here is a step-by-step comparison of the six classes of BS EN 124:
• Class A15: This class is the lowest class of manhole covers and gully gratings, with a load-bearing capacity of up to 1.5 tons. These covers are suitable for use in pedestrian areas and residential areas pathways.
• Class B125: This class has a load-bearing capacity of up to 12.5 tons and is suitable for use in pedestrian areas, residential areas with low-speed vehicles, and areas with slow-moving traffic.
• Class D400: This class has a load-bearing capacity of up to 40 tons and is suitable for use in areas with moderate-speed traffic, such as in urban areas and industrial areas.
• Class E600: This class has a load-bearing capacity of up to 60 tons and is suitable for use in areas with high-speed traffic, such as on highways and in ports and airports.
• Class F900: This class has the highest load-bearing capacity of up to 90 tons and is suitable for use in areas with extremely heavy traffic, such as on highways and in ports and airports.
It's important to note that the classification of manhole cover or gully grating is not only based on the load-bearing capacity but also on the durability requirements of the cover, which are specified in the standard.
