Building Drainage

Load class
What does it really mean and how to choose it?

When selecting the correct grating for your application, careful attention must be given to number of factors. The most important challenge is selecting the right type of grating with appropriate load class. Careful consideration of this will positively influence the grating lifespan.

The grating itself is the most exposed part of gully or channel in regards to traffic. To minimize the risk of failures, a proper grating type and load class have to be considered based on the defined traffic during all future operations.

You can read and watch an explanatory video about each of the four key topics below. You can also use a grating selection guide, which will help you with the grating selection process by recommending the right grating for your application based on the input criteria.

12.5 tonne does not always equal 12.5 tonne

It is essential to ensure the gratings specified in your facility can cope with the loads to which they will be subjected but there is still a great deal of confusion among specifiers about what load class ratings (or standards) their gratings need to satisfy.

Gratings manufactured to meet EN 1253 or EN 1433 appear to have the same tolerance to load – but that’s not in fact the case.

EN 1433 applies to products which will be used in car parks, pedestrian areas and routes which are subject to vehicle traffic with large pneumatic tyres.  As a result, when a product is tested to EN 1433, a 12.5 tonne load (for example) is applied to a larger area than it is if the product is tested in accordance with EN 1253.

In contrast, EN 1253, applies to products that will be used in buildings which experience forklift vehicle traffic with small rubber tires and the 12.5 tonne load is applied over a relatively small area such as where a wheel contacts the grating.   

As a result, a grating which has a load class of 12.5 tonne under EN 1433 would be damaged, if not destroyed, when used in an area which has vehicle traffic which includes forklifts and pallet trucks.

Laboratory tests are not the same as real life

When it comes to grating specification, it’s important not to consider load class in isolation. Specifiers need to pay attention to the type of traffic load that a grating will be subjected to and, if required, change the type of grating they have specified in order to ensure the grating specified is fit for purpose and to prevent future damage.

For example, a mesh grating may be capable of withstanding a 1.5 tonne load under EN 1433 but only if the load is spread over a relatively large area and not if the load is coming from the small wheels on a trolley or vehicle which concentrate the load onto a small point.  In this example, a cover which shields almost the entire drainage would be more appropriate.

Application is as important as the load

When it comes to grating specification it is important to ensure you have the correct grating for your application. All too often specifiers look only at load classes and do not consider how the grating will be used in operation, and as a result gratings are damaged or even destroyed.

Fork lift truck wheels, for example, apply heavy loads over a relatively small area and the torque of the wheels can cause damage to mesh gratings even if they meet the load class requirements. In this type of application, it would be more appropriate to specify slot or more robust ladder gratings which are able to cope with demands of this type of application.

It is vital that specifiers consider how a grating will be used in a specific application as well as the loads to which it will be subjected to by ongoing operations and future equipment updates or maintenance.

Using small wheeled trolleys

A mesh grating may be manufactured to the load class required at your manufacturing facility but if you use small wheeled trolleys, which create small point loads, it may not be fit for purpose. 

Small trolley wheels apply high small point loads to gratings which may exceed their load class and destroy the grating.  As a result, in this type of application, ACO recommends the specification of slot and not mesh gratings.

Detailed specification guidance regarding gratings and any other aspect of your drainage system design is available from the ACO team who will be happy to provide specification advice for your individual project requirements.