Living room in a basement

Waterproofing Grades explained: What will you use the basement for?

Living room in a basement

Any waterproofing design should start with a question on what is the intended purpose of the space that is going to be waterproofed. What will be stored there and what finishes will it have. This is what will determine what grade of waterproofing protection we need.

Confusion about the “Grades” was one of the main drivers behind the recent update of the BS8102 Standard.

The Code of practice 2009 used to say that Grade 2 as an example was a plant room and can be damp.

In fact some plant  rooms can have very expensive finishes and can be used to house plant and electrical equipment and boards which cannot be in a damp environment.

So examples have been removed from the Standard.

Another issue with previous Standard was that it was not clear if Grade 2 was referring to penetrating damp or just environmental damp / condensation? Two different issues.

We still have 3 Grades, same as before, but Grade 1 is split into A and B. The focus is on the acceptable moisture level so it will be entirely up to the client to decide what grade is acceptable for whatever they will be putting in the basement, no examples are provided now.

cinema room in basement

This is what Grades are in the updated BS8102:2022 standard:

GRADE 1a Seepage and damp areas from internal and external sources are tolerable, where this does not impact on the proposed use of below ground structure.

GRADE 1b No seepage. Damp areas from internal and external sources are tolerable.

GRADE 2 No seepage is acceptable. Damp areas as a result of internal air moisture/ condensation are tolerable; measures might be required to manage water vapour/condensation.

GRADE 3 No water ingress or damp areas is acceptable. Ventilation, dehumidification or air conditioning necessary; appropriate to the intended use.

The agreed grade should meet with client’s expectations for the intended use of the below ground space. Reducing the grade could increase the risk of not meeting the expectations of the client.

The grade of waterproofing protection should be agreed at the earliest stage. Reducing the grade increases the risk.

Seepage has been defined separately to damp, and specifically mentioned as either acceptable or unacceptable depending on the Grade of protection.

If you want to discuss this document in more detail or simply prefer an interactive approach, book a FREE CPD on BS8102:2022.

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