BS 8102:2022, Table 2
The four performance grades for basement waterproofing, in practice.
Selecting the right grade is a decision about the space's intended use. Not the basement's depth, not the contractor's preferred system. The grade governs everything downstream. This is how CLW reads Table 2.
The four grades
Selected by intended use of the space. Never by basement depth.
Performance Grade
G1A
Car parks, plant rooms, storage where seepage is tolerable
Some seepage tolerated
Read in depth
Performance Grade
G1B
Storage with ventilation; non-critical plant
No water penetration; damp tolerated
Read in depth
Performance Grade
G2
Workshops, retail backs of house, secondary commercial
No water penetration; some damp
Read in depth
Performance Grade
G3
Habitable accommodation, offices, retail, leisure, food, archives
Dry environment, controlled humidity
Read in depth
BS 8102:2022 Clause 6 places the grade selection with the waterproofing design specialist. Not the contractor. The grade governs the design strategy, not the cost ceiling.
The 2022 edition
Key changes since BS 8102:2009.
The 2022 edition is materially different from the 2009 version most contractors and many designers still reference from memory. The biggest shifts are around competence, combined protection, and the design specialist's role.
Read the full summary →FAQ
What people ask us first.
What is BS 8102? read
BS 8102:2022 is the British Standard for protection of below ground structures against water from the ground. It is the single most-cited reference document for waterproofing design on UK basements and below-ground structures.
How many performance grades does BS 8102 define? read
Four, G1A, G1B, G2, and G3. Set out in Table 2 of the 2022 edition. The grade is selected by intended use of the space, not by the depth of the basement.
Who is responsible for selecting the grade? read
BS 8102 is clear that the waterproofing design specialist is responsible for the recommendation, in consultation with the client and the rest of the design team. A grade selected by a contractor with commercial interest in the system being installed is a common failure pattern.
What changed in the 2022 edition? read
Significant changes to Type A, B, and C definitions; a stronger emphasis on competence and the role of the waterproofing design specialist; explicit guidance on combined protection and how it should and should not be relied upon. See the key-changes summary linked below.
Need help selecting a grade on a live scheme?
CLW writes the grade recommendation as part of the design philosophy at RIBA Stage 2–3. Defensible, documented, and traceable through to the performance specification.