Basement gym conversion protected from flooding

Context

Delta Membrane Systems was involved in the renovation of the basement of a mews property in South West London to create a gym area.

The project involved excavating under the front drive to increase the available space. The newly extended/excavated basement had to be made watertight with a waterproofing system which provides a Grade 3 waterproof environment (in accordance with Table 2 BS8102:2009).

BS8102:2009 sets out the limitations and scope for below ground structures. Areas covered include:

• Waterproofing barrier materials
• Waterproofing to construction joints
• Ensuring buildings are structurally integral with watertight construction
• Drained cavity construction
• Ground water assessment
• Ground water drainage
• Associated risk assessments

All basements must be constructed (or retrofitted) to cope with groundwater levels up to the full retained height of the basement inorder to preserve the integrity of a structure whilst ensuring the usefulness of the basement.

The area of potential weakness (where moisture could penetrate into a structure) in a below ground structure is the wall/floor junction. The structural waterproof concrete box was provided by the main contractor. Advance Property Preservation Limited were called upon to ensure the basement was structurally waterproofed to BS8102:2009 requirements.

Products used

Delta’s Waterproofing Design Specialist suggested incorporating Köster NB1 to wall/floor joints (where the masonry walls meet the concrete slab).

For external junctions, fillets were created using Köster Repair Mortar Plus (a unique expanding waterproof material) to keep important junctions protected and watertight. The coved fillets were further waterproofed using two coats of Köster NB1 crystallizing mineral waterproofing slurry. Insulation screed and further fillets were incorporated to create a robust waterproofing solution