Basements are constructed below ground level and are therefore subject to ground water pressure. If insufficient external drainage or a failure in waterproofing, water ingress will result. The following information is designed for practical advice in three situations:
In Australia we do not have a specific Standard, as such we rely on a Performance Solution which is designed as “Deemed-to- Satisfy”. However a useful guideline is the British Standard 8102. The design of the construction can be designed to three grades of Watertightness; Grade 1 – some seepage and damp patches being tolerable; Grade 2 – no water penetration acceptable, but some moisture vapour tolerable; Grade 3 – Total Dry environment. Which every Grade of watertightness the project demands, it is advisable to have multiple strategies of defence. Having a waterproofing expert on your design team prior to construction phase has many advantages.
Most residential projects have a relatively kind environmental impact and the strategy will involve drainage, structural integrity and positive waterproofing. many commercial constructions have far more demanding criteria and strategies need to well thought through in the design phase. NB: A final tip in basement construction is to allow sufficient ventilation to avoid condensation issues.
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Principles of Below Ground Waterproofing – BS 8102
Existing walls which have moisture or water penetrating internally, require treatment from the ‘negative side’. The two most common strategies is to either treat the brick, block, mortar with a crystalline growth treatment to stop the water, or to form a new barrier on the surface. Both methods are valid, but results will vary by situation.
FLOOR JOINT REPAIR
The most common failure occurs in the floor/wall joint. Depending on circumstances, the water needs to be managed or stopped by repair. To repair from the ‘negative side’ usually requires mechanical assistance to penetrate the surface. If it is a rising damp issue, form a line barrier through damp coursing. Mortar or cracks can be repaired with crystalline growth treatment. Whilst weaknesses in the slab or wall can be retarded via forming a new barrier on the surface.