Basement Waterproofing Cost Estimator
Pick a system, enter your floor area, choose the intended use — and get an instant range aligned with BS 8102 practice and real North London pricing.
How much will basement waterproofing cost? The two retrofit systems price differently: tanking (Type A) at £40–£80/m² of treated surface suits sound masonry and lower water loads; cavity drain membranes (Type C) at £70–£140/m² — plus a £1,500–£3,500 sump pump system — are the habitable-space standard on London Clay. Full schemes run £5,000–£30,000+ by area, depth and finish; cellar projects range £1,000–£3,000 (dry storage) to £8,000–£30,000+ (habitable). Estimate below, then start any real project with a £250–£450 BS 8102 design survey — system choice must follow the water, not the brochure.
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Your estimate
Enter your basement's floor area and choose the options. Treated surface area (walls + floor) is estimated automatically from floor area.
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Read the guideBasement Waterproofing Cost Estimator FAQs
For habitable ambitions on London Clay, estimate with cavity drain (Type C) — it's the standard recommendation because it manages water pressure and is maintainable. Tanking suits storage/utility grades with lower water loads. The design survey makes the real decision.
Type C systems collect water that must be ejected, and habitable grades on clay need pumped drainage with battery back-up as standard. The £1,500–£3,500 system plus £120–£250 annual servicing is part of honest budgeting, not an extra.
Excavation for drainage falls, party-wall process in terraces, high inflow demanding duplex pumps, head-height digging, and finish specification. The BS 8102 design survey (£250–£450) surfaces these before anyone quotes.
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