UK Basement Response converts damp cellars into dry, habitable spaces. We underpin to gain ceiling height (dig down 500-800mm), tank walls to BS 8102 Type A/B standards, install pumped drainage for below-ground WCs, handle Party Wall Act for terraced properties, and meet Building Regs Part C (moisture) and Part F (ventilation).
Survey week 1. Underpin weeks 3-6. Tank and membrane weeks 7-8. Screed week 9. Dry by week 11.
Structural engineers design underpinning in 1m sections (mass-fill or mini-piled method). Waterproofing to BS 8102:2022 Grade 3 (habitable basement standard). CSSW-qualified damp specialists. Pumped macerator systems for below-sewer-level drainage. Mechanical ventilation with heat recovery (MVHR) for Part F compliance. Party Wall Awards for all terraced/semi basements (wall underpinning always triggers Party Wall Act).
From damp cellar to dry habitable space
Victorian cellars typically 1.8-2.0m high—below 2.1m minimum for habitable rooms. Solution: dig down 500-800mm to increase ceiling height to 2.4-2.6m. Process: excavate under existing foundation walls in 1m sections (prevents wall collapse), pour mass concrete underpinning (1:3:6 mix with 40mm aggregate) to new depth, move to next section. Takes 3-4 weeks for typical 30m² cellar. Cost: £15k-25k (£500-800/m² floor area). Building Control inspects every section before backfilling. Triggers Party Wall Act in terraced/semi houses (underpinning within 3m of neighbour). Alternative: mini-piled underpinning for difficult ground (£25k-35k, faster but more expensive). Result: 2.5m ceiling height—comfortable habitable space.
Basements surrounded by damp soil—water ingress inevitable without proper waterproofing. Three BS 8102:2022 systems: Type A (barrier protection): External tanking slurry applied to walls before backfilling. Cost: £8k-12k. Only possible if external access to walls. Type B (structurally integral): Waterproof concrete construction (expensive, £120-150/m² vs £80/m² normal concrete). New-build only. Type C (drained cavity): Internal membrane system—plastic cavity membrane on walls/floor, collects water into perimeter channel, pumps out via sump. Cost: £5k-9k for 30m² cellar. Most cost-effective retrofit. We recommend Type A+C combination (belt-and-braces approach): external tanking where accessible + internal cavity membrane. Guarantees dry space even if one system fails. 10-year insurance-backed warranty provided.
Basement toilets/showers below sewer level cannot drain by gravity—need macerator pump. System: WC/shower/basin drain into sealed pump unit, grinds waste, pumps up to main soil stack (3-4m lift typical). Pump units: £800-1,500 (Saniflo/Grundfos brands). Installation: £1,200-1,800 including boxing-in and connection. Limitations: noisy when flushing (60-70dB), requires mains power (basement floods if power cut during use), higher maintenance (descale annually, £120 service). Building Regs Part H applies—pump discharge must be accessible for maintenance, must have non-return valve to prevent backflow. Alternative for high water tables: full sewage pump in sump (handles all basement drainage). Cost: £3k-5k. Necessary if basement prone to flooding/water ingress—macerator units fail if flooded.
Basements have no natural ventilation (windows below ground level). Building Regs Part F requires mechanical ventilation for habitable rooms. Options: MEV (Mechanical Extract Ventilation): Extract fans in bathroom/kitchen, passive inlets elsewhere. £800-1,200 installed. Cheap but creates negative pressure (pulls damp air in through gaps). MVHR (Mechanical Ventilation with Heat Recovery): Balanced supply/extract with heat exchanger. Recovers 90% of heat from extracted air. £2,500-4,000 installed for basement. Expensive but essential for comfortable basement living (no stuffiness, no condensation). Also required for Part L thermal regs (ventilation heat loss calculations). Ducting runs in ceiling void (needs 400mm depth for plenum). Noise: 25-30dB on continuous mode (whisper-quiet). Service every 2 years (£150 filter change/cleaning).
Underpinning shared walls ALWAYS triggers Party Wall Act (excavating below neighbour's foundation level = Party Wall Act Section 6). Process more complex than extensions: structural engineer prepares method statement (underpinning sequence, temporary support, monitoring), party wall surveyor prepares Award (pre-work condition survey with photos/crack monitoring), neighbour's surveyor inspects before/during/after work, crack monitoring throughout (movement gauges on walls—£400 for set). Surveyor costs: £2k-4k typical for basement (higher than extension due to monitoring visits/complexity). Timeline: 3 months from serving notice to starting work (surveyor inspections, neighbour concerns). Common neighbour objections: subsidence risk (addressed by phased underpinning), noise/vibration (10-12 weeks heavy work), access (scaffolding/skips). Cannot proceed without Award—injunction risk if you start early.
Habitable basements need emergency egress windows (Building Regs Part B—same as loft conversions). Problem: windows below ground level. Solution: excavate light well in front garden (1.5m deep x 2m wide typical), install steel retaining frame, fit window with min 800x600mm opening, drainage gully at bottom (connects to main drains, prevents well flooding). Cost: £3k-5k per light well including excavation, steelwork, drainage, reinstatement. Planning: usually Permitted Development if <1m forward of front wall. Benefits: emergency escape, natural light (transforms basement feel), ventilation option (reduces MVHR reliance). Drawback: loses front garden space, railings needed for safety (trip hazard). Alternative: glass pavement lights (£1,500-2,500 each)—allow light from pavement above, but don't provide escape route (only use for non-bedroom basements).
Structural underpinning and BS 8102 waterproofing
Tell us your cellar dimensions and what you want to create