Waterproofing & Tanking
QA inspection checklist

Substrate Preparation

1. 1.

   Substrate clean, dry, and free from defects
   What to look forConcrete substrate cured, swept clean, free of laitance, oil, dust and form release. No protruding tie-bars or sharp edges that would damage membrane. Honeycombed areas filled. Surface within manufacturer roughness limits — typically CSP 3-5 (ICRI scale).
   Acceptable whenConcrete age ≥ 28 days for cementitious tanking, ≥ 21 days for self-adhesive bitumen. Moisture content per system: ≤ 4-5% by Tramex / hygrometer for adhered systems. Surface profile per BS 8102 — smooth steel-floated for sheets, profile for sprays.
   StandardBS 8102:2022 — Code of practice for protection of below-ground structures against water from the ground. ICRI Guideline No. 310.2R.
   Common defectsConcrete too damp — adhesion failure, blistersLaitance and form-release oil left on surface — no bondHoneycombed areas not pre-filled — voids behind membraneSharp edges puncture membraneTie-bars not cut back and patched — water path through wall
2. 2.

   All penetrations identified and prepared
   What to look forService pipes, ducts, and structural penetrations marked on the waterproofing drawing. Fillet/cove formed at re-entrant angles. Hydrophilic strip or proprietary sleeve at each pipe. Internal corners reinforced with manufacturer detail strip.
   Acceptable whenPer BS 8102 and waterproofing designer (CSSW): all penetrations sealed using designer-approved details. Cove fillet ≥ 20 mm radius at internal corners for sheet membranes. Hydrophilic strips per manufacturer (Sika SwellStop, Volclay Waterstop-RX).
   StandardBS 8102:2022. Property Care Association — CSSW (Certificated Surveyor in Structural Waterproofing) requirement.
   Common defectsPenetrations not sealed at all — direct water pathNo cove fillet — sheet stretched over sharp angle, tearsHydrophilic strip squashed flat — no swell on contactPenetration sealed externally only — Type A failure pointPipe boxed in before sealing — leak hidden behind cladding
3. 3.

   Primer applied as per manufacturer requirements
   What to look forPrimer applied at correct rate (manufacturer's coverage figure). Continuous across all bonded areas including upstands and details. Allowed to dry to "tack-free" before membrane applied. No ponding or runs. Type matches substrate (porous/non-porous/damp).
   Acceptable whenPer manufacturer technical data sheet — typical bitumen primer 0.2-0.4 L/m²; epoxy primer 0.15-0.3 L/m². Drying time observed (typically 30 mins to 24 h). Primer-to-membrane window not exceeded (typically 24-72 h).
   StandardManufacturer technical data (Bauder, Sika, Newton, Triton, RIW). BS 8102:2022.
   Common defectsPrimer too thin — bond failurePrimer too thick (puddled) — tacky for days, dust contaminationMembrane applied before primer dry — wet-on-wet, no bondPrimer-to-membrane window exceeded — no bond at re-coatWrong primer (water-based on damp substrate) — no penetration

Membrane Application

1. 4.

   Membrane type matches specification (type A/B/C)
   What to look forType A (barrier — bonded sheet/liquid), Type B (integral — water-resistant concrete with hydrophilic waterstops), or Type C (drained cavity system) per BS 8102 and waterproofing designer. Product matches design — manufacturer code on packaging cross-references the design specification.
   Acceptable whenBS 8102:2022 mandates a CSSW-qualified waterproofing designer who specifies the type and grade of protection per environment. Habitable basement typically requires combined Type A + B or B + C. Single-system reliance no longer accepted in Grade 3 environments.
   StandardBS 8102:2022 — Code of practice for protection of below-ground structures. PCA / BSI CSSW Scheme.
   Common defectsSingle Type A only used in habitable space — no redundancyType B (water-resistant concrete) without hydrophilic waterstops at construction jointsType C cavity drain not properly drained to sump — water builds upGeneric membrane substituted for specified product — system incompatibilityNo CSSW-qualified designer — design liability gap
2. 5.

   Application thickness correct

   Record: DFT (mm)
   What to look forLiquid systems: WFT measured during application with comb gauge; multiple coats stepped to achieve DFT. Sheet systems: full lap roll-out, no creases, no bridging. Cementitious: trowelled to manufacturer's coverage rate per coat.
   Acceptable whenPer manufacturer DoP / TDS: typical liquid bitumen DFT 3-4 mm; epoxy/PU 1.5-3 mm; cementitious 2-3 mm in 2 coats. Sheet thickness as DoP (1.5-2 mm typical for HDPE, 4 mm for SBS bitumen). DFT verification by sample / wet film during application.
   StandardBS 8102:2022. Manufacturer ETA / BBA certificate. BS EN 1504-2 for cementitious systems.
   Common defectsSingle coat where two specified — DFT not achievedLiquid pulled too thin at upstands — pinholesSheet creases at corners — voids behind, water tracksCementitious coverage rate ignored — under-appliedNo WFT readings recorded — cannot verify coverage
3. 6.

   Laps and joints sealed continuously
   What to look forSide and end laps to manufacturer minimum (typically 75-100 mm side, 150 mm end on bitumen sheets). Self-adhesive sheets rolled with pressure roller. Heat-welded sheets show full bead of melt at edge. Liquid systems re-coated at laps with reinforcement strip.
   Acceptable whenLap dimensions per manufacturer DoP — minimum 100 mm typical for side, 150 mm for end laps. Welded laps tested by probe at random points (no penetration of weld). Adhered laps fully bonded — no open edges visible.
   StandardManufacturer technical specification. BS 8102:2022. SPRA / NFRC waterproofing guidance.
   Common defectsLap < 75 mm — capillary water tracks backCold weld between welded sheets — pulls apart at probeSelf-adhesive lap not rolled — bond is point-onlyLiquid system has no lap reinforcement — coating thinned at jointLap edge visibly open — water enters between layers
4. 7.

   Details at penetrations, corners, and changes of direction
   What to look forInternal corners coved with reinforcement strip lapped onto each face. External corners pre-formed sleeves or 3-piece welded detail. Pipe penetrations: collar/flange welded or bonded with overflashing. All details photographed before being covered.
   Acceptable whenPer manufacturer detail library: cove ≥ 20 mm radius; corner reinforcement strip ≥ 200 mm wide centred on angle; pipe collar with ≥ 100 mm flange welded to membrane. Photo record per BS 8102 and PCA.
   StandardBS 8102:2022. Manufacturer detail library (Sika, Bauder, Triton, RIW, Newton).
   Common defectsSharp internal corner not coved — sheet bridges, voids behindExternal corner welded over a creased fold — pinholePipe penetration with no flange — relying on mastic sealDetail not photographed — no proof at warranty claimReinforcement strip omitted at re-entrant angles
5. 8.

   Protection board installed before backfill
   What to look forProtection board (e.g. dimpled HDPE, hardboard, cement board) installed against finished membrane before any backfill or concrete is placed. Joints butted and continuous. Mechanically fixed to top of membrane only — fixings do not penetrate the waterproofing field.
   Acceptable whenPer BS 8102: protection board to manufacturer system spec (typically 1.5 mm HDPE drainage composite or 3 mm hardboard). Fixed at top with washer fixings into structural concrete (above tanking line). Backfill placed in compacted layers to BS 6031.
   StandardBS 8102:2022. BS 6031:2009 — Earthworks. Manufacturer system specs.
   Common defectsBackfill placed directly on membrane — punctures from stonesProtection board fixings driven through into membraneCompaction plant used too close to wall — local damageDrainage composite gap at top — silt enters drainNo protection at horizontal slab membrane before screed

Testing

1. 9.

   Flood test completed (if required)
   What to look forHorizontal surfaces (podium decks, planters, balcony tanking) flooded to design depth (typically 50 mm) for minimum 24 hours. Water level marked and monitored. Soffit inspected for leaks. Test water free of contamination. Test result signed off before screed/finish placed.
   Acceptable whenPer BS 8102 / NHBC and manufacturer warranty conditions: 24-72 hour flood test at 25-50 mm depth, no measurable drop after evaporation correction. No water visible on soffit or at perimeters. Photographic record of fill and drain.
   StandardBS 8102:2022. NHBC Standards 7.2 — Pitched roofs / 4.4 — basements. NFRC TB 60 (flat roofs).
   Common defectsFlood test skipped — leaks discovered after finishes completeTest duration too short to identify slow leaksDrains not closed — water disappears giving false passSoffit not accessible during test — leaks not seenNo record kept — disputes with warranty provider
2. 10.

   Warranty documentation provided
   What to look forManufacturer warranty certificate naming the project, naming the approved installer, listing the system applied, and the warranty period. Single-point warranty preferred (single party covers materials + workmanship). Insurance-backed warranty for high-grade environments.
   Acceptable whenWarranty period typically 10-25 years per system. Single-point warranty per LABC/NHBC. Approved installer status verified with manufacturer (e.g. Sika Approved Contractor, Triton Approved Installer). Inspection sign-offs filed with warranty.
   StandardBS 8102:2022. NHBC Standards. LABC Warranty Technical Manual.
   Common defectsNo warranty issued — installer not on manufacturer's approved listTwo warranties (material + workmanship) — disputes when leak occursInspection records missing — manufacturer voids warrantyWarranty for shorter period than design lifeConditions excluded (e.g. dynamic movement, ground-gas) — warranty hollow

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