Method Statement: Liquid-Applied Polyurethane Waterproofing for Internal Wet Areas – Method Statement

Work Summary

• Supply and install liquid-applied polyurethane (PU) waterproofing membrane systems to internal wet areas such as bathrooms, showers, toilets, pantries, laundries, and kitchens.
• Includes substrate preparation, moisture testing, priming, elastomeric fillet at wall–floor junctions, reinforcement at stress points/penetrations, multi-coat PU application to achieve specified dry film thickness (DFT), detailing to upstands/thresholds, curing, 24-hour flood test, rectification, and handover for tiling/protection.

Areas Included

• Floor areas with upturns to surrounding walls/partitions, shower recesses, around drains, pipe penetrations, thresholds, and wet walls as indicated on drawings.

Exclusions

• Structural repairs beyond minor crack/spall repairs.
• Final floor/wall finishes and screeds unless noted.

Key Performance Targets

• Slope to drain prior to membrane: typically 1:80 to 1:60 toward outlets [Verify per project specifications].
• Minimum DFT: typically ≥ 1.2 mm overall, uniform, pinhole-free [Verify per product datasheet].
• Flood test: 24 hours minimum, no leakage, no unacceptable water loss.
• Adhesion to substrate (if specified): pull-off ≥ 0.7 MPa, predominantly cohesive failure [Verify per project specifications].

Approvals and Submissions

• Method Statement and ITP approved by Engineer/Consultant prior to works.
• Manufacturer’s datasheets, SDS, and compatibility statements submitted for primer, membrane, sealant, and reinforcement.
• Applicator qualifications/approval letter and toolbox talk records available.

Site and Substrate Readiness

• Plumbing pressure tests for concealed services in wet areas completed and passed prior to membrane works [Verify per project specifications].
• Substrate age: cement-sand screed typically ≥ 7 days (rapid-set) or ≥ 28 days (standard) before PU application unless moisture barrier is used [Verify datasheet/spec].
• Surface finish: sound, clean, dry, free from laitance, dust, oils, curing agents, and contaminants; repairs completed and cured.
• Level and falls: confirm slopes to drain 1:80–1:60; tolerances typically ±3 mm under 2 m straightedge [Verify per spec].
• Movement/control joints identified and bond-breaker details agreed.

Environmental Conditions

• Ambient/substrate temperature typically 5–35°C; RH < 85%; dew point: substrate temperature ≥ 3°C above dew point to prevent condensation [Verify datasheet].
• Ensure adequate mechanical ventilation for enclosed rooms; no ignition sources near solvent-based primers [Verify per project HSE plan and local regulations].

Permits and Controls

• PTW for chemical use/solvent use and flood test authorization in occupied buildings.
• Electrical tools PAT-checked; RCDs in wet areas.
• Adjacent finishes and drains protected/masked.

Mock-Up

• Execute a mock-up area (e.g., 1–2 m²) including a corner, a penetration, and a drain. Demonstrate WFT/DFT, reinforcement, and cure. Obtain written approval.

Risk Assessment Controls

• Hazard: Solvent vapors from primers (flammable, irritant)
• Likely consequence: Fire/explosion; respiratory irritation; CNS effects
• Engineering/procedural control: Use low-VOC/solvent-free where possible; eliminate ignition sources; provide forced ventilation achieving ≥6 air changes/hour; decant in well-ventilated areas; use intrinsically safe lighting where required
• Required PPE: Organic vapor respirator (A2 filters) where needed, safety glasses, nitrile gloves, long sleeves
• Collective preventive measure: No Hot Work within 10 m; flammable cabinet for storage; spill kits ready

• Inspection/permit/supervision: Chemical use PTW; gas/vapor checks if confined; SDS on site; HSE walkdowns [Verify per project HSE plan and local regulations]

• Hazard: Isocyanate exposure from PU products

• Likely consequence: Respiratory sensitization/asthma; dermal sensitization
• Engineering/procedural control: Avoid spraying; apply by roller/squeegee; local exhaust ventilation; restrict access; training on isocyanate handling
• Required PPE: Half-mask respirator with A2/P3 filters, nitrile gloves (0.4 mm), coveralls, eye protection
• Collective preventive measure: Signage “Isocyanates in Use”; emergency eyewash; medical surveillance per policy

• Inspection/permit/supervision: HSE monitoring; verify SDS and exposure limits; supervision during mixing

• Hazard: Silica dust during grinding/abrading

• Likely consequence: Respiratory illness; eye injury
• Engineering/procedural control: Tools with shrouds and HEPA vacuums; wet suppression where safe; isolate area
• Required PPE: P3 disposable respirator or half-mask with P3, safety goggles
• Collective preventive measure: Enclosure/curtains; housekeeping plan

• Inspection/permit/supervision: Equipment inspection; dust monitoring if required

• Hazard: Slips on wet membrane or flood test water

• Likely consequence: Falls, sprains
• Engineering/procedural control: Sequence to exit; restrict access; non-slip overshoes; barriers and signage; pump/absorb spills immediately
• Required PPE: Non-slip safety footwear
• Collective preventive measure: Temporary edge/door bunds with visible marking

• Inspection/permit/supervision: Supervisor to maintain exclusion zone

• Hazard: Manual handling of 15–25 kg pails

• Likely consequence: Strains, musculoskeletal injuries
• Engineering/procedural control: Use trolleys; team lifts; decant into smaller containers
• Required PPE: Gloves with grip, safety footwear
• Collective preventive measure: Material staging near workface

• Inspection/permit/supervision: Manual handling training and observation

• Hazard: Electrical hazards in wet environments

• Likely consequence: Electric shock
• Engineering/procedural control: Use 110V tools or RCD-protected circuits; keep cords elevated; no live cords during flood tests
• Required PPE: Dry-hand procedures; insulated gloves when needed
• Collective preventive measure: Lockout/tagout of outlets near flood test area

• Inspection/permit/supervision: Electrical PTW/LOTO as required; PAT test records

• Hazard: Ingress to lower floors during flood test

• Likely consequence: Property damage; mold risk
• Engineering/procedural control: Pre-inspect below ceiling; establish bunds ≥25 mm; continuous monitoring first 2 hours; emergency drain plan
• Required PPE: As standard
• Collective preventive measure: Notify occupants; place drip trays below historical leak points

• Inspection/permit/supervision: Flood test PTW; consultant witness; log start/finish levels

• Hazard: Fire from solvent storage

• Likely consequence: Burns; facility damage
• Engineering/procedural control: Store in ventilated, bunded, locked flammable stores; decant minimum quantities only
• Required PPE: Standard + fire-resistant gloves if handling large volumes
• Collective preventive measure: Foam/CO2 extinguishers; no-smoking zone
• Inspection/permit/supervision: Weekly store inspection; extinguisher checks

• VOC and Odor Management: Prefer low-VOC products. Use mechanical ventilation and schedule work off-hours where sensitive receptors exist. Monitor odor complaints and adjust airflow.
• Waste Management: Collect empty pails, roller covers, masking waste in labeled containers. Triple-rinse if required by supplier; otherwise treat as hazardous waste if solvent residues remain. Maintain waste transfer notes [Verify per local regulations].
• Spill Prevention: Secondary containment for liquids; spill kits at mixing points; train crew on immediate containment and reporting.
• Water Use and Discharge: Flood test water must be drained via sanitary systems only; do not discharge to storm drains. Prevent silt/paint solids; use strainer at drains.
• Noise/Dust: Use low-noise equipment; dust extraction during grinding; maintain doors closed to contain dust; clean with HEPA vacuums (no dry sweeping).
• Material Storage: Keep products between 10–30°C, off the floor, out of direct sunlight; segregate incompatible chemicals.
• Energy/Carbon: Optimize batch mixing to reduce waste; use LED task lighting and high-efficiency fans.
• Documentation: Keep SDS, batch logs, and waste manifests; include environmental inspection checklists.

Controls and Records

• Calibrations: WFT/DFT gauges and pull-off testers calibrated within the last 6 months [Verify per QA plan].
• Batch Traceability: Record product names, batch/lot numbers, manufacture/expiry dates, and mixing ratios on Batch Log.
• Environmental Records: Record ambient and substrate temperature, RH, and dew point each shift.
• Testing Frequencies:
• Moisture tests: Minimum 1 per room (≤25 m²) and 1 per additional 50 m² or part thereof.
• WFT: Minimum 3 readings per room per coat, plus one per 10 m² for larger rooms.
• DFT: Minimum 1 location per 10 m²; more at edges/penetrations.
• Adhesion (if specified): Minimum 3 tests per area or 1 per 200 m², whichever is greater.
• Flood test: 100% of wet areas.
• Acceptance Criteria:
• Substrate falls: 1:80–1:60 toward drains; tolerance ±3 mm under 2 m straightedge [Verify].
• Moisture: RH ≤ 75–85% or MVER ≤ 3–5 lb/1000 ft²/24 h as product allows [Verify].
• Film thickness: Overall DFT ≥ specified (typ. ≥1.2 mm) with no local thin spot < 90% of specified.
• Integrity: No pinholes, blisters, or fish-mouths; full coverage at corners and penetrations.
• Flood test: No leakage; water loss ≤ 2 mm after evaporation compensation.
• Adhesion: ≥ 0.7 MPa (or per spec); cohesive failure preferred.
• Nonconformance: Mark defects, raise NCR, correct by abrading, re-priming if needed, re-coating, and re-testing.
• Handover Dossier: Approved ITP, WFT/DFT logs and maps, moisture test reports, flood test certificates, batch logs, MSDS/SDS, calibration certificates, as-built marked-up plans.

• Manufacturer Technical Data Sheets (TDS) and Safety Data Sheets (SDS) for primer, membrane, sealant, and reinforcement.
• Pre-application checklist (substrate, moisture, environmental conditions).
• WFT/DFT logging templates and example DFT map.
• Flood test certificate template and permit to work (PTW) forms.
• Equipment calibration certificates (WFT/DFT gauges, pull-off tester).
• Mock-up approval record and photo documentation.
• Nonconformance/Corrective Action Report (NCR/CAR) templates.