Method Statement: Installation of Roof Rainwater Drainage Outlets and Vertical Downspouts (uPVC/HDPE) with Waterproofing Integration and Flood Testing – Method Statement

Work Scope

• Install roof rainwater drainage outlets (gravity type) including waterproofing flange integration, clamping ring tightening/verification, and leaf strainer placement.
• Install vertical downspouts and horizontal collectors in uPVC or HDPE heavy-duty stormwater piping, including supports, anchors, expansion provisions, access fittings, and terminations to rainwater stacks or external discharge points.
• Coordinate and execute penetrations, sleeves, and firestopping/acoustic treatments where downspouts pass through slabs/walls [Verify per project fire strategy and acoustic specs].
• Conduct outlet flood testing, downpipe sectional water testing, and functional flow tests.
• Deliver complete QA/QC documentation: material approvals, inspection records, torque logs, fusion logs, test certificates, as-built redlines, and O&M manuals.

Exclusions (unless noted otherwise)

• Design of hydraulic capacity and storm intensity calculations (assumed by Designer); contractor to verify compliance with BS EN 12056-3 and project design.
• Structural works beyond small core drilling/sleeving.
• Permanent connection to external stormwater network outside building footprint unless specified.

Interfaces

• Waterproofing trade (bituminous, TPO, PVC, EPDM, or liquid-applied membranes).
• Structural and architectural works (slabs, upstands, parapets, roof finishes).
• MEP services sharing shafts/risers (clash coordination).
• Firestopping contractor for service penetrations.

• Approved shop drawings, coordinated with architectural, structural, and MEP services.
• Approved Material Inspection Requests (MIR) for outlets, pipes, fittings, supports, adhesives, and waterproofing system.
• Permits to Work (PTW): Working at Height, Hot Work (if torch-on membrane), Confined Space (for risers/shafts), Penetration/Drilling permits [Verify per project HSE plan and local regulations].
• Design confirmations: hydraulic design compliant with BS EN 12056-3; overflow provisions and parapet scuppers where specified [Verify].
• Weather and substrate: Substrate dry and clean for membrane and solvent welding; ambient temperature within manufacturer limits (typ. 5–40°C for PVC solvent cement; membrane cure per datasheet) [Verify].
• Calibration: torque wrenches and fusion machines within validity; laser level checked.
• Utilities and structure: Services scanned before drilling; structural approval for core drilling; check allowable temporary water loading on roof during flood test (kN/m²) [Verify].
• Mock-up (if required): One outlet and 3 m of downpipe to prove details and quality benchmarks.
• Toolbox talk and method/HSE briefing with involved trades (plumbing + waterproofing).

Key Task-Specific Hazards and Controls

• Hazard: Work at height on roof and at façades/shafts.
• Likely consequence: Falls leading to serious injury or fatality.
• Engineering/procedural control: Install edge protection/guardrails; use full-body harness with double lanyards on certified lifelines; MEWP/scaffold with valid tags; maintain 3:1 rule for ladders only for access; exclude unprotected edges within 2 m.
• Required PPE: Helmet with chin strap, full-body harness EN 361, lanyard EN 355, non-slip safety boots.
• Collective measure: Guardrails, toe boards, access control, rescue plan.

• Inspection/permit/supervision: Working at Height PTW; daily scaffold/MEWP inspection; competent supervisor present. [Verify per project HSE plan and local regulations]

• Hazard: Penetrations/core drilling into slabs/walls.

• Likely consequence: Striking rebar/services; structural damage; flying debris.
• Engineering/procedural control: GPR/service scan and permit before drilling; use drill stands with vacuum extraction; set drilling depth stops; exclusion zone and eye/face shields.
• PPE: Safety glasses/face shield, gloves, hearing protection, dust mask (P2/P3 if silica risk).
• Collective measure: Local extraction and wet suppression where applicable; barriers and signage.

• Inspection/permit/supervision: Penetration PTW; structural approval; tool pre-use checks.

• Hazard: Hot works (torch-on membranes) and ignition of combustibles.

• Likely consequence: Fire, burns, smoke inhalation.
• Engineering/procedural control: Prefer cold-applied systems where possible; if torch-on, clear combustibles 5 m radius, fire watch during and 60 min after; use flame guards and fire blankets.
• PPE: Flame-resistant gloves, goggles, long sleeves, fire-retardant clothing.
• Collective measure: Fire extinguishers (CO2/dry powder), charged hose nearby.

• Inspection/permit/supervision: Hot Work Permit; gas leak checks; trained operatives.

• Hazard: Handling solvents/primers and PVC cement.

• Likely consequence: Dermal/respiratory irritation; flammability.
• Engineering/procedural control: Use low-VOC products; work in well-ventilated areas; keep away from ignition; closed containers; follow SDS.
• PPE: Nitrile gloves, safety glasses, half-mask organic vapor respirator if ventilation inadequate.
• Collective measure: Spill kits and absorbents; decanting trays.

• Inspection/permit/supervision: SDS available; COSHH assessment; storage in flammable cabinets.

• Hazard: HDPE fusion equipment (hot surfaces, pinch points, electrical).

• Likely consequence: Burns, electric shock, crush injuries.
• Engineering/procedural control: Guarded plates; insulated leads; lock-off during setup; trained certified welders only; cooling time enforced.
• PPE: Heat-resistant gloves, eye protection, safety footwear.
• Collective measure: Barriers and signage around fusion area.

• Inspection/permit/supervision: PAT/inspection of equipment; calibration records; supervision by welding lead.

• Hazard: Manual handling of pipes/fittings and awkward postures.

• Likely consequence: Strains/sprains; dropped objects.
• Engineering/procedural control: Team lifts; use slings, pipe jacks, or MEWP; store pipes on racks; pre-cut lengths.
• PPE: Gloves with grip, safety boots.
• Collective measure: Lift plans for heavy components; exclusion below hoisting.

• Inspection/permit/supervision: Manual handling briefing; lifting plan approval.

• Hazard: Confined/service shafts and poor ventilation.

• Likely consequence: Asphyxiation, limited egress.
• Engineering/procedural control: Confined Space PTW where applicable; gas test; forced ventilation; standby watch and rescue kit.
• PPE: Gas detector (if required), harness, headlamp.
• Collective measure: Barricade shaft openings; communication protocol.

• Inspection/permit/supervision: PTW and gas test logs; trained entrants/attendants.

• Hazard: Water accumulation during flood testing.

• Likely consequence: Slip hazards; water ingress to lower levels; overloading slab.
• Engineering/procedural control: Temporary bunds sized/secured; control inflow; monitor structural load; continuous supervision; emergency drainage plan.
• PPE: Non-slip boots, gloves.
• Collective measure: Signage and restricted access to wet zones.

• Inspection/permit/supervision: Test method statement approval; supervisor presence throughout test.

• Hazard: Noise and dust from drilling/cutting.

• Likely consequence: Hearing loss; respiratory irritation.
• Engineering/procedural control: Select low-noise tools; fit extraction/vacuum; wet methods if compatible.
• PPE: Hearing protection, dust mask (P2/P3 as needed).
• Collective measure: Schedule noisy works in permitted hours.
• Inspection/permit/supervision: Noise monitoring where required.

• Water management: Use clean water for flood tests; capture and route discharge to designated drains only after QA sign-off; do not release to unfinished areas. Record volumes and avoid overloading storm network. [Verify per project EMP]
• Chemical management: Store primers/solvents in bunded flammable cabinets; keep lids closed; collect solvent wipes and adhesive containers as hazardous waste; segregate per waste codes.
• Waste and microplastics: Collect plastic swarf and offcuts immediately; prevent entry to rainwater system; use on-tool extraction and site vacuuming.
• Noise and working hours: Comply with local limits and permitted work hours; use acoustic shrouds where possible.
• Dust control: Vacuum extraction on drills; damp wipe surfaces; no dry sweeping.
• Spill prevention: Spill kits within 20 m of workface; treat any adhesive/primer spill as hazardous; report and record.
• Material efficiency: Cut lists to minimize waste; return unused, unopened materials to storage.
• Protection of finished membranes: Use protection boards/walk mats; prohibit solvent contact with incompatible membranes; no storage of sharp/metal items directly on membrane.

Controls and Records

• Material approvals: MIRs with certificates for outlets, pipes, fittings, supports, adhesives, gaskets, and membrane.
• Calibration: Torque wrench and fusion machine calibration certificates; laser level checks.
• Installation checklists: Outlet seating, membrane bonding, clamping ring torque, strainer fit, jointing procedures, support spacing, expansion provision, verticality and slope checks.
• Tolerances/targets:
• Outlet position: ±5 mm; flange flush within 1 mm rocking.
• Clamping torque: As per manufacturer ±10% [Verify].
• Pipe verticality: ≤3 mm per 3 m; horizontal slope ≥1:100; slope tolerance ±0.2% [Verify].
• Support spacing: Vertical 1.8–2.4 m; horizontal 0.8–1.2 m; within 150 mm of fittings [Verify per manufacturer].
• Testing:
• Flood test: 25–50 mm water head; 24 h duration (unless spec differs); acceptance: no leaks, negligible evaporation loss.
• Downpipe sectional water test: Head 1.5–3.0 m (or to highest joint in section); 15 min; acceptance: no visible leakage.
• Functional flow test: No standing water >5 mm after 15 min cessation [Verify].
• Documentation: Torque logs, fusion logs (with parameters), joint logs (cement/primer batch numbers), photos, IRs, NCRs and corrective actions, as-builts, O&M manuals.
• Hold and witness points per ITP.

• Approved shop drawings and coordination drawings (roof drainage layouts, sections, details).
• Manufacturer installation manuals: roof drains, membrane systems, solvent cements/primers, HDPE fusion.
• Material approvals: MIRs, certificates of conformity.
• Calibration certificates: torque wrenches, fusion equipment, survey instruments.
• Method-specific checklists: outlet integration, jointing, supports, pretest.
• Test documentation: flood test procedure and reports, downpipe water test certificates, functional flow logs.
• Firestopping approvals/details and inspection records.
• Risk assessments and Permits to Work (Working at Height, Hot Work, Confined Space, Penetration).
• As-built drawings and O&M manuals.