Pre-Specification Inspection Checklist

Blistering mapped across full roof area

Hard blisters (partially dried) vs soft blisters (active moisture). Distribution pattern indicates moisture source.

Felt lap and joint separation probed

All sheet edges and laps tapped and probed. Separation from deck indicates adhesion failure below surface.

Gutter fall measured with level or string line

Effective fall along full gutter length. Low spots marked. Falls below 1:200 typically inadequate.

Outlet capacity confirmed against catchment area

75mm outlet draining 1,000m² is undersized. Outlet size must match roof catchment.

Parapet and upstand heights measured

Minimum 150mm from finished membrane level. Below this, overlay requires raising parapets.

Previous repair sealants identified

Silicone-based sealants are chemically incompatible with liquid rubber. Must be removed before application.

Drainage overflow staining documented

Staining on fascias confirms sustained drainage inadequacy. Silt at gutter centres confirms standing water history.

Penetration and detailing inventory completed

All roof penetrations, upstands, gutters and edge details counted and photographed. Detailing scope drives programme.

Electronic moisture meter grid survey completed

Readings at 5m intervals across entire roof area. Drainage zones and low points tested separately.

Moisture readings documented with location references

Each reading logged with grid reference. Readings above 15% indicate trapped moisture requiring remediation.

Blister moisture content tested

Soft blisters pierced and moisture confirmed. Hard blisters may indicate partially dried moisture.

Substrate type confirmed

Concrete, metal, felt, asphalt — substrate type determines primer requirements and moisture thresholds.

Weather history reviewed (7 days prior to survey)

Recent rainfall elevates substrate moisture. Application day readings required — survey readings alone insufficient.

Deck condition assessed (opening up where required)

Where deck age and specification unknown, core samples or opening up at representative locations may be necessary.

Thermal movement joints identified (metal roofs)

Ridges, eaves, and intermediate movement joints mapped. Movement accommodation required before overlay.

Structural deflection checked (large span decks)

Ponding zones may indicate structural deflection. Level survey distinguishes deflection from inadequate falls.

Corrosion penetration probed (metal substrates)

Active rust probed at lap positions. Through-corrosion requires mechanical repair before lining.

Insulation condition assessed (probe or core sample)

Saturated insulation beneath felt not detectable by moisture meter through felt. Requires opening up.

Building occupation status confirmed

Occupied vs vacant determines access hours, noise restrictions, and phasing requirements.

Spray equipment access confirmed (if spray specified)

Hardstanding or vehicle access for spray rig, minimum 30m operational radius, electrical supply.

Scaffold or MEWP requirements assessed

Gutter work, edge details and elevated roof areas require safe access. Working-at-height legislation applies.

Weather window identified (programme planning)

Cold-spray requires dry conditions and temperatures above 5°C. Northern England Oct-Mar: 3-4 suitable days/week average.

Phasing strategy agreed (large roofs)

Roof areas above occupied spaces may require phased strip-out with temporary waterproofing between phases.