Global House, Surbiton — External Roof Encapsulation
A 1,575 m² external roof project for Global Property Investments Limited, combining 25 mm of closed-cell roofing foam with a GacoFlex S42 silicone finish at Red Lion Business Park.
Discuss a similar project →Project at a glance
- Client
- Global Property Investments Limited
- Location
- Global House, Red Lion Business Park, Surbiton
- Completed
- June 2025
- Installer
- Spray Foam Tech Limited
- Specification
- Duratite Building Products Limited
- Roof area
- 1,575 m²
- Existing covering
- Asbestos-cement roofing
- Roofing foam
- 25 mm closed-cell polyurethane
- Exterior finish
- GacoFlex S42 silicone
- Preparation product
- GacoWash
- Setting
- Nearby occupied homes and business units
The building and the original brief
The roof showed age-related weathering, staining and suspected deterioration around fixings and valley intersections. Duratite’s account describes the sheets as suitable for the selected encapsulation route, with occupied homes and active business premises close to the site.
The work needed to address the roof as a connected surface, including the four pitched bays, valley and eaves gutters, rooflights and the office roof. Planning for neighbouring properties and containment of the application was therefore part of the project, alongside the choice of foam and coating.
The specified system
Prepare the existing roof
GacoWash formed the cleaning stage. The project account records controlled low-pressure application, soft agitation and recovery of cleaning residues under the site safety plan.
Apply the roofing foam
Closed-cell polyurethane roofing foam was spray-applied in successive lifts to a recorded 25 mm thickness. The insulation layer followed the existing roof profile.
Complete the silicone finish
GacoFlex S42 was airless-sprayed over the foam. S42 is the silicone roof coating in this build-up; it is not the spray foam.
Include drainage and connected areas
The source describes the system continuing through the integral valley gutter and external eaves runs, with work to restore falls towards the outlets. The office roof and rooflight areas were included in the recorded treatment.
How the work was carried out
Protect the surrounding site
Perimeter scaffolding, harness arrangements, netting and sheeting formed part of the access and containment measures. The source also records a spray booth used to help contain overspray.
Work within application conditions
Ambient and substrate conditions were logged daily. Application was stopped when the project’s wind limits were exceeded, rather than continuing regardless of conditions.
Check foam and coating coverage
The team spot-checked foam depth using calibrated probes and used wet-film comb gauges during silicone application. Product batch numbers were recorded in the site log.
Prepare the completion record
The completed roof was registered for the applicable GacoFlex limited material warranty. A formal works report recorded roof condition, the selected encapsulation approach, specification and site protocols.
Project photography
The documented result
The published project record shows the roof beneath the finished foam-and-silicone system, including the connected gutter treatments. The asbestos-cement sheets were retained in place rather than being removed as part of the works.
The case demonstrates the importance of detail continuity: a large treated pitch is only part of a roof, and valleys, eaves, outlets and adjoining areas need their own scope. It also records the checks made during installation, giving more context than a finished aerial photograph alone. The encapsulated asbestos remains part of the building and must continue to be managed.
Planning a similar project
For an external refurbishment near occupied buildings, include neighbouring uses, access boundaries, drainage defects and the full set of connected roof areas in the survey brief. The quote should identify the completed roof system and its documentation.
Explore our relevant insulation and roofing service or use the quotation checklist to prepare your brief.
Project details and photography adapted from Duratite’s original Surbiton project record. ThermoFoam is part of the Duratite Group.
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