Warm Deck Flat Roof Replacement in Cobham

Completed project · Cobham, Surrey

A new roof, from the deck to the finishing details

We replaced this Cobham flat roof with a new warm deck construction and a three-layer felt waterproofing system. The work included a new deck, Alutrix vapour control layer (VCL), bonded PIR insulation, new lead flashings, felt coping and lead outlets.

Location

Cobham, Surrey

Roof system

Warm deck with three-layer felt

Key detail

Bonded insulation above an Alutrix VCL

Before & after

Existing flat roof and roof lantern in Cobham before replacement — **Before**The previous roof covering, roof lantern and stone coping before the work.

Completed three-layer felt warm roof in Cobham with new perimeter detailing — **After**The new felt roof, finished around the retained roof lantern with renewed perimeter details.

The Project Brief

The existing flat roof needed a full replacement. Its covering, insulation and decking were removed so that the new roof could be built up from the structure. The existing roof lantern was retained, with the new roof layers and waterproofing detailed around its base.

The scope covered the concealed layers as well as the visible finish: the deck and upstands, vapour control, insulation, felt covering, wall junctions, perimeter and drainage outlets.

Work Completed

New deck and Alutrix vapour control layer

We installed new 18mm OSB3 decking and formed the perimeter upstands. An Alutrix VCL was bonded to the prepared deck beneath the insulation, with the layer dressed at the edges and around the roof details.

Bonded insulation without screws through the VCL

The PIR insulation boards were bonded in place rather than screwed through the insulation and vapour control layer. This avoided screw penetrations through those layers as part of the insulation installation.

Three-layer felt waterproofing

The new roof was finished with a torch-on base layer, reinforced underlay and mineral-finished cap sheet. Felt detailing continued around the roof lantern, upstands and perimeter.

Lead flashings, felt coping and outlets

New lead flashings were fitted at the wall junctions. We also installed new felt coping to the perimeter and new lead outlets, completing the edges and drainage details as part of the roof replacement.

Project Photos

These photographs show the layers beneath the finished felt and the completed roof details.

Alutrix vapour control layer installed across the Cobham flat roof deck and upstands — **Alutrix vapour control layer**The foil-faced layer installed across the deck, with attention to edges and pipe details.

PIR insulation being fitted above the vapour control layer around the roof lantern — **Bonded insulation**The insulation stage, with boards fitted around the existing lantern and roof perimeter.

Finished felt waterproofing and felt-covered perimeter around the Cobham roof lantern — **Finished felt and perimeter**The mineral-finished felt surface and new felt coping around the roof.

The Finished Result

The completed roof has a new warm deck build-up and three-layer felt covering around the retained lantern. The lead flashings, felt coping and lead outlets were renewed alongside the main roof, bringing the waterproofing and finishing details into the same project.

Planning a flat roof replacement in Cobham?Tell us about your roof and we can arrange the next step. Explore our flat roofing services, visit our Cobham roofing page, or request a free written quote.

Project by Surrey Roofing & Windows Ltd.
Meet the team · flat roofing services · Roofing in Cobham