Case Study - Three-layer Torch-on Felt Flat Roof Installation in DA10

Location: 75 High Street, Swanscombe DA10 0AQ

Project Overview

PSE Roofing was appointed to install a new three-layer torch-on felt roofing system to a flat roof requiring a robust, long-lasting waterproofing solution. The project involved replacing the roof decking and installing a high-performance built-up felt system designed to provide excellent weather resistance and durability.

The installation was carried out using industry best practice, ensuring each layer was correctly bonded and detailed to deliver a fully waterproof roofing system.

Scope of Works

Erection of safe access equipment where required. Preparation of the existing roof structure for the new roofing system. Installation of new 18mm OSB roof decking. Installation of a venting/tack base layer to prepare the substrate.

Installation of the torch-on underlay, ensuring all joints were staggered by a minimum of 300mm to minimise the risk of water ingress. Installation of the mineral cap sheet, with all seams offset from the underlay to provide maximum waterproof integrity.

Completion of all perimeter detailing, upstands and edge terminations. Final inspection and site clearance upon completion.

Challenges

Achieving a fully bonded waterproof membrane across the roof area. Ensuring all felt joints and seams were correctly staggered to reduce the potential for water tracking. Producing high quality detailing around roof edges and terminations. Maintaining consistent workmanship throughout the hot works installation process.

Solution

The roof was prepared before installing new 18mm OSB decking to provide a sound and stable substrate. A venting/tack base layer was then applied to promote adhesion and allow for the correct installation of the built-up roofing system.

A torch-on underlay was installed with all joints staggered by a minimum of 300mm, reducing the likelihood of water penetration through aligned seams.

The mineral cap sheet was subsequently applied, with seams offset from those below to create a durable, multi-layer waterproof barrier. All perimeter details, upstands and edging were completed in accordance with good roofing practice, ensuring the roof achieved a neat finish and secure weatherproof terminations.

Outcome

The completed three-layer torch-on felt roofing system provides a durable, low-maintenance waterproof solution designed to deliver long-term performance and protection against the elements.