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EXTERNAL ENVELOPE The case for bespoke fl at roofs


With ensuring effective drainage and insulation being essential for all fl at roof projects, Matthew Evans of Kingspan Insulation explores how tapered systems can be used to meet both requirements, and adhere to designs.


A


s we head towards the winter months, fl at roofs across the country are set to be put to the test from


wind, rain, sleet and freezing temperatures. When working on any project involving a fl at roof, whether it be a new build or refurbishment, ensuring the surface will drain properly is essential for the lasting health of the roof. At the same time, these constructions also need to be effectively insulated to limit the heating demand for the building. Tapered insulation systems combine both insulation and a fall for drainage in a simple, lightweight solution which is designed especially to meet the demands of your project.


WWW.ARCHITECTSDATAFILE.CO.UK


Despite their name, fl at roofs are laid to a slight angle (fall), which allows any moisture to drain down to internal or external guttering and be channelled off the roof. The fi nished fall should be at least 1:80 in all areas of the roof, including at the hip and valley joints. Where the fall is either insuffi cient or fails to channel water to the correct points, it can lead to water ponding on roofs. This standing water can contribute to mould and algae growth, increase the thermal stress on the waterproofi ng layer during freeze thaw cycles, and add additional weight to the deck – potentially causing it to defl ect over time, shortening the lifespan of the roof.


ADF OCTOBER 2025


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