Traditional lead roof replaced with Sarnafil high performance membrane

Contractor: DLR Flat Roofing, Roof Assured by Sarnafil installer

The old original lead crown roof
Lead roof replaced with Sarnafil single ply membrane

Approximately 78m2 of lead grey Sarnafil single ply membrane was installed on a crown top roof o heritage property in Cambridge by Roof Assured by Sarnafil approved installer, DLR Flat Roofing based in Kettering.  Dave Redhead, managing director, DLR Flat Roofing had previously installed the Sarnafil membrane on two smaller extensions at the property and while working on-site the homeowner asked for an estimate to replace the lead roof on the main house.

Because the property is located in a conservation area height restrictions applied, so it had been built with a crown top roof, meaning it was pitched to a certain height and then flattened to form a flat roof. This style of roof does carry an additional level of complexity in designing, detailing and building but is an elegant feature adding to the character of the property.

The first challenge was to strip off the old lead from the roof and then re-board the area with 18mm plywood.  The lead was over 60 years old and, as well as suffering from wear and tear, had been patch-repaired a few times compromising its look and performance.  Dave and his team removed all the lead which weighed in at almost two tonnes. The sale value of the lead was then deducted from the final cost of the project.

The next challenge was to install the Sarnafil membrane over the original roof deck. Because of the nature of the material, a lead roof installation requires the lead to be installed in small ‘steps’ up to a maximum step of 1.5 metres. This meant that the Sarnafil membrane had to be installed to accommodate these steps, so required careful planning and detailing.  This wasn’t, by any means, a straightforward flat roof installation.

Sarnafil G410-15ELF lead grey membrane was used on the flat area of the roof and Sarnafil G410-15EL for the details. Sarnafil G410-ELF is adhered directly to the substrate and then hot-air welded to form seams which are stronger than the membrane itself. The membrane also has a unique lacquer coating applied to the top of the membrane to resist staining from airborne dirt and pollutants. Both membranes are certified by the BBA (British Board of Agrément), in their opinion, to have a “life expectancy in excess of 40 years”.

Dave adds: “It was a complex installation because we had to install the Sarnafil membrane to the same steps as the previous lead roof.  This meant that there was a lot of planning and detailing work to be done but we are all very pleased with the result.  The project shows how a traditional lead roof can be replaced with a modern, high performing alternative. Another successful Sarnafil job completed!”

The new Sarnafil roof not only compliments the look and feel of this lovely heritage home but will keep it well protected for many years to come.

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