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In January 2017, we were contacted by Warwick Shaw Construction to quote for a large project in Salcombe, Devon.
The new roof design consisted of two eyebrow dormers on front and rear elevations, 40˚ pitch slopes on each end of the building, consisting of three lead hips joining all elevations together.
The pitched slopes on both ends of the building were straight forward. Done using Triso Multifoil insulation, Premium Gold battens and 250mm by 500mm Spanish Lugo slate. All hips were fitted with Code 5 lead, fixed using stainless steel straps, finished with patination oil.
The eyebrow dormers were quite a challenge, due to the fact that you are trying to fit slates that are flat to a surface which is curved.
After Warwick Shaw Construction had constructed the timber framework of the eyebrows, they were then finished in two layers of 9mm Marine Ply. Battens would normally be used to fit slates but because of the shape of the eyebrows, and the need to keep a gentle curve, Marine Ply is used instead.
The main challenge with the curved shape, was getting the straight lines measured for the slates. This is done by measuring from the ridge to the front of the eyebrow, then going to one side of the eyebrow and taking the same measurement and marking from one side to the other at intervals of 300mm. Using a thin flat strip of metal we joined the marks together, creating our straight line. The same process is then used to create the rest of the lines, (I never thought I’d miss a chalk line so much).
We decided to use the same size slates on the eyebrow as we did on the side elevations but increased the head lap from 100mm to 125mm, due to decrease in the pitch on the centre of the eyebrow. These were fixed using 35mm stainless ringed nails. Another important technique when slating a curved surface is to ‘dog ear’, or clip, both corners off the top of the slate. This helps the slates to sit tighter and prevents the bottom corners from sitting too high.
When the slates start to meet in the centre of the eyebrow we then had to taper the slates, going from 250mm down to 175mm, keeping them slightly wider at the bottom of the slate.
Due to the shape of the roof, you have to deal with rainwater running sideways, rather than down across the face. The solution to this, is to create a soaker on top of every course of slate that is laid. It is time consuming but essential. Strips of lead, stainless steel or good quality DPC can be used to achieve this.
After several weeks, and lots of cropped slates, the roof was completed. The eyebrow dormers looked great, as did the rest of the project. The roof really stands out amongst some of the other impressive designer properties in Salcombe. When completed to the architects design, the owner decided that he would prefer Terracotta hip tiles on the hips, matching the Terracotta ridge tiles on the ridge of the eyebrows, instead of the lead. This was not a problem and we came back to do this for him.