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Read our policy.

Pitched roof coveringsCapital cost £/m2Net present value for 60 years £/m2Life expectancy in years
Plain clay tiles to BS EN 1304. Flexural strength 600N minimum. Frost resistance: pass frost test D to BS EN 539-2; 265 × 165mm678150-70
Concrete interlocking tiles to BS EN 490, interlocking tiles;420 × 330mm304350-60
Concrete plain tiles to BS EN 490, double lap; 265 × 165mm537050-60
Fibre cement slates to BS EN 492 with third-party approval; 600 × 300mm437120-30
Natural slate to BS EN 12326-1; 500 × 250mm879275-100
Western red cedar shingles Grade no 1 “blue label”, preservative treated; 400 × 75 – 350mm658830-50
Notes: Service lives represent average lives. In practice there is evidence of clay tiles with more than 100 years of service life and natural slates extant after 250 years. There are also examples of premature failures. Capital costs are based on an inclusive rate for a simple 35° duo-pitched roof area of 250m² for a row of terraced houses with gable ends, no protrusions through the roof. Costs include tiles and detailing at eaves, verge and ridge; fixings, underlay and battens. Lap suited to a sheltered environment. A discount rate of 3.5% is used to calculate net present values. A cost analysis based on project specific information is essential for a realistic best value appraisal. BLP provides latent defect warranties for buildings (www.blpinsurance.com).