1. Acknowledge the problem
Recent figures show that pitched roof claims account for more than £14m of the NHBC’s annual claims spend, with roof-related issues resulting in about 60% of all claims. The updated NHBC Standards Chapter 7.2 Pitched Roofs, published last year, include a number of changes aimed at improving standards and quality.
2. Follow the standards
The NHBC has surveyed 3,000 live sites that adopted the new standards. Where ridges and hips are bedded on mortar, a third of sites surveyed are still using mortar only and not providing mechanical fixings – whereas Chapter 7.2 states that where mortar is used, ridge and hip tiles must also be mechanically fixed. Where verges are bedded on mortar, less than half of the sites used the correct method.
3. Ensure the mortar mix is correct
The correct mortar mix could be positively confirmed on only two-thirds of the sites surveyed. The mix should be 1:3 cement:sand with plasticiser, and be based on sharp sand with soft sand added to achieve workability. The proportion of sharp sand should not be less than a third of the total sand content.
4. Use cut tiles with care
Housebuilders should use setting out to avoid cut tiles. Where this is not possible, cut tiles should be at least half-tile width and use the manufacturer’s approved methods of securing the tile.
5. Specify the correct system
Where dry systems are used it is vital to ensure the correct system is specified for the pitch of the roof, they are being installed in accordance with the manufacturer’s or third-party certification recommendations and that all elements of the tile and dry system components are compatible.
By Mark Jones, NHBC group head of house building standards. For details, visit www.nhbc.co.uk
Comments are closed.