BS5534:2014 – Roof slating/tiling

Updated: 22nd February 2016

Due to ever worsening weather conditions which are predicted to keep declining, and the number of insurance claims, and claims against building warranties like NHBC, relating to roofs, BS5534 was revised in 2014, changing the requirements for roof slating and tiling. This is also more in line with European standards.

One of the main changes is to the recommended number of fixings per slate/tile. Generally speaking, under the new standard, all perimeter tiles/slates – at eaves level, under hips, under ridges, at verges etc… - should be nailed twice. All other tiles/slates should be nailed at least once. The specific requirements for fixings should be found from the manufacturers guidance which will follow this updated standard, but generally speaking this will be the requirement.

The next significant change is the bedding of ridge and hip tiles. It is no longer sufficient to bed them in mortar alone. There have been too many cases of cracked mortar beds and dislodged tiles to ignore and this method is now deemed inadequate. A dry fixing method should be adopted and there are plenty of systems on the market. So soon the age old technique of bedding ridge tiles in mortar will be a thing of the past. You can already see the dry fixing of ridges and dry verges being used on new build projects across the country.

Another interesting issue raised is the breathable roof felts and the potential for ballooning unlike the former bitumen felts which were too heavy to suffer this action. Underlay laps should now be covered with a batten or sealed with a felt tape, and should have a 10mm drape length, meaning the sag of the felt between rafters. Felts have to meet a certain stiffness strength to resist wind uplift.

Fortunately manufacturers have done a lot of the work for us – Marley has a fixing calculator on their web site where you can just input the dimensions and pitch of the roof and it automatically specifies fixings (although the Pu and Pd values stated for felt seems to be a total mystery to suppliers and manufacturers alike!). And Tyvec Supra felt meets the most stringent requirements under the standard. 

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