GOOFS ON THE ROOF – code of practice in 2014 which regularised these changes. As a result, many developers have migrated to dry-fix systems as they are a lot faster to fit than double-fixed wet systems. Clearly, as the number of dry-fixed roofs increases, so does the risk of problems related to dry-fixed systems. Sometimes these problems are caused by failures in the products and systems themselves. It could be that the fixing systems cannot withstand the wind loading, the adhesive on the ridge roll has not stuck adequately to the roof tiles, or the physical design of a verge causes water to run down the face of the wall. We have seen some other manufacturers’ verges that have been perfectly installed but, due to their design, have caused extensive staining after only a few years. In the worse-case scenario, if these problems are not dealt with, the wall of the property becomes damp with all the ensuing issues that this can cause. In other situations, installers are to blame. For instance, we hear of the wrong type of fixings being used – whatever came to hand – to fix a roof verge piece or in some cases, there are no fixings at all FEBRUARY 088 2018 RCIMAG.COM because the roofer has wrongly assumed they are not needed. This problem is often exacerbated by the product arriving without any fixing instructions. Prior to BS 8612, the dry-fix ridge, hip and verge market has been largely unregulated other than via third party certification, and so this is why the market has been crying out for the implementation of a British standard. Getting it right The new standard aims to ensure that none of the above problems occur. It talks about material properties, dimensional tolerance, required performance and how dry-fix systems should be tested to demonstrate that they conform and are fit for purpose. One important new requirement is testing for resistance to wind uplift and horizontal forces. While BS 5534 currently says that dry-fix verges and ridges can be used if they can withstand wind uplift forces, it does not say how the products should be tested to verify this. The new BS 8612 defines tests to determine mechanical resistance to wind load and shows how specifiers should use data from these tests to verify whether a product is suitable or not, given the wind exposure of the location under consideration. The standard also sets down a test for dry-fix ridge-roll products to measure whether they can meet the profile of the roof tile at ridges and hips without breaking or splitting. A third test checks whether roof verges shed the water away from the surface of the wall, to avoid staining and damp issues. The type and quality of the material is also specified, with respect to durability. Plastics must withstand UV exposure without significantly changing appropriate mechanical properties within certain limits. Ridge-roll products must cope with freeze-thaw cycles and the impacts of heat and humidity. Dry-fixed for the future Given the fact that the NHBC has been a driving force behind these changes, we can expect it to mandate the use of dry-fixed systems that are compliant with BS 8612 in the near future. Over time, it is likely that all products will be updated so that they meet the standard. In the meantime, specifiers must check that dry-fixed products meet the standard, and that they are compliant with the slates or tiles on the roof. BS 8612 says that manufacturers must provide, if requested, a product declaration of performance, which includes design resistance to wind-loading and states which tiles they can be used with. They must also issue instructions – which the contractor must follow! It is important to get this right. Failures are costly and wasteful and distressing for the homeowner. Reputable manufacturers will be more-than-happy to provide technical information and advice around this subject to specifiers and installers.
RCI Feb 2018
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