75 RCI 0514

RCI May 2014

PITCHED ROOFING Traffic calming: working over laid roof tiles By John Mercer, technical director at Sandtoft, a Wienerberger brand John Mercer, Sandtoft’s technical director RCIMAG.COM MAY 2014 075 Asubject that raises much debate in pitched roofing is that of access over laid roof tiles, in other words, foot traffic that causes damage to the roof tiles. As we are all aware, higher theoretical wind loadings in recent revisions to UK design and installation standards have meant more tiles being mechanically fixed; with requirements for fixings about to increase further still when the revised British Standard Code of practice for slating and tiling; BS 5534 is published later this year. This is all good news for the security and long-term durability of buildings. But, it is having some unforeseen consequences on the working practices of roofers and the way in which roofs are constructed. The traditional way for the roofer to access parts of the roof, such as the ridge, or chimney flashings etc. once the tiles were laid, was to push up a few tiles so that he could step on the battens. This was easy to do when the roofer had only nailed or clipped tiles in every alternate, or even every third course. Of course, this option is not available if all the tiles are fixed. Roof tiles are not specifically designed to be walked on. Manufacturers design their tiles to be as strong as possible, within the confines of the manufacturing standards, taking into account considerations such as size and weight, and by avoiding small-point contacts between laid roof tiles so that pressure is transferred through the tiling to the battens by compression. The trend in recent years for lower roof pitches has encouraged foot traffic over roof tiling, as has building design; for example, where the window cleaner or painter must access first storey windows over a single storey extension or bay window etc. It is common practice in many European countries to install walkways and even special step tiles to provide roof access to upstairs windows, chimneys etc. BS 8000-6: the British Standard for workmanship on building sites, states that roofing work should be planned so that the battens can be used as footholds – over the rafters though, not mid-span – to avoid walking directly on the tiles or slates. It also recommends that where it is not possible to walk on the battens; for example when completing hips, valleys and ridges, work should be done from a roof or access ladder, with suitable packing under the ladder to spread the load and avoid point contacts that could damage the tiles or slates. Similarly, the Health and Safety Executive document; HSG33: Health and safety in roof work, advises that, for safety reasons, roof workers should avoid walking on roof coverings and should tile or slate in such a way that the battens always support them, bringing valleys, ridge and hip tiles through as the roof is covered. Interestingly, traditional slaters understand the risk of standing on slates, but tilers do not always accept that the same precautions should apply to concrete or clay roof tiles. Foot traffic directly on roof tiles can cause obvious damage, such as broken tiles. But it can also cause less obvious damage, which is not immediately apparent. For example, tiles may crack imperceptibly or in places out of sight, such as within interlocks. These cracks may remain undetected, sometimes for several years, until the action of wind or frost opens up the cracks and causes the roof to start leaking. A common complaint that roof tile manufacturers receive is that roof tiles are breaking up on the roof a year or so after the roof has been installed; wrongly assuming that the tiles are breaking ‘by themselves’. When nailed or clipped tiles are broken as the roofer walks on them, the problem he then faces is how to replace the damaged tiles and fix them in accordance with the fixing specification. It is not usually possible to secure a single replacement tile by nailing or clipping if all the surrounding tiles are fixed. The only way to re-fix a replacement tile in the normal way is to remove all the tiles above it as far as a junction such as a ridge or hip. Generally, this leaves the roofer with the option of either using an adhesive to secure a replacement tile to an adjacent, fixed tile, or to drill the replacement tile through its exposed surface and secure it to the batten using a screw with a sealing washer; neither of these solutions being ideal. In conclusion, with fixing specifications likely to increase in the near future such that there will be no unfixed tiles on a roof, it is important that roofers consider their working practices carefully to avoid damaging foot traffic over unprotected roof tiling. In summary: – Remember that roof tiles will all be mechanically fixed, so replacing a damaged tile becomes much more difficult. – Walking on unprotected roof tiles or slates runs the risk of damaging them and is a health and safety risk. – Try to plan work to avoid or at least minimise foot traffic over tiles or slates and, where possible, bring valleys, ridge and hip tiles through as the roof is covered. – Where access is unavoidable, protect the tiling or slating using access ladders with appropriate packing to avoid point contact. www.sandtoft.com “The traditional way for the roofer to access parts of the roof, such as the ridge, or chimney flashings etc. once the tiles were laid, was to push up a few tiles so that he could step on the battens. This was easy to do when the roofer had only nailed or clipped tiles in every alternate, or even every third course. Of course, this option is not available if all the tiles are fixed”


RCI May 2014
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