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RCI March 2018

2013 1 07/05/Layout Project1_GOOFS ON THE ROOF Mind the gaps In the second of our Goofs on the Roof series, Mat Woodyatt, technical training manager of Redland, explains how spotting poorly matched tiles gives clues to other problems on the roof Just say you live at the house on the left. Your roof is an established plain tile installation in reasonable order. Next door on the right decide to re-roof their house and the result is plain to see: not good. The fi rst thing that catches your eye is the poor tile match where the roof has been made ‘good’ on the left-hand side. The nice, neat, plain tiled roof is weathered and those bright terracotta gable tiles, used to complete the tiling, are a totally different colour. The roofer has clearly made no attempt whatsoever to source matching tiles. When that happens, you can’t help but wonder about their overall professionalism and what other less-obvious problems might be lurking up there as a result. And one doesn’t have to look too far to have this query answered, as you begin to spot a whole host of poor practices involved with this job. First, the tiles either side of the bonding gutter are kicking up and not lying in the same plane as all the other tiles either side of the party wall are. The resultant gapping will allow rain penetration into the roof and then both properties. Typically, this is caused by the bonding gutter being fi xed directly on top of the tiling battens that run straight through and across the party wall. Consequently, the tiles either BUILD TO 096 MARCH 2018 RCIMAG.COM side of the central upstand of the bonding gutter foul on the weather bars and channels of the bonding gutter; causing the tiles to ‘kick up’. This is not as obvious on the left side as plain tiles are not interlocking, and so have more fl exibility when laid on an uneven surface. Yet the interlocking tiles on the right are less forgiving of an uneven surface, and the results are for all to see. To avoid this, the tiling battens should have been cut back either side of the party wall, and the bonding gutter inset, such that the weather bars were at the same height as the top of the tiling battens. Second, the bottom edge of the central upstand of the bonding gutter has been left open. This too allows for rain penetration and maybe even small birds and insects and, in time, will result in rotting timbers at the eaves. It should have been tapered down towards the gutter, and then fl ashed with lead or fi lled with a suitable gap-fi ling foam. Given what we can assume about this roofer already, you can bet it’s the same at the top as there is no saddle fl ashing to be seen where the bonding gutter meets the ridge – meaning rain ingress at that junction too. Third, it looks like they’ve damaged the fl ashing to the left of the chimney stack – and have just applied a mortar patch. This mortar is porous and will just Bonding gutter and other bodges add to the rain ingress problems already caused by the tile gaps and open bonding gutter ends. Fourth, they’ve made a complete mess of the ridge where it meets the bonding gutter. This has been lifted and bedded back down with mortar. As we know from the revised British Standards Code of Practice (BS 5534), mortar alone can no longer be relied on as a method of fi xing, as it has been deemed not to provide reliable adhesion. Mortar can still be used, but only if accompanied by mechanical fi xings. There are none, anywhere. You must then wonder if the tiles are even fi xed down properly, and then about the quality of the batten, the underlay and all the other detail that can’t be seen from the ground. For more information on Redland’s training courses, visit www.redland.co.uk/training, or call the Redland National Training Centre on 01285 863545. W STANDARD Copyright © 2018 DuPont. All rights reserved. The DuPont Oval Logo, DuPont™, For Greater Good™, Tyvek® are trademarks or registered trademarks of E.I. du Pont de Nemours and Company or its affiliates. Keep the weather out and the comfort in. Achieve added durability, weather protection and DuPont™ Tyvek® wall and roof membranes provide superior air and water holdout to EN13859-2 W1 An installation combining AirGuard® vapour control layers and Tyvek® membranes and tapes ensures an even better level of airtightness and provides Not all membranes are the same - make certain TM www.construction.tyvek.co.uk


RCI March 2018
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