In the first of the new series Goofs on the Roof, 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 first 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 fixed directly on top of the tiling battens that run straight through and across the party wall. Consequently, the tiles either 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 flexibility 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 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 flashed with lead, a good lead replacement such as Redland’s Wakaflex Rapid Flashing or filled with a suitable gap-filing 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 flashing 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 flashing to the left of the chimney stack – and have just applied a mortar patch. This mortar is porous and will just 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 fixing as it has been deemed not to provide reliable adhesion. Mortar can still be used but only if accompanied by mechanical fixings. There are none. Anywhere! You must then wonder if the tiles are even fixed down properly, and then about the quality of the batten and the underlay and all the other detail that can’t be seen from the ground.
All in all, this job is a pretty poor advertisement for the trade; and the kind of work that can give all professionals a bad name just by association.
For more Goofs on the Roof, click here. Do you have any first-hand examples of dodgy building work? Send them on us and they may be included in a future newsletter!
