Rubber roof drip edge retrofit

29 Jul 2013
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United Kingdom
Hi, I'm hoping for some advice.

I posted on here last year that I'd employed some roofers who didn't seem to know what a spirit level is. I can't afford to pay another professional so I've been slowly going around and putting things right. One thing they did was fit a small rubber roof above a dormer. I've checked, and it seems to extend out and upward quite a way under the surrounding tiles, and there have been no leeks for the 12 months that it's been fitted. My concern is that, although it slopes very slightly away from the main roof, the lowest edge has been finished with a raised kerb. This means that the water pools at the edge of the roof and then slowly drips out through small gaps between the plastic kerb trim and the folded down edge of rubber.

If nothing else, I want to fit a gutter along this edge, simply because the drips land on some lead under the window and make a noise. I am, though, thinking I should also replace the raised edge with a drip edge to avoid the pooling. Is this necessary?

The offending edge is fitted with a batton, with the rubber membrane sandwiched (on the vertical overhang) between the batton and the plastic kerb trim. The rubber membrane currently extends down at least to the bottom of the plastic trim (which itself is 5 inches total height and so approx. 4 inches below the roof surface).

My plan is to remove the kerb trim and replace it with something like this:

I'd need to slide the lower half under the trailing edge of the already fitted membrane, put mastic in the old pin holes, and then fix the upper piece on top. I'm a little concerned, though, that the membrane might contract when I remove the existing trim and won't sandwich effectively between the two pieces of new drip edge. I'm Also unsure if the existing corner pieces can still be used. The low edge is 5m long and the roof is about 1m deep.

It sounds like a simple and straightforward job, but I'm worried I may be overlooking something and will wreck a non-leaking roof which I can't then afford to replace. Perhaps I'm best off leaving it alone.

I'd be really grateful for any advice.

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