Roof Underlay Flapping in Wind

5 Jan 2014
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United Kingdom
Hi - Moved into a new property six months ago, the house was significantly extended and refurbished about six or seven years ago. As part of this work a new roof was installed.

Whenever there is a strong wind an annoying 'flapping' sound comes from directly above our bedroom window - loud enough to lead to a lot of lost sleep! Observation from the ground confirmed that this is the roof underlay so I climbed up to take a look today.

The underlay itself extends well into the guttering, actually laying right to the bottom curve of the gutter itself all the way along. There is a small split above the window in question, which has led to the edges sticking up, which I'm guessing is where the wind get underneath it. Of course it's entirely possible that the find is blowing up between the gutter and the fascia board too....

On another part of the roof the underlay protrudes only slightly beyond the tiles, but still well over the gutter (without laying in it).

This poses a couple of questions:

Which is right - Should it be laying in the gutter, or just comfortably overhanging?

How can I fix this - my first inclination is to trim it back a bit, but I'm mindful that I can't put it back if I cut if off!

I'm not looking for a big project here - just a way to get more sleep so the quicker the better

Photos below show 1) The roof where the felt is not laying in the gutter 2) a shot along the gutter where the felt is laying 3) The split part above the window.

Thanks in advance for any advice.
View media item 71239 View media item 71241 View media item 71240 [/img]
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Current practice is to fit an eaves carrier strip at the edge of the membrane, you can see how they fit in the Tyvek installation guide from about page 15..

You should be able to retrofit them to your roof without too much disturbance, Screwfix sell these for example..

You may need to unclip the gutter to get access but other than that they should just slide under the membrane. You could think about trimming the membrane back afterwards but personally I wouldn't bother unless it still annoys you with noise.
The type of underlay you have should not extend past the slates. There should be underlay support trays fitted which overhang the facia and provide the drip into the gutter.

If you cut the membrane back it is possible although unlikely that some water could come of the slates and blow back behind the gutter.

To correctly fit the support trays now would be quite a big job.
Go to a pvc fascia supplier and ask for a 25mm x 5m trim you can roll it up to fit it in your car, when you get home lay it on the ground and screw a 50mm screw every 12" or so then take it up the ladder lay it in your gutter and then screw it through the membrane and the back of your gutter and that will stop it flapping about.
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That's confirmed my suspicions that it was not ideal, and given me a couple of ideas to fix it.

Thanks for the rapid response guys.

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