Replacing Dormer Flat Roof

22 Jan 2007
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United Kingdom
Just got back after 2 weeks holiday, and found loads of mould growth in the ceiling in the bathroom. Climbed to the top of the dormer roof, and the edge of the felt where it turns over the roof edge is full of holes and the roof itself all up and down, and after standing on it i Suspect the plywood is rotted through.

I've therefore decided next week to re-felt it all and put a new plywood roof on as I intend it to last another 15 years plus. Having never done this before So my questions are what materials do i need, eg what type of roofing felt, plywood, underlay etc do i need for a good job.

Secondly the felt at the back of the dormer, appears to run under the main roof tiles, which i Can no doubt rip off but how is it tucked back under when laying new. there is also no visible drip line or guttering so is it advisable to create one at the front edge of the dormer roof.

The size of the roof is 1.3m x 2.9m so not too big I suspect to give it a go, all advice welcome on the above

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The felt will run up a layboard where the tiles meet.

How are you going to bond it? If the felt has split at the drip edge, it sounds like it has the old type felt on there, which indicates its been there a few years, so replacing is the reverse of removal. The inexperienced using heat near a roofspace always gives me the jitters, if you want a proper job that will last, get a proffesional in.
I suspect it may well be the original flat roof, when the house was built if so its 30 years old. Its a chalet style house and the dormer is one side of the roof pitch. I was thinking of just ripping off the old felt which I presume would reveal the rotted plywood etc. However the plywood may well go under the roof tiles that abutt the flat roof, so not sure how to get it fully out, or what a layboard is or how its fitted.

Id like to give it a go myself as theres another flat roof on the first floor which is larger but will probably need doing soon as well. If I can do the first relatively small roof, I'd feel happier to tackle the larger roof, hence my posting, so all advice gratefully received for a roofing novice ;)
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The deck will be fitted to the structure, probably chipboard if it feels spongy underfoot.

Layboard should be fixed to rafters, and should be ok.

I have seen facias fixed to the edge of the deck so be prepared to go back the the frame, Bonding is my concern. You obviously won't have a bitumen pot, and not posses a gasgun, cold adhesives are crap.

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