leaky bay window roof

11 Oct 2016
Reaction score
United Kingdom
hi, With the current downpours my bay window roof is leaking.

I noticed the dead end of the gutter looked dropped so I propped it up, but its still leaking.
Theres maybe 1 and 1/2 inch gap under the gutter,looks like just plywood under there, I wonder if thats the problem, or something else ?
pic attached
Sponsored Links
Whereabouts is the water appearing inside?
That full gutter won't be helping matters (if it is overflowing at the back it'll be wetting non-weathered areas) so fixing that should be a priority. If there isn't room to get the fall right then consider a downpipe at that side.
The flashing in that corner looks as if its had a mend at some stage, looks like Flashband pretending to be the upstand of the roofing felt. Not ideal...
Thanks the water seems to be coming from this area , but there is some towards the middle.
I had a roofer look at it he didnt notice what you did, he did say theres lots of small holes in the felt, but Im not sure that would cause dripping water inside.

Is there anything I can do about the flashband pretending to be an upstand ?

ps I propped the gutter up so water moves along, I did notice the gutter joint is leaky though, maybe thats running underneath.
Looking again at the pics there are traces of sealant and pitch above the gutter as if there was a larger bodge piece stuck on that has blown away in the wind or dropped off from old age.
If there's plenty of fall on the bay then pinholed felt wouldn't be a short term problem. If water is ponding on the roof then you'll get enough going through to get under the deck planks (you may find the original lead under that felt as well).
Dripping gutter won't help either- it is amazing how much damage a small drip can cause.
Sort the guttering so it drains properly and doesn't drip. If its plastic, take it off,clean the seals out, make sure they're seated properly and replace any broken or missing clips. Make sure there is enough fall to the side with the downpipe (1:500 is usual)
Short-term you could paint the roof with Acrypol or similar and try getting a piece of Flashband behind/under all the layers in the pictured corner.
Medium term felt doesn't last forever, get it replaced. There are various options (felt again, GRP, lead, EPDM)- whichever it'd be wise to budget for new roof deck and while the job is being done, stuff some loft insulation in the void between deck and ceiling.
Lead done properly would look lovely and last 100 years or so but there's the theft risk and finding someone who knows what they're doing.
Felt is probably cheapest but short life (20 years max) and hot felt work is a chunky fire risk
GRP would probably be better than EPDM (because of the fiddly shape), GRP is DIYable as well, plenty of Youtube videos to show you how
Sponsored Links
Thanks so much for taking the time to give that very detailed answer, I appreciate it.
Ill give it a go.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local