Flat roof over bay window leaking

[stefj]

A downstairs room has a rectangular bay window with a flat roof approx. 2.7m x 1m (106 x 40 inches).

The roof is covered with lead sheet (one piece). I can't see any holes/cracks where water might be getting in and the flashing on the brickwork looks ok.

What I'm thinking of doing is adding a pitched roof on top. I can only have a pitch angle of approx 15 degrees as there's another bay window in the bedroom above.

What would be the best method?
I'd thought of a timber wall plate screwed along the wall under the bedroom bay window and some timber rafters from the plate to the edge of the existing roof.
Then using a sheet of timber roofdeck covered with felt.

I occasionally need to stand on the roof to clean the bedroom window.

Any thoughts or suggestions for methods/products would be very welcome.

Thanks

Stef

 

[HERTS P&D]

Check the flashing.

Andy

 

[MINDEX]

any chance if you can attach side view picture of bay window and flat roof?
maybe easiest way will be find the source of the leak instead of installing pitched roof?
Salute
MINDEX

 

[tim00]

1. Lead flats must have a fall, to shed water. You might have ponding. How is your flat roof drained?

2. Your one-piece dimensions are too large - sheet lead can only extend 1.5M in any direction. You might have minute stress cracks. If you go for another lead flat then you will need a lead roll in the centre.

3. As has been said, flashings are always suspect.

4. There are tiles available that will accommodate a 15degree pitch.

5. For long term results it's best to lift the in-situ lead and examine the state of the structure/woodwork below.

 

[stefj]

Thanks for the replies.

I'm attaching a side view of the roof showing the overhanging bay window above.
Also, I've inset a photo of the tiles (red outline) used on the the rest of the house.
I like the idea of tiling the bay window with identical tiles, but wonder if these tiles (approx 6.5 x 10.5 inches) would be suitable for a 15 degree pitch.

I'm not very keen on disturbing the existing lead sheet and would rather cover with either roofdeck board or tiles.

Any further ideas very welcome.

Thanks
Stef

Bay window Flat roof + bay above

• stefj
• 27 Dec 2011
• 1

Bay window Flat roof + bay above + inset of house roof tiles

 

[ladylola]

To be honest it's a little hard to tell it's lead from the photo other than the colour but I'll take your word for it. Either way it doesn't look very well laid in my opionon, it looks to be wrapped tightly around the ends which will prevent thermal movement and encourage cracking. It also looks like whatever boards are underneath have very large gaps between them and this has encouraged sagging. Board gaps should be around 3mm at most. I can see a horizontal line at the bottom of your picture on the deck that puzzles me too. The pointing looks ropey too, there certainly aren't any brickies who would put their name to that mess.
As to fitting a tiled roof then yes quite possible but I'd come off the front and side edges of the upstairs bay and end up with a hipped affair connecting the corners of the two bays.
I'd also remove the lead covering to do this as well, it'll be a much better job and you can insulate and check out the condition of the exsisting roof timbers and replace as neccessary.

 

[cotswoldbuilders]

Id rip the existing covering of, weigh the lead in and put it towards an EPDM roof.
Check the boards and timbers are sound, overlay with osb or ply then one piece rubber glued down.

 

[tim00]

Excellent suggestions and observations above. You really must remove that lead:
1. it's ponding. flat roofs must be laid to falls.
2. it appears to have been laid over an in-situ felt flat roof.
3. As it drain's, because there's no rim fillet, it's discharging behind the guttering.Google a section view of a flat roof edge/fascia detailing.
4. for all the suggested reasons others have made.

I'd go for an EPDM as suggested - that way you would have future access to the bay ( you are going to need it, that Oriel bay looks pretty ramshackle with failing render and the T&G underboarding rotting at the uncapped "ends". )
How is the Oriel bay ( ie. the upper bay ) roof drained? I noticed a horizontal RWP(?) or waste, at lower right.

 

[stefj]

The house was built in the 1920's and the lead sheet on the roof was there when we moved in over 30 years ago.
Last year, I coated the roof with Wickes roof sealant and that may be why it doesn't look like lead sheet- but it definitely is lead!

The roof has plastic guttering and water does tend to 'pool' for a while after heavy rain.

Not sure of the methods for using EPDM, but I'll look them up as this seems the most popular solution.

As mentioned, the roof is approx 106 x 40 inches (almost 9ft wide).
I've noticed that sheet materials tend to be 8ft x 4ft, which means I would have to join 2 pieces together.
Does anyone know if sheets say, 10ft X 4ft are avaliable?

Also, are the tiles I described (and inset in photo) suitable for a 15 degree pitch?


Stef

 

[tim00]

EPDM is cut from a roll for a one piece installation on your roof.

You could actually achieve a 20 degree - 28 degree workable pitch, but stay away from that option, you will only be giving yourself difficulties.

 

[ladylola]

Ply is available in sizes bigger than 8x4 but it's special order and a special price to boot so just do the job in two pieces and joint it over a joist.
15* is really too shallow for those tiles, but if you were to form a roof as I mentioned above you'd achieve over 40* looking at your picture.

 

[stefj]

I'll look into all the suggestions in more detail and make a decision.

Thanks to everyone for the advice and tips.

Stef