Flat roof leak.

[charliesaunders1]

Hi there, My flat roof has a small leak and I am unsure as to where it is coming from. One thing that I am aware of is that it is located behind the skylight where water fails to drain correctly. I have narrowed it down to three causes;
1, water building up so much that it gets under the lead and capillary action occurs.
2, Possibility that the leak is located around the soil pipe due to poor weathering.
3, The lead flashing above the boxed in pipes is causing capillary action as the lead just overhangs boxing.

please take a look at the images attached and offer any guidance, all help is appreciated. Thanks.

Untitled

• charliesaunders1
• 23 Apr 2014
• 1

Untitled

• charliesaunders1
• 23 Apr 2014
• 1

Untitled

• charliesaunders1
• 23 Apr 2014
• 1

Untitled

• charliesaunders1
• 23 Apr 2014
• 1

 

[ree]

You have ponding which means falls are lacking behind the skylight - gravity cannot drain that area.

Its the worst possible place, as you've recognised, because of the difficulty in correctly flashing around the SVP as the branch enters the wall.

Any lead cover flashing that is touching the ponding, or even the felt "back gutter" arrangement, can be clipped short, say by 25mm.

The precautionary(?) length of lead and felt dont seem to be doing anything except obscuring what might be going on - perhaps, unless its actually covering some damage, remove it and make good.
Is this the reference to "boxed in pipes"?

I think that you will have to open up around the soil pipe and the ponding gutter area and expose any faulty detail, and to then make good to falls.

Presumably the skylight guttering is discharging someplace else?

How to permanently seal the SVP Tee i dont know - i can only think up codges. Hopefully someone else who's more experienced and has perhaps tackled this kind of detail might come along.

 

[catlad]

I would have advised moving the soil stack before building the extension good luck

 

[foxhole]

Is the dark area on the render a hole, any cracks in the render and rain goes straight thru and cannot dry out.
Where does the leak appear internally?

 

[freddiemercurystwin]

I would look at the detailing around the soil pipe first and go on from there, as mentioned always unfortunate to leave them in place after extensions but all too common unfortunately.

 

[cotswoldbuilders]

Theres to much water holding there, plus not enough space to work in.

Do you have enough height to do away with the gutter that side, raise the roof level all along the edge of the roof light, ie form some boxing and finish the top in lead.

Disconnect the soil pipe to fit a new pipe seal, and reroute the black down pipe.

 

[s60tsy]

the roof level needs raising near the soil pipe so water moves away from it, then it needs making water tight, try a weather collar and/or cromopol

 

[Nige F]

Where does the black rainwater pipe go - onto the roof behind the soil pipe or thu` roof ? . Also which way should the water drain off the flat roof in relation to the rendered wall/skylight .

 

[charliesaunders1]

Thanks for all of your helpful advice, there is a lot for me to think of now in order to come to a desciscion as to what is the best option. In awnser to some of your questions;
The black on the render is remains of the old flashband used, not holes.
The black downpipe drains the water past the side of the skylight and into the main gutter. And in relation to te render, the roof has a natural fall away from the render and towards the skylight. In that part of the roof there is very little cross fall which is causing the ponding.
Thanks , Charlie.

 

[alwaystryitonce]

Try reading 'felt and torch on roofing - a practical guide' amazing book for DIY and builders& roofers. This will point you in the right direction.