Water collecting on a flat roof

[Bilis]

Hi all,

Looking for advice / opinions of those with experience. We had a flat-roof extension built and the water mostly runs away except for the section between the house wall and the skylight where a fairly big puddle forms every time it rains (if I had to guess, I'd say up to 10mm deep).

The fall is towards the back of the house (perpendicular to the house) but in the section in question the skylight is preventing the water from running away.

There are quite a few of felt joints there and I'm worried that water will eventually, with time, find its way down through the gaps.

How much of a problem is this and is it worth worrying about /requesting for corrections from the builder.

As an aside, is there any paperwork to collect from the roofing company for the guarantee? I think they said 10 year guarantee.

Thanks so much for the advice!

 

[blup]

Worth having roofer back to establish if ponding is structural, or caused by poor or blocked drainage. Ponding is going to greatly speed up the process of water finding its way through the joints. He should be able to remedy either scenario

Blup

 

[Odds]

It looks like its puddling between the skylight and the wall - is there a way to channel water away from that area into the guttering?

 

[Bilis]

Worth having roofer back to establish if ponding is structural, or caused by poor or blocked drainage. Ponding is going to greatly speed up the process of water finding its way through the joints. He should be able to remedy either scenario

Blup

Thanks for the feedback, that was my concern too.

The general fall is away from the house (green arrows) and the area behind lantern either follows the same fall direction or has no fall. Not sure what the standard practice is in such situations like behind the roof lantern, would you expect the fall to be perpendicular to the overall fall direction behind the lantern, so that water runs around thr lantern?

The red lines are where I think the felt is overlapping and it creates a bit of a barrier for the water to leave the area behind the lantern. However, I'm not entirely convinced that the water would drain away even without that barrier.

What would be a potential solution here?

Thanks!

 

[freddiemercurystwin]

He should raise the centre and fall it back down to the red bits.

 

[freddiemercurystwin]

Latest best practice is to design flat rooves to achive a fall of 1:40 to allow for tolerances etc.