To ask about my flat roof

[Perpagilliam]

We bought our (first) house about two years ago. It’s a Victorian terrace with a 1980s flat roof extension at the back. We bought it quickly (as needed to move urgently) so didn’t pay as much attention as we probably should; we also only had the basic survey.

Everything is fine with the house but shortly after moving it became apparent that there’s a leak in the roof of the flat roof extension. It only happens when the rain is very heavy, so maybe once every 3 months or so. On very close inspection there’s evidence of historic water damage where the leak comes through.

We got a roofer to replace the flat roof, an experienced guy that my family have used before. However, the leak has continued. He’s back back a number of times to add more sealant and try to sort but nothing has been successful. He’s at a loss as to why the roof should still be leaking.

I want to get this sorted but I’m not sure how to proceed. I’m starting to think it might not be the roof at all, as I’ve read there could be other explanations.

Should I get a surveyor to come and look at the extension and report on the issue and ways of sorting it?

Or do I just need a good builder / roofer to come and give a second opinion?

Never had a house before so not sure which is best!

I think you might be better posting this in Property than AIBU.

Could it be drainpipes and gutters rather than the roof itself? If you've had the roof replaced then the source should have become apparent. Or do you mean that you've just put more roofing felt on the top?

I think you are going to need to post some photos, and hopefully PigletJohn will come along (in Property).

Is the rainwater forming a puddle somewhere where there's a join in the felt? It'll come through the tiniest gap if it isn't able to drain away. If the timber under the felt has started to rot (this often happens due to condensation) this can create a bit of a dip.

Flat roofs are a nightmare in a wet country. Can you get it redone to a hipped/gable? Or does the building shape not accommodate that

It's probably not getting in where you expect it is, it will be elsewhere and running down to the point it leaks. Can you cover likely areas with plastic and see if this stops it to identify where this is ? It's a long game as you'll need to wait for heavy rain. Also if its only when heavy it may be blowing upwards underneath where you wouldn't expect it. May take a while to locate but will be easy to fix once you have.

I'm an ex insurance claims manager. Get someone else, preferably a specialist flat roof company to look. Flat roofs are a complete mare, you guy may be a good general builder, but it's clear he isn't up to the job.