Help! New roof leaking worse than old one!

LandM1 · 25 December 2017 at 8:32PM

We have just paid to have the flat roof on our porch replaced as it had several leaks which had been happening for some years. The builders assured us they guaranteed it wouldn't leak. They replaced the damaged lead and rotten wood underneath, this time with one piece of plastic type stuff, no joins to leak. They also put a slight slope on it. They replaced the flashing by reusing the original lead flashings but reseating them and rsplinting.
Today it rained and the wind was blowing hard in the direction of the flashing. Water poured in down the walls in about 3 places worse than before.
Obviously we'll get them back as soon as we can, I think it must be the flashing that's the problem, any ideas what they've done wrong?
Thanks.