Advice needed: Extension flat roof leaking despite upstands (flashing not yet installed)

HopelessJoe

If there are any roofers here that could give advice:

My extension flat roof (single-ply PVC) was recently installed, including upstands, but the lead flashing hasn’t been fitted yet. After the first rain, water got through between the membrane and the wall and into the house.

As far as I understand, the membrane upstand itself should form a continuous waterproof barrier. I thought the lead flashing is more of a secondary protection, rather than the main waterproofing, but I’m not sure. The builder says it will dry out, but clearly it’s leaking.

Has anyone seen this before? Should the membrane-to-wall seal be fully watertight before flashing is installed, or is it normal to rely on the flashing? Any tips on how to fix this properly would be really appreciated.

WIAWSNB

Need more info. 
But, lead flashing is usually used at the joints, say where a vertical wall meets the 'horizontal' roof. It's what diverts any water coming down that wall on to the roof, and safely away. Without that flashing, the rain can usually carry on down past the joint.
So, fair chance what you've been told is correct.
Does the roof come with a proper warranty?

grumpy_codger

What sort of 'upstand' is it?

Whatever it is, it's next to impossible to stop water flowing down the wall from getting between the 'upstand' and the wall. Hence the flashing - led or plastic - it embedded into the mortar between the bricks and goes over the membrane directing water away from the gap. It is 'secondary', but not optional or decorative.