Flashing corrugated roofing sheet outhouse to main building

[DSA]

Hi,

We have recently had a side "annexe" re-roofed with opaque corrugated roofing sheets, however there is significant rain ingress at the junction between the pebbledash rendered surface of the house and the abutting "flat" roof (ie the floor of the annexe was soaking wet after the heavy storm today!). The annexe roof is sloped to allow the water to run away, and the problem is clearly a flashing issue at the house/flat roof junction.

The builder returned and "fixed it" by applying some sort of "emergency roof repair paste" at the junction (he had filled the final corregation with mortar, however the problem still exists.

We would rather just sort this ourselves now. What is the best way of flashing this type of junction? Will flashing tape work? Or does it need to be lead etc.??

Any help most appreciated!

 

[Deluks]

So this is like a lean to extension? Covered in corrugated PVC sheeting?

I assume that this extra 'room' does not form any part of the house, is external and that the door into it (from the house) is a proper exterior one?

A flashing section is available for the corrugated stuff, one edge is corrugated also, then there's a hingey bit and the other half is flat, which sits against the wall. This should be flashed with lead by cutting into the wall and chasing the lead into the groove. I really wouldn't advise using flashband in this instance, you can get away with it sometimes but against the uneven wall surface it would just fail.

 

[DSA]

Yes, it is not part of the house - just a secure shed-type area really with outside toilet. There is a secure exterior type door between the main house and this structure.

I should point out that a dip in the corrugations runs parallel with the pebbledash render - ie there is not an undulating surface to flash against (except for the render itself), because the roof is flat perpendicular to the house wall, but dips from front to back (ie parallel to the wall). The builder had filled the closest corrugation to the house with mortar presumably so that an easier seal would be formed with the repair paste.

Perhaps this information changes your suggestion?

Thanks!