Water penetration through single skin wall.

tony3619

Long story short I had a few leaks over the last 4 years due to weak mortar over the joining between the flashing and brick which seemed to be solved by using sealant over the existing flashing.

This revealed the bigger issue of missing cavity trays as the external wall turns Into an internal one further down as it's an extension. I've been declined a warranty repair as it's in a "sheltered" area of the uk where penetrating damp is unlikely ( I know)

I don't know whether to pay for retro fitting cavity trays myself and fight the decision for reimbursement as i'd probably need to take out a loan/save or just forget about it until something possibly happens. 

The wall has been hit by alot of wind driven rain since I repaired the flashing and no sign on the plasterboard ceiling of leaks but it's always present in my mind that it might be leaking and damaging further up but not showing signs on the ceiling or that a long enough period of rain could push it over the edge. 

What would you guys do? Anyone have experience with leaking single skin walls or retro Fitting cavity trays?