Faulty box gutter and damp issue

plumb1_2

It looks like it’s the opposite end from the outlet 
most probably powder coated steel or Ali, they just join them with silicone and bolts.. maybe leaking into the cavity 
Youll need a good roofer, they need to etch the metal, apply a primer, before applying a seal like aquapol  but only really a repair job. 

Always best to have it relined in one continuous length, would need bottom row roof tiles removed and any metal trims, so not cheap, but a long term fix.

magn8p

plumb1_2 said:

It looks like it’s the opposite end from the outlet 
most probably powder coated steel or Ali, they just join them with silicone and bolts.. maybe leaking into the cavity 
Youll need a good roofer, they need to etch the metal, apply a primer, before applying a seal like aquapol  but only really a repair job. 

Always best to have it relined in one continuous length, would need bottom row roof tiles removed and any metal trims, so not cheap, but a long term fix.

Thanks for the quite a detailed response. Will wait for NHBC's response to the seller and then speak to the agent. Especially since multiple properties in that area have a similar issue, so this one isn't alone.