Damp patches on inside of gable (?) wall

Ben1989

So, still having this problem and it is all over the gable wall.

We only have a downpipe on the gable wall from the toilet and bath/sink waste feeding into it so no guttering to check.

However, the downpipe (above the toilet pipe) does have a crack in it but there's nothing feeding into that area at all. 

Is it possible the end caps (?) on each row of the roof could be a culprit? How and who would check these? Also, what would be a way of checking the bare brick wall in the loft. It 'seems' dry but is there a way of checking? Then I would know for sure it's the roof. With it being bare there's no plaster to amplify the issue.

I just really don't think it's the render. I've had scaffolding up and filled every single crack I could find and repainted it all. Also, there are approx 20 other houses of our design which have never had the gable wall re-rendered. Plus, being quoted £5-7k I really want to try everything else.

Ben1989

Would anyone be able to help?

Ben1989

Could anyone offer some opinions? Thanks