Leaking roof barges?

MarkP

Hi

we're looking at a house in rural Co. Galway that has a penetrating damp issue. Only built about 15-20 years ago but with concrete roof barges in the traditional style. There's some water ingress at both gable ends on the inside (brown stains on plastered wall and the blocks are visibly damp in the attic space where it's not plastered). Might be a bit of cracking/failure to a patch of external render high up on one gable. Looks like they've had a go fairly recently at sealing/painting over externally. Most likely fault would be inadequate leading under the barges where they meet the roof tiles?

We've heard there may have been similar barge issues with other roofs put on by the same builder in the past. What might be rough cost of taking off and relaying barges? How would that compare to taking off the barges and extending the roof structure to overhang the gables (and would that raise any architectural planning retention questions)?

Thanks