I'm thinking of getting an attic conversion. The roof is welsh slate and in
very good condition, timbers fine, nails ok and ridge tiles etc. However, as
it's the original 1930's roof, there is no felt.

The question is, does it matter if we get an attic conversion. I have asked
all 3 companies who have provided quotes ( all reputable, with good
recommendations) and they've said it should be ok. Any reason why they
should be lying. Is roofing felt a must if you're having an attic
conversion. Can you fit felt without riping off the existing roof, or am I
just asking stupid questions.

TIA

Jon