Hi. I have a big old barn and the roof needs so minor repairs. The rafters and perlins are perfect but the A Frames need replacing. I can do this without having to take the roof down lucky. But my roof hasn't got felt due to an old protection act. So I was wondering when I take down an A Frames one at a time can I use a felt substitute or felt on the inside between the perlins and new A Frames? If I have to take the roof down it will cost me a fortune so was hoping that there's a solution. Cheers