[Closed] Flat roof felt repair garage

New felt over existing felt, start from bottom of slope and work up, 2 x1 roofing battons, then downwards securesd to roof, use small clout nails to hold felt down.

Thanks Project,

forgot to mention it is a flat roof, so a bit more concerned about it leaking

Remove felt to a join, then try and genmtly lift the edge, aply adhesive or bitumne paint under, then apply more adhesive then felt, when complete apply more bitumen paint over roof with a paint roller.

You need to stick it down I think.
I did mine using stuff from wickes.
All cold adhesive system, a primer, and adhesive then a roll of felt.
You prob looking at £100.
1st repair I did was 7 years ago, still fine, just done my second, both on a rubbish flat roof with not enough drop, so far all watertight.

Current felt is just one layer (no underlay), but looks like it has been heat sealed on.

Would I get best results trying to nail the old felt back on (to give a kind of underlay) then glue on top new felt or discard the old felt, cut back to a clean line in the undamaged felt then just stick direct to the roof boards?

In my case the old felt had been painted so was fairly smooth. Where it blistered I cut it away to leave it flat, but I did go over the top. I don't think it would work going onto those flaky stone things, even if you swept it.
But if you're going to strip it, I'd be tempted to get a single sheet of rubber membrane, but that's a proper job.
May be worth painting it with bitumen type waterproofer to see the winter out.

Roofing suppliers sell a stuff called teckatorch or something like that. You heat it up as you roll it out. Melts the underside and sticks to anything!

Rip it off and replace with rubber? Cost a bit more but would add some bragging rights if/when you sell.