roofing felt deteriated and hanging down?

First tape as Rich says but a it's a bodge job and will need doing again in a very short period even if you get it to stick with all the dust floating about.
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Check with your local building control office at council offices. They will then tell you what you can and can't do/use.
Price up materials they suggest do the job and forget for at least 20yrs. There might even be a 'Green' grant towards cost, worth enquiring.

BB
November 2009

DON'T EVEN THINK ABOUT TAKING THE TILES OFF,years ago they only had tiles on the roof,the loft got filled with muck and soot blown in from under the tiles,the felt stops this and allows condensation to evaporate out of the roof.I suspect it won't be much so it won't cause a problem,tape it up with gaffa tape or wedge some thin battens across the rafters,don't go to the expense of having tiles removed.

Rich
November 2009