Roofing felt foof

[N Cook]

Can't complain , it must be more than 25 years old. Leaks due to the felt disappearing over the tacks holding down the bottom layer of felt. What causes this and how to reduce the possibility when re-felting? Is thermal movement wearing away at the upper felt or local heating from the sun and insufficient pea grit on top, or what - they're quite neat holes ? When re-doing perhaps place a square of upholstery tape over each tack before applying the top layer and tar or perhaps tacks pushed through rings of cut-up bicycle inner tube for rubber washer below the tack heads and above.? For the moment temporarily patched with hot-melt glue and patches of felt with extra heating from a hot air gun , well tar and hotmelt seem to melt at about the same temperature.

[Phil L]

This post doesn't make much sense to me, 'tacks in the bottom layer of felt'? - if it's a flat roof, then the felt isn't tacked at all, it's laid into hot bitumen as are the layers over the top, the only time tacks are used is at the edges where it meets the fascia boards...am I missing something here?

[N Cook]

Perhaps roof is overstating it, 18 inch wide flat roof over a bay window. There's definitely tacks, 6 eruptions , so far, over felting tacks, central area, no problems at the edges.

[Phil L]

Either way it shouldn't have tacks in it at all, it should have been done with hot bitumen and had 2 or 3 layers of felt laid into it. If you put it back the way it was, it will leak again, tacks are not meant to be used in this way, how long has it been like this?

[N Cook]

At least 25 years.

Surely roofing felt has to be tacked down or any half decent wind in the wrong direction round a corner or whatever, generating negative pressure, would suck the felt off the roof.

[John Rumm]

It sounds like it has been felted in the same way you would do a pitched roof (i.e. shed etc), with a nail prep layer (hessian reinforced felt), then bonded middle and top coats.

In your case, someone may have been cutting costs and missed out the middle coat of under felt!