Roofers - any advice on roofing felt?

PaulJM

I might be pushing even the knowledge on MSE with this one, but you can only try!

I've having a dormer put onto my house, and they've built the frame.
I've had roofers today, who wanted to 'get it dry' - so they've stuck a load of what they've called felt over the frame, and hammered batons over - from what I see, you don't want to stare at people working! I don't have any issues with either my roofers or my joiners by the way - they've all worked well.

My question is this - the 'felt' they've put over is quite thin - it's like a thin, plasticky tarpaulin type thing. The stuff that is on the rest of the roof is very thick and tar-ey - and snaps if you mess with it.
The house is 1950's, by the way, and I can't imagine that the roof has been changed.
This old stuff is fine, no rips or tears, but it seems about a million times more resilient and strong than the new stuff.

Have I been given cheap rubbish, or is this just the modern difference?

fatbikersbouncebetter

Building regs state than all new builds must use MEMBRANE, this can be light green, silver or blue (usually)
Its the new wave stuff that is breathable and has fibreglass strands and will not tear or let water in, but will let moisture out. If ever you get a re=roof they will use this too.
Its 1000% better than the old stuff.

Don't worry be happy:T:T:T:T

PaulJM

fatbikersbouncebetter wrote: »

Building regs state than all new builds must use MEMBRANE, this can be light green, silver or blue (usually)
Its the new wave stuff that is breathable and has fibreglass strands and will not tear or let water in, but will let moisture out. If ever you get a re=roof they will use this too.
Its 1000% better than the old stuff.

Don't worry be happy:T:T:T:T

Great ta.
Well it's black, but I guess doesn't matter.
It's got strands in yes, but it is slightly torn in places where they've hammered it into the battons.

iamcornholio

fatbikersbouncebetter wrote: »

Building regs state than all new builds must use MEMBRANE

That is not correct. Bitumen felt or polyethylene and polypropylene roofing felt can be used.

In the OP's case, it seems that the plasticky stuff would be one of the two poly type felts

The issue is whether the "felt" is breathable or not. If not then there should be a means of ventilating the roof void - this will be covered in the design plans

There is no harm in asking the roofers about the felt or how it will be ventilated.

I would just caution that the poly type felts are very prone to condensation, so if that material has actually been specified (check the plans) then ventilation is much more important.

I would hate to think that the roofers have just bought the wrong felt (and the cheap one at that) where as breathable membrane was actually specified