Which Underlay for felt shingles? Modern Membrane or Felt?..

[moppit]

Been getting quotes for materials for me to cover my 50m sq shed roof. Some offer old style underlay felt, some offering cromar vent 3 breathable membrane or equivalents.
eg.
http://www.sandpipersupplies.co.uk/...eathable_Membrane_122gsm_50m_x_1-dot-5m_Roll/

The membranes are attractive since they are cheaper, quicker, easier to fit (ie. staple gun, scissors!) and I am being told will allow breathability (under shingles? thought they are supposed to seal the roof?)

Is this seriously an option or am I being misinformed?

Deck is 18mm OSB 3.

Xenon very helpfully said no to membranes but two suppliers say its OK? Now I'm confused....

 

[catlad]

I would listen to Xenon then as I have never seen shingles laid with a breathable underlay, why would you as you will put a thousand holes in it.

 

[Xenon]

I actually said use a felt underlay, sand faced. Nail/staple this on. You will see a bitumen strip on the back of the shingle, once you have nailed the head, lift the shingle and wave a small blowlamp over this strip then press down onto the head of the previous shingle, this will make sure they hold properly and stop the wind lifting them.

 

[moppit]

Thanks again Xenon. Will use felt.

Blowlamp rather than a dab of mastic?

Cheers

Moppit