What underlay for a shallow roof pitch?

[milbo1990]

Hi All,

Finally got the roof structure finished and I'm ready to start felting, lathing and tiling.

My pitch is quite shallow at 15 degrees and I did read somewhere that you should use a 1F underlay with shallow pitches, rather than a breathable membrane.

If this is the case, does that affect how I should ventilate the roof? I'm having a vaulted ceiling if that makes any difference.

Thanks in advance.

 

[Toproofer]

Never herd of using 1f felt on a shallow pitch roof breathable should be fine.Procter roof shield is what I use all the time,with tiles suitable for the pitch you shouldn't have a problem

 

[milbo1990]

Thanks, I thought it was a bit strange.

I'm trying to calculate how much lath to buy too - what's the spacing that I should use, or does that depend on the pitch?

 

[freddiemercurystwin]

The technical blurb for the tiles will tell you the lap, which is determined by the pitch and exposure and then allow for a little wastage, overhangs etc and getting the lap evenly spaced up the slope which might mean an extra course.