30# tar paper over SIPs

[FrankLad]

Just put our 6-1/2"structural insulated roof panels on the roof last week.  Forecast shows rain coming in soon so I immediately started tacking down 30# felt paper.  Spoke with one of the reps at the panel company about this - told him that we are putting 1x4 strips and metal roofing over the panels and tar paper.  He says it shouldn't be an issue as far as moisture goes.

I asked him, and am asking you guys because I'm recently finding out about "roof wrap" material that is a moisture/water barrier, but allows vapor to escape.  In our scenario of having an air gap, would it make a difference?

What do you guys think?

Main thing for me is to keep the SIPs dry until the metal comes in, but I'd like to leave the felt paper if possible.  However, if an actual roof wrap is better then I'd like to know while I still have time to change things.

Thanks!

[Kevin K]

I'd have no qualms about installing the felt as a temp. water barrier (for now).

It sure won't hurt to keep it there either, it does not act as a vapour barrier.

Kevin

[Raphael]

  15 or 30# felt is what the engineer at my panel company recomended I use for our roof, he also didn't feel an air gap was needed under the metal as it's free floating and vents at the ridge.  Officially they are recomending the expensive high tech stuff but as he said why pay more for something that works the same.

[Radar67]

Frank, I have to agree on the tar paper as well. When it gets wet, it swells and acts as a waterproof barrier, when it dries, pores open up to allow it to breath. There was a good link on here, that I can't find now, that showed different vapor barrier methods for the different regional climates. That link referenced felt paper as the vapor barrier of choice for the southern climate. Our biggest problem down here is getting our houses too tight, it only causes a festering ground for mold. We need to stay as far away from "plastic" products as possible in this area.

Stew

[FrankLad]

Thank you guys very much for the affirmation!