4Mill Plastic liner under Roof skin?

[SSTear]

I'm thinking about putting a 4 mill plastic liner over my foam board and cross ribs before skinning the roof with .040 alum skin.

Has anyone done this or have suggestions whether to do this or not? My build will be sitting outside in the New Hampshire winters after finished. I was thinking about extreme whether conditions. I'll be covering it when possible with a custom cover when not in use.

Thanks in advance for any suggestions.

[KCStudly]

I see that as hindering the ability to get a good seal around the edges of the aluminum and where screws penetrate. The plastic might release from whatever sealant you use and create a leak path. $0.02

[les45]

I don't see any benefit. The skin, if properly sealed, is what keeps the water out. If it gets through a crack in a joint or seam then it will get to your wood even with the plastic over your foam board. I agree too with KC that it could cause problems in sealing your joints.

[SSTear]

Thanks Guys! I'm glad I asked. Makes sense to get a good seal on the edges. I'm always the one to over kill things. I'm finishing up the skin work this weekend. I'll try to post pictures next week. Thanks again.