Vinyl on a Gambrel Roof??

[Gibsonguy]

Hi Guys,

I was wondering if anyone has seen siding installed on a gambrel roof before? The owners said they chose to do this, rather than use shingles which wear our. Usually mansard faces stay for a very long time. There is no shingles underneath. The owners said they removed the shingles and they installed a Tyvek building wrap under. I know the siding isn't water tight, just wondering what the long term effects would be especially on siding not installed perfectly vertical? Has anyone seen an installation like this? It's been 10 years and I haven't seen it yet. Looking for any info on vinyl siding that states it must be installed vertical if possible.

Thanks!

[Tom Raymond]

Vinyl siding is a rain screen. The good stuff installed to best practices techniques allows 20% of the water that hits it behind it.

The only way this will work is if the underlayment is water tight. Tall order for tyvek.

[Jim Katen]

I agree with Tom. It's a rain screen system and whatever's behind it has to be a good water barrier. Tyvek might work if the wall were vertical, but I'd be worried about water seeping through all the nail & staple holes. It could have worked better if they'd put fanfold foam behind it. 

[Gibsonguy]

Thanks for the replies Jim & Tom, I was thinking the same thing. Anything on vinyl siding not to be used on anything but a vertical surface? 

[Jim Katen]

I don't see any specific prohibition in the VSI's Vinyl Siding Installation Manual, but I wouldn't expect to. They're going to tell you how to install it, not how not to install it.  It's *siding*, not *roofing.*  I doubt that there's anything in there that says you shouldn't install it on your car, but that doesn't mean doing so would be ok. 

I'd just say, "Some moron installed vinyl siding in lieu of roofing. It's unlikely to work well. Hire a roofer to install proper roofing in its place." 

(Ok, I wouldn't actually write, "moron," but I'd mean it.) 

 

[Tom Raymond]

Fanfold would reduce the volume of water that reached the tyvek, but also hold a significant amount in place without a gap to promote drainage.

I wouldn't count on it unless it were installed like a tile roof. A completely waterproof underlay with the cover on battens.

It wouldn't look any better, but it wouldn't leak.

 

[Marc]

I'd like to visit on a rainy day and see just how much water is coming out at the starter strip.