Cedar shingle question

[kevin nee]

I am about to put white cedar shingles on a barn on my property. I did the back last year and replaced all trim with PVC.
This year I am going to do another side. My question is I have leftover Ice & Water from some recent roofs. I am thinking about using the Ice & Water on the sidewall before applying the shingles. To me it makes sense to use up the material and it could even make for better weather protection down the road. The whole project is only about 3 squares.
Does this plan have a downside? Has anyone done this.
Thanks in advance, Kevin

[John Pendery]

I would be wary applying ice and water on a wall and go with a traditional house wrap like tyvek or a similar product that allows moisture vapor movement so your walls will stay dry. You might be fine with the ice and water, but it could also potentially trap unwanted moisture in the wall. Wall and roof assemblies are treated differently in certain ways, this being one of them. Building science has a lot of different angles and approaches though, so I could be missing something.

[Steve Rozmiarek]

You could use it, but you'd have to use a mesh type airgap material under the shingles to provide a little breathing room for wet shingles or they won't last as long. The extra thickness would need to be planned for in trimming, may be more trouble than it's worth.

[Jim Becker]

A rainscreen under the shingles is a good practice in current methodologies as far as I know. This is independent of any kind of house wrap or water sealing on the structure and is designed to allow any moisture that is trapped between the shingles/siding and the physical wall to be able to flow down and out, rather than collecting and causing other mischief over time.

[Tom M King]

The more wooden shingles can breathe on both sides, the longer they will last.