Cedar roof: ice/water guard versus a shorter starter course of cedar shingles

We have skip-sheathing. I am comparing two quotes for a new cedar roof.

One of the quotes has an ice/water membrane being installed and then a double-course of 24" shingles for the bottom course.

The other quote has a starter course of 12" cedar shingles, and on top of them a double-course of 24" shingles.

How would the membrane be installed on skip sheathing?

What is the purpose of the starter course of 12" shingles?

The bottom 3’ of your roof (maybe more) should be solid decking.

It may be a good idea to put cedar breather over the solid decking part, after the ice & water shield is installed.

The 12" shingles are starter shingles, a 12" course with 2 more over it is how I do it in Michigan, it’s for snow.

Thanks. I was wondering how the membrane would be applied to the skip sheathing. Solid sheathing makes a lot more sense. I found a page on the nachi site that agrees 100% with you.

I am trying to make sense of what was done to the house back in 1993 when this roof we’re replacing was installed. There’s a gap of about an inch, insect-screened, invisible from the ground, but visible when you peek behind the gutters when standing on a ladder. This diagram shows what it would look like if solid decking were present. Were the carpenters who installed the cedar fascia trim making an intake vent? We have no overhanging eaves. The house is made of brick, if that has any bearing on the issue.

Better recommendation. Go back with a synthetic composite instead of cedar shake. Get some Brava Tile samples and put them on your roof. Looks great without all the issues and maintenance you have with cedar shake. Cosmetics aside, I’d rather have a 20 year 3 Tab on my roof than cedar shake.