One car detached garage 12x22 - one of those that is just about falling down...at my daughters. 4/12 pitch - no heat, etc. no gutters, no inside ceiling, etc - just a shed really. I am removing two layers of shingles, fixing any sheathing and then will install new shingles. Do I have to use that ice blocking stuff along the bottom, or is just the 15lb felt and then one layer of shingles backwards (or however we used to do it) OK? I do have a permit on the job, but nothing was specified.