Question regarding a layover or overlay roofing project. 40 year old ranch house with a large rear addition, breezeway, attached garage, with 4 valleys. Last roofing was a tear-off about 20 years ago. Over last couple of years, I’ve been re-roofing sections, one at a time, and as time allows.
The re-roofing has been all layovers, using the standard layover technique for 3-tab shingles of a 5" starter course, a cut 10" first course, and full shingles butted up against bottom of existing shingles to the cap. The existing shingles are in good shape (no broken or curled), but some leaks in 2 valleys. I did one side of garage in 2011. Another section of garage and breezeway with a valley in May 2018, and a large section of addition and main house with a valley in October 2018. A 2’ wide Grace ice shield was laid into valleys. Each of these sections was done in under 40 hours labor, over a couple of weeks each.
Now getting ready to layover front of house, about 768 square feet. At my current working pace (active 75 year old), time schedule, weather breaks, and whether I hire some labor (a nephew), this section could take upwards of 3 weeks.
So my question is… If I stop shingling for a few days, weeks, or more, and dab some roofing sealant on any exposed nail heads on the last course laid that day, is there any risk of leaks during any rain showers? I’ll probably start this project this month (May 2019), but may back off during the heat of Summer. I don’t want to be oozing tar standing on new shingles in 90 degree temps.
Enclosed is a photo from last May with a closed cut valley, but not yet completed to the cap. Would I expose myself to any leaking if this roofing layover is not completed for several weeks or a month or 2? As a solo DIY project, I’m not going to blow it out over a couple of days, and it could go on for several months.