05/14/2026
"I’m considering adding a layer of insulation to the exterior of my roof, then another layer of sheathing, and finally asphalt shingles. Since I only have a single layer of asphalt shingles on my roof, am I able to just apply the foam right over the shingles, or do I need to strip the roof first?"
Here's our expert’s answer: https://www.finehomebuilding.com/2018/06/21/retrofitting-foam-insulation-roof