Q&A – Should the underlayment be visible?

This homeowner was up in their attic and noticed they could see the underlayment of their roof. 

Samantha, a homeowner in Missouri, came to our experts after some renovations were done on their house, including the roof. This is what they asked:

We recently had a house fire and have gutted part of our 1916 house. We just had new asphalt shingle roof put on less than two years ago. I noticed once they demolished the ceiling into the attic I could see the underlayment from the roof exposed in multiple areas. Is this normal? Should plywood have been added to the roof?

Below is what our roofing expert John Kenney with Cotney Consulting Group had to say in response to Samantha's question:

Samantha, seeing roofing underlayment from the attic is not typical in a roof assembly. In a properly built roof, the shingles should be installed over solid decking — usually plywood or OSB — which serves as the structural base for the roof system. The underlayment, whether felt or synthetic, is applied on top of that decking, directly beneath the shingles.

If you see the underlayment exposed from inside the attic, it likely means there’s no solid sheathing under the shingles—something more common in homes built before the 1940s, when spaced plank decking was standard. While older roofs can technically be reroofed over those boards, there should not be significant visible gaps exposing the underlayment. Gaps that wide can compromise shingle fastening, insulation and performance.

Given your home’s age and the recent fire damage, I’d recommend having a qualified roofing contractor or structural professional inspect the deck. They can confirm whether new sheathing should be installed over the existing boards to meet current codes and ensure long-term roof integrity.

In addition to John's response, Henry Staggs from the Arizona Roofer sent in this answer for Samantha!

Continue the conversation in our Forum!