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Roofing Terms Explained: Nailable Surface, Decking, Underlayment and More
Roofers have their own vocabulary. Here is what the words on your estimate actually mean.
By Sealed Solutions Roofing, Cloverdale, IN · Updated October 2026
Nailable surface
The layer the new roof gets nailed into, usually the roof decking. When a roofer says they need a “nailable surface,” they mean the deck has to be solid enough to hold nails securely. Rotted, soft or badly gapped boards must be replaced before new roofing goes on.
A to Z of common terms
- Decking (sheathing)
- The plywood, OSB or boards that form the roof surface under the shingles.
- Underlayment
- A water-resistant layer installed over the decking and under the shingles.
- Ice and water shield
- A self-sealing membrane used in leak-prone areas like eaves and valleys.
- Flashing
- Metal that seals joints around chimneys, walls and vents. See roof flashing.
- Drip edge
- Metal along the roof edge that directs water into the gutter.
- Ridge cap
- Shingles that cover the peak where two slopes meet.
- Valley
- The channel where two roof planes meet.
- Square
- A unit of roof area equal to 100 square feet.
- Pitch
- How steep the roof is.
- Tear-off
- Removing the old roof down to the decking.
- Architectural shingles
- Thicker, layered shingles with a dimensional look.
- Granules
- The mineral coating on shingles that protects them from sun and weather.
Have a question about your roof?
Call or text (317) 903-8298. We are open 24/7, and estimates are free.
Quick answers
What is a square in roofing?
100 square feet of roof area. Estimates often price materials by the square.
Why would my roofer replace decking?
If the deck is rotted or soft, it cannot hold nails securely, so it has to be replaced for the new roof to last.