Knowledge is Power: Know Your Roof — Roof Decking (sheathing)


So far in this series, we have described a roofing system’s anatomy, taken an in-depth look at its ventilation, and explained what’s involved in a successful relationship between a roof and its chimney.  Now it’s time to discuss roof decking, also known as sheathing, and the products that pertain to it.


Roof decking (or sheathing) is the layer of the roof that is used as the base for nailing roof coverings. Decking acts as a layer of protection for the roof and usually consists of a wood material such as plywood. Decking is a crucial part of roofing because it ties all the structural parts of the roof together; it is where your waterproofing material attaches or adheres.

New decking install.

A Note About Older Structures

Older homes may very well have a different type of roof decking than newer structures. It is important for us to point this out because here in Maine, many historic homes are maintained for both residential, and business uses.

In older houses, decking is typically made of lumber place perpendicular to rafters/trusses. The lumber could be spaced from 1 to 4 inches apart or e right next to each other.  When we come across this type of sheathing, we assess its structural integrity and discuss with the owner whether it needs to be addressed or not. If the sheathing is sound, it’s likely that roofing can be done as usual for the project.

Deck Assessment

After removing old roofing material, we can assess the health and condition of the decking. When our crew begins a new project,  they sometimes discover a need for decking repairs or replacement. This discovery, which happens in about 40 to 50 percent of roofing projects, causes unforeseen delays. Failing roof decking is a major reason it is challenging for roofing contractors to maintain their expected schedule for projects — although the weather is the #1 culprit.

The decking is typically the starting point for roofers. Once we are confident we will be able to apply the materials to a sound base (deck), we can move forward.

Moisture Protection

Ice and Water, the product roofers use, is a self-adhesive waterproofing membrane. It is used three feet up on the eaves, along rakes and valleys, and around obstructions (chimneys, vent pipes, skylights, etc.) to protect these sensitive areas from ice damage and wind-driven rain.

Horch Roofing uses CertainTeed WinterGuard HT (high tack/temperature) for this purpose.

Key features:

  • Provides waterproof underlayment for shingle, metal, slate and tile roofs.
  • Resists high roof temperatures under metal roofs.
  • Has a tough, tear-resistant top surface film that protects metal roofing sheets from being scratched.
  • Seals the roof against the infiltration of water into the building due to ice dams and wind-driven rain.

Check out the CertainTeed WinterGuard warranty here.

More Layers of Protection  

Synthetic Underlayment

Roofing underlayment is a critical secondary barrier that helps preserve the life your roofing system even after the life of your shingles. We use Titanium UDL30 synthetic underlayment, not traditional felt. UDL30 is 100 percent synthetic, therefore totally unaffected by water; this means it is impervious to mold. It is also 20 times stronger than felt products and lasts far longer, too.

Drip Edge

A drip edge is an L-shaped piece of roof flashing (we sometimes use cedar shakes for an alternative look). It ensures that water falling from the roof is directed toward the edges without reaching the underlying fascia, window trim, and siding. Drip edge can help prevent rot, ice dams, and other problems water can create.



Having robust, high-quality roof decking is just one aspect of keeping your home safe and dry. Check our previous posts in this series for more details — and keep an eye out for our next post, which will focus on asphalt shingles and the various textures, colors and brands that are available.

If you have questions or are interested in further discussing roofing, or would like a FREE estimate- Call us or stop in, we are happy to help! 207-273-1111

Horch Roofing – 2414 Camden Road, Warren, Maine 04864  (207) 273-1111 or visit us at