Understanding the Parts of a Roof System

Understanding the Parts of a Roof System

The Parts that Make Up Your Roof


A roof is made up of multiple components. Other than the shingle, which most people are familiar with, we have the underlayment, flashing, ventilation and more. Each of these are listed below with a brief definition. Every component of a roof works to support the others. If someone were to cut corners and neglect a portion of the roofing system, the other components would suffer.

Understanding Roofing: What are the components of a roof?

1. Decking

Decking is the component that is installed between the trusses and the water proofing material. It will typically be made of plank boards or plywood. Often found on older homes, plank boards are 1x6, 1x8, or 1x12 boards. They tend to be more expensive to replace than plywood because of the labor involved. Plywood comes in 4'x8' sheets with differing thickness. Often plywood is replaced due to water damage, delamination, mold, waviness, lack of plywood clips, improper building code application or if the wood is unable to withstand the weight of a new roof. Decking must be installed to meet fire and building code requirements.

This Decking Glossary Covers Everything you Need to Know Before your Roof Replacement

2. Plywood clips

Every piece of plywood needs multiple clips to help hold it in place. Without these clips the decking will become wavy and uneven, causing leaks and leaving your roof susceptible to damage from high winds.

3. Ice and Water Guard

Along the eaves, valleys, chimney and other penetrations in your roof, Ice and Water guard is installed to protect against snow and ice when it builds up on your roof. It’s also used in low slope areas to increase the protection of your system.

4. Underlayment

This is installed everywhere else on your roof deck and provides a necessary layer of defense between your shingles and decking while enabling your roof to breathe so that moisture doesn’t build up and cause leaks or mold. Your underlayment also affects how well your shingles will lay on the roof. Underlayment come in different types depending on the needs of your roof system, from the standard felt to the higher quality synthetic underlayment.

5. Drip edge

Drip edge is installed at the eaves and rake edges of your roof. This is an item of flashing that helps prevent water from running off the edge of the shingles and back into the house. It also ensures that the water running off the eave goes directly into the gutter as it’s designed to.

6. Starter shingles

Installed along the eaves for water protection and along the rake for a higher wind resistance, starter shingles are necessary for waterproofing your roof at the eave. Neglecting to install them can cause your gutter to fall off, among other issues. For wind resistance they come with a special adhesive that keeps all the edges of your roofing material snug to each other, preventing it from blowing off.

7. Shingles/Tile

The top portion of the water proofing system designed to withstand the elements. “Shingles” often refer to asphalt based roofing material while “tiles” often refer to a stone or concrete type of system. Every type of shingle comes with a different life expectancy, thickness and wind resistance.

How to Choose the Right Shingle for Your Roof Replacement

8. Wall flashing

Metal that covers the transition between your roof deck and a wall. One of the most important components of your roof that keeps water out.

9. Pipe flashing

This is the flashing that goes around the pipes in your roof. Designed with either a plastic or metal base and a rubber gasket to go around the pipe. Plastic flashing is often the first part of a roof system to break down and leak. Valley. The connecting point of two separate sections of sloped roofing. Valleys are often susceptible to build up of debris from trees and snow that can both cause a leak.

Check out our Flashing Glossary

10. Valley

The connecting point of two separate sections of sloped roofing. Valleys are often susceptible to build up of debris from trees and snow that can both cause a leak. Ice and Water guard is an essential component to the valley to protect against leaking.

11. Ventilation

Every sloped roof requires ventilation, a system of intake and exhaust vents that cool down the roofing material to prolong the life of the shingles and prevent moisture from building up and causing a leak. There are multiple types of ventilation systems that vary depending on the type of house and roof system you have. Having two opposing ventilation systems can cancel out each other and cause moisture and rapid aging problems.


Would you like to download this information as part of a handy guide about Residential Roofing?


Residential roofing ebook



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