Whether installing a new roof or replacing an existing roof, much wringing of hands and gnashing of teeth gets directed to the choice of roofing material. Should you pick tile for the Mediterranean aesthetic? Maybe an asphalt shingle roof better suits the budget? In all the discussions about roofing, don’t forget to think about the roofing underlayment.
What do you mean, roofing underlayment? Why worry about that? Turns out, the roofing underlayment plays an important role in the integrity of your roof.
The Job of Roofing Underlayment
Roofs primarily work to keep the outside out. The roof might contribute to the energy efficiency of a home, but the main job is keeping a house dry.
You may think the shingles on the outer layer of the roof keep the house dry. While that is the job of the outer layer, the real waterproofing happens under the tile.
Your roofing underlayment sits immediately on top of the roof decking and serves as the final barrier between moisture and the inside of your house.
In the end, it’s the roofing underlayment keeping the house watertight. Rain might make it under a shingle but when the underlayment works right, that moisture never makes it any further.
Let’s look at the roofing process to better understand the role of roofing underlayment.
Typical Roofing Process
The roof-building process typically begins with the installation of plywood substrate. This plywood becomes the base upon which the roof is built. If water penetrates the roof, it causes moisture damage to this substrate. Neglected leaks damage the plywood and increase the cost of repairs as this plywood decking must be replaced.
Next, the roof underlayment goes down. This layer keeps the plywood dry. Vents, pipes, chimneys, and other structural elements that penetrate the roof create opportunities for water to penetrate the underlayment. This is why roofers install crickets and seal around these penetrations after the underlayment goes down.
Finally, the shingles go down.
Types of Underlayment
Traditionally, roofing felt won the top prize for underlayment. Asphalt-impregnated felt still wins the prize for affordability.
But new synthetic roofing underlayment takes the cake when installing asphalt and synthetic shingles or metal roofs. It stands up to high temperatures (important in Orange County, California) and offers incredible durability and long life.
When you discuss your new roof, be sure to discuss the roofing underlayment. And most importantly, when comparing quotes, make sure everyone creates quotes using the same materials.
California Rules for Underlayment
In addition to the type of roofing underlayment, you must consider California building codes and laws regarding the use of underlayment materials.
If the slope of the roof is between 21% and 33%, you’ll need two layers of underlayment.
When the roof slope exceeds 33%, you’ll need a single layer of underlayment applied shingle-like. Chapter 9 of the 2022 Residential Code covers everything roof-related.
The Right Roofing Underlayment and Roofer
Trust Crank Waterproofing for answers to all your roofing questions. When it comes to roof repairs and new roofs, understand your options.
With 79 years of business in roofing, decks, and waterproofing, you know when Crank is on the job it is done right and it’s watertight.
