When you look up at your roof, you typically only see the outer layer. These shingles or tiles are essential, but to do their job well, a professional roofer must pair them with other quality roofing materials. One of those materials is the roof underlayment. You can’t see the underlayment, but it is there, protecting your home in silence. Keep reading to learn more about roof underlayment, its job, and how roofers install it.
Roof Underlayment: Defined
Generally, residential roofs have three layers.
First, there’s the roof deck, which is the wood that forms the base of the roof. These days, most roof decks are made from OSB or plywood. If you go into your attic and look up, the flat wood you see as the attic “ceiling” is the roof deck.
The underlayment is the middle layer. It’s secured over the roof deck but under shingles, tile, or metal. You can think of it as the filling of the sandwich. The roof deck and shingles are the bread.
The underlayment is not nearly as thick or rugged as the shingles or roof deck. It’s made from either felt or a synthetic material. Underlayment comes in rolls. To install it, roofers unroll it and tack it down. Once they cover the whole roof deck in underlayment material, the roofers install the shingles on top of the underlayment.
Why Roofers Install Underlayment
Roofers install underlayment as a secondary means of protection for your roof deck. Shingles and other “outer” roofing materials are not impervious to damage. If a shingle cracks, gets pried from the roof by ice buildup or blows off in the wind, the underlayment helps keep the roof deck dry. This layer is vital since a wet roof deck will soon become a rotten roof deck. And rotten roof decks can lead to all sorts of issues, from mold growth to collapsed roofs.
In short, underlayment protects your roof deck if the shingles fail. This thin yet essential layer helps protect against leaks, water damage, and mold growth.
What Happens Without Underlayment?
Installing shingles directly over a roof deck without underlayment is not wise. All it takes is one shingle to lift or fail, and water will begin seeping behind it. This water often gets “stuck” between the remaining shingles and the roof deck. Over time, the roof deck begins to deteriorate with this continued water exposure. Your other shingles may also start breaking down prematurely. They are not designed for their backs to be consistently wet. Roofs installed without underlayment are more likely to leak, even if they only suffer minor shingle damage.
Without underlayment, you’re also more likely to get mold and mildew in your attic. Your attic insulation may become moist and stop doing its job well.
Eventually, parts of your roof deck may become weak and start sinking in, giving your roof a dreaded sagging appearance. Sagging roofs are at risk of collapsing, so you definitely don’t want to let things get to this stage. A good underlayment can prevent all of this, extending the life of your roof and reducing your need for repairs.
Underlayment Versus Drip Edge
Homeowners sometimes confuse underlayment with the drip edge. A drip edge is also important to protect your roof from water damage. It’s a piece of metal (or sometimes plastic) flashing installed along the edge of your roof – just under the last rows of shingles. The drip edge helps prevent water from seeping under the edge of your roof. On the other hand, underlayment is installed over the entire roof deck and offers protection should any of your shingles fail.
Types of Roof Underlayment
Any good roofer will be sure to put down a good layer of underlayment before they install your shingles. There are two key types they can use.
Felt underlayment has been around for many years. It is an affordable option and offers reasonable protection for the average roof. The type of felt used to make underlayment is covered in a thin asphalt layer, so it is water-resistant and durable.
The downside to felt roofing is that it can be tough to install. It’s heavy and, therefore, a bit cumbersome to unroll and prone to tearing during installation.
Synthetic underlayment is newer and more advanced. It costs more than felt. However, it is lighter and easier to install. It also offers better protection against moisture and is far less prone to tears and damage.
If you’re having a roof replaced, make sure your roofer plans on using a quality underlayment. Your roof deck depends on the underlayment for longevity and protection.
Are you looking for a roof replacement company in North Port, FL? Contact Mark Kaufman Roofing to schedule an estimate soon.