When you have your roof replaced, the contractor will probably replace the underlayment too. If your roof is old, it might have felt underlayment that often wears out faster than the shingles, and that means new underlayment is needed.
There are other options than felt to choose from. Some types of synthetic underlayment can last twice as long as felt, and that provides extra protection against leaks as your roof ages. Here's why your roof needs underlayment and why your roofer might recommend a synthetic material even though it costs more than felt.
How Underlayment Protects Your Home
Underlayment is attached to the roof deck before the shingles are put on. The material is waterproof and resistant to tears. This provides added protection to the wood parts of the deck in case a shingle is damaged or is blown off.
Underlayment also provides an important function when having your roof replacement done. The material protects the deck of your roof in case it starts raining before the shingles are all put on. The underlayment keeps the deck dry, and once the underlayment is dry, the roofing work can continue.
Why Synthetic Underlayment Is a Good Choice
Different types of synthetic underlayment are made from unique materials. However, they're all tougher than they feel, which means they don't tear as easily when caught by the wind. When shingles are blown off in a storm, felt underlayment might tear and blow off too. Synthetic material is tougher, so it has a better chance of staying in place and protecting the roof.
Synthetic underlayment lasts a long time, and that could be important for preventing roof leaks. When old felt underlayment wears out, your roof leaks more easily when a shingle is damaged. A damaged shingle could lead to a rotted deck and water damage in your attic.
When you buy high-quality underlayment that has an expected lifespan of several decades, the risk of leaking is diminished since the underlayment will be in place doing its job long after felt underlayment would be worn out. Synthetic underlayment is also slower to deteriorate due to UV exposure and it has a high fire rating.
The main downside to synthetic underlayment is its cost. The least expensive type of synthetic underlayment costs much more than the least expensive type of felt. Both felt and synthetic materials come in various grades that have different prices, so you may need to discuss the underlayment you want and want to pay for with your contractor. You may want the best protection you can afford, especially if you get a roof replacement with luxury shingles or tile.