Understanding Roofing Underlayment
Most roofing systems consist of multiple layers that are adhered together in order to form a roof that is durable and long lasting. The foundation is the decking, usually made of plywood. The top layer is the roofing material. This is can be tile, asphalt shingles, or metal. The layer in the middle is known as underlayment.
Underlayment Explained
Underlayment is the thin layer inserted between the decking and the shingles. Its primary function is to seal your roof and protect it from wind and water intrusion. It is not as tough as plywood decking, and not as attractive as shingles, but it may be the most important layer in protecting your roofing system. Neither the decking nor the shingles have this protective feature.
Comparing Three Types of Underlayment
There are 3 basic types of underlayment:
• Asphalt-saturated felt
• Rubberized asphalt
• Non-bitumen synthetic
Asphalt-Saturated Felt
Felt underlayment is constructed from either organic or fiberglass materials. It is water-resistant, but not 100% waterproof. Contractors install 15-pound or 30-pound felt on residential roofs. There is a considerable difference in thickness and strength between 15 and 30-pound felt. 30-pound felt is more resistant to damage during installation of the roof-covering material, and will protect the roof longer when exposed to the elements.
Roofers are slowly phasing out of felt underlayment. It tears easily and does not perform well under UV rays or heat. Tears and punctures are common during installation. Overall, it is seen as a low-quality type of underlayment compared to other types.
Rubberized Asphalt
Rubberized asphalt is used for all types of applications including concrete. It is hard, resilient rubber-like material that is ideal for roof underlayment. It is adhered directly to the decking without the need for nails. The rubber-like qualities of rubber create a rigid seal that keeps water away from the decking.
Bitumen is the key ingredient in rubberized asphalt. Bitumen is utilized in both residential and commercial roofing and can be made from various combinations of other materials. To maximized strength and elasticity, bitumen is sometimes altered using polymers that are custom-designed to give the material specific properties.
• Asphalt-saturated felt
• Rubberized asphalt
• Non-bitumen synthetic
Asphalt-Saturated Felt
Felt underlayment is constructed from either organic or fiberglass materials. It is water-resistant, but not 100% waterproof. Contractors install 15-pound or 30-pound felt on residential roofs. There is a considerable difference in thickness and strength between 15 and 30-pound felt. 30-pound felt is more resistant to damage during installation of the roof-covering material, and will protect the roof longer when exposed to the elements.
Roofers are slowly phasing out of felt underlayment. It tears easily and does not perform well under UV rays or heat. Tears and punctures are common during installation. Overall, it is seen as a low-quality type of underlayment compared to other types.
Rubberized Asphalt
Rubberized asphalt is used for all types of applications including concrete. It is hard, resilient rubber-like material that is ideal for roof underlayment. It is adhered directly to the decking without the need for nails. The rubber-like qualities of rubber create a rigid seal that keeps water away from the decking.
Bitumen is the key ingredient in rubberized asphalt. Bitumen is utilized in both residential and commercial roofing and can be made from various combinations of other materials. To maximized strength and elasticity, bitumen is sometimes altered using polymers that are custom-designed to give the material specific properties.
Besides being durable, weather resistant, and completely waterproof, rubber roofing is also resistant to thermal shock. It will not crack or become brittle due to hot or cold temperatures. It’s able to withstand hail and other extreme weather conditions and shows very high resistance to UV rays.
Non-Bitumen Synthetics
Roofing synthetics are lightweight and extremely durable. They have a tight grip on both the decking and the shingles, which reduces sliding. This makes them perfect for roofs with steeper slopes.
Synthetics do not absorb water. This prohibits mold and algae growth and protects the wood structure. This type of roofing is also resistant to UV damage and can be left exposed to weather for periods from six months to a year, depending on the manufacturer’s specifications.
One of the biggest concerns non-bitumen synthetic underlayment is that it fails to meet Texas state roofing codes. As such, it may not be covered under most manufacturer warranties. Your homeowners insurance may not cover it as well. Synthetic underlayment also requires precise installation. If not implemented onto your roof correctly, it may fail to serve its purpose. If you decide to use non-bitumen synthetic underlayment, only hire a contractor that is certified to install this type of roofing material.