Most roofing systems feature lots of seams, especially if the roof is made of traditional shingles. That’s the reason why homeowners need to ensure that they put in a layer of protection between the shingles and the house. This layer of protection is called roofing underlayment.
In early days, asphalt-saturated building paper was the material of choice for use as a weather barrier between the shingles and the roof. These days, we are no longer limited to a single option, as underlayment materials can run the gamut from rubberized asphalt to organic, fiberglass to synthetic. The primary function of underlayment is simple: to keep the elements at bay–from scorching summer heat to torrential downpours to ice and snow. Many of today’s materials for re-roofing in Bellevue WA also feature anti-slip technology to make roof work safer for contractor.
Are you environmentally conscious? If so, you’ll be pleased to note that organic underlayments are now readily accessible, as well as synthetic ones that can help your home become Leadership in Energy and Environmental Design (LEED)-certified. LEED certification is a globally recognized symbol of sustainability achievement.
Sloped roof systems are generally built with multiple layers starting with foundation–also called the decking–which is usually made of plywood. You roofing material of choice –whether tile, asphalt shingle, metal or some other material — will typically make up the top layer. The layer in the middle is your underlayment. While some contractors may claim that underlayment isn’t necessary, it should always be applied to low-sloped roofs, as well as specific high-water risk areas of your home.
The underlayment plays the primary role of sealing your roof and protecting it from wind and water intrusion. While your plywood decking will certainly be tougher and shingles more attractive, the underlayment serves to protect your roofing system, which makes it the most important layer.
Types of Underlayment
There are three basic types of underlayment:
• Asphalt-saturated felt
• Rubberized asphalt
• Non-bitumen synthetic
Constructed from organic or fiberglass materials, felt underlayment is water-resistant, but not 100% waterproof. Contractors typically install 15- or 30-pound felt on residential roofs; the heavier the felt, the more resistant to damage during installation of the roof-covering material and the longer the lifespan.
Asphalt-saturated felt was one of the most common and widely used types of underlayment before the other types gained traction. Made from refined crude oil residue, asphalt effectively repels water and provides extra weather protection; it also boasts added fire resistance and water damage control. However, because it tears easily and does not perform well under UV rays or heat, roofers are beginning to phase it out in favor of better-quality underlayment.
Used for all types of applications including concrete, rubberized asphalt is a hard, resilient rubber-like material that many consider ideal for underlayment. Adhered directly to the decking without nails, it can create a rigid seal to keep water away from the decking. Rubberized asphalt is self-adhering and features a peel-off membrane to seal roof fasteners better. Known for superior weather and moisture resistance, it also has non-skid properties to make installation easier for contractors. What’s more, rubberized asphalt is highly heat resistant, making it the perfect underlayment for roofs in areas that experience extreme heat.
Rubberized asphalt is made of a key ingredient called bitumen, which is popular in both residential and commercial roofing applications. For better strength and elasticity, bitumen is sometimes custom-designed to give the material specific properties. Homeowners and contractors like it for its durability, weather resistance, waterproof nature and resistance to thermal shock. It won’t crack or become brittle due to hot or cold temperatures; it can withstand hail and other extreme weather conditions and is highly resistant to UV rays.
Lightweight and durable, synthetics can grip the decking and the shingles tightly, which reduces sliding and is more suitable for roofs with steeper slopes. Created from polypropylene or polyethylene fibers, synthetics are popular because they’re lightweight yet strong and also very resistant to the elements and insects.
Because they do not absorb moisture, synthetics aren’t prone to mold and algae growth and are resistant to UV damage. This is both a rare and highly coveted feature in every roofing system, because most roof damage comes from moisture. One downside, however, is that synthetic underlayment requires precise installation, and if improperly installed, may fail to serve its purpose. Be sure to hire a contractor that is certified to install this type of roofing material.
Flat Roof Systems
Traditional roofing systems are installed by overlapping one row on top of another. In flat roofs, which have very little pitch, water would likely work itself underneath the shingles. This will eventually rot the substrate and cause indoor leaks.
Because of this, covering a flat roof requires different considerations than sloped roofs. You want to avoid any type of seam, as your biggest threat is going to be water infiltration. Your main goal: to create a water-impenetrable barrier. How can you do this? By applying a material to create a barrier, by either physically covering it with something like a PVC membrane or applying a tar or spray-on silicon coating.
Flat roofs bring two things to the table: 1) aesthetics and 2) convenience. But to deliver good results, flat roofing materials need to be able to absorb the brunt of the weather and to withstand ponding water. T PVC, EPDM, TPO, modified bitumen, BUR and spray on coating are the most popular options.
Roofing is complex work. Roof workers are exposed to the elements, need to work on a sloped surface, and have to deal with a lot of lifting, bending and climbing throughout the workday.
Some jobs are better left to the pros–and roofing is definitely one of them. In addition to skills, safety is another big consideration, with experienced roofing professionals well trained on the best practices to ensure a safe work environment. Never entrust your roof repair or replacement project to an amateur; only hire reputable professionals with a track record of success.