Synthetic Roof Underlayment

Until the twenty-first century, most residential sloped roofs received a layer of asphalt-saturated felt building paper underneath the roofing material. Mimicking the attributes of housewraps, synthetic roof underlayments are now available to serve the same function as a secondary weather barrier with better resistance to tearing, moisture, and ultraviolet rays than traditional roofing felt. Synthetic underlayments are typically made from polypropylene, polyester, or fiberglass fabric which weighs less than felt building paper, can be manufactured with an anti-slip surface, and can withstand exposure to the elements for six months.

Recent natural disasters and subsequent rebuilding efforts highlighted the versatility of synthetics as roof underlayment by providing a real-life test environment. After several hurricanes ravaged southern coastal areas of the United States, many people were forced out of their damaged homes. At the same time, large numbers of homes required quick roof repair and "drying in" to minimize further damage due to water intrusion. With limited resources, contractors triaged homes, repairing the critical components and installing synthetic underlayments as temporary roofing. The underlayments performed better than FEMA’s blue tarps and didn’t require removal and discard when a roofing crew eventually arrived to install shingles.

One manufacturer offers a Class I fire-rated synthetic underlayment for roofs that require resistance to fire, as well as, the durable attributes of synthetic fabrics while the building is under construction.