At Harlan Roofing, we typically recommend a variety of moisture barriers/underlayments depending on the type of roof, the manufacturer of the roof, the situation of the home, and any applicable codes or manufacturer specifications that should be adhered to. We recommend a 30lb ASTM D226 Heavy Duty Asphalt Saturated Organic Roofing Underlayments. This underlayment is tried and true; it has been used with great success for many decades. Another option is a double (two layers) 15lb felt on low slope applications below 4/12 pitch as required by code. We provide options for one 15lb and one 30lb underlayment. (If you use two 30lbs underlayments together it can cause buckling on standard composition shingles. The overlaps in the double 30lb felts telegraph through the shingles occasionally because the felts are too thick.) A third underlayment option is two layers of 30lb ASTM on tile roof installations and heavy grade asphalt shingles. This choices of underlayments doesn’t cause imperfections and provides excellent protection on low slope roof systems. We offer many Synthetic Underlayment options and specifications for manufacturer recommended synthetic options such as CertainTeed Diamond Deck, GAF Tiger Paw, and Owens Corning ProArmor, which are required if a homeowner wants to take advantage of the Manufacturer Extended Warranties as well as Reinforced UDLs, Bigfoot HD Synthetic underlayments and a number of additional options. We install self-adhering Ice & Water shield underlayment around the roof penetrations such as plumbing and code vents, fire places, roof mounted HVAC units and skylights on all of our roofs. These are roof material brand specific. CertainTeed Winterguard, GAF WeatherWatch or Storm Guard, Owens corning WeatherLock or WIP and Grace High Temperature Self-adhering Underlayments. We have high quality options to address every roof application, unique roof designs, High temperature applications, heavy water flow transitions/locations.