Bids for Roofing/Underlayment 

We are in need of a new roof and following your advice we obtained three bids, requesting a separation of labor, material and product description.  We also verified that tax was charged appropriately.  Our question is:  Subcontractor A quoted 15# underlayment, subcontractor B quoted 30# underlayment and subcontractor C quoted synthetic underlayment.  Would you please walk us through the difference and what should we do?

 As defined by the International Building Code: un?der?lay?ment n. “One or more layers of felt, sheathing paper, nonbituminous saturated felt, or other approved material over which a steep-slope roofing covering is applied.” There are a multitude of material types, compositions and installation techniques that are available for underlayments for roof assemblies, with felt being the most commonly used one. There is no one size fits all for the type of roofing underlayment, since the guidelines of underlayment pertain to the pitch of the roof, and the various types of roofing material. Using an example of the most common type of roof material which would be asphalt shingles and the most common roof pitch of 4/12 the underlayment requirements are using a 15# felt only. Other types of roof covering and pitch will require increased poundage of underlayment. If the pitch of your roof is 4/12 or less, the 15# underlayment is per code and it could be that Subcontractor B was just adding a second layer for “protection”. There is not a huge cost difference for a double layer of felt vs. a single layer. Synthetic underlayment which Subcontractor C quoted can be used as long as it meets UL listing. There are advantages to using synthetic underlayment and in talking with Dave Kinion of Central Basin Roofing and Greg Barstad of Granite Basin Roofing, they only use synthetic underlayment. Felt material serves a minimum purpose and is it the best underlayment – no. Synthetic underlayment is engineered to withstand heat and weather and has a specific purpose which is better and longer protection for your roof system. Synthetic underlayment has a much higher strength factor (will not tear around nails and requires fewer nails to hold in place); resistant to bugs, rot and fungus and can remain exposed for extended periods such as 6 to 12 months without degradation. Synthetic is promoted to be a “premium” performance upgrade for an underlayment as compared to the traditional felt products and yes, it does cost slightly more, but it has better performance and has a longer warranty. The only question I would have pertaining to your quotes would be if your roof has a higher than 4/12 pitch because if it does, you are required to have #30 felt vs. #15 pound and synthetic will work on both applications.