Can I Use Felt Paper Under Metal Roof

15 pounds per hundred square feet and 30 pounds per hundred square feet.

Can i use felt paper under metal roof.

What is roofing felt. The 15 pound was for lighter weight projects while the 30 offered more heavy duty protection. Synthetic underlayment is a newer innovation that is taking over the metal roofing industry as a better more advanced replacement for felt underlayment. When hot roof construction is done a roof with no ventilation a breathable underlayment is recommended.

Underlayment must also act as a secondary weather barrier in case the roof fails. Synthetic underlayment is a roofing accessory created by weaving spinning together polypropylene or polyethylene and a polymer to form an all over protective barrier to put between the roofing material and the roof deck. With metal roofing its also a good idea to put a layer of red rosin paper between the felt or ice water shield and the metal that way it wont potentialy stick to it and cause oil canning and would allow for expansion. Of course it is a bit more technical than that but this is the basic idea behind how felt works.

Traditionally metal roofs have used standard 30 pound felt paper underlayment. The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. Generally speaking roofing felt is a felt paper that is soaked in asphalt and other water resistant compounds to produce a membrane. 30 felt doesn t come with any kind of warranty as opposed to synthetic underlayment which can come up to a 50 year warranty.

There are several types of felt underlayment including both organic reinforced and inorganic reinforced. Most codes and good roofing practice would require felt. The temperature under a metal roof can get very hot and over time 30 felt which is composed of asphalt will dry out quickly leaving not much in the way of a secondary weather barrier. Felt is commonly sold in either 15 or 30 rolls measuring 36 inches wide.

For many years roofers used asphalt saturated felt under roofing shingles and it was historically available in two standard weights. The traditional and most common material used for roof underlayment on a steep slope metal roof is non perforated asphalt impregnated felt underlayment. When most people think of roofs they typically think of shingles or metal roofing. Once again this is used on cold roof construction.