Can I Use Felt Paper Under Metal Roof

When hot roof construction is done a roof with no ventilation a breathable underlayment is recommended.

Can i use felt paper under metal roof.

The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. 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. There are several types of felt underlayment including both organic reinforced and inorganic reinforced.

Underlayment must also act as a secondary weather barrier in case the roof fails. Most codes and good roofing practice would require felt. But what some may not know is there s another layer of protection directly on top of the roof deck and under the roof covering that performs a critical role in protecting your home from moisture damage. 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.

Synthetic underlayment is a newer innovation that is taking over the metal roofing industry as a better more advanced replacement for felt underlayment. Generally speaking roofing felt is a felt paper that is soaked in asphalt and other water resistant compounds to produce a membrane. For many years roofers used asphalt saturated felt under roofing shingles and it was historically available in two standard weights. 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.

Traditionally metal roofs have used standard 30 pound felt paper underlayment. 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. This allows moisture that can become trapped in the roof deck to evaporate and escape. 15 pounds per hundred square feet and 30 pounds per hundred square feet.

The 15 pound was for lighter weight projects while the 30 offered more heavy duty protection. What is roofing felt. Felt is commonly sold in either 15 or 30 rolls measuring 36 inches wide. Once again this is used on cold roof construction.