Roofing Felt Vapor Barrier

When and why condensation occurs inside buildings explains the problems caused by excessive indoor condensation explains how moisture enters building wall and ceiling cavities.

Roofing felt vapor barrier.

The purpose of tar paper on real wood floors is to elimate squeeks and it provides a vapor barrier if needed. Inadequacy of roofing felt as a vapor barrier for asphalt shingles in hot humid climates. Rosin paper is also used for real wood to cut down on squeeking. What is roofing felt.

Roofing felt is not considered toxic and is not listed as a carcinogen. A vapor barrier is a product that would stop all water vapor from passing through it. What is a vapor barrier. By weaving together polypropylene and polymer a water resistant and vapor resistant underlayment was created.

A building sciences corporation report at the citations section of this article lso elaborates the usefulness of placing a vapor barrier on the roof deck below shingles in hot humid climates. Under normal use the product is considered stable and. Felt provides an excellent seepage barrier 2 especially when applied in thicker layers. Wooden floors will act as a vapor barrier and are often laid directly on top of the felt.

That reduction of air and moisture infiltration can then help improve roof longevity. A technical white paper produced in 2011 shows that 15 felt paper has a vapor permeance rating of 7. Why cant i use roofing felt for laminate floor re. Initially cloth felt which came from recycled cotton rags was used to make asphalt felt.

Synthetic underlayment is more susceptible to wicking 1 or capillary action than asphalt felt underlayment which can lead to moisture damage to the roof. One of the main barriers to using synthetic underlayment for roofing contractors is the cost is higher per square foot than traditional felt. Roofing felt is comprised of a base made from natural materials such as wood cellulose or synthetic ones such as fiberglass or polyester and then coated or saturated with a protective coating such as bitumen asphalt which repels water but still allows the product to breathe. It s better to use the term vapor retarder as there are many products that slow down the passage of water vapor through them.

A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system. A vapor barrier such as kraft paper will trap any such fumes but may not be necessary depending on the flooring material. Today asphalt felt is made from a mixture of sawdust and recycled corrugated paper. This new underlayment is lighter and stronger than its predecessor.

Asphalt felt paper as a weather resistant barrier. Bsc points out that.