Roofing Felt Vs 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 vs vapor barrier.

Grade d paper is commonly use is under stucco in the western united states. First paper was impregnated with coal tar. The vapor permeance of grade d paper is similar to asphalt felt and it blocks liquid water effectively in tests for anywhere from 10 to 60 minutes. The underlayment provides a secondary weather barrier against wind driven rain and snow.

Since 30 pound paper is quite a bit thicker you might want to use underneath upstairs flooring applications where the sounds of footsteps can be heard more frequently throughout the house. The shingles are the primary weather barrier. House wrap and felt paper when properly installed and undamaged are both weather resistant barriers wrb that create permeable and water and air resistant exterior walls. Of course it is a bit more technical than that but this is the basic idea behind how felt works.

Today glass fiber or polyester fabric may be used instead of paper. A gypsum fiber board has a perm rating of approximately 24 to 30 perms depending on thickness and if this board is fastened to a steel deck and the joints and transitions are taped it could be an effective air barrier that allows some drying. The use of roofing felt or 15 pound felt as a building house wrap or vapor barrier and the permeability moisture problems and indoor condensation problems that may occur vapor barriers and condensation in buildings. Also known as tar paper roofing felt originated in finland in the 1870 s as a waterproofing underlayment for roofs.

Generally speaking roofing felt is a felt paper that is soaked in asphalt and other water resistant compounds to produce a membrane. Felt is commonly sold in either 15 or 30 rolls measuring 36 inches wide. Asphalt felt and synthetic underlayments are products installed under all the roofing materials and directly on a roof deck. The choice of 15 or 30 pound felt paper is up to you.

Later asphalt was used in the manufacture of roofing felt. What is roofing felt. Residential and commercial roofing shingles slate roof ventilation roof underlayments asphaltic and tpo roof membranes. The main advantage of house wrap over felt paper is the superior strength and durability of house wrap.

Synthetic roof underlayment vs. Roofing shingles and materials plus factory certified roofers including ratings from real homeowners from north america s largest roofing manufacturer.