Roofing Felt Vs Vapor Barrier

Asphalt felt and synthetic underlayments are products installed under all the roofing materials and directly on a roof deck.

Roofing felt vs vapor barrier.

First paper was impregnated with coal tar. When and why condensation occurs inside buildings explains the problems caused by excessive indoor condensation explains how moisture enters building wall and ceiling cavities. Felt is commonly sold in either 15 or 30 rolls measuring 36 inches wide. Generally speaking roofing felt is a felt paper that is soaked in asphalt and other water resistant compounds to produce a membrane.

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. Also known as tar paper roofing felt originated in finland in the 1870 s as a waterproofing underlayment for roofs. Grade d paper is commonly use is under stucco in the western united states. Residential and commercial roofing shingles slate roof ventilation roof underlayments asphaltic and tpo roof membranes.

What is roofing felt. 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. 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. Unlike asphalt felt it is made from new wood pulp rather than recycled material.

Of course it is a bit more technical than that but this is the basic idea behind how felt works. Roofing shingles and materials plus factory certified roofers including ratings from real homeowners from north america s largest roofing manufacturer. Another option for the roofing system is to recognize a hardboard or sheathing layer can be a vapor open air barrier. 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. Synthetic roof underlayment vs. Adding other materials on top of the felt paper could radically change the felt paper s ability to transfer water vapor back out to the atmosphere you bet it can be you may want to know if felt paper is a vapor barrier or vapor retarder. The main advantage of house wrap over felt paper is the superior strength and durability of house wrap.

The shingles are the primary weather barrier. The choice of 15 or 30 pound felt paper is up to you.