Permability Of Roofing Paper

The research performed indicates that nonbreathable.

Permability of roofing paper.

Asphalt felt is paper based and has no memory meaning once it attracts moisture by being left on the roof overnight or if it gets wet it will ripple and curl and will not lay flat once it dries. Unlike asphalt felt it is made from new wood pulp rather than recycled material. Normally used on roofs tar paper makes a great barrier for the exterior walls of your housing building or shed. The focus of this paper is to investigate the system performance of standard asphalt shingles and to evaluate the impact of installing nonbreathable underlayments between the shingle layer and the roof deck.

Tar paper keeps the wood beneath it dry. Fs 148 sd 137. Tar paper has been time tested as a weather barrier. Among the most vapor permeable of exterior sheathings.

Notes to the table above. At saturation marginal increase in permeability 2 8 3 4 perms. Permeability 14 20 5 perms. Find below the technical bulletins papers standards used as sources for these perm ratings.

Some grade d pape. Grade d building papers must have a 10 minute rating under astm d779 commonly called the boat test in which a piece of building paper is folded in the shape of a boat and floated in a dish of water until it soaks through and wets a powder on top. When then used with asphalt shingles especially traditional 3 tab shingles it sometimes telegraphs the ripples through the finished product. Grade d building paper is an asphalt impregnated kraft type paper similar to the backing on fiberglass insulation.

The vapor permeance of grade d paper is similar to asphalt felt. More information more information. Fiberboard asphalt impregnated. Its most common use is under stucco in the western united states.