Tar paper

Tar paper is a heavy-duty paper used in construction. Tar paper is made by impregnating paper with tar, producing a waterproof material useful for roof construction. Roofing felt, one common type of tar paper, is a glass fibre or polyester fleece impregnated with bituminous material (tar, asphaltic bitumen); it is produced in roll form. In some cases mineral material (e.g. sand) is applied on one side to help prevent the material from sticking together while in roll form and to provide protection from atmospheric conditions. A distinction is drawn between tarred board and bitumen board.

Uses

Tar paper is used, among other things, for waterproofing roofs to prevent ingress of moisture. It is used as underlayment for asphalt, wood (a.k.a. shake), or other shingles, or even gravel, since tar paper itself isn't particularly wind- or sun-resistant. It is sold in rolls of various widths, lengths, and thicknesses [3-foot-wide (0.91 m) rolls, 50 or 100 feet (15 or 30 m) long and "15 lb" (7 kg) and "30 lb" (14 kg) weights are common in the U.S.], often marked with chalk lines at certain intervals to aid in laying it out straight on roofs with the proper overlap (more overlap for flatter roofs).

It can be installed in several ways, such as staples or roofing nails, but it is also sometimes applied in several layers with methods such as a torch, hot asphalt, cold asphalt (adhesive), non-asphaltic adhesives, and heat (torch, hot air) and additional hot tar.

Older construction sometimes used a lighter-weight tar paper, stapled up with some overlap, as a water- and wind-proofing material, but modern construction uses 8 or 10 feet (2.4 or 3.0 m) widths of "Housewrap". One brand is Tyvek, which is extremely durable and wind- and water-proof since there are far fewer seams than with the 3-foot-wide (0.91 m) rolls of tar paper.

File:Roofing felt.jpg

Workers using special "roofing shovels" to remove composite shingles as part of a roof repair. Roofing felt is here used as underlay between the wooden sheathing and exterior shingles.

Many new pitched roofs however use a TPO (thermoplastic polyolefin) membrane for increased protection against leaks. These membranes (usually made of advanced fabrics) have advantages over traditional 1F roofing felt. They are more durable and less prone to puncture and tear, and are lighter and stronger, though quite recent (2003) in the market. There are also breathable variations, which allow water vapour to pass through the felt; when used in conjunction with proper ventilation, they help minimize condensation in loft spaces.

External links

• Roofing felt at the Transportation Information Service.de:Dachpappe