Tar paper
Encyclopedia
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. It can be distinguished from Roofing felt:Asphalt-saturated felt. Roofing felt has been in use for over a hundred years. Originally felt was made from recycled rag but today felts are
made of recycled paper products (typically cardboard) and sawdust. The most common felt product is the so-called #15 felt. Before the oil crisis felt weighed about 15 pounds per square (one square = 100 square feet) and hence the asphalt-impregnated felt was called "15#" or "15 pound felt". Modern felts no longer weigh 0.73 kg/m2, and to reflect this fact the new felts are called "#15" asphalt felt. In fact, #15 felts can weigh from 7.5 to 12.5 pounds/sq ft depending on the manufacturer and the standard to which felt is made (i.e., CGSB, ASTM, or none). Thirty pound felt, of 30# felt, is now #30 felt, and actually usually weighs between 16 and 27 pounds per square. Hence, to get a product similar to a 15# felt of old, one could specify a modern #30 felt.
Tar paper is more accurately a Grade D building paper (the Grade D designation derives from a US federal specification) is widely used in the west. Building paper is manufactured from virgin kraft paper, unlike felts, and then impregnated with asphalt. The longer fibres in the kraft paper allow for a lighter weight product with similar and often better mechanical properties than felt. Grade papers are rated in minutes -- the amount of time it takes for a moisture sensitive chemical indicator to change colour when a small boat-like sample is floated on water. Common grades include 10, 20, 30, and 60 minute. The higher the rating the more moisture resistant and the heavier. A typical 20 minute paper will weigh about 3.3 pds per square, a 30 minute paper 3.75, and a 60 minute paper about six. The smaller volume of material however does tend to make these papers less resistant to moisture than heavier felts.
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 (0.9144 m) rolls, 50 or long and "15 lb" (15 pounds (6.8 kg)) and "30 lb" (30 pounds (13.6 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 widths of "Housewrap
".
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.
Paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
used in construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
. Tar paper is made by impregnating paper with tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
, producing a waterproof material useful for roof
Roof
A roof is the covering on the uppermost part of a building. A roof protects the building and its contents from the effects of weather. Structures that require roofs range from a letter box to a cathedral or stadium, dwellings being the most numerous....
construction. It can be distinguished from Roofing felt:Asphalt-saturated felt. Roofing felt has been in use for over a hundred years. Originally felt was made from recycled rag but today felts are
made of recycled paper products (typically cardboard) and sawdust. The most common felt product is the so-called #15 felt. Before the oil crisis felt weighed about 15 pounds per square (one square = 100 square feet) and hence the asphalt-impregnated felt was called "15#" or "15 pound felt". Modern felts no longer weigh 0.73 kg/m2, and to reflect this fact the new felts are called "#15" asphalt felt. In fact, #15 felts can weigh from 7.5 to 12.5 pounds/sq ft depending on the manufacturer and the standard to which felt is made (i.e., CGSB, ASTM, or none). Thirty pound felt, of 30# felt, is now #30 felt, and actually usually weighs between 16 and 27 pounds per square. Hence, to get a product similar to a 15# felt of old, one could specify a modern #30 felt.
Tar paper is more accurately a Grade D building paper (the Grade D designation derives from a US federal specification) is widely used in the west. Building paper is manufactured from virgin kraft paper, unlike felts, and then impregnated with asphalt. The longer fibres in the kraft paper allow for a lighter weight product with similar and often better mechanical properties than felt. Grade papers are rated in minutes -- the amount of time it takes for a moisture sensitive chemical indicator to change colour when a small boat-like sample is floated on water. Common grades include 10, 20, 30, and 60 minute. The higher the rating the more moisture resistant and the heavier. A typical 20 minute paper will weigh about 3.3 pds per square, a 30 minute paper 3.75, and a 60 minute paper about six. The smaller volume of material however does tend to make these papers less resistant to moisture than heavier felts.
Uses
Tar paper is used, among other things, for waterproofingWaterproofing
Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...
roofs to prevent ingress of moisture. It is used as underlayment for asphalt
Asphalt shingle
An asphalt shingle is a type of roof shingle. They are one of the most widely used roofing covers because they are relatively inexpensive and fairly simple to install.-Types:...
, wood
Wood shingle
Wood shingles are roof shingles made of cut wood, used for roofing material. Such roofing material made from split wood is referred to as "shakes"....
(a.k.a. shake
Shake (shingle)
A shake is a basic wooden shingle that is made from split logs. Shakes have traditionally been used for roofing and siding applications around the world. Higher grade shakes are typically used for roofing purposes, while the lower grades are used for siding purposes...
), or other shingles
Roof shingle
Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat rectangular shapes laid in rows from the bottom edge of the roof up, with each successive higher row overlapping the joints in the row below...
, 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 (0.9144 m) rolls, 50 or long and "15 lb" (15 pounds (6.8 kg)) and "30 lb" (30 pounds (13.6 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
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
(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 widths of "Housewrap
Housewrap
Housewrap defines all synthetic replacement materials for sheathing tar paper. These materials are all lighter in weight and usually wider than asphalt designs, so contractors can apply the material much faster to a house shell. Housewrap functions as a weather-resistant barrier, preventing rain...
".
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
polyolefin
Polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
) 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.
- Tar Paper Under Roof Shingles