Openings in the waste piping system that permit cleaning obstructions from the pipe.

The horizontal distance between the interior edges of supporting members.

Classification of roofing materials by their resistance to fire when tested in accordance with ASTM E108.

A transparent protective and/or decorative film.

A unit made from fired and sometimes glazed clay and used as a finish surface on floors and walls.

- Minimum fire rating issued by the Underwriters' Laboratories for roofing materials.

Optimum fire rating issued by Underwriter's Laboratories on roofing. The building codes in some areas require this type of roofing for fire safety.

An opening providing access to a drain line. Closed with a threaded plug.

Sharp, cut metal wires that protrude out of a concrete foundation wall (that at one time held the foundation form panels in place).

A very cohesive material made up of microscopic particles (less than 0.00008 inches or 0.002 mm).

A paint, varnish, lacquer, or other finish used to create a protective and/or decorative layer.

Total amount of heat that passes through an assembly of materials, including air spaces and surface air films. Expressed in Btu per hr., per sq. ft., per °F temperature difference between inside and outside air (beyond the surface air films). "U" values are often used to represent wall and ceiling assemblies, floors and windows. Note: "k" and "C" values cannot simply be added to obtain "U" values. "U" can only be obtained by adding the thermal resistance (reciprocal of "C") of individual items and dividing the total into 1.

A dark brown to almost black hydrocarbon material derived by distilling coke-oven tar.

Tar produced through the destructive distillation of coal during the conversion of coal to coke.

An abbreviation for "Certificate of Occupancy". This certificate is issued by the local municipality and is required before anyone can occupy and live within the home. It is issued only after the local municipality has made all inspections and all monies and fees have been paid.

See Thermal Expansion.

Convenient factor represents the amount of heat (in Btu) that passes by conduction through a one inch thickness of homogeneous material, per hr., per sq. ft., per °F. Measured as temperature difference between the two surfaces of the material.

Amount of heat (in Btu) that passes through a specific thickness of a material (either homogeneous or heterogeneous) per hr., per sq. ft., per °F. Measured as temperature difference between surfaces. The "C" value of a homogeneous material equals the "k" value divided by the material thickness: C = k/t (where t = thickness of material in inches)It is impractical to determine a "k" value for some materials such as building paper or those only used or formed as a thin membrane, so only "C" values are given for them.

A fixed ratio of total rainfall that runs off a surface.

See Hygrometric Expansion.