Glossary of Roofing and Waterproofing Terms

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NAHB: National Association of Home Builders

Nailer: (commonly referred to as Blocking) a piece or pieces of dimensional lumber and/or plywood secured to the structural deck or walls, which provide a receiving medium for the fasteners used to attach membrane or flashing. Generally, it is recommended that nailers be the same thickness as the adjacent insulation, and may be treated with a non-oil-borne preservative, and be of sufficient width to fully support the horizontal flashing flange of a metal flashing (where used).

Nailing: the application of nails. May be: (1) exposed nailing of roofing wherein nail heads are exposed to the weather; (2) concealed nailing of roofing wherein nail heads are concealed from the weather by an overlapping material.

NBP: acrylonitrile butadiene polymer blend. One proprietary NBP membrane is commonly referred to as nitrile butadiene copolymer.

Needle Punched Fabric: a fabric where barbed needles (in multiple punches) achieve mechanical bonding/locking or carding of fibers.

Negative Side Waterproofing: an application wherein the waterproofing system and the source of hydrostatic pressure are on opposite sides of the structural element.

Neoprene: a synthetic rubber (polychloroprene) used in liquid-applied and sheet-applied elastomeric roof membranes or flashings.

Nesting: a method of reroofing with new asphalt shingles over existing shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle.

Net Free Vent Area: the area, measured in square inches, open to unrestricted air flow and commonly used as a yardstick to measure relative vent performance.

Newton (N): Sl unit of measure for force.

NICA: National Insulation Contractors Association

Night Seal (or Night Tie-Of0: a material and/or method used to temporarily seal a membrane edge during construction to protect the roofing assembly in place from water penetration. Usually removed when roofing application is resumed.

Nineteen-lach Selvage (Double-Coverage or Split-Sheet): a prepared roofing sheet with a 17 inch (430mm) granule surfaced exposure and a non-granule surfaced 19 inch (485mm) selvage edge. This material is sometimes referred to as SIS, double-coverage, or according to ASTM Standard D 371-89, Standard Specification for Asphalt Roll Roofing (Organic Felt) Surfaced with Mineral Granules, Wide Selvage.

Ninety-Pound: a prepared organic felt roll roofing with a granule surfacing that has a mass of approximately 90 pounds per 100 square feet, (4400 g/m2).

NIST: National Institute of Standards and Technology

Nitrile Alloy: an elastomeric material of synthetic non-vulcanizing polymers.

Nitrile Rubber: a membrane whose predominant resinous ingredient is a synthetic rubber made by the polymerization of acrylonitrile with butadiene.

Noble: in reference to metal, inert; opposite of active.

No-Cutout Shingles: shingles consisting of a single solid strip with no cutouts.

Non-Breathing Membrane: a membrane that does not allow significant amounts of water vapor or air to pass through; which has a perm rating 1.0 or less per ASTM E 96, Procedure E.

Non-Destructive Testing (NOT): a method to evaluate the disposition, strength, or composition of materials without damaging the object under test. Typically used to evaluate moisture content in roofing assemblies, the three common test methods are electrical capacitance, infrared thermography, and nuclear back-scatter.

Non-Flammable: liquid having no measurable flash point.

Non-Friable: a material that, when dry, cannot be crumbled, pulverized or reduced to powder by hand pressure.

Non-Oxidizing: a material which resists oxidation in exterior exposures or accelerated weathering.

Non-Traffic Bearing: for waterproofing purposes, a membrane system requiring some form of protection barrier and wearing surface.

Non-Volatile Content: that portion of a material that does not evaporate under normal ambient conditions.

Non-Vulcanized Membrane: a membrane manufactured from thermoplastic compounds that retains its thermoplastic properties throughout the service life of the membrane.

Nonwoven: a term used to describe the random arrangement of reinforcing fibers (glass, polyester, etc.) in a mat or scrim.

NRCA: National Roofing Contractors Association

NTRMA: National Tile Roofing Manufacturers Association

Nuclear Testing (Nuclear Back-Scatter): a device that contains a radioactive source to emit high velocity neutrons into a roof system. Reflecting neutrons are measured by a gauge that is used to detect moisture.

Nylon: generic name for a family of polyamide polymers, used as a scrim in some fabric-reinforced sheeting.


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