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.
Sometimes called Blocking.
N
NBP
Acrylonitrile butadiene polymer blend. One proprietary NBP membrane is commonly referred to as nitrile butadiene copolymer.
Negative Side Waterproofing
An application wherein the waterproofing system and source of hydrostatic pressure are on opposite sides of the structural element.
Neoprene
A synthetic rubber (polychloroprene) used in liquid and sheet-applied elastomeric roof membranes or flashings.
Nesting
(1) the installation of new metal roof deck directly on top of existing metal roof deck; (2) 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; the area of the opening of a vent minus the area displaced by the screening material.
Newton (N)
SI unit of measure for force.
Night Seal (Night Tie-In)
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.
NIST
National Institute of Standards and Technology
Nitrile Allow
An elastomeric material of synthetic nonvulcanizing polymers.
Nitrile Rubber
A membrane whose predominant resinous ingredient is a synthetic rubber made by the polymerization of acrylonitrile with butadiene.
No-Cutout Shingles
Shingles consisting of a single solid strip with no cutouts.
Noble Metal
A metal that readily receives electrons from an anodic metal (see Galvanic series).
Non-Traffic Bearing
For waterproofing purposes, a membrane system requiring some form of protection barrier and wearing surface.
Non-Volatile Content
The portion of a coating that does not evaporate during drying or curing under specified conditions, comprising the binder and, if present, the pigment. (The percent volatile content is obtained by subtracting the nonvolatile content from 100.).
Nondesructive Testing
A method to evaluate the disposition, strength or composition of materials or systems 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.
Nonflammable
Not easily ignited and not burning rapidly if ignited.
Nonfriable
A material that, when dry, cannot be crumbled, pulverized or reduced to powder by hand pressure.
Nonoxidizing
A material which resists oxidation in exterior exposures or accelerated weathering.
Nonwoven Fabric
A textile structure produced by bonding or interlocking of fibers, or both, accomplished by mechanical, chemical, thermal, or solvent means and combinations thereof.
NRCA
National Roofing Contractors Association
Nuclear Hydrogen Detection (NHD) Meter
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 hydrogen; the quantity of hydrogen detected may be linked to the pressure of water.
Nylon
Generic name for a family of polyamide polymers, used as a scrim in some fabric-reinforced sheeting.