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Term Definition
Perlite

A lightweight material made from volcanic rock.

Perm

A unit of measurement of Water Vapor Permenance (ASTM).

Phenol

A class of acid organic compounds used in the manufacture of various resins, plastics, and wood preservatives.

Phenolic

A synthetic resin made by the reaction of a phenol with an aldehyde.

Photovoltaic Cells

Thin, flat semiconductors that convert light energy into direct-current electricity.

Physical Properties

The properties associated with the physical characteristics of a material, such as thermal expansion and density.

Pier

A column designed to support a load.

Pig

An ingot of cast iron.

Pig Iron

A high-carbon-content iron produced by the blast furnace and used to produce cast iron and steel.

Pigments

Paint ingredients mainly used to provide color and hiding power.

Pilaster

Projecting, square column or stiffener forming part of a wall.

Pile

A wood, steel, or concrete column usually driven into the soil to be used to carry a vertical load.

Pile Cap

A concrete slab or beam that covers the head of several piles, tying them together.

Pile Hammer

A machine for delivering blows to the top of a pile, driving it into the earth.

Pillar

Column supporting a structure.

Pit, Elevator

The part of the hoistway that extends below the floor of the lowest landing to the floor at the bottom of the hoistway.

Pitch

(1) The slope of a roof or other plane surface.

(2) Related to carpets, the number of tufts in a 27-inch width of carpet.

Pitch of Roof

Slope of the surface, generally expressed in inches of vertical rise per 12" horizontal distance, such as "4-in-12 pitch."

Plaster

A cementitious material, usually a mixture of Portland cement, lime or gypsum, sand, and water. Used to finish interior walls and ceilings.

Plaster Base

Any material suitable for the application of plaster.

Plaster of Parts

A calcined gypsum mixed with water to form a thick, pastelike mixture.

Plastic

An organic material that is solid in its finished state but is capable of being molded or of receiving form.

Plastic Behavior

The ability of a material to become soft and formed into desired shapes.

Plastic Deformation

The deformation of a material beyond the point at which it will recover its original shape.

Plastic Liimit

Related to soils, the percent moisture content at which the soil begins to crumble when it is rolled into a thread 1/2 inch (3mm) in diameter.

Plasticity

The ability of a material to be deformed into a different shape.

Plasticizer

Liquid material added to some plastics to reduce their hardness and increase pliability. Also, an additive to concrete and mortar to increase plasticity.

Plate

"Top" plate is the horizontal member fastened to the top of the studs or wall on which the rafters, joists or trusses rest; "sole" plate is positioned at bottom of studs or wall.

Plate Glass

A high-quality glass sheet that has both surfaces ground flat and carefully polished.

Platform

Floor surface raised above the ground or floor level.

Platform Frame

A wood structural frame for light construction with the studs extending only one floor high upon which the second floor is constructed.

Platform Framing

Technique of framing where walls can be built and tilted-up on a platform floor, and in multi-story construction are erected sequentially from one platform to another. Also known as "Western" framing.

Plenum

(1) The space above a suspended ceiling.

(2) Chamber in which the pressure of the air is higher (as in a forced-air furnace system) than that of the surrounding air.

Ply

One of a number of layers in a layered construction.

Plywood

A glued wood panel made up of thin layers of wood veneer with the grain of adjacent layers at right angles to each other or of outer veneers glued to a core of solid wood or reconstituted wood.

Plywood Stressed-Skin Panel

A structural panel constructed with outer skins of plywood applied over an internal frame of wood members forming a rigid panel.

Plywood, Cold-Pressed

Interior type plywood manufactured in a press without external applications of heat.

Plywood, Exterior

Plywood bonded with a type of adhesive that is highly resistant to moisture and heat.

Plywood, Interior

Plywood manufactured for indoor use or in locations in which it would be subject to moisture for only a brief time.

Plywood, Marine

Plywood panels with the same glue as exterior plywood but with more restrictive veneer specifications.

Plywood, Molded

Plywood that is glued to the desired shape either between curved forms or by fluid pressure applied with flexible bags or blankets.

Plywood, Postformed

Panels formed when flat plywood sheets are reshaped into a curved configuration by steaming or the use of plasticizing agents.

Pole Construction

Construction using large-diameter log poles in a vertical position to carry the loads of the floors and roof.

Polycarbonate

A polyester made by linking certain phenols through carbonate groups.

Polyester

A linear polymer mad by linear linking of oxybenzoyl units.

Polyethylene

A thermoplastic resin made by polymerizing ethylene.

Polyimide

A polymer based on the combination of certain anhydrides with aromatic diamines.

Polymer

A chemical compound formed by the union of simple molecules to form more complex molecules.

Polymerization

A chemical reaction in which molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of that of the original substance.

Polyolefin

A polymer composed of open-chain hydrocarbons having double bonds.

Polypropylene

A polymer produced by the linking of repeated propylene monomers.

Polystyrene

A clear, colorless plastic resin made by polymerizing styrene.

Polyurethane

A thermoplastic or thermosetting resin derived by the condensation reaction of a polyisocyanate and a hydroxyl.

Polyvinyl Chloride

A thermoplastic resin derived by the polymerizatoin of vinyl and acetate.

Ponding

The collection of waters in shallow pools on the top surface of a roof.

Porcelain

A strong vitreous material bonded to metal at high temperature.

Porcelain Enamel

An inorganic metal oxide coating bonded to metal by fusion at a high temperature.

Portland Cement

Hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition.

Post, Plank, and Beam Framing

A wood-framing system using beams for horizontal structural members that rest on posts, forming the vertical members.

Posttensioning

A method used to place concrete under tension in which steel tenons are tensioned after the concrete has been poured and hardened.

Power

The rate at which work is performed, expressed in watts or horsepower.

Pozzolan

A siliceous or siliceous and aluminous material blended with portland cement that chemically reacts with calcium hydroxide to form compounds possessing cementitious properties.

Pozzolan Cement

A cement made from volcanic rock that contains considerable silica.

Precast Concrete

Concrete cast in a form and cured before it is lifted into its intended position.

Prescription Specification

Traditional procedure used on building projects to describe by name products, equipment or systems to be used.

Pressure-Treated Lumber

Lumber that has chemicals forced into it under pressure to retard decay and provide resistance to fire.

Prestressed Concrete

Concrete that has been pre-tensioned or post-tensioned.

Pretensioning

A method used to place a concrete member under tension by pouring concrete over steel tendons that are under tension before the concrete is poured.

Primer

A base coat in a paint system. It is applied before the finish coats.

Property Line

A legal boundary of a land parcel.

Proportional Limit

The upper limit at which stress is proportional to strain.

Purlin

Horizontal member in a roof supporting common rafters, such as at the break in a gambrel roof. Also, horizontal structural member perpendicular to main beams in a flat roof.

Quarry

An open excavation in the earth from which building stone is removed.

Quarry Tile

A large clay tile used for finished flooring.

Quartersawing

Sawing lumber so the hard annual rings are nearly perpendicular to the surface.

R-Value

The numerical value used to indicate the resistance to the flow of heat.

Raceway

An enclosed channel designed to carry wires and cables.

Racking

Forcing out of plumb of structural components, usually by wind, seismic stress or thermal expansion or contraction.

Radiant Heat

Heat transferred by radiation.

Radiation

Transfer of heat energy through space by wave motion. Although the radiant energy of heat is transmitted through space, no heat is present until this energy strikes and is absorbed by an object. Not all of the radiant heat energy is absorbed; some is reflected to travel in a new direction until it strikes another object. The amount reflected depends on the nature of the surface that the energy strikes. This fact explains the principle of insulating foil and other similar products that depend on reflection of radiant heat for their insulating value. Radiant heat travels in straight lines in all directions at about the speed of light. In radiant heating systems, heat is often radiated down from the ceiling. As it strikes objects in the room, some is absorbed and some reflected to other objects. The heat that is absorbed warms the object, which, in turn, warms the surrounding air by conduction. This warmed air sets up gentle convection currents that circulate throughout the room.

Rafter

That member forming the slanting frame of a roof or top chord of a truss. Also known as hip, jack or valley rafter depending on its location and use.

Rafter Tail

That part of a rafter that extends beyond the wall plate -- the overhang.

Rainscrean Principle

The principle that states that wall cladding can be made watertight by placing wind-pressurized air chambers behind the joints, which reduces the air pressure differentials between the inside and outside that could cause water to move through the joints.

Rake

The board along the sloping edge of a gable.

Ready-Mix Concrete

Concrete mixed in a central plant and delivered to the site by truck.

Rebar

Steel bar used to reinforce concrete.

Receptacel Outlet

An outlet box in which one or more receptacles are installed.

Receptacle

A device installed in an electrical outlet box to receive a plug to supply electric current to portable equipment.

Reduction

(1) A process in which iron is separated from oxygen with which it is chemically mixed by smelting the ore in a blast furnace.

(2) In regard to aluminum, the electrolytic process used to separate molten aluminum from the alumina.

Reflectance

The ratio of the intensity of light reflected by a material to the intensity of the incident light.

Reflectance Coefficient

A measure stated as a percentage of the amount of light reflected off a surface.

Reflected Coated Glass

Glass having a thin layer of a metal or metal oxide deposited on the surface to reflect heat and light.

Reflected Heat

See Radiation.

Reflected Sound

Sound that has struck a surface and "bounced off." Sound reflects at the same angle as light reflects in a mirror; the angle of incidence equals the angle of reflection. Large curved surfaces tend to focus (concave) or diffuse (convex) the sound when reflected. However, when the radius of the reflecting surface is less than the wavelength of the sound, this does not hold true. Thus, a rough textured surface has little effect on diffusion of sound.

Reflective Insulation

Material that reflects and thus retards the flow of radiant heat. The most common type of reflective insulation is aluminum foil. The effectiveness of reflective barriers is diminished by the accumulation of dirt and by surface oxidation.

Reflectivity

The relative ability of a surface to reflect sound or light.

Refractive Index

The ratio of the speed of light in a material to the speed of light in a vacuum.

Refractory

Nonmetallic ceramic material used where high temperatures (above 270 degrees F) are present, such as in furnace linings.

Refrigerant

The medium of heat transfer that absorbs heat by evaporating at low temperatures and pressure and giving up heat when it condenses at a higher temperature and pressure.

Reinforced Brick Masonry

Brick masonry construction that has steel reinforcing bars inserted to provide tensile strength.