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Construction Terms and Slang

Click on a letter to go to the appropriate set of definitions (e-mail us if we forgot a term!)

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R-Value
The measure of a material's ability to resist heat flow (commonly applied to building insulation). The higher the R value, the less heat is transmitted throughout the material. The R-value is the reciprocal of the U-value.

Rabbet
A rectangular longitudinal groove cut in the corner edge of a board or plank.

Radial Saw
A circular saw which hangs from a horizontal arm or beam and slides back and forth. The arm pivots from side to side to allow for angle cuts and bevels. When sawing finish plywood, the good side should face up as the saw cuts on the down stroke.

Radiant Heating
A method of heating, usually consisting of a forced hot water system with pipes placed in the floor, wall, or ceiling; or with electrically heated panels.

Radiation
Any heated surface loses heat to cooler surrounding space or surfaces through radiation. The earth receives its heat from the sun by radiation. The heat rays are turned into heat as they strike an object which will absorb some or all of the heat transmitted.

Radiator
A heating unit which is supplied heat through a hot water system.

Rafter
A sloping roof member that supports the roof covering which extends from the ridge or the hip of the roof to the eaves. A common rafter is one which runs square with the plate and extends to the ridge. A hip rafter extends from the outside angle of the plate towards the apex of the roof. They are 2" deeper or wider than common rafters. A valley rafter extends from an inside angle of the plates toward the ridge of the house.

Raggle Block
A specially designed masonry block having a slot or opening into which the top edge of the roof flashing is inserted and anchored.

Rail
Cross members of panel doors or of a sash. Also the upper and lower members of a balustrade or staircase extending from one vertical support, such as a post, to another.

Rake
(1) Trim members that run parallel to the roof slope and form the finish between the wall and a gable roof extension. (2) The angle of slope of a roof rafter, or the inclined portion of a cornice.

Rankin
Thermometer scale on which unit of measurement equals the Fahrenheit degree.

Raw Linseed Oil
The crude product processed from flaxseed and usually without much subsequent treatment.

Rebar
Reinforcing bar used to increase the tensile strength of concrete.

Red Knot
(slang) A knot caused by cutting through a live pine branch.

Reflective Glass
Glass with a metallic coating to reduce solar heat gain.

Reflective Insulation
Sheet material with one or both sun faces of comparatively low heat emissivity, such as aluminum foil. When used in building construction the surfaces face air spaces, reducing the radiation across the air space.

Register
A fixture through which conditioned air flows. In a gravity heating system, it is located near the baseboard. In an air conditioning system, it is located close to the thermostat.

Reglet
A horizontal slot, formed or cut in a parapet or other masonry wall, into which the top edge of counter-flashing can be inserted and anchored. In glazing, a reglet is typically a pocket or keyway extruded into the framing for installing the glazing gaskets.

Reinforced Concrete
A combination of steel and concrete using the best properties of each. The steel consists of rebar or reinforcing bars varying from 3/8 " to 2 1/4 "in diameter and is placed before concrete is poured.

Reinforced Masonry
Masonry units, reinforcing steel, grout and/or mortar combined to act together to strengthen the masonry structure.

Reinforcing
Steel rods or metal fabric placed in concrete slabs, beams, or columns to increase their strength.

Relative Heat Gain
The amount of heat gain through a glass product taking into consideration the effects of solar heat gain (shading coefficient) and conductive heat gain (U-value).

Relative Humidity
The amount of water vapor in the atmosphere, expressed as a percentage of the maximum quantity that could be present at a given temperature. (The actual amount of water vapor that can be held in space increases with the temperature.)

Resistance
The internal structure of wires even in the best conductors opposes the flow of electric current and converts some current into heat. This internal friction-like effect is called resistance and is measured in ohms. Resistance equals Voltage divided by Amperage.

Resorcinol Glue
A glue that is high in both wet and dry strength and resistant to high temperatures. It is used for gluing lumber or assembly joints that must withstand severe service conditions.

Return
In heating and cooling systems, a vent that returns cold air to be warmed. In a hot air furnace system, it is located near an inside wall.

Ribbon (or Girt)
Normally a 1- by 4-inch board let into the studs horizontally to support ceiling or second-floor joists.

Ridge
The horizontal line at the junction of the top edges of two sloping roof surfaces.

Ridge Board
The board placed on edge at the ridge of the roof into which the upper ends of the rafters are fastened.

Rigid Metal Conduit
This conduit resembles plumbing pipe, protecting wires from damage.

Rise
In stairs, the vertical height of a step or flight of stairs.

Riser
Each of the vertical boards closing the spaces between the treads of stairways.

Rod Buster
(slang) An iron worker.

Roll Roofing
Roofing material, composed of fiber and satin rated with asphalt, that is supplied in 36-inch wide rolls with 108 square feet of material. Weights are generally 45 to 90 pounds per roll.

Romex
A nonmetallic sheathed cable consisting of two or more insulated conductors having an outer sheath of moisture resistant, nonmetallic material. The conductor insulation is rubber, neoprene, thermoplastic or a moisture resistant flame retardant fibrous material. There are two types: NM and NMC - described earlier.

Roof Sheathing
The boards or sheet material fastened to the roof rafters on which the shingle or other roof covering is laid.

Roof System
General term referring to the waterproof covering, roof insulation, vapor barrier, if used and roof deck as an entity.

Roper
(slang) An electrician whose main projects are residences using Romex (non-metalic sheathed cable).

Rough Opening
The opening in a wall into which a door or window is to be installed.

Rough Plumbing
All plumbing that should be done before the finish trades (sheetrock, painting, etc), including all waste lines and supply water lines that are in the walls or framing of the building. See also: Plumbing, Sub Rough, and Finish Plumbing.

Rough-In
In hardware, metal fastenings on cabinets which are usually concealed, like staples

Rpm
Revolutions per Minute.

Rubber Emulsion Paint
Paint, the vehicle of which consists of rubber or synthetic rubber dispersed in fine droplets in water.

Rubber-Tred Roller
A roller with rubber tires commonly used for compacting trimmed subgrade or aggregate base or clay type soils.

Run
In roofing, the horizontal distance between the eaves and the ridge of the roof, being half the span for a symmetrical gable roof. (stairs) The net width of a step or the horizontal distance covered by a flight of stairs.