Architectural and Engineering Glossary



1.Abbr. for “radius.” 2.Abbr. for “right.” 3. Symbol for the capacity of a pile (for example, 3R indicates three times design capacity). 4. Symbol for the thermal resistance of a  material or component of construction. 5.Symbol for electrical resistance.


Abbr. for “registered architect.”


A rod or stick used by masons in mixing hair with mortar.

Rabbet Bead

A bead in the reentrant angle of a rabbet.

Rabbet Depth

In glazing, the depth of the glazing rabbet; equal to the sum of the bite and the edge clearance.

Rabbet Joint

An edge joint formed by fitting together rabbeted boards or timbers.

Rabbet Size

In glazing, the actual size of the rabbeted glass opening; equal to the glass size plus two edge clearances.

Rabbet, Rebate

1.A longitudinal channel, groove, or recess cut out of the edge or face of a member; esp. one to receive another member, or one to receive a frame inserted in a door or window opening, or the recess into which glass is installed in a window sash. 2.A rabbet joint.3.A shallow recess in one body to receive another, as at the edges of a pair of doors or windows so shaped as to provide a tight fit; one half of the edge projects beyond, and serves as a stop for, the other edge of each leaf. 4.A rabbet plane.

Rabbeted Doorjamb, Rabbeted Frame

A doorjamb with a rabbet, 3, to receive a door. 

Rabbeted Lock, Rebated Lock

 A lock or latch in which the face is flush with the rabbet on a rabbeted doorjamb.

Rabbeted Stop

 A stop, 1 which is integral with a door or window frame.


Any channel designed to enclose and loosely hold electric conductors; may be of metal or of an insulating material; various types include rigid conduit, flexible metallic conduit, nonmetallic conduit, metallic tubing, underfloor raceways, cellular floor raceways, surface metal raceways, structural raceways, wireways and busways, and auxiliary gutters or moldings.

Raceway Cable Distribution System

A system for distributing cable in an open or closed metal tray that is suspended within a false ceiling from the structural floor above; generally used in large buildings where complex cable distribution systems require special support.

Rack Saw

A saw having wide teeth.

Rack-and-pinion Elevator

An elevator having electrically driven rotating gear pinions mounted on the car; rotation of the gear pinions moves the car up or down on a stationary gear rack which is mounted vertically in the hoistway. 


Descriptive of timbering which is braced, providing additional support to prevent deformation.


1.The distortion or movement of a frame.2.The out of plumbness of a structure, or any of its components, that are a result of seismic stress or wind acting on the structure; may also result from thermal expansion and contraction.

Racking Back

The stepping back of courses of brick during the construction phase of a wall, usually in expectation of the wall’s completion at a later date.

Racking Load

A load applied in the plane of an assembly in such manner as to lengthen one diagonal and shorten the other.


Abbr. for radiator.

Radial Arch

Same as segmental arch

Radial Arch Roof

A roof supported by a system of arches radiating from a central point.

Radial Grating

Nonrectangular grating, in which the bearing bars extend radially from a common center and the cross bars have a pattern of concentric circles.

Radial Road

One of a group of roads which radiate outward from the center of a city, as spokes on a wheel.

Radial Shrinkage

The shrinkage of wood across the growth rings during drying; the loss in dimension along the radius of a log.

Radial-arm Saw, Radial Saw

A circular saw which is suspended from, and moves along,a cantilevered arm, mounted above the saw table; the blade can be set at any angle (or tilted) with respect to the work.

Radial-blade Fan

A heavy-duty industrial fan used for severe service, e.g., where foreign material (such as wood chips) passes directly through the fan.


See quarter-cut.

Radially-cut Grating

Rectangular grating that is cut into panels shaped as annular segments, for use in circular or annular areas.


The rate of radiant emission per unit solid angle and per unit projected area of a source in a stated angular direction from the surface.

Radiant Glass

Glass containing radiant heating elements.

Radiant Heating

Heating which results from heat transmitted by radiation, as contrasted with heat transmitted by conduction or convection.

Radiant Heating System

A system for heating a room or space by means of heated surfaces (such as panels heated by the flow of hot water  or electric current) which provide heat primarily by radiation.

Radiant Panel Test

An ASTM  standard method of test for the surface flammability of a material, using a radiant heat source.

Radiating Chapels

Chapels projecting radially from the curve of an ambulatory or rarely of an apse.


The transmission of heat through space by means of electromagnetic waves; the heat energy passes through the  air  between the source and the heated body without heating the intervening air appreciably.

Radiation-shielding Door

See lead lined door. 


A heating unit usually exposed to view within the room or space to be heated; transfers heat by radiation to objects within visible range, and by conduction to  the  surrounding  air,which in turn is circulated by natural convection;usually fed by steam or hot water.

Radius Diffusion

The horizontal axial distance an airstream travels after leaving an air outlet before the maximum stream velocity is reduced to a specified terminal value.

Radius Gauge

See fillet gauge.

Radius Of Gyration

In mechanics, the distance from the axis to a point such that, if the whole mass of a body were concentrated at it, the moment of inertia would remain unchanged.

Radius Rod

1.A plastering tool;a wooden arm fixed at one end to a mold and attached at the other end to a center about which it swivels;a gig stick.2.A long wooden arm with a marker at one end for tracing large curves.

Radius Shoe

A zinc plate attached to one side of a plasterer’s radius rod at midpoint.

Radius Tool

A radius rod.

Radius Wall

A curved wall that is a segment of a circle.


A gaseous emanation produced by the radioactive decay of radium,given off by some soils and rocks;it may collect and constitute a health hazard in buildings with poor ventilation.

Raft Footing

See floating foundation.

Raft Foundation

Same as floating foundation.


One of a series of inclined structural members from the ridge of the roof down to the eaves,providing support for the covering of a roof.For special types of rafters,see beveled rafter,binding rafter,common rafter,compass rafter, compound rafter,fly rafter, hip rafter,jack rafter,knee rafter,notched rafter,principal rafter,valley rafter.

Rafter Fill

Same as beam fill.