Architectural and Engineering Glossary



1.Abbr.for “left  side.” 2.Abbr.  for loud speaker.


On drawings,abbr. for light.


A  small  dormer  window  in  a  roof   or spire.

Lucome Window

A term once used for a window in the gable end of a house,usually providing light for a room in a loft or attic.


A variety of black marble used in ancient Roman construction;first brought to Rome from Assan on the Nile River.


Same as louver.

Luffer Board

Same as louver board.

Luffing-boom Crane

A heavy duty crane having a tower mounted boom,2.

Lug Angle

See clip angle.

Lug Bolt

A round bolt to which is welded a flat iron bar.

Lug Sill

A sill,3,with its ends extending beyond the window or door and built into the masonry at the jambs.


In early Russian architecture,an onion dome.


Timber sawn or split in the form of beams,boards,joists,planks,etc.,esp.that which is smaller than heavy timber. Also see board,1,dimension lumber,matched boards,and yard lumber.

Lumber Core, Stave Core

Wood core consisting of narrow strips of lumber edge-glued together;usually held in place by veneer which  is glued to both faces with the grain of the  veneer at 90 to that in the core.

Lumber Grade

A classification used by the lumber industry for pieces of lumber:the categories arestandard,structural,and utility.


The SI unit of luminous flux equal to the luminous flux received on a unit surface,all points of which are equidistant from a point source having a uniform intensity of 1 candela.

Lumen Method,flux Method

A procedure in lighting design used to determine the number and types of lamps or luminaires required to provide a desired average level of illumination on a work plane;takes into account both direct and reflected light flux.

Lumiline Lamp

A tubular incandescent lamp having a lamp base at each end.

Luminaire Dirt Depreciation Factor

A factor (used in illumination calculations) which relates the initial illumination provided by a clean,new luminaire to the reduced illumination that it will provide as a result of the accumulation of dirt on the luminaire at the time when it is next scheduled for cleaning.

Luminaire Efficiency

The ratio of luminous flux emitted by a luminaire to total flux emitted by the lamp or lamps in the luminaire.


The luminous intensity of any surface in a given direction per unit of projected area of the surface, as viewed from that direction;a directional property of luminous radiation.

Luminance Contrast

The relationship between the luminance of an object and the luminance of the immediate background.

Luminance Factor

The ratio of the luminance of a surface or medium under specified conditions of incidence,observation,and light source to the luminance of a lossless,perfectly diffusing surface or medium under the same conditions.

Luminance Meter, Brightness Meter

A visual instrument or a photoelectric instrument used to measure luminance.


The emission of light not ascribable directly to incandescence.

Luminous Efficacy

The ratio of the total emitted luminous flux,in lumens,to the total electric power consumption in watts.

Luminous Energy

The time integral of luminous flux;given by the product of the luminous flux and the time that the flux is maintained,if the luminous flux is of constant value;usually expressed in lumen hours.

Luminous Flux

The rate-of-flow of radiant energy emitted by a lamp.

Luminous Transmittance

Of a lens,light dif- fuser,or the like:the ratio of the total transmitted light to the total incident light.

Luminous-intensity Distribution Curve

A polar plot representing the light intensity as a function of angle about a light source.

Lump Lime

A high quality quicklime.

Lump Sum Agreement

Same as stipulated sum agreement.

Lunding Beam

See tie beam.


A tapering wedge-shaped unit forming the covering of a hemisphere.


1.A crescent-shaped or semicircular area on a wall or vaulted ceiling,framed by an arch or vault.2.An opening or window in such an area.3.A painting or sculpture on such an area.


1.An  iridescent decorative surface appearance.2.A surface or coating which imparts a gloss,sheen,glitter,or sparkle.


1.A scraper having a straight cutting edge; used to level plastic concrete.2.A bricklayer’s straightedge used for striking off clay from a brick mold.3.See sulfur cement.

Lutheran Window

Same as dormer window.


Same as dormer window.


The SI unit of illuminance equal to the illumination on a surface,all points of which are at a distance of 1 meter from a uniform point source of 1 candela;1 lux is equal to 1 lumen per square meter (1 lm/m2).


Abbr.for lightweight concrete.


Abbr.for lux.


A building for general education by means of public discussions,lectures,concerts,etc. 

Lych-gate, Lich-gate

A roofed gateway at the entrance to a church or cemetery where a coffin may be placed temporarily before proceeding to the grave.


A stone at the entrance to a churchyard,intended to receive a bier.


Same as low-side window.

Lying Panel

1.A panel so placed that the fibers of the wood lie in a horizontal position.2.A panel whose longer dimension is in a horizontal position.3.Same as lay panel.


A plinth or step above the cornice of the podium of some Roman temples; when present in a columnar edifice,it constitutes the stylobate proper.