Architectural and Engineering Glossary

Incertum Opus

See opus incertum.

Inch Of Water

A unit of pressure equal to the pressure exerted by a column of liquid water 1 in. high at a temperature of 39.2F (4C).

Inch Stuff

Building materials having a nominal 1-in. (2.5-cm) thickness,although actually measuring less.

Inches Of Mercury

A unit used as a measure of pressure;equal to the pressure exerted by a column of mercury 1 inch (2.54 cm) high;equivalent to a pressure of 3386.4 newtons per square meter.


On drawings, abbr. for incinerator.


An apparatus in which solid,semisolid,or gaseous combustible wastes are ignited and burned.

Incipient Decay

Early stages of decay in wood in which the color has changed but the strength and hardness have not yet been affected.


1.To decorate by cutting or indenting a surface,as ceramic ware. 2.To perforate the sur- face of timbers, poles, posts, etc.,to increase penetration of wood preservatives.


On drawings, abbr. for “include.”


The angle which a line or surface makes with the vertical,horizontal,or with another line or surface.


A sloping surface,i.e.,neither horizontal nor vertical;a slope.

Inclined End Post

An inclined compression member at the end of a truss.

Inclined Lift

A powered passenger elevator,installed on a stairway;used to raise or lower a person from one floor to another.

Inclined Shore

A raking shore.

Inclined-axis Mixer,high-discharge Mixer

A truck equipped with a body for mixing concrete;consists of a revolving drum which rotates about an axis inclined to the bed of the truck chassis.


A device for measuring the horizontal movement within a soil mass.


The presence of foreign matter in a finished material.


Same as noncombustible.


In plumbing,a tapered coupling for joining a pipe or conduit to another of larger size. 


1.The deposition of materials on the interior of pipes,vessels,or equipment from chemicals in the conveyed liquid.2.A decorative skin or coating of rich materials applied over commoner construction.


On drawings,abbr.for “industrial.”


A contractual obligation by which one person or organization agrees to secure another against loss or damage from specified liabilities.


1.The gap left by the omission of stone,brick,or block units in a course of masonry;used for bonding future masonry.2.In a wall of a church,a space hollowed out of stone to receive a brass effigy.

Indented Bar

A type of deformed bar.

Indented Bolt

A type of anchor bolt with surface indentations to increase its grip.

Indented Joint

A joint used in joining timbers end to end;a notched fishplate is attached to one side of the joint to fit into.2 corresponding notches in the joined timbers;the entire assembly is fastened with bolts.

Indented Molding,indenting

A molding with the edge toothed or indented in triangular toothl ike shapes.

Indented Wire

A type of wire having surface indentations to improve its bond when used in concrete reinforcement or for pretensioning tendons.

Independent-pole Scaffold

Same as double pole scaffold.

Index Of Key Words.

Part Four of the uniform system for construction specifications,data filing,and cost accounting.

Index Of Plasticity

See plasticity index.

Indian Architecture

The architecture of the Indian subcontinent,originally a timber and mud brick architecture of which nothing survives.Early Buddhist monuments,chaitya halls,stupa rails,and toranas clearly imitate wood construction,and timber buildings appear on relief representations.All surviving architecture is of stone,using exclusively a structural system of post and lintel,brackets,and corbels.The basically simple Indian architectural forms are generally obscured and overwhelmed by a rhythmical multiplication of pilasters, cornices,moldings,aediculae,roofs,and finials,and an exuberant and sensuous overgrowth of sculptural decoration.

Indian Oak

See teak.

Indian Shutters.

In many American colonial houses,sliding panels placed along the inner walls whose purpose may have been to increase protection against Indian arrows.

Indicator Bolt

A door bolt which indicates whether a water closet is vacant or occupied. 

Indicator Button

A device incorporated in the lock of a door of a hotel room to indicate whether or not the room is occupied.

Indicator Valve

A valve whose design includes some mechanism to show that the device is open or closed.


Said of a plant or tree which is native to the area in which it is grown.

Indirect Cost

On a building project,those costs that are attributed to overhead,as opposed to any specific task or component;for example,the cost of supervisory personnel in the site office.

Indirect Drain Pipe

Same as indirect waste pipe. 

Indirect Expense

Overhead expense;expense indirectly incurred and not directly chargeable to a specific project or task.

Indirect Footlight

A footlight unit with light sources placed so that the light rays strike the area to be illuminated from a reflecting surface rather than directly.

Indirect Heating

See central heating.

Indirect Lighting

Lighting from luminaires which distribute 90% to 100% of the emitted light upward so that illumination is provided primarily by reflected light rather than by direct light.

Indirect Luminaire

A luminaire which emits 90% to100% of its total output above a horizontal plane through it.

Indirect Solar Water Heating System

A solar water heating system employing a closed circulation loop through a heat exchanger;the fluid which flows through the solar collector is isolated from contact with other fluids in the system.

Indirect System System

A heating,air-conditioning, or refrigeration system in which a fluid is circulated to the space or material to be heated or cooled, or is used to heat or cool air which is so circulated;the fluid (such as air, water, or brine) is heated or cooled by products of combustion,by electric heating,or by a refrigerant.

Indirect Waste Pipe

A waste pipe which does not connect directly with the building drainage system,but discharges into it through a properly trapped fixture or receptacle.

Indirect Water Heater

A water heater in which the temperature of the water in the system is increased by means of a remotely located heat exchanger.

Individual Sewage-disposal System

A system of sewage treatment tanks and disposal facilities,designed for a single building,establishment,or lot,not served by a public sewer.