An agreement with a client by whom a contractor takes full responsibility for design and construction - this form of contract can reduce the delays of co-ordination between consultants.

Detritus

A loose mass of stones, silt etc.

Detritus slide

The slow movement of detritus downhill on a shale or clay layer, a common sort of landslip - not dangerous.

Detritus tank

A tank in which grit is removed by settlement from sewerage.

Diffuser

A part of a lighting fixture consisting of a translucent or frosted covering or of a rough reflector; used to scatter the light and prevent glare.

Distributed load

A design load uniformly distributed along a beam.

Ditch

Drainage or irrigation channel.

Double glazing

Two pieces of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between.

Drain rods

One of a series of flexible rods with threaded ends that screw together and can be pushed to and fro in a drain run to clear a stoppage.

Draughtsman

One who prepares drawings for use on a building or civil engineering site.

Dry joint

A place of contact between two structures or parts of a structure, to allow relative movement caused by shrinkage, expansion, or settlement.

Dry pack

Concrete or mortar which is dampened and used for filling to join up two load bearing members by ramming it in with a hammer and cold chisel or piece of wood - it is used between the head of a cast insitu pile and the building above it which it underpins - it is also used for joining pre-cast members in pre-stressed structures.

Dry riser

A fire riser that is kept empty and thus cannot suffer frost damage from freezing water, as a wet riser can - dry riser inlets are located near the front entrance, giving the fire services easy access.

Dry rot

The most serious form of fungal decay in timber and is caused by sepula lacrymans which can spread and cause extensive destruction the airborne spores of this fungus settle on timber where the moisture content is greater than 20% thus allowing it to germinate - timber which is affected by this fungus turns dark brown and shrinks and dries into a cracked powdery dry mass.

Drywall

Refers to a covering of gypsum board or similar dry sheets as opposed to plaster that is applied wet.

Dubbing out

The filling of hollows in a wall surface before plastering.

Duckboard

The timber boards nailed to joists, as a temporary floor.

Duct

A protective tube or a brick or concrete trench or corridor along which pipes or cables pass through the ground. Also used in air conditioning for the passage of air.

Ductile

Able to be moulded; pliant; plastic-able to sustain large deformations without fracture such as gold and copper - able to be hammered into sheets or drawn out into wires.

Dumpy level

A simple levelling instrument in which the telescope with its level tube is attached rigidly to the vertical spindle.

Dusting

Disintegration of a concrete floor surface producing dust -it is often caused by lack of curing or by excessive water in the mix, which may be caused by dirty sand.