Guide to Building Terms

Airbrick

Perforated brick used for ventilation, especially to floor voids (beneath timber floors) and roof spaces.

Architrave

Joinery moulding around window or doorway.

Asbestos

Fibrous mineral used in the past for insulation. Can be a health hazard specialist advice should be sought if asbestos (especially blue asbestos) is found.

Asphalt

Black, tar-like substance, strongly adhesive and impervious to moisture. Used on flat roofs and floors.

Barge Board

See Verge Board.

Balanced Flue

Common metal device normally serving gas appliances which allows air to be drawn to the appliance whilst also allowing fumes to escape.

Beetle infestation (Wood boring insects: woodworm)

Larvae of various species of beetle which tunnel into timber causing damage. Specialist treatment normally required. Can also effect furniture.

Benching

Smoothly contoured concrete slope beside drainage channel within an inspection chamber. Also known as Haunching.

Bitumen

Black, sticky substance, related to asphalt. Used in sealants, mineral felts and damp-proof courses.

Breeze block

Originally made from cinders ("breeze") the term now commonly used to refer to various types of concrete and cement building blocks.

Carbonation

A natural process affecting the outer layer of concrete. Metal reinforcement within that layer is liable to early corrosion, with consequent fracturing of the concrete.

Cavity wall

Standard modern method of building external walls of houses comprising two leaves of brick or blockwork separated by a gap ("cavity") of about 50mm (2 inches).

Cavity wall insulation

Filling of wall cavities by one of various forms of insulation material: Beads: Polystyrene beads pumped into the cavities. Will easily fall out if the wall is broken open for any reason. Foam: Urea formaldehyde form, mixed on site, and pumped into the cavities where it sets. Can lead to problems of dampness and make replacement of wall-ties more difficult. Rockwool: Inert mineral fibre pumped into the cavity.

Cavity wall-tie

Metal device bedded into the inner and outer leaves of cavity walls to strengthen the wall. Failure by corrosion can result in the wall becoming unstable specialist replacement ties are then required.

Cesspool

A simple method of drain comprising a holding tank which needs frequent emptying. Not to be confused with Septic Tank.

Chipboard

Also referred to as "particle board". Chips of wood compressed and glued into sheet form. Cheap method of decking to flat roofs, floors and (with formica or melamine surface) furniture, especially kitchen units.

Collar

Horizontal timber member intended to restrain opposing roof slopes. Absence, removal or weakening can lead to Roof Spread.

Comination Boiler

Modern form of gas boiler which activates on demand. With this form of boiler there is no need for water storage tanks, hot water cylinders etc.

Coping/coping stone

Usually stone or concrete, laid on top of a wall as a decorative finish and to stop rainwater soaking into the wall.

Corbel

Projection of stone, brick, timber or metal jutting out from a wall to support a weight.

Cornice

Ornamental moulded projection around the top of a building or around the wall of a room just below the ceiling

Coving

Curved junction between wall and ceiling or (rarely) between ceiling and floor.

Dado rail

Wooden moulding fixed horizontally to a wall, about 1 metre (3ft 4in) above the floor, originally intended to protect the wall against damage by chair-backs.

Damp proof course

Course Layer of impervious material (mineral felt, pvc etc) incorporated into a wall to prevent dampness rising up the wall or lateral dampness around windows, doors etc. Various proprietary methods are available for damp proofing existing walls including "electro-osmosis" and chemical injection.

Deathwatch beetle (Xestonbium Refovillosum)

Serious insect pest in structural timbers, usually affects old hardwoods with fungal decay already present.

Double glazing

A method of thermal insulation usually either: Sealed unit: Two panes of glass fixed and hermetically sealed together; or Secondary: In effect a second "window" placed inside the original window.

Dry rot (Serpula Lacrymans.)

A fungus which attacks structural and joinery timbers, often with devastating results. Can flourish in moist, unventilated areas.

Eaves

The overhanging edge of a roof.

Efflorescence

Salts crystallised on the surface of a wall as a result of moisture evaporation.

Engineering brick

Particularly strong and dense type of brick, sometimes used as damp-proof course.

Fibreboard

Cheap, lightweight board material of little strength, used in ceilings or as insulation to attics.

Flashing

Building technique used to prevent leakage at a roof joint. Normally metal (lead, zinc, copper) but can be cement, felt or proprietary material.

Flaunching

Contoured cement around the base of chimney pots, to secure the pot and to throw off rain.

Flue

A smoke duct in a chimney, or a proprietary pipe serving a heat-producing appliance such as a central heating boiler.

Flue lining

Metal (usually stainless steel) tube within a flue essential for high output gas appliances such as boilers. May also be manufactured from clay and built into the flue.

Foundations

Normally concrete, laid underground as a structural base to a wall: in older buildings may be brick or stone.

Frog

A depression imprinted in the upper surface of a brick, to save clay, reduce weight and increase the strength of the wall. Bricks should always be laid frog uppermost.

Gable

Upper section of a wall, usually triangular in shape, at either end of a ridged roof.

Ground heave

Swelling of clay sub-soil due to absorption of moisture: can cause an upward movement in foundations.

Gully

An opening into a drain, normally at ground level, placed to receive water etc. from downpipes and wastepipes.

Haunching

See Benching. Also term used to describe the support to a drain underground.

Hip

The external junction between two intersecting roof slopes.

Inspection chamber

Commonly called "man-hole". Access point to a drain comprising a chamber (of brick, concrete or plastic) with the drainage channel at its base and a removable cover at ground level.

Jamb

Side part of a doorway or window.

Joist

Horizontal structural timber used in flat roof, ceiling and floor construction. Occasionally also metal.

Landslip

Downhill movement of unstable earth, clay, rock etc. often following prolonged heavy rain or coastal erosion, but sometimes due entirely to sub-soil having little cohesive integrity.

Lath

Thin strip of wood used in the fixing of roof tiles or slates, or as a backing to plaster.

Lintel

Horizontal structural beam of timber, stone, steel or concrete placed over window or door openings.

Mortar

Mixture of sand, cement, lime and water, used to join stones or bricks.

Mullion

Vertical bar dividing individual lights in a window.

Newel

Stout post supporting a staircase handrail at top and bottom. Also, the central pillar of a winding or spiral staircase.

Oversite

Rough concrete below timber ground floors: the level of the oversite should be above external ground level.

Parapet

Low wall along the edge of a flat roof, balcony etc..

Pier

A vertical column of brickwork or other material, used to strengthen the wall or to support a weight.

Plasterboard

Stiff "sandwich" of plaster between coarse paper. Now in widespread use for ceilings and walls.

Pointing

Smooth outer edge of mortar joint between bricks, stones etc.

Powder post beetle (bostrychidae or Lyctidae family of beetles)

A relatively uncommon pest which can, if untreated, cause widespread damage to structural timbers.

Purlin

Horizontal beam in a roof upon which rafters rest.

Quoin

The external angle of a building; or, specifically, bricks or stone blocks forming that angle.

Rafter

A sloping roof beam, usually timber, forming the carcass of a roof.

Random rubble

Primitive method of stone wall construction with no attempt at bonding or coursing.

Rendering

Vertical covering of a wall either plaster (internally) or cement (externally), sometimes with pebble-dash, stucco or Tyrolean textured finish.

Reveals

The side faces of a window or door opening.

Ridge

The apex of a roof.

Riser

The vertical part of a step or stair.

Rising damp

Moisture soaking up a wall from below ground, by capillary action causing rot in timbers, plaster decay, decoration failure etc.

Roof Spread

Outward bowing of a wall caused by the thrust of a badly restrained roof carcass (see Collar).

Screed

Final, smooth finish of a solid floor, usually cement, concrete or asphalt

Septic Tank

Tank Drain installation whereby sewage decomposes through bacteriological action, which can be slowed down or stopped altogether by the use of chemicals such as bleach, biological washing powders etc.

Settlement

General disturbance in a structure showing as distortion in walls etc., possibly a result of major structural failure. Sometimes of little current significance.

Shakes

Naturally occurring cracks in timber; in building timbers, shakes can appear quite dramatic, but strength is not always impaired.

Shingles

Small rectangular slabs of wood used on roofs instead of tiles, slates etc.

Soakaway

Arrangement for disposal of rainwater, utilising graded aggregate laid below ground.

Soaker

Sheet metal (usually lead, copper or zinc) at the junction of a roof with a vertical surface of a chimney stack, adjoining wall etc.. Associated with flashings which should overlay soakers.

Soffit

The under-surface of eaves, balcony, arch etc.

Solid fuel

Heating fuel, normally coal, coke or one of a variety of proprietary fuels

Spandrel

Space above and to the sides of an arch; also the space below a staircase.

Stud partition

Lightweight, sometimes non-loadbearing wall construction comprising a framework of timber faced with plaster, plasterboard or other finish

Subsidence

Ground movement, generally downward, possible a result of mining activities or clay shrinkage.

Sub-soil

Soil lying immediately below the top-soil, upon which foundations usually bear.

Sulphate attack

Chemical reaction activated by water, between tricalcium aluminate and soluble sulphates. Can cause deterioration in brick walls and concrete floors.

Tie bar

Heavy metal bar passing through a wall, or walls, to brace a structure suffering from structural instability.

Torching

Mortar applied on the underside of roof tiles or slates to help prevent moisture penetration. Not necessary when a roof is underdrawn with felt.

Transom

Horizontal part of a step or stair.

Tread

The horizontal part of a step or stair.

Trussed rafters

Method of roof construction utilising prefabricated triangular framework of timbers. Now widely used in domestic construction.

Underpinning

Method strengthening weak foundations whereby a new, stronger foundation is placed beneath the original.

Valley gutter

Horizontal or sloping gutter, usually lead-or-tile-lined, at the internal intersection between two roof slopes.

Ventilation

Necessary in all buildings to disperse moisture resulting from bathing, cooking, breathing etc. and to assist in prevention of condensation. Floors: Necessary to avoid rot, especially Dry Rot; achieved by airbricks near to ground level. Roofs: Necessary to disperse condensation within roof spaces; achieved either by airbricks in gables or ducts at the eaves.

Verge

The edge of a roof, especially over a gable.

Verge board

Timber, sometimes decorative, placed at the verge of a roof: also known as barge board.

Wainscot

Wood panelling or boarding on the lower part of an internal wall.

Wall plate

Timber placed at the eaves of a roof, to take the weight of the roof timbers.

Wet rot (Coniophora Puteana)

Decay of timber due to damp conditions. Not to be confused with the more serious Dry Rot.

Woodworm

Colloquial term for beetle infestation: usually intended to mean Common Furniture Beetle (Anobium Punctatum): by far the most frequently encountered insect attack in structural and joinery timbers.