Aggregate: pebbles, shingle, gravel etc. Used in the manufacture of concrete, and in the construction of "soakaways”.

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

Architrave: joinery moulding around window or doorway.

Artex: common name for proprietary ceiling coverings, older versions of which can have some asbestos content.

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.

Asbestos cement: cement with 10-15% asbestos fibre as reinforcement. Fragile, will not bear heavy weights. Hazardous fibres may be released if cut or drilled.

Ashlar: finely dressed natural stone: the best grade of masonry.

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 (woodboring insects: woodworm): larvae of various species of beetle, which tunnel into timber causing damage. Specialist treatment normally required. Can also affect 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Breeze block: originally made from cinders ("breeze"), the term now commonly used to refer to various types of concrete and cement building blocks (blockwork).

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 tie 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 that 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.

Combination 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., and generally the pressure is much better for showers.

Condensation: occurs when warm moist air meets a cold surface. The water in the air then either settles as water droplets on the surface (as it does on windows for example), or if the surface is absorbent, it soaks into the surface. In the latter case condensation is often not noticed unless or until mould appears. (see also ventilation)

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.

Corbell: 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.

Dado rail: wooden moulding fixed horizontally to a wall, approximately 1 metre above the floor, originally intended to protect the wall against damage by chair backs, now very much a decorative feature.

Damp proof course (dpc): 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 (xestobium 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 glazing: this is a second "window" placed inside the original window. It can be quite effective.

Downpipes: vertical drainage pipes from guttering.

Dry rot (serpula lacrymans.): a fungus that attacks structural and joinery timbers, often with devastating results. Can flourish in moist, unventilated areas. Not to be confused with wet rot.

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 a 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, or solid fuel appliance such as a wood-burning stove.

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.

Fused spur: power socket that does not have a plug going into it, but rather the cable from an appliance like a fridge, radiator, burglar alarm, etc., and has a fuse socket built into it.

Gable: upper section of a wall, usually triangular in shape, at either end of a ridged roof - gable end.

Gang: referred to for 13-amp power points: 1 gang = 1 single socket; 2 gang = 1 double socket.

Ground heave: swelling of clay subsoil due to absorption of moisture: can cause an upward movement in foundations.

Gulley: an opening into a drain, normally at ground level, placed to receive water, etc., from downpipes and waste pipes.

Haunching (see benching hip): external junction between two intersecting roof slopes.

Inspection chamber: commonly called a manhole. 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 subsoil having little cohesive integrity.

Lath: thin strip of wood used in the fixing of roof tiles or slates, or as a backing to plaster. Lath and plaster walls were very common in houses from late 1800s to 1950s.

Lintel: horizontal structural beam of timber, stone, steel or concrete placed over window or door openings.

Lime mortar: a hydrated lime mortar mix found in older buildings since roman times; offers a flexible joint with good properties for conservation.

Lpg: liquid petroleum gas or propane. Available to serve gas appliances in areas without mains gas. Requires a storage tank.

Manhole: see inspection chamber

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 or above the roof line between terraced or semi-detached buildings; can form the edging of older roofs, for example london butterfly roofing.

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 that can, if untreated, cause widespread damage to structural timbers.

Purlin: horizontal beam in a roof upon which rafters rest.

Quoin: 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 pebbledash, stucco or tyrolean textured finish.

Reveals: side faces of a window or door opening.

Ridge: apex of a roof.

Riser: 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 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. Not to be confused with cesspool.

Settlement: general disturbance in a structure showing as distortion in walls, etc., possibly a result of major structural failure, very dry weather conditions etc. Sometimes of little current significance. (see also subsidence)

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 chimneystack, adjoining wall etc. Associated with flashings, that 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.

Strut: bracing timber in roofs that spreads loads form rafters and purlins to the structural components below.

Stud partition: lightweight, sometimes non-load bearing wall construction comprising a framework of timber faced with plaster, plasterboard or other finish.

Subsidence: ground movement, generally downward, possibly a result of mining activities or clay shrinkage.

Subsoil: soil lying immediately below the topsoil, upon which foundations usually bear.

Sulphate attack: a 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.

Tread: the horizontal part of a step or stair.

Trussed rafters: a method of roof construction utilising prefabricated triangular framework of timbers. Now widely used in domestic construction.

Underpinning: a method strengthening weak foundations whereby a new, stronger foundation is placed beneath the original.

Valley gutter: the 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. (see condensation)

Verge: the edge of a roof, especially over a gable.

Verge board: timber, sometimes decorative plastic material, 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.

Waste pipe: the drainage pipe for baths, basins, wcs.

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.

Frequently asked questions

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