Glossary of building terms

Aggregate: Pebbles, shingle, gravel, etc., used in the manufacture of concrete, and in the construction of “soakaways”.

Air Brick: Perforated brick or metal/plastic grille 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 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 (see also “Fan Assisted Flues”).

Batten: Thin lengths of timber used in the fixing of roof tiles or slates.

Beetle Infestation: (Wood boring insects: eg woodworm) Larvae of various species of beetle which tunnel into timber causing damage. Specialist treatment is 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.

Bossing (Lead): A method used to form lead into shapes on roofs.

Bossing (Plumbing): A technique for joining two fluid carrying pipes. E.g. Joining a kitchen waste pipe onto a soil and vent pipe.

Breeze Block: Originally made from cinders (“breeze”) – the term now commonly used to refer to various types of concrete and cement building blocks.

Buttering: Spreading mortar on the vertical joint of bricks before laying. Also the application of adhesive to the back of tiles before pressing into place.

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 thecavities. Will easily fall out if the wall is broken open for any reason.
Fibreglass: Can lead to problems if becomes damp.
Foam: Urea formaldehyde form, mixed on site, and pumped into the cavities where it sets. Can lead to problems of dampness and make investigation/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 wall. Failure by corrosion can result in the wall becoming unstable – specialist replacement ties are then required.

Cesspool: A simple method of drainage comprising a holding tank which needs frequent emptying. Not to be confused with “Septic Tank” or “Klargester”.

Chipboard: Also referred to as “Particle Board”. Chips of wood compressed and glued into sheet form. Cheap method of decking to flat roofs and (with formica or melamine surface) furniture, especially kitchen units. Also commonly used on floors. Tends to swell if moisture content is increased.

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 but are complex and more expensive to repair. Water supply rate can be slow.

Condensation: The change in state of water vapour to liquid water when in contact with a liquid or solid surface. Sometimes manifesting in dampness, mould, rot, corrosion and/or health issues.

Coping/Coping Stone: Usually stone, tile 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 piece to cover the join between wall and ceiling surfaces.

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: Layer of impervious material (mineral felt, PVC, etc) incorporated into a wall to prevent dampness around windows, doors, etc. Various proprietary methods are available for damp proofing existing walls including “electro-osmosis” and chemical injection.

Damp Proof Membrane: Usually polythene, incorporated within ground floor slabs to prevent rising dampness.

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

Differential Settlement: When a building’s foundations settle unequally in different areas after construction.

Double Glazing: A method of thermal insulation usually either: (A) Sealed unit:- Two panes of glass fixed and hermetically sealed together; or (B) Secondary:- In effect a second “window” placed inside the original window.

Drip: A groove along the underside of a cill, which prevents rainwater from tracking back to the brickwork under the cill.

Dry Rot: 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 at gutter level.

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. Usually blue in colour.

Fan Assisted Flue: Similar to “Balanced Flue” but with fan assistance to move air or gases.

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

Fillet: Mortar used to seal the junction between two surfaces, ie between a slate roof and a brick chimney stack.

Flashing: Building technique used to prevent leakage at a roof joint. Normally metal (lead, zinc or copper).

Flaunching: Contoured cement around the base of cement 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.

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

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.

Half-Engineering Bricks: Also known as ‘Semi-Engineering’ bricks. They are bricks that, whilst harder than most ordinary bricks, are not so hard as Engineering bricks.

Haunching: See “Benching”. Also term used to describe the support to an underground rain.

Hinge Bound: A door which won’t close easily, due to the hinges being cut into the frame incorrectly.

Hip: The external junction between two intersecting roof slopes.

Hip Iron: Shaped metal profile used on corner of hips. Screwed to rafter and bedded in mortar to prevent ridge tiles from falling off.

Inspection Chamber: Commonly called “manhole”; provides access 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.

IP (Ingress Protection) Rating: Standards used to define levels of sealing effectiveness of electrical enclosures, against intrusion from tools, dirt, moisture etc.

Jamb: Side part of a doorway or window.

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

Key: The roughness of a surface, which may provide a mechanical bond.

Klargester®: A sewage treatment plant that uses a biological disc and aerobic digestion to treat sewage.

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 as a backing to plaster.

Lifestyle Condensation:Condensation within buildings caused by the lifestyle of the occupant. Caused by; cooking, washing/drying clothes indoors, lack of ventilation, lack of heat etc.

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

Longhorn Beetle: A serious insect pest mainly confined to the extreme south east of England, which can totally destroy the structural strength of wood.

LPG: Liquid Petroleum Gas (or Propane). Available to serve gas appliances in areas without mains gas. Requires a storage tank.

Mortar: Traditionally a mixture of lime and sand. Modern mortar is a mixture of cement and sand.

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.

Non-Traditional Construction: Sometimes referred to as ‘Non-Standard Construction’ or ‘Prefabricated’ (Prefab for short) houses.

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 papers. Now in widespread use for ceilings and walls.

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

Powder Post Beetle: 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 based (externally), sometimes with pebbledash, stucco or Tyrolean textured finishes.

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 structure (see “Collar”).

Screed: Final, smooth finish of a solid floor; usually mortar, concrete or asphalt.

Septic 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, usually as the result of the initial compacting of the ground due to the loading of the building.

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

Shingles: Small rectangular pieces of wood used on roofs instead of tiles, slates, etc.

Snagging: A snag is a defect found in your property after building work has been completed. A snag is typically something that is damaged or broken, not fitted properly, or unfinished.

Soaker: Sheet metal (usually lead, zinc or copper) 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.

Spalling: Concrete that has broken, flaked, become pitted or fallen away.

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 possibly as a result of mining activities, clay shrinkage or drainage problems.

Subsoil: 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, concrete floors and external rendering.

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 bar of wood or stone across a window or top of door.

Tread: The horizontal part of a step or stair.

Trickle Vents: Small openings in a window or building envelope intended to provide natural ventilation.

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

TRVs: Self-regulating valves fitted to radiators to allow room by room temperature control. Also known as Thermostatic Radiator Valves.

Underpinning: Methods of 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 air bricks near to ground level.
Roofs: Necessary to disperse condensation within roof spaces; achieved either by air bricks 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 a “Barge Board”.

Voussoir: The wedge shaped bricks of masonry of an arch.

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

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

Wet Rot: 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, by far the most frequently encountered insect attack in structural and joinery timbers.