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Glossary of 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”.

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Breeze Block: Originally made from cinders (“breeze”) – the term now commonly used to refer to various types of concrete and cement building blocks.

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 fallout 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.

Collar: Horizontal timber member intended to restrain opposing roof slopes. Absence, removal or weakening can lead to roof spread.

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 piece to cover the join between wall and ceiling surfaces.

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.

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.

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.

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

Hip: The external junction between two intersecting roof slopes.

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.

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 as a backing to plaster.

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.

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.

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 load.

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.

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.

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.

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.

Transom: Horizontal bar of wood or stone across a window or top of door.

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: Methods of strengthening weak foundations whereby a new, stronger 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”.

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.