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Originally made from cinders ("breeze") - the term now commonly used to refer to various types of concrete and cement building blocks.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

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 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.

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.

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.

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

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 Flues

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

Thin sheet material 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 drain.

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 (see also “reveals”).

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.

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. Used for bonding brickwork, etc.

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.

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

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 (see also “jambs”).

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

The thrust of a badly restrained roof structure (see "Collar") causing outward bowing of a wall.

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.

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.

Spandrel

Space above and to the sides of an arch.

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.

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 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".

Wainscot

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.