A ventilated opening in a wall, usually formed by a specially designed, perforated brick.


A bituminous, flat roof covering laid in liquid form, usually over concrete, now rarely used.


An additional storey or room contained at least partly within the roof space.


Door surround, often formed with timber.





Balanced flue

A flue outlet from a boiler or room sealed heating appliance which uses natural convection to draw the air from outside the building for combustion and expels it back to the outside through a separate compartment of the flue, avoiding the need for a long flue pipe of chimney.

Ball valve(or ball

A device which controls the flow of water from the water supply line into a gravity-operated toilet tank or other cistern, controlled by a float mechanism. 


The protective structure alongside a staircase or around a landing, usually incorporating a series of spindles (or balusters) supporting a handrail.

Barge Board

Wide board (on older often carved) fitted below tiles of overhanging verge to gable of a property.



Timber members to which roof tiles of a property are fitted.

Concrete in the base of an inspection chamber, cast to form a deep channel sloping gently up to the walls each side.

Bituminous felt

A traditional covering for a flat roof, usually applied in several layers, the top layer often incorporating very small stone or mineral chippings embedded in the felt, as a reflective layer.


See "collar below



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Carrying beam

A large beam providing intermediate support for floor joists in place of a supporting wall.


The hinged, opening section of a window

Cavity wall

Perforated wall of building, comprising inner and outer "skins" or either brick or of block work spaced apart by 50-100mm.  "Skins" linked by wall ties, which should be kept clean of mortar droppings during construction of the property, other wise "bridging can occur, leading to dampness internally.  Properly constructed cavity walls are more resistant to damp penetration that solid walls and thermal insulation is also higher.  In modern timber framed dwellings , timber framing forms an inner "skin," then often clad with an outer skin of brick, or similar, to give property a traditional appearance.

Cavity wall insulation

In recent years cavity filling with insulation materials has come into use to preserve warmth in buildings.  Not always suitable for exposed positions.  Unless properly installed, can form "bridge" between skins of walls across which moisture can pass.  Some concerns have also been expressed as to the possibility of toxic fumes emanating from some forms of foam insulation such as Urea Formaldehyde.  There is no evidence that this is a significant problem in this country, but this type of insulation is not generally suitable of timber framed walls.  It is essential that work is done be an experienced and reliable company.

Cement weathering

A narrow band of cement mortar around the base of a chimney stack, at its junction with the roof covering, often used in place of flashings in an older building.

Cess pit

Watertight chamber in which sewage effluent is collected.  Has to be emptied at regular intervals, a service usually provided by the Local Authority for which is a charge is made.  

Chipboard flooring

Larger manufactured flooring panels of a square or rectangular shape, with tongued and grooved edging.


The outer facing of a wall, usually applied to a building or structure of framed construction


Sloping area below a window or door opening to facilitate rainwater run off.

Collar (in roof)

Timbers around a chimney breast within a roof structure, sometimes referred to as "Bridles" or "Trimmers".

Collar  (in drain)

Wider end of pipe into which another pipe fits.

Combination Boiler

A central heating boiler which also provides domestic hot water directly from the mains, heating it directly as it passed through the boiler.


The formation of water droplets on a cold surface in conditions of high humidity. 

Condensing boiler

A modern, efficient central heating boiler which, by means of a 2nd heat exchanger, reduces the amount of heat lost through the flue, by cooling down combustion gasses.


A metal or plastic duct containing mechanical pipes on electrical cables

Consumer unit

An electrical panel on which the main fuses and trip switches are located, otherwise known as a 'distribution board or fuse box'.

Coping stones

Slabs of stone or concrete fixed onto the top of a wall either as a decorative capping piece or to throw off water from the face of the wall. 


A slab of stone or concrete at the top of the chimney, usually projecting beyond the face of the stack


A projecting course of brick or stone, or individual blocks of masonry built out from the top of the wall, usually supporting a gutter or other projecting structure.

Cornice gutter (or parapet gutter)

A gutter which is hidden from the ground, usually behind a decorative cornice or low level parapet wall.


A decorative feature at the top of a wall, usually of stone construction and often concealing a hidden gutter.


A metal device fitted into the top of a chimney pot to prevent down-draughts.



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Externally the area of a wall below the damp proof course level of a property, often having an alternative finish to the brickwork, or roughcast on the sections above damp course level.  Internally, a horizontal decorative band approximately one third wall height above floor level.

Damp-Proof Course (DPC)

Layers of impervious material to prevent the passage of water.  Either horizontal, inserted at the base of walls to stop rising damp, or vertical, e.g. Where a  room is below ground level to prevent lateral passage of water from the ground into wall.  In older buildings, slates often used.  When inserting a new DPC in older buildings a "chemical" form is frequently used, consisting of impregnating wall, at ground level with silicone, which percolates walls and forms barrier against rising damp.

Damp-Proof Membrane

Similar to DPC, but in a solid ground floor to prevent damp rising up  through the floor.  Should be connected to DPC in surrounding walls to be fully effective.



Decorative projecting band course of brickwork with alternate raised and recessed profile.

A raised window set within a flat roof.


A window or other structure projecting out from a sloping roof to provide additional space in an attic room.


Round or square cast iron or plastic tubing to take water from the gutters to the drainage system of a property.

Dressed Stonework (or Ashlar)

Squared and smooth faced stonework, laid in regular courses.

Dry rot

The term given to a destructive fungal decay in timber which can spread rapidly.



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Projecting edge of roof a commercial or residential property.


Another term for the particular view of a building from a certain direction e.g. South elevation, or front elevation.




English Bond

Expansion joint (or movement joint)

A brickwork bond in which each course is either all stretchers or all headers.

A joint built into a wall or other structure, designed to prevent cracking caused by thermal movement.

Expansion tank

A small water tank located at the top of a building which receives excess hot water from a central heating system, resulting from thermal expansion.



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Vertical board at eaves level to which guttering is often attached.

Fibre quilting

Glass fibre insulation.  It should be noted that there is some medical evidence to suggest this form of insulation may be carcinogenic.


Fire door

A narrow strip, triangular in cross section, at the angle between two surfaces.  Can be formed in timber, asphalt, cement mortar, etc.

A door suitable construction to withstand the passage of fire for a specified period(e.g. 30 minute fire door).


Tapered sections of timber fixed above the joists of a flat roof, designed to provide a slight fall on the roof for drainage purposes.


Method of weather-proofing joint between roof covering and walls; often formed in lead  or other metals such as copper.


Flemish Bond

Cement based compound applied to the top of a chimney stack, into which the chimney pots are bedded.

Brickwork that shows stretchers alternating with headers along each coure, and alternating vertically between courses.  Single Flemish bond shows on one wall face, double Flemish bond on both wall faces.

Floating floors

A solid based floor with a timber or other floor finish, laid over a layer of insulation.

Floor screed

The top surface or layer of a solid floor.


A duct within a chimney or an independent pipe which conducts smoke or exhaust gases from a fire, boiler or heating appliance.


Two types: Suspended or Solid.  Suspended means a system of timber joists covered with floor boarding or chipboard, supported by small "sleeper" walls  at ground floor level.  Cavity between solum and floor boarding should be ventilated by air bricks set into external walls, to avoid formation of stagnant pockets of damp air, conducive to growth of rot.  Suspended floors are often how formed with concrete beams/blockwork infill, or precast concrete planks.  Solid floor usually formed in in-concrete with a damp-proof membrane,  surfaced with a sand and cement screed.


A traditional name for a foundation, where the base of a wall is thickened with brickwork, stone or concrete to spread loads into the ground.


A structural device below ground level, usually of concrete construction, designed to support and transfer the weight of the building into the ground.

Fresh-Air inlet (FAI)

Perforated brick or grating set into wall to provide ventilation.  Most frequently used at the base of walls to ventilate areas beneath joists and boarded ground floors.



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Side end of property.

Gully (or Gulley)

The collection chamber at the base of a downpipe, or set within an area of paving, covered with a metal or plastic grating, conveying rain or waste water into an underground drain, or a drainage channel cut into the ground, often with a protective cover or grating.

Gusset Plate

A timber or metal plate fixed across the joint of a roof truss or other framed structure to provide additional strength.


Open piping at lowest point of roof for the collection of rain water, usually formed in plastic, aluminum or cast iron in older properties and to two standard designs:  Half-round; a semi-circular section, fixed to fascia with brackets.  Ogee; a molded pattern.  In more recent times, plastic guttering commonly used, as these have the advantage of not requiring painting, but can fade and become brittle.



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Header tank

Small storage tank linked with the central heating system to top up water in that system (normally independent of a main cold water storage tank.)

Hermetically Sealed Double Glazing

A factory made double glazed window, sealed to prevent moisture or air entering the void between the glazed panels.


External angle formed by a sloping roof instead of ending in a gable.

Hipped roof

A roof which slopes down to the top of the walls, usually on three sides.

Hopper head

A small, open-topped collection vessel receiving rain or waste water from two or more pipes, connected to a single pipe below.



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In-situ concrete

Concrete which is formed or laid on site

Indirect (or unvented) hot water system

Domestic hot water is heated by a boiler and stored in a cylinder or tank, often incorporating a secondary means of heating, such as an electric immersion heater.

Inspection Chamber

A chamber of brick, concrete or pre-formed plastic construction, sunk into the ground, as a means of giving access to underground drains for inspection and/or maintenance.



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The side post or lining of a door or window frame.


A horizontal beam supporting the floor



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King Post

Traditional pitched timber roof detail.  The vertical member of a roof truss which usually provides support centrally for the horizontal tie beam across the base of the truss



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Land Drain

Method of disposal of water beneath ground.  Usually comprises a drain laid with open joists and surrounded by pea shingle or similar material through which water can disperse into surrounding soil.

Lath and Plaster

A traditional finish for internal walls or ceilings comprising timber laths fixed across timber studs or joists as a base for plasterwork


A beam over a door or window opening supporting the structure above.

Load bearing wall

A wall which supports another structure directly above, such as a floor, beam or a partition wall on an upper storey.



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A large chamber sunk into the ground, allowing physical access to underground drains ( see Inspection Chamber).

Mansard roof

A steeply sloping, almost vertical roof, often containing windows, housing accommodation within the roof space, usually with a flat or shallower roofed section above.


A general term used for stones, bricks or concrete blocks in an external wall, bonded together with mortar.


A flexible and waterproof sealant, often used to fill small gaps around window or door frames, or applied to the outer face of an expansion joint.


A mixture of sand, cement and/or lime, used to bind together bricks, stones or other masonry.


Vertical member between a window sill and a window lintel.  Usually of stone or precast reinforced concrete.



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A defect whereby slates become dislodged and slip down the roof due to failure of the fixing nails.


A short horizontal timber in a framed partition extending between two studs.


The section of a stair tread which projects out beyond the riser.



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The secondary part at the rear of a traditional house or other building, often of slightly inferior construction and commonly housing the kitchen and bathroom (otherwise known as a back addition outrigger or rear projection.

Overflow pipe

A pipe discharging from a storage tank or WC cistern which allows excess water to drain off when it overfills for any reason.



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Section of wall protruding  above the external wallhead,  usually with internal parapet gutter behind.  In older properties, these are commonly of lead in good quality work.  Normally only found in Victorian or older properties.



Party Wall

An internal wall dividing two rooms, either of solid or timber construction, and either load bearing or non-loading bearing.

The dividing line between two adjoining properties, either a 'party structure' (where one, or both, sides form habitable accommodation) or a 'party fence wall' (which is garden wall).  Works relating to Party Walls are now regulated under the Party Wall Etc Act 1996.

Pebble dashing

A type of rendering where pebbles or small stones are embedded in the cement compound.

Pier (or column)

A vertical pillar or masonry providing support for a structure above.

Pitched roof

A sloping roof, usually covered with tiles or slates.


A course of stone or brickwork projecting out from the base of the wall, built up from the foundation.


The outer face of mortar joints applied with a trowel.

Pre-cast concrete

Concrete units which are factory made, such as paving flags or coping stones.

Principal rafter

The main sloping member of a roof truss, following the pitch of the roof and often providing intermediate support for horizontal beams or purlins.


A horizontal beam in a roof supported by a roof truss, or extending between two supporting walls.



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Quoin stones

Queen Post Trust

Large squared stones located at the corner of a building

A truss with no central post, unlike the King Post truss, but with two puncheons on either side of centre which can be replaced by long steel bolts if the members act only in tension.



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Inclined timber immediately beneath the roof covering to which the tiling battens or sarking felt for sloping roofs are fixed.  (sometimes referred to as a "spar")

Reinforced concrete

Concrete which incorporates a series of metal rods to provide additional strength.


A compound, usually cement or lime based, applied to the outer face of a wall, either smooth finished or textured.

Retaining wall

A structure built to retain land which is higher on one side of the wall than the other.

Ridge and hip tiles

Tiles which are located at the apex of the roof and at the junction between two roof slopes respectively.


Vertical side of face of an opening for a window or doorway between the frame and face of the wall.


The horizontal line at the apex of a roof.  Usually has tile, zinc or lead covering.


A window set within the plane of a sloping roof.

Roof Truss

Triangular framework of structural members supporting a roof, carrying horizontal members (purlins) which in turn support common rafters.

Roof verge

The edge of the roof where it meets a gable wall.

Rubble stone

Stonework laid in an irregular pattern, using natural stones of a variety of shapes and sizes.



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Sarking felt 

Material laid on top of rafters to which slates/tiles are fixed.

Septic tank

Sewage disposal system normally comprising two or three linked chambers within which self purifying (bacterial) process takes place, beyond which is an outfall to drain (land) or soakaways, for the purified liquid effluent.  Occasional emptying desludging may be needed, but dependent upon soil conditions and method of use, septic tanks can remain undisturbed for a number of years.  New land drainage or soakaways may also be required, but on average probably at intervals of no less than ten years.


Wallhead details normally above slate level.


Method of water disposal usually for surface water, i.e., hole dug in ground and then filled with brick, rubble or similar material, and covered over.  Disperses water from drains leading to it, provided surrounding soil conditions are suitable.


The underside of an overhanging eaves.


Load bearing timbers normally supporting purlin and fixed at an angle down to a wall or some other load bearing point.



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Thermal movement

Expansion and contraction caused by temperature changes in a material.

Tie beam

The horizontal beam across the base of a roof truss, fixed to the lower ends of the main, or principal rafters.

Tile nibs

Small projections on the underside of roof tiles which hold them in place on timber laths or battens.

Tongued & grooved boarding

Traditional floor boards, with interlocking connection.


Cement or limed based mortar applied to the underside of tiles or slates in an older roof.


A horizontal member or a frame dividing two windows.

Treads and risers

The horizontal and vertical sections of a staircase respectively.


A timber beam fixed across the ends of trimmed floor joists to accommodate an opening such as a stairwell, or around a projecting structure such as a chimney breast.

Trussed rafters

Modern lightweight roof trusses located at regular intervals across the roof, usually pre-fabricated in a factory.



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A secondary barrier against wind-driven rain penetration at roof level and also acts to conduct any rainwater which may get access beneath the slates back into the gutters.  Laid between the external roof covering and sarking/ roof felt.



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Valley/valley gutter

Angle formed by the outside surfaces of two adjoining roof slopes.  Can be tiled or formed in lead or, less durably, in felt or zinc, particularly between two parallel adjacent sloping roofs.

Vapour check/barrier

An impervious layer, usually heavy gauge polythene sheeting, used to prevent passage of moisture in vulnerable parts of a structure.


Edge of a roof which runs from eaves to ridge at a gable (usually sand/cement pointed)



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Wall head

The upper most section of an external wall.

Wall plate

Horizontal timber at top of wall on which roof timbers, rafters or joists rest.

Wall tie

Metal connector used to provide structural link between inner and outer skins of cavity walls

Waste pipe

A drainage pipe conducting waste water from a bathroom, kitchen sink or washing appliance. 



A traditional term for a course of stone projecting out beyond the face of a chimney stack to throw water off.

A galvanised steel bar 25x6mm, bedded on edge in a groove along the top of a precast concrete sub cill in a window opening.


Weathermould (or drip mould)

A building component which keeps out the weather, particularly rainwater, or drains it away, such as cappings, baffles, channels, drips or flashings, found on roofing, door thresholds, glazing, etc.

A moulded section of timber fixed across the base of a door, or above a window or door frame, to throw off water from the face of the door or window.

Weatherboarding (or shiplap boarding)

Overlapped timber boarding, usually hardwood, providing an external cladding.

Wet rot

A fugal decay commonly affecting external timbers which have not been kept well painted or otherwise maintained, whereby the timber becomes soft.


The general term given to infestation by certain wood-boring insects such as the common furniture beetle.

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