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Building terms explained

EXTERNAL FEATURE DEFINITIONS
The definitions below are for features found on the outside of a building.

CHIMNEYS AND ROOFS
Party Structures . - Party Wall Act Etc. 1996
A structure which both parties enjoy the use of or benefit from. An example of this would be where both parties gain support from a wall or utilise a common chimney or chimneys with respective flues in either side. In terraced housing the wall between the two properties is the party wall.
Any work to party structures, such as party walls or party chimney stacks, require agreement under the Party Wall Act.
Tile on Edge
A tile sitting sideways, bedded in cement mortar which is being utilised as a flashing, this is not an ideal material. We would always recommend the use of lead flashings.
Flaunchings .
A low, wide cement mortar fillet surrounding the flue terminal on top of the chimney stack to throw off rainwater.
Flashings .
Flashings prevent dampness from entering the property, usually at junctions where materials change. Such a junction is the one between the chimney and the roof. Flashings in this area are traditionally made from lead.
Flashband .
Flashband is a sticky backed thin flashing which is best used for temporary repairs only.
Soakers
Soakers are the upstand below the flashings and direct rainwater away from the tile or slate edge
Spalling .
Spalling occurs to brick or stone when water penetrates the surface and via freezing and thawing starts to cause deterioration to the surface. This in turn allows further water penetration and the surface breaks up further. This ultimately can lead to water damage or structural damage to the area.
Re-Pointing .
Re-pointing is carried out where the existing mortar has failed and broken away to stop damp penetration and further deterioration. The mortar should be raked out to approximately 20mm and then replaced with a mortar of a similar type, therefore, stopping damp penetration occurring.
Capping .
Capping is a practice used when chimneys are no longer in use to prevent moisture from entering the structure in the form of rainwater via the chimney. This usually involves the closing of the chimney with a tile or slab positioned across. It should include vents to allow air circulation.
Parapet Walls .
These walls are usually above the roof line and often sit on the boundary of the property. Due to their position they are relatively exposed and suffer from deterioration due to the elements.
Blinding .
On a roof this is where a mortar is used to bed slate or tile.
Polycarbonate .
Transparent, extremely tough plastic sheet, used for security glazing. It may also be an insulating light panel, double walled or triple walled, or 10 or 16mm thick. It is not a fire hazard as it has low ignitability and low flame spread, and releases little heat and little smoke if burnt. It can be coated to resist damage from ultraviolet.
Proprietary Flashings .
These are usually supplied by the manufacturer of the roof covering and will be specially made to fit the profile of the roof covering. Typically they are aluminium.
Cement Fillets/Cement Flashings
This is where cement has been used to cover up or fill the junctions between two areas, for example between a roof and a wall to help prevent dampness. Cement is a brittle material and prone to cracking which in turn allows dampness into the structure. we would always recommend they are replaced with lead.
Torching .
Usually lime mortar dabs (but can be moss) which the slates sit upon. These are used to reduce the wind traveling through the building therefore reducing the risk of wind damage.
Nail Sickness .
The weakening of the nails which fix slates or tiles to the roof battens rusting. This is normally attributed to problems with slate roofs.
Lead Tingles or Lead Slaps .
These are strips of lead usually about 25mm wide which are used to secure slates where they have slipped.
Turnerising .
"Turnerising" is a process used usually when roofs have started to deteriorate or leak and it involves the covering of a roof with a mesh and coating in bitumen. It is almost impossible to economically save or re-use materials which have been treated in this manner.
Nibbed Clay Tiles .
A nibbed tile is one which has raised areas known as nibs, usually two in number, at the top of the tile to enable the tile to be fixed to the roof batten which, in turn, fixes to the roof structure.
Delamination .
This occurs in items built up of layers. It simply refers to the layers breaking down.

WITHIN THE ROOF SPACE
Sarking Felt/Underfelt .
This is the felt that sits between the roof covering and the timber battens and forms an additional protective layer to stop the wind lifting the roof and to stop the elements from penetrating the structure. This was first used in the late 1940's/early 1950's and is a requirement for current Building Regulations, though now we have moved onto breathable membranes such as Tyvek whih allow air through but not moisture.
Close Boarding .
These are timbers positioned on the common rafters which are butt jointed together. They add to the wind resistance and water-tightness of the roof together with the overall structural integrity of the roof. Usually this type of roof does not have an underfelt, this can lead to problems if the roof is not cross-battened as wet rot can occur to the underside of the timbers. This is very difficult to identify.
Feather Edge Boarding .
These are timbers positioned on the common rafters which form the slope of the roof. These timbers are butted together but they are cut at an angle, or feather edged, to give a lip for the nibs of the tiles to sit upon.
Fire Walls .
Fire walls help prevent the spread of fire through roofs and are a relatively recent Building Regulation requirement .
Purlins .
The purlin is the horizontal timber member usually running from gable end to gable end and parallel with the walls which supports the jack or common rafters (the angled rafters forming the slope to the roof).
Ridge Board .
The ridge board forms the apex of the roof and usually denotes that the roof was constructed on site and joins the jack rafters or common rafters together. These are the rafters that form the slope to the pitch of the roof.
Common Rafters .
The rafters form the slope to which the battens are secured and in turn the roof covering is also secured too.
Principle rafters
These are the larger rafters which can form part of a roof truss that in turn supports the purlins, principle rafters generally sit on top of a king post at their top ends, they are named principle rafters as they follow the same line as the common rafters, they do however serve a different purpose alltogether.
Couple Roof .
A traditional pitched roof with rafters and no tie beam, used for short spans up to 3m, assuming standard joist centres.
Close-Couple Roof .
This is a traditional framed roof with common rafters joined at the wall-plate level with a tie beam, also used for ceiling joists, used for spans up to about four metres, assuming standard joist centres.
King Post Truss .
A traditional timber roof truss with a vertical post from the apex to the centre of the bottom tie beam, suitable for spans up to about 11m, but like the queen-post truss not now used for new work in Britain.
Prefabricated Truss .
This is a roof truss made in a factory using gang nails at the joints, it is then transported to the site and normally lifted into place. This type of construction has been used for about the past 30 to 40 years.
Wall Plates .
Wall plates are the horizontal members normally timber, although they sometimes can be metal RSJ's, fixed to the top of the wall within the roof space. They hold the common rafters from the roof in place but can be susceptible to dampness.
Battens .
A small section, normally of timber, to which the slates and roof tiles are fixed.
Wind Bracing .
These are timbers fixed across the roof structure to stop movement when it is windy.

GUTTERS AND DOWNPIPES
Surcharging .
This term is usually used in relation to valley gutters and is where there is too much rain for the valley gutter to cope with.

WALLS
Cornice (external)
This is the top course of bricks where the house meets the roof.
Efflorescence .
This is where salts appear on the surface of the brickwork, render or plaster in a white dust or crystal formation
Lime Mortar .
mix used to bed bricks upon; its characteristics being that it flexes and moves with the structure. It was used up to the War years.
Cement Mortar .
sand cement mix used commonly in brick houses from about the First World War onwards and is relatively strong and brittle and therefore does not allow much movement.
Re-Pointing .
Re-pointing is carried out where the existing mortar has failed and broken away to stop damp penetration and further deterioration. The mortar should be raked out to approximately 20mm and then replaced with a mortar of a similar type, therefore, stopping damp occurring.
Engineering Brick .
A clay brick of high compressive strength and low absorption, eg Staffordshire blue bricks and some reds. Class A bricks are stronger than 70 N/mm² and have an absorption below 4.5%. Class B have a 50 N/mm² compressive strength and maximum 7% water absorption.
Fletton Brick .
A low cost pale red brick made from Oxford clay with traces of coal that burn during firing, saving energy. It is pressed like many clay bricks and can be sand faced, pigmented, or textured for use as facings.
Bonding Timbers .
These are timbers used in construction of walls usually using a lime mortar construction. Bonding timbers are used horizontally and add strength to the wall enabling additional lifts of brickwork.
Render .
A sand and cement coating applied in two or three coats or layers.
Bell-Mouths .
A bell-mouth is a curve usually formed by use of a metal bead, at the base of a wall which throws the water away from the structure therefore preventing dampness.
Pier .
This can be the load bearing brickwork in a wall between openings, or a short buttress on one or both sides of a wall, bonded to it for stability.
Cavity Wall Ties .
A fastener across a cavity wall to hold the two leaves together. Now usually made of stainless or galvanised steel wire or strip, sometimes plastic, and has a twist or bend near the middle to form a drip so that water cannot pass. Wall ties are built into the brickwork bed joints as work proceeds and may have a large plastic washer to hold cavity insulation in place. In the early days of wall ties they were manufactured from a low grade steel or iron which was prone to decay causing them to expand. This is characteristically identified by horizontal cracking through brickwork courses and in extreme cases a gap clear through the wall revealing daylight from the inside.
Recessed Joint .
A mortar joint set back about 6mm from the face of the wall, either a raked-out joint or one made by tooling. It is used for brickwork, and for stonework to prevent flushing, and is strongly shadowed.
Influencing Distance .
This is the distance in which a tree may be able to cause damage to the subject property.

EXTERNAL JOINERY
Over Lights (or fan lights).
This is a window above the door allowing light into the hallway area. Sometimes also known as fanlights
Secondary Glazing .
This is where a secondary window has been added, usually to prevent draughts. We would also draw to your attention that these type of windows can be restrictive in the case of the emergency when, for example, a fire has occurred in the property.
Trickle Vents .
Small vents to the windows to allow air movement inside the property to stop a build up of fumes or humidity.

INTERNAL FEATURE DEFINITIONS

CEILINGS AND WALLS
Lath and Plaster .
Laths are thin strips of timbers which are fixed to the structure. Wet plaster is applied to the laths, usually in several layers. The plaster forms a key as it is forced between the laths. This plaster, once dry, is given further coats and often a decorative finish. If plasterwork is referred to as having ‘lost it’s key’ it has become separated from the lath structure and is in danger of falling from the wall or ceiling.
Plasterboard .
The usual name for Gypsum plasterboard which is building board with a core of aerated gypsum, usually enclosed between two sheets of heavy paper, used as a dry lining.
Dry Lining (Old Properties)
This technique is usually used on solid walls particularly where dampness is occurring. In older properties, where the internal wall is not flush, battens would be added and then lath and plaster. In more modern properties, the walls may be lined with plasterboard on battens or plaster dabs .
Dry Lining (Modern Properties)
Within modern properties, dry lining is a technique used to give an improved drying out time, the plasterboards have a taper to the edge and this is taped and filled, the finish is then sanded smooth. This reduces the amount of moisture as no actual plaster is used and so decoration can commence rapidly. This has obvious benefits for homebuilders.
The term comes from the fact that plasterboard is dry and used as an inner lining within the property. Prior to this a wet plaster was used and required drying out periods which slowed the construction process down. Therefore almost universally in modern properties dry lining is used both as a finishing to internally line the walls and ceilings.
Blown Plaster .
This is where the plaster has come away from its base leaving a hollow area. Often caused by a build up of salts behind the plaster as a symptom of rising damp
Studwork .
Usually a timber frame, clad in either lath and plaster or plasterboard and used to divide areas. Studwork can be structural, i.e. load bearing, or alternatively non-structural depending upon its construction. Modern Building Regulation requirements also require minimal sound transfer and this is usually adhered to by the incorporation of insulation material between the studs.
Stud wall
A wall constructed from studwork as opposed to a solid wall of brick, Block or stone

FLOORS
Suspended Timber Floor Construction .
A suspended timber floor usually consists of timbers spanning the ground floor, supported on piers (usually brickwork), vented via air bricks within the walls.
Beam and Block Flooring Construction .
This form of construction uses concrete beams to span the floor in between which blocks are fitted. The floor was not opened up. The floor void was not accessed.
Chipboard Flooring/Boarding Construction .
This is formed from small particles of timber which are bonded together into a board normally 1200 x 2400mm (2' x 8') which are then fitted over or secured to the joists forming a floor vented via air bricks within the walls.
Floating Floor Construction .
This type of flooring is relatively modern (last 20 years). It consists of a chipboard flooring (chipboard is formed from small particles of timber which are bonded together into a board), on a vapour barrier on a solid insulation board on a damp proof membrane onto a concrete floor slab. A floor void is not present in this type of construction.
Joist and Floorboard Construction.
Sometimes referred to as suspended floors or timber deck floors These are usually consisting of joists suspended from the external walls, either built in or, in more modern times, sitting upon joist hangers, sometimes taking additional support from internal sleeper walls beneath the floor, with floorboards fixed down upon it.
DOORS
Hollow Core Doors .
This is a modern door which uses hardboard as its outer surface and a cardboard latticework as its inner surface. It is very common on modern properties and relatively cheap, but they do damage easily.
DEFINITIONS OF OUTSIDE AREAS
Bund Wall .
A lined wall around oil tanks designed to catch all oil that leaks from it. It therefore should have the capacity to retain the volume of oil held within the oil tank and also be oil tight.
Back Siphonage .
The sucking back of dirty water from within a building leading to backflow into a water main if its pressure drops. All water authorities have regulations to prevent this pollution of the main, eg. by having an air gap under the draw-off taps of sinks or drinking fountains, or ballvalves of cisterns. A ballvalve with a silencing pipe must have an anti-siphon hole
Benching .
Concrete in the base of an inspection chamber, cast to form a deep channel sloping gently up to the walls each side. It ensures that no solids are left after flooding and is stood on when rodding.
Manholes .
As part of the current Building Regulations, you are required to have a manhole (or in some instances a rodding eye is allowed) at each change of direction of the drains or where new drains join an existing run.
Rodding Eye .
This is a small access hatch that is used for rodding the drains should they block.

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