ABBE L6 Building Surveying key terms

Moisture drawn upward through porous masonry by capillary action from ground contact, typically reaching about 1 metre above floor level and leaving a horizontal tide mark with salts at its upper edge.

A continuous impermeable layer built into a wall near ground level, or a remedial injected barrier, that interrupts capillary movement of moisture between the ground and the structure above.

Chlorides and nitrates left in plaster or brickwork that absorb water vapour from humid air, causing damp patches that are unrelated to any active water ingress.

A localised path of higher heat conductance through the building envelope, such as a lintel or balcony slab, which cools the adjacent surface and encourages condensation and mould.

Water vapour that diffuses or convects into a construction and condenses within it when the temperature falls below the dew point, hidden from view but reducing insulation performance and risking decay.

The temperature at which air becomes saturated and water vapour begins to condense onto surfaces or within materials as it is cooled.

A low-permeability membrane positioned on the warm side of insulation to limit the passage of water vapour into the construction, reducing the risk of interstitial condensation.

A vapour-permeable sheet placed on the cold side of insulation that resists wind and rain but allows moisture vapour to escape, keeping the construction able to dry outward.

Chemical reaction between soluble sulphates in ground, brickwork or gypsum plaster and cement compounds, producing expansive crystals that crack and disrupt mortar and concrete.

An expansive crystalline mineral formed when sulphates react with tricalcium aluminate in cement, causing internal swelling, cracking and, in severe cases, disintegration of concrete.

Expansion caused when reactive silica in certain aggregates reacts with alkalis in cement pore water, producing a gel that swells and cracks concrete, often seen as map cracking.

The gradual reaction of atmospheric carbon dioxide with calcium hydroxide in concrete, lowering its alkalinity and, once it reaches reinforcement depth, removing the protective passivating layer.

Penetration of chloride ions, typically from de-icing salts or marine exposure, which breaks down the passive film on steel reinforcement and promotes localised pitting corrosion.

An electrochemical survey using a reference electrode to map the probability of active corrosion of embedded reinforcement, producing a potential contour plan of the element.

A magnetic instrument that detects reinforcement bars within concrete and estimates the depth of cover, used to assess durability risk and locate steel before drilling or coring.

A horizontal line of staining and salt deposit on a wall marking the upper limit of a damp zone, useful for identifying the extent and possible cause of moisture.

Separation of one layer or material from another, such as plaster from its backing or render from masonry, often indicated by a hollow sound when tapped.

The breaking away of fragments from a surface, commonly concrete or brick, usually driven by corrosion of embedded steel or by moisture and frost action.

A simple non-destructive inspection technique in which a hammer or rod is tapped over a surface to detect voids, delamination or loose material by the change in sound.

An impermeable sheet or coating laid beneath a concrete floor slab or within a floor build-up to prevent ground moisture from rising into the internal construction.

A structured inspection that records the current physical state of a building or element, grading defects and providing a baseline from which maintenance and repair planning can proceed.

A document, usually with photographs, recording the existing state of premises at the start of a lease so that the tenant's obligations to repair can later be judged against it.

Breaches of lease covenants to repair, decorate and reinstate, commonly assessed at lease end through a schedule of dilapidations and resolved by negotiation or claim.

A wall, or other structure, shared by owners of adjoining properties or separating buildings, subject to statutory notice and dispute procedures before certain works can proceed.

A formal written decision by appointed party wall surveyors setting out how notifiable works are to be carried out and any compensation for adjoining owners.

A statutory notice requiring the owner or occupier of premises to remedy specified defects or disrepair, with a timetable and, where appropriate, enforcement powers if it is ignored.

The rate of heat transfer through one square metre of a building element per kelvin of temperature difference, expressed in W/m2K, where lower values indicate better thermal performance.

The capacity of a material to absorb, store and later release heat, which damps temperature swings and helps moderate overheating in heavyweight construction.

A measure of uncontrolled air leakage through the building fabric, tested by pressurising the building and expressed as air changes per hour at a reference pressure.

The total greenhouse gas emissions associated with extracting, manufacturing, transporting, installing and eventually disposing of building materials and components over their life cycle.

Combined embodied and operational emissions of a building across its entire life, including construction, use, maintenance, refurbishment and end-of-life, used to guide low-carbon design decisions.

Upgrading an existing building's fabric, services or systems to improve energy performance, comfort or usability, often requiring careful detailing to avoid moisture and overheating risks.

A designated area of special architectural or historic interest whose character and appearance are protected, giving the local authority extra control over demolition and certain works.

A building of special architectural or historic interest entered on the statutory list, for which consent is required before any works affecting its character as a building of special interest.

The original or significant physical material, structure and finishes of a heritage building, whose retention and minimal intervention are central principles of conservation practice.

The conservation principle that interventions should be capable of being undone without damaging the historic fabric, so that future generations retain the option of different treatment.

A priced or unpriced document listing the items of work, quantities and standards to be carried out under a contract, forming the basis for tendering and valuation of variations.

A formal instruction changing the scope, quantity, quality or timing of contracted works, which must be valued and recorded to adjust the contract sum and programme.

A periodic assessment of the value of work properly executed and materials on site, used to determine payments to the contractor during the progress of the works.

A percentage of each payment withheld by the employer as security for performance and defects correction, released in part at practical completion and the remainder after the defects period.

The stage at which the works are complete except for minor items and can be taken over and used for their intended purpose, triggering release of retention and the defects period.

The process of identifying and compiling a list of minor defects, incomplete items and faults near completion so they can be corrected before or shortly after handover.

A person with defined health and safety responsibilities under construction regulations, such as client, principal designer, principal contractor or contractor, each owing specific duties.

A document prepared before construction begins that sets out site arrangements, management controls and welfare provisions for managing health and safety during the works.

A structured inspection to locate and record asbestos-containing materials in a building, either presumptive and management-focused or fully intrusive and sampling-based.

A fully intrusive asbestos survey carried out before major works that may disturb the fabric, intended to locate all asbestos-containing materials as far as reasonably practicable.

Insurance covering a professional against claims for negligence, error or omission in the services they provide, usually required as a condition of appointment and of practice.

The legal and professional obligation to exercise reasonable skill and care towards those who may foreseeably be affected by one's work, acts or advice.