An A–Z of construction technology for APC

The APC pathway guide for building surveying requires that candidates for the Construction technology and environmental services competency must 'demonstrate knowledge and understanding of the principles of design and construction relating to [their] chosen field of practice'.

They need to be able to apply their knowledge to the design and construction processes. This includes using their knowledge of regulations, design standards and legislation, preparing annotated sketches and specification detailing, and identifying mechanical and engineering services relevant to the area of work.

Candidates need to also advise clients on construction and design and processes and the impact of these on cost and programme, as well as liaising with other specialists and consultants to develop project-specific measures.

Breaking these subjects and issues down can help candidates digest them more easily.

Air conditioning: often found in commercial buildings, and sometimes residential ones, air conditioning removes both heat and moisture from the internal environment. Air conditioning can also provide treated or filtered air. There are three main types of system: monoblock, or one unit; split-systems, with an internal and external unit; and multi-split, with an external unit and two or more internal units. 

Surveyors should be aware of the ban on the use of the R22 refrigerant in air conditioning systems, which is known to damage the environment. Older systems using this substance can no longer be refilled or repaired, although they can be serviced if in good working order.

British Standards: published by the British Standards Institution (BSI), these provide consistent technical standards or practices for a range of services and products. There are many examples in the construction sector, including BS 9999 on fire safety, BS 7913 on conservation and BS 8000 series on the quality of work on construction sites.

Construction (Design and Management) Regulations (CDM) 2015: CDM 2015 relate to health and safety on construction sites. Various roles and duties are allocated under the regulations, including those of client, principal contractor, principal designer, contractor and designer.

Although all construction work is covered by CDM 2015, only projects that last longer than 30 days with more than 20 workers at any time or that last more than 500 person-days must be notified to the Health and Safety Executive using a F10 form.

Drainage: most residential properties will have two types of drainage: foul and surface. Remote rural properties off the main drainage network will have their own drainage system which must conform to the general binding rules. The former removes waste water from kitchen and bathroom appliances that is eventually taken away to local treatment plants.

Surface drainage takes rainwater from gutters and hard surfaces such as patios or driveways into soakaways or local watercourses. Some older properties have systems that combine foul and surface drainage, although it is illegal to install new combined systems. Commercial properties will generally have much larger drainage systems, carrying a higher volume of water and using sturdier pipe materials, such as clay or concrete.

Envelope: the building envelope includes the walls, floors, roof, windows, doors, roof windows and roof lights of a building, which separate the internal environment of the building from the external climate. The type of envelope and individual building components will depend on a variety of factors, such as the location, applicable regulations, client's requirements for the internal climate, structural requirements and the desired lifespan of the building.

Floors: floors separate buildings horizontally and come in a variety of types, including solid concrete, suspended timber and suspended concrete. Victorian houses tended to have suspended timber floors, although some had ground floors constructed of stone or clay flagstones on top of the underlying foundations or ground.

During the 1920s, a concrete oversite – or slab – was laid before the suspended timber floor was constructed. By the 1950s, ground bearing concrete floors became popular due to timber shortages during the Second World War. Damp-proof membranes were installed in the 1960s onwards, while modern concrete floors now have insulation and floor screed on top. Suspended concrete floors, such as beam and block, are now commonly used in the construction of new dwellings, primarily due to their speed and convenience.

Glazing: many different types of glazing are found in construction. Traditional buildings used single glazing although, due to its poor insulating properties, double glazing was introduced. Triple glazing is an even more energy-efficient type of glazing, although this comes at a substantial cost. Secondary glazing can be used as a retrofit measure where single glazing is retained. Other types of glazing, depending on the context of use and installation, include safety glass, fire-rated glass, self-cleaning glass, stained glass, wired glass and laminated glass.

Heat pumps: these have become popular as a renewable form of heat supply, and in simple terms they take heat from outside and move it into a building. There are two main types of heat pump: air- and ground-source. In an air-source pump, air from outside is used in a heat exchanger to heat water, which is then used in radiators or underfloor heating. A ground-source heat pump works on the same principle, but instead uses heat from the earth rather than the air.

Insulation: this is used in a building to minimise the loss of heat, prevent the transmission of sound and stop the fire spread between building components. Insulation comes in many forms, including foam board; blankets made of materials such as mineral wool; loose or blown-in fill; and structural insulated panels. Some older forms of insulation are prone to defects; such as loose-fill cavity wall insulation, which is at risk of damp. Spray foam insulation may also be found, but issues can arise where the installer did not consider how the property was designed to function.

Joinery: this traditionally encompasses timber building components such as stairs, doors, door frames, windows and window frames. Many traditional houses were timber-framed, while timber-framed buildings also represent a modern method of construction (MMC). Traditional joinery uses mortise and tenon joints, whereas steel connector plates might be used in contemporary structures.

Approved Document K: part of the Building Regulations, Approved Document K relates to minimum standards for protection from falling, collision and impact. Specifically, section 1 provides guidance on issues such as the steepness of and headroom and handrails on stairs; section 2 gives guidance on ramps; section 3 covers guardrails; section 4 offers guidance on vehicle barriers and loading bays; sections 5 and 7 present guidance on glazing; sections 6, 8 and 9 provide guidance on windows; and section 10 covers doors.

Lifts: these are used in buildings to give occupants access between floors and allow transport of goods. They also facilitate access for disabled users under Approved Document M. Lift safety is covered by the Lifting Operations and Lifting Equipment Regulations 1998, which require six-monthly safety assessments, or yearly if used for transporting goods only.

Mechanical and electrical (M&E) systems: mechanical systems in buildings include some already mentioned such as air conditioning, heating and lifts, as well as plumbing, escalators and other plant, machinery, infrastructure, tools and equipment. Electrical systems include lighting, cabling, telecommunications, control systems and power supplies. Careful design and specification of M&E systems is required when a building is constructed. Systems then need to be maintained regularly and operated correctly to ensure they are safe and remain in good condition. Some surveyors will specialise in M&E, so this is an area where liaison with such a specialist or other professional, such as a quantity surveyor specialising in M&E, may be required.

NHBC Standards: surveyors dealing with new homes will need to be aware of the standards set by the National House Building Council (NHBC). These set technical and performance requirements where a NHBC warranty is sought, and include guidance on achieving them. The NHBC Standards were updated earlier this year to strengthen specific requirements for the weathertightness of windows, doors and glazing, as well as requirements for decorative coatings to steelwork, and concrete upper-floor design.

Operation and maintenance (O&M) manual: when a building is handed over at practical completion, it is best practice to include an O&M manual. This should contain instructions, manufacturers' documentation, as-built drawings, test sheets and commissioning documents. Depending on the use and size of the building, the O&M manual could also include BIM documentation, the health and safety file and occupier guidance.

Piled foundations: foundations come in different forms, and piled foundations are used where the ground's bearing capacity is poor to transfer the load of the building to stronger underlying ground. Piled foundations comprise a number of steel or reinforced concrete columns supporting the building above. They can be formed in a number of ways, including being bored or augered.

Quick: MMCs often make it quicker to erect buildings than more traditional brick or block approaches. MMCs can involve both off- and on-site techniques, with examples including 3D volumetric construction, flat concrete slabs, timber frames, precast panels, and twin wall technology. The uptake of MMCs has perhaps been slower than the industry first expected, although they could offer an efficient way of meeting current housebuilding targets.

Retrofit: retrofitting is the process whereby existing dwellings are improved using energy efficiency measures or features. Examples include improving insulation, replacing windows and doors and renewing heating systems, all of which aim to improve energy efficiency and thermal performance of the dwelling. PAS 2035 provides a specification for the retrofitting of a whole building, identifying and designing potential areas of improvement.

Superstructure: this relates to the frame, upper floors, roof, stairs, ramps, external walls, window, doors, openings in external walls, internal walls, and internal doors. In contrast, the substructure relates to the building components below ground level, such as the foundations and any basement or lower-ground floor.

Trial pits: at the design stage, subsurface site investigations may be required to assess the ground's bearing capacity and decide on the appropriate foundation design. Trial pits can be used to determine the geology and water table of a specific site. They are generally dug at 1–4m intervals, either by hand or by machine. Trial pits can pose a health and safety risk if they are more than 1.2m deep, though, in which case shoring and guarding measures must be used.

Underground services: these can include telecommunications and electricity cables, gas, sewage and water pipes, and other equipment. Such services can pose a health and safety risk if their routes are not known or they are damaged during construction works. The risk can be mitigated by checking utility service drawings, marking out services on site, using a cable avoidance tool or a ground-probing radar, and checking existing site plans.

Ventilation: this comes in a number of forms – natural, mixed mode and mechanical. Natural ventilation relies on fresh air being supplied to a building, for example, through a window, trickle ventilation or doors. Differences in air pressure – for example, wind or thermal buoyancy – cause the air to enter and exit the building without mechanical input. Mechanical ventilation can involve extraction only, for instance with the use of an extractor fan in a bathroom or kitchen; or it can be supply and extract, using a central air handling unit including air filters, supply fans and extractor fans, which both cool and heat the air.

Positive pressure ventilation systems use a positive input ventilator to introduce fresh air into a building, forcing existing air out and reducing internal moisture levels. Mixed-mode ventilation incorporates both natural and mechanical means. Heat recovery systems use a heat recovery ventilation unit drawing heat from air being removed from a building and adding it to air that is being drawn in from the outside. The pipework is separate so there is no contamination of incoming and outgoing air flows. These systems can contribute to the heating of a building and can improve overall energy efficiency and reduce external energy costs.

Walls: before the 1920s, solid brick walls were common in either English or Flemish bond showing both headers and stretchers. Solid walls, which are normally about 220mm wide, are typically narrower than cavity walls, which are normally about 270–300mm wide. Cavity walls preventing the direct transfer of moisture from the outside to the internal parts of a dwelling became popular from the 1930s onwards, with wall ties joining the two brick leaves together, and are typically built in stretcher bond with stretchers, the long side of the brick, facing the outside, one brick thick. Cavity insulation in turn became popular in the late 20th century.

Y-values: a Y-value can be calculated to represent the total heat loss as a result of thermal bridging. Thermal, or cold bridging arises when heat is lost through specific elements or areas of a building; for example, where there is a gap in insulation, or where wall ties interrupt the building fabric. Y-values are used to determine whether a building meets the requirement of Part L of the Building Regulations, using the Standard Assessment Procedure (SAP) for residential buildings and Simplified Building Energy Model (SBEM) for commercial buildings.