Building design and materials

How British homes are built, period by period

Construction is a good guide to a home's age, and age is a good guide to how it behaves. Most homes built before the First World War have solid walls: brick laid in a bond such as Flemish or English, where headers pass through the full thickness, or stone in rubble or ashlar coursing set in lime mortar. Solid walls have no cavity. They absorb rain outside and let it evaporate again, relying on lime mortars and porous plasters to move moisture. Treating a solid wall as a modern sealed wall, by rendering it in dense cement or lining it with impermeable materials, is the usual cause of damp in older houses.

The cavity wall became common in the 1920s and 1930s: an outer brick leaf and an inner leaf of brick or lightweight block, separated by a gap and tied with metal wall ties. The cavity was left empty, and its purpose was to stop rain crossing to the inner leaf. From the 1970s cavities were increasingly filled with insulation, and in modern construction the cavity is wider and the insulation is a designed part of the wall. Two problems recur: wall tie corrosion in interwar houses, and cavity fill that has slumped, been badly installed or bridged the cavity so water tracks across.

The post-war years produced the widest variety. Short of homes and of bricklayers, government and councils built at scale using system building: precast reinforced concrete panels, in-situ concrete, steel frames clad in a thin skin, prefabricated timber types and the temporary prefabs. Many are sound and have been repaired or reclad. Others became known for particular defects, most famously corrosion of reinforcement in certain precast concrete types, some designated as defective under housing legislation and very hard to mortgage until repaired to an approved scheme. The umbrella term is non-standard construction, and it is the most important question a buyer of a post-war home can ask.

Modern timber frame returned in volume in the 1980s and now dominates Scottish output. In a timber frame house the inner leaf is a load bearing panel and the outer brick skin is cladding, not structure. Since the 2000s a wider set of approaches has been grouped as modern methods of construction: factory made panels, volumetric modules, insulated formwork and hybrids, all aimed at shorter site programmes and more consistent fabric.

Natural methods and earth-sheltered homes

Straw bale walls are built inside or around a timber frame and rendered in lime, giving a thick, breathable, well insulated wall. Cob mixes subsoil, aggregate, straw and water in built up courses, and survives in thousands of homes in the south west of England. Rammed earth compacts moist subsoil in shuttering to form dense walls. All three are breathable systems needing a good hat and good boots: a generous roof overhang and a plinth clear of splashing water. All three count as non-standard, so a specialist valuer and insurer are usually needed.

Earth sheltered homes are built into a slope, under a green roof or under banked ground. The surrounding earth damps the swing between day and night and between seasons, so heating and cooling loads fall and visual impact can be very low. The engineering questions are structural loading, waterproofing, drainage and ventilation; the practical ones are daylight, escape and access for services.

Homebinding is developing one idea in this family through the Whitehole project: dwellings formed from large diameter twin-wall high density polyethylene tube, buried and linked into connected spaces. Twin-wall HDPE pipe is an established civil engineering product used at large diameters for drainage and culverts, corrosion resistant and jointed by well understood methods. Using it as habitable structure is not a proven housing method, and we describe it as an idea under development rather than a product. It would need structural design for burial loads, a fire strategy, ventilation, daylight, escape and building control approval, and it would be non-standard construction to every lender and insurer. This is not advice.

The Building Regulations and the Approved Documents

Building control in England rests on the Building Act 1984 and the Building Regulations 2010. The regulations set functional requirements; the Approved Documents are guidance on ways of meeting them, not the only route to compliance. Work is signed off by local authority building control or a registered building control approver, and the completion certificate is what a conveyancer looks for.

Part A covers structure, including loading, ground movement and disproportionate collapse. Part B covers fire safety: escape, spread of flame, fire resistance and access for the fire service. Part C covers site preparation and resistance to contaminants and moisture. Part D covers toxic substances, in practice urea formaldehyde cavity foam. Part E covers resistance to the passage of sound, between and within dwellings. Part F covers ventilation. Part G covers sanitation, hot water safety and water efficiency. Part H covers drainage and waste disposal, foul, rainwater and building over sewers. Part J covers combustion appliances and fuel storage, including flues and hearths. Part K covers protection from falling, collision and impact, so stairs, ramps, guarding and glazing. Part L covers conservation of fuel and power. Part M covers access to and use of buildings. Part O covers overheating in new residential buildings. Part P covers electrical safety in dwellings. Part Q covers security in new dwellings, principally doors and windows. Part R covers infrastructure for electronic communications. Part S covers infrastructure for electric vehicle charging. Regulation 7, and the Approved Document with it, covers materials and workmanship: adequate and proper materials used in a workmanlike manner.

The Building Safety Act 2022 in outline

The Building Safety Act 2022 followed the Grenfell Tower fire and the independent review of building regulations and fire safety. It created the Building Safety Regulator and a stricter regime for higher risk buildings, defined by height and by the number of storeys and dwellings. Their design and construction pass through gateways: approval before planning permission is implemented, approval of the design before construction starts, and a check before occupation, with the regulator able to stop the project at each point. In occupation, an accountable person must register the building, assess and manage building safety risks and prepare a safety case.

Running through all of it is the golden thread: an accurate, current and accessible digital record of the building, its design intent, the materials used and the decisions taken, handed from design into construction and then into occupation. The Act also strengthened competence requirements on those carrying out and certifying work, extended limitation periods for certain claims about defective dwellings, and changed how remediation of unsafe cladding is funded and pursued. Most houses fall outside the higher risk regime, but the direction it sets, better records and clearer accountability, affects the whole industry.

Energy and fabric performance

A U value measures how readily heat passes through an element of construction: the lower the figure, the better it resists heat loss. A solid brick wall performs poorly by modern standards, an unfilled cavity better, a filled cavity better again, and a well designed modern wall very much better. Rather than quoting numbers that change with each revision of Part L, think about the fabric as a whole: insulation in walls, roof and floor, the quality of glazing, continuity of insulation at junctions where cold bridges form, and airtightness, meaning how much uncontrolled air leaks through the envelope. A tight building needs deliberate ventilation, which is why Part F moves in step with Part L and why mechanical ventilation with heat recovery is common in low energy homes.

Heat pumps, air source or ground source, move heat rather than making it, delivering more heat energy than the electricity they consume. They work best in a well insulated home with generously sized emitters at a low flow temperature, which is why fabric comes before plant. The Future Homes Standard is the government's stated policy for a step change in the energy performance of new homes in England, with low carbon heating rather than fossil fuel heating and a fabric standard to match. It is a policy in progress delivered through changes to Part L and Part F, so check the current position rather than rely on a summary. Existing homes are also covered by the Energy Performance of Buildings (England and Wales) Regulations 2012, which require an energy performance certificate before a property is marketed.

How we handle construction on Homebinding

Approved Documents Building Safety Regulator Scottish building standards RICS

Sources: the Ministry of Housing, Communities and Local Government and its Approved Documents; the Building Safety Regulator; Welsh Government building regulations guidance; the Scottish Government building standards division and its technical handbooks; the Department of Finance in Northern Ireland; Historic England, Cadw, Historic Environment Scotland and the Department for Communities; legislation.gov.uk; the Royal Institution of Chartered Surveyors; the Planning Portal.