Policy provides the net. Architecture acts as the fisher.

In 2026, World Habitat Day and World Architecture Day fall on the same date, 5 October. Both are held on the first Monday of October each year, and the International Union of Architects (UIA) created World Architecture Day in 1985 to run alongside the UN observance. This year, the two themes point the same way. UN-Habitat has chosen “Adequate Housing for All”. The UIA has chosen “Housing is a Human Right. Build It.” The former sets the public goal, while the latter calls on architects to help achieve it through design, research and advocacy.

Between a housing target and a finished home sit two sets of decisions. Planning and tax rules decide whether a scheme can pay for itself. Design decides how quickly, how efficiently and how well it can be built. This article looks at both, using three examples, two from England and one from Sweden.

The housing shortfall is large and the sums have to work

UN-Habitat estimates that about 2.8 billion people face some form of housing inadequacy, and close to 1.1 billion of them live in slums and informal settlements.

Bridging a gap of this magnitude demands private capital alongside public funding. Where land is expensive, a developer has less room to build lower-priced homes, and capital tends to follow the highest returns. Delivering more mid-market and affordable homes therefore needs progress on two fronts at once. Planning and tax rules must make schemes viable, and design must cut the time and cost of building them.

Planning and tax rules set the limits before design begins

Rules decide what can be built, how it is approved and what it costs before an architect finalises a drawing. Four tools show how this works.

Density allowances let more homes sit on the same plot. Measures such as floor area ratio or plot ratio change how much floor space a site can hold. This spreads the cost of land across more homes and can leave room for affordable housing within the same scheme.

Tax relief can lower building costs. In the UK, qualifying conversions of non-residential buildings into homes carry a reduced VAT rate of 5 per cent instead of the standard 20 per cent. The reduced rate covers the contractor’s labour and the materials the contractor supplies, but not professional fees such as an architect’s.

Prior approval routes offer a narrower process than a full planning application. A change of use can go ahead once the council has assessed a limited list of matters, which include transport, flooding, contamination, noise and light.

Developer contributions tie private schemes to public goals. In England, Section 106 agreements let councils require developers of homes for market sale or rent to include affordable homes on the same site. Those homes are then sold to registered providers.

Design decides how fast and how well homes get built

Once a scheme is allowed, design drives cost, speed and long-term performance. Three areas matter most.

Efficient floor plans make more of each floor usable. Compact cores, tidy routes for mechanical, electrical and plumbing (MEP) services and flexible structural grids all raise net internal area (NIA) within a fixed building footprint.

Factory-built methods can shorten building programmes. A 2019 McKinsey report found that modular projects, including 3D volumetric modules, had been completed 20 to 50 per cent faster than comparable on-site builds. The same report said construction cost savings of up to 20 per cent were possible but not guaranteed. It warned of cost increases of up to 10 per cent where labour savings were outweighed by logistics or materials costs.

Reusing existing buildings avoids part of the work of building new. Keeping a frame and foundations in place saves the materials and carbon already invested in them. The UIA names the reuse of existing building stock as one of the practical routes to more housing.

Class MA shows how a planning rule can open up reuse in England

Class MA is a permitted development right in England. In force since August 2021, it allows buildings in commercial, business and service use (Class E) to change to homes through prior approval, without a full planning application. The building must have been in Class E use for at least two years. Since 5 March 2024, there has been no 1,500 square metre limit and no requirement for the building to have been empty for three months. Councils can still remove the right in specific areas through Article 4 directions. Qualifying conversion work receives the reduced VAT rate described above.

Design is where many conversions succeed or fail. The homes must meet national space standards, and the council can assess matters such as light and noise through prior approval. Designers of former offices therefore have to show that older and often deep floors can provide good flats.

Official figures reported from the Ministry of Housing, Communities and Local Government show that change-of-use permitted development added 7,681 homes in England in 2024-25. That total covers all permitted development change-of-use routes, not Class MA alone. Within it, 5,154 homes came from former offices and 1,048 from commercial, business and service use. Office conversions delivered 17,751 homes in 2016-17 under the earlier rules, more than three times the 5,154 delivered in 2024-25.

London links affordable housing to a faster route through planning

The London Plan 2021 uses what it calls a threshold approach. A scheme that offers at least 35 per cent affordable housing, or 50 per cent on public land and certain industrial land, can follow a fast track route that avoids a detailed viability assessment at application stage. Fast track schemes face an early viability review if they do not reach substantial implementation within a set period.

For architects, this means the affordable share has to be planned in from the first sketch, because a scheme that reaches the threshold can use the quicker route.

Section 106 agreements delivered about 36 per cent of the affordable homes completed in England in 2024-25, down from 44 per cent in 2021-22. A draft replacement London Plan published in July 2026 proposes thresholds that vary by location band and type of land, so these rules may change once it is adopted.

Sweden shows what changing building rules can do

For more than a century, Sweden banned timber-framed buildings above two storeys for fire safety reasons. In 1994 the country moved to function-based building rules, which let builders choose how to meet fire safety requirements, and the ban ended. A Nordregio historical overview records that the Swedish firm Lindbäcks built multi-storey residential timber buildings from factory-made volumes that same year.

Swedish Wood, the industry body, says building with timber modules moves more than 80 per cent of the work indoors and that a five-storey building can be assembled in about 10 weeks once the foundation slab is cast. Volumetric units arrive almost entirely finished, with plumbing and electrical cables already in place.

These are industry figures, not independent measurements. The 1994 change was a general reform of how building rules are written, not a rule written for modular construction, and Nordregio notes that factory timber building already existed before it.

Rules and design work best together

Planning and tax rules open the door. Design decides what comes through it. Policy provides the net. Architecture acts as the fisher. Legislation sets the legal frameworks, planning incentives and funding schemes, and design uses layout, materials and construction methods to turn a site into homes. A net without a fisher remains empty, and a fisher without a net catches nothing.

The examples above show that neither is enough alone, and that results can shift. Office conversions in England are well below their 2016-17 peak, and the Section 106 share of affordable homes has fallen since 2021-22.

As World Habitat Day and World Architecture Day remind us, a housing target becomes a built home only when the rules that make a scheme viable and the design that makes it buildable move together.