How to build the perfect extension and what to avoid
Open-plan living spaces, natural light and a greater connection to nature are the most common motivations for adding an extension to a property today. Yet these were of little concern to the Victorian architects and builders who were responsible for designing much of the terraced housing that exists in our towns and cities. The country’s housing stock more than doubled in the period between 1851 and 1911; during that time—and for decades after—the main aim of house builders was to provide shelter for the occupants from the elements.
Lifestyles and expectations have changed, of course. With complex family structures, long working hours and home-working arrangements, floorplans have had to play catch up. Space costs more and yet is more desirable than ever; the result is that every room has to work harder. That leaves many owners of both historic and newer housing stock considering the often-overwhelming task of undertaking an extension, navigating pithy planning permissions and the logistics of finding the right professionals and tradesmen to carry out the work.
Anyone who has undertaken such a project will know the process isn’t without its headaches but don’t automatically assume things will be impossible - even if the property is listed. “The best way to preserve these houses is to ensure their ongoing use and enjoyment - planners and conservation officers know this to be true,” says architect Darren Price of ADAM Architecture. “If the layout is no longer fit for purpose because it was designed for a time when we lived differently, then there’s a case to make changes provided that any perceived harm is outweighed by the benefit.”
High inflation, the pandemic and the war in Ukraine sent the cost of building materials soaring. Prices are now stabilising, but labour shortages are still a problem. Figures from the ONS show that there are now 244,000 fewer workers in the construction sector compared to three years ago, as a result of some returning to the EU or taking early retirement.
It’s having an impact on projects. In 2023, the number of planning consents given for home developments in England totalled 160,000, a 30 per cent decrease from a pandemic peak in 2021. “The higher the house prices in an area, the more extending makes financial sense, meaning more value can also be unlocked in London and the South compared with the Midlands and the North,” says Frances McDonald, director of research at Savills. Here are some striking examples of how to get it right.
Two-storey extension
Old Schoolhouse, Somerset
A three-bedroom, three-bathroom, two-storey extension of 1,450 sq ft/135 sq m by Bindloss Dawes Architects
It was during a weekend staying with friends in Somerset that Joa Studholme, colour curator for the Dorset-based paint brand Farrow & Ball, and her husband made the snap decision to buy a country house in a nearby hamlet. Then based in London, the property in question was a 19th-century Grade II-listed stone-built former schoolhouse set on the side of a steep valley, overlooking a church and among flocks of grazing sheep. So far, so idyllic.
The original school room had been converted into a kitchen and living area, meaning it benefitted from lofty ceilings and lots of natural light (albeit from raised windows, as was the tendency among Victorian school architects who thought views were too distracting for young minds). Part of her role for Farrow & Ball is developing their range of colours and so, in no time at all, she set to work using the house as a taste tester for new colours. The company’s “School House White” is one of the results.
Having lived in the house for a time, however, it became clear that the flow didn’t work well. All three bedrooms were located in a two-storey “tower” extension that was added on in the 1970s. “They were all small, dark and gloomy and there was a lot of corridor space wasted,” she explains. “Not only that, but it was damp and particularly unpleasant during the winter.”
Through a local friend, the couple were introduced to architect George Dawes of Bindloss Dawes, who had recently relocated to nearby Bruton from London. The practice is known for its sensitivity in handling historic buildings. “It started with a small request about how to remedy the main bedroom but quickly became evident that the only solution was to knock down the 70s extension and start again. It had been built to match the original house, but the fa?ade and roofline were deeply unsympathetic - plus we discovered asbestos.”
When a building is listed, the entire property is protected both inside and out, including any structures added to the building such as extensions. Heritage assessments are often put together when approaching planners with a sensitive building; they point out what is important historically and what is not. “Getting rid of an extension does seem a bit drastic with a listed building, but we demonstrated to the planners why it made sense.”
While planning guidelines for unlisted properties are managed by each local authority, Historic England encourages designs to be distinct from the original so that the addition is obvious to the naked eye. “It’s about allowing the original building to be easily discernible from the new—most planners dislike anything that confuses the legibility of the original building,” says Dawes.
The design he came up with for Studholme’s house was to make references to the original building but also make it “unapologetically contemporary”. The new, 1,450 sq ft two-storey extension is partly sunk to align with the low eaves of the original building, ensuring the new structure is—to use architect parlance—subservient to the original, which normally pleases planners.
As the original building is made from locally quarried honey-coloured Hadspen stone, the pressure was on to find a cladding material that would respond well.
Narrow-width timber boards arranged vertically on the top floor and horizontally below was the answer. They are made of locally sourced sweet chestnut and match the bespoke pivot windows. “It all will weather beautifully to a silver,” adds Studholme. The extension is connected by a patinated galvanised steel-framed, glazed sunroom with a flat roof.
The new addition has 360-degree views up, down and around the valley and is made up of a main bedroom, dressing room and bathroom on the top floor with two bedrooms and bathrooms below. She then set to work with finding colours to complement the new spaces. “One of the bedrooms looks directly up the valley and I’ve painted it in Sap Green [by Farrow & Ball], so it feels like you’re in among the hills. Just two feet from the window are about 20 cows checking you’re cleaning your teeth correctly each morning.”
As the children have moved out, the bold colours, particularly in the bathroom, are there to amuse and something of a treat for those who come to stay. In her bedroom, she’s used a new earthy hue inspired by the colour of porridge, Stirabout. “It’s beautiful; it glows.”
The Studholmes are delighted with the results, which won a RIBA award for architecture in the Southwest. “We haven’t gained any extra rooms, but what we’ve gained is light. George was so clever. It’s not a showy-offy extension; it’s understated. And amazingly, we never had one issue with planning.”
Budget
￡3,500 per m sq for a similar size of project, depending on location and materials used
Ground floor extension
Cast Corbel House, Norwich, Norfolk
Reorganisation of ground floor measuring 121 sq m/1,300 sq ft including adding a kitchen/living room extension of 22 sq m/237 sq ft by Grafted
Architect Lemma Redda and project manager Nicole Fassihi established the design-and-build studio Grafted in 2022 with a focus on ambitious architecture and crafted design. As soon as they were up and running, the couple were asked by the owners of a five-bedroom, detached Victorian property in Norwich to reorganise the congested and inefficient layout of the ground floor. The aim was to make working from home more comfortable and create more space for hosting visiting family and friends.
The clients had been living in the house for years, but it wasn’t possible to sit by the windows on the ground floor without extra jumpers and blankets in the cooler months. The reason was a poor-quality extension had been added in the 1990s; it was clear that it had to be removed and replaced. “These extensions were built in an era when cheap energy was abundant,” explains Redda. “People just turned up the heating to cope and the thermal performance of a house wasn’t taken into consideration. Now, it’s built into the design. Without it, you can’t introduce green energy solutions such as air source heat pumps.”
Most clients instinctively want to add as much space as possible, but there’s no point in adding it for its own sake. “Regardless of how deep pockets are, money doesn’t go as far as it has done in the past,” adds Fassihi. “Here, we persuaded the clients that adding less space meant the quality could be maximised. Our role was to make sure every area had a function.”
Even before pens hit the drawing board, orientation and solar gain are dominant topics of conversation. “My old boss always said we need to prepare houses for the climate here being similar to that of Barcelona by 2050,” says Redda. “We also consider how the light will move throughout the day to designate the right area for a breakfast table or a reading chair. That’s how architects add value.”
The new facade has an eye-catching columnal pattern of piers celebrating the heritage details of the red-brick house, which stands in a “mannered” conservation area of the cathedral city. Its location on a street corner makes it highly visible. “We wanted to create a high-quality and robust extension that tied into the existing house and was respectful to its original design,” explains Fassihi.
Wrapping around the top of the extension are expressive, hand-made concrete corbels pigmented red using iron oxide and poured into inverted moulds. Using a single colour palette (even the window frames are coated red rather than the ubiquitous grey found in many other modern extensions) means there is less overall distraction and the eye is drawn to the way the light plays across the fa?ade.
Two large rooflights above internal beams allow light to fall down into the new room while picture windows frame the garden. A central structural column splits the extension into cooking and dining zones, with bespoke cabinetry in oak – a painted kitchen was feared to date quickly. “Timeless is a much-overused phrase in the design world,” says Redda. “I think it means listening to the building rather than stamping authority, working with heritage rather than fighting against it. The result feels more honest.”
Budget
￡3,500 per sq m inclusive of kitchen and fitted joinery, depending on location and materials
Rear extension
Copper House, Nunhead, south-east London
Contemporary, copper-clad rear extension of about 10 sq m/108 sq ft by Studio Webster Dale
The owners of this five-bedroom terraced property in Nunhead were growing increasingly dissatisfied with the gloomy and cramped kitchen. In its former layout, the only access to the garden was via a poor-quality lean-to extension housing the utility room. Like many terraced houses, the space down the side of the house was unused. They approached architect Stephanie Dale of Studio Webster Dale for help.
An obvious solution was to remove the existing extension, fill in the side return and create an open-plan kitchen and living room. So far, it’s an approach that has been copied on terraced streets up and down the country. Fortunately for Dale, her clients requested something with a bit of flair. The answer was a visually arresting structure clad in copper.
A fixed rooflight runs the length of the side return. Slimline sliding doors were deeply recessed with cedar-clad reveals. This serves two functions: it shades the end elevation from overheating while also allowing uninterrupted views to the garden. “Even in the passage of a couple of years, with concerns about rising temperatures, using shade-giving elements such as fins on the roof light and having the ability to open them for ventilation is now more important.”
The kitchen centres around the imposing new polished concrete island, matching the flooring that runs out to the patio beyond and is reflected in the garden seating and barbecue. This solidity is offset with delicate light fittings and playful flashes of copper on the backsplash. Bespoke joinery was made from natural birch plywood, a theme that continues throughout the house.
To save money, some will avoid going to the expense of hiring an architect. The risk is the results can be very generic. “Whatever way you approach building an extension, it’s going to cost a lot of money. I firmly believe that spaces should be joyful,” says Dale. “With so many people working from home, being there should make you smile.”
Elements of the garden, such as the banana palm, reflect the Brazilian influence of one of the owners, an illustrator. “Whenever we design extensions, the garden—even if it’s only a small patio—needs to be included. Otherwise, what’s the point of spending all the money to look out at nothing?”
Budget
Between ￡150,000 to ￡180,000 for a similar design, depending on location and materials