April 29 2018, 12:01am, The Sunday Times
The ultimate guide to building your dream extension
Moving up the ladder is harder than ever — so more of us are choosing to transform our existing space. In part one of our ultimate home-improvement guide, Home explains how to make sure your ground-floor extension lives up to the dream
We’re no longer a nation of movers, but one of improvers. Every month, almost 40,000 property owners across Britain are applying for planning consent to improve their homes — up 3% over the past year, and the highest figure since the financial crisis hit a decade ago.
Like Sarah Tomlin, 46, a science writer who shares her 1930s semi in Queen’s Park, northwest London, with her three daughters, we all dream of “a big garden and lots of light”. Now, after a £270,000 makeover and a full-width rear extension with metal-framed doors to the 100ft garden, their 30ft-wide living space brims with brightness even on a grey day.
Does extending pay?
Sarah can keep an eye on Miya, 9, Sula, 8, and Sadie, 6, as they rollerskate around her larch and concrete kitchen island — offset by Farrow & Ball Black Blue tongue-and-groove cabinets — and pin their art to the acoustic felt that lines the play corner. “This was a generous house, but opening it out has transformed our higgledy-piggledy downstairs space,” Sarah says of the design by the Vawdrey House (thevawdreyhouse.com).
“Homeowners in London are far more likely than those anywhere else in Britain to improve rather than move — around twice the national average,” says Michael Dall, lead economist at the data analyst Barbour ABI, which has provided its latest research on building trends to The Sunday Times. Even so, home improvement across the capital slid by 3% in 2017, compared with the average across the previous two years. The basement boom in the city’s richest boroughs is over: Kensington and Chelsea — “The spiritual home of the iceberg house,” as Dall calls it — had topped the improvers table since 2013, but last year it fell the fastest (-21%).
The skips and scaffolding are moving to “less conspicuously wealthy areas” in the commuter belt, such as the Mole Valley, around Dorking, Surrey. St Albans, Hertfordshire, had the highest concentration of extension applications last year: one for every 35 homes, compared with one per 120 countrywide. Even so, growth in home improvement has slowed in the southeast and east. Cambridge, which in the space of two years had leapt from 71st to third place in the extensions league table, is now down to sixth — the “epitome of an ‘improve not move’ location”, according to Dall. “A rapid surge in prices led to sales in the city falling back sharply, but a rise in home improvement.”
The new hotspot is the northwest. The region saw the fastest growth in applications last year (9%), as younger families in parts of Greater Manchester make the most of rising incomes and house prices, and wealthy fiftysomethings enlarge their manors in the picturesque Ribble Valley, Lancashire. The West Midlands, too, had solid growth — Herefordshire shone brightest in all of Britain, with a 47% rise in applications.
So, where do you start? In part one of our guide for the renovation nation, Home talks to experts and expanders about the dos and don’ts of ground-floor extensions — the most popular project, making up 40% of home-improvement applications.
Ask the big questions first
There are two types of extenders: those who “just want a cheap box” to make money from their house within a certain time frame, and the “blue-sky thinkers” who have been inspired to create a space that will bring together their growing family. First, work out what is at the root of your desire to extend, she says. A loft will likely add more value for the former camp, while a side return might suit the latter.
For Jeni and Jim Davis, spending £120,000 to extend to the rear and subdivide one of their four bedrooms meant they didn’t have to sell their 1930s semi in Northampton to get the perfect home for them and their children, Sophie, 10, and George-Hamish, 7. “Our house ticked so many boxes — we couldn’t get what we had plus the extra bedroom without spending £300,000-£400,000,” says Jeni, 41, a personal assistant. They kept two cosy receptions to limit TV noise, but knocked down the “horrible old conservatory” to create an L-shaped space with an inky Shaker-style kitchen by the Main Company (maincompany.com), a dining area and a garden room with two sets of bifold doors.
The more expensive the postcode, the more profitable an extension tends to be; conversely, build costs usually see you make a loss in the cheapest areas. A basic single-storey rear extension, three metres deep and five metres wide — the average width of a Victorian terrace — starts at about £48,000 in London, £42,000 in the southeast and £36,000 countrywide.
Three-quarters of applications for extensions are in boroughs with average house prices above £175,000, according to the Barbour ABI report. At the bottom of the scale, Blackpool, where the average home costs £105,743, had only one application for every 250 homes — the lowest rate in Britain. To see if extending will add value to your home, use the calculator on our digital editions.
Use permitted development wisely
If you have a set deadline or want to finish building before, say, your baby is born, do it under permitted development (PD) rights. This is easier than applying for planning permission, which — in an ideal scenario — takes about a year from paperwork to paintwork, but it is still wise to get a lawful development certificate from the council. PD allows single-storey rear extensions up to three metres deep on terraces and semis (but not flats), or four metres on detached houses, even in conservation areas (planningportal.co.uk).
Under temporary PD rights, you can double these measurements if you first notify your local planning department, which will ask your neighbours whether they object. To qualify, you’ll have to start now — your project must be complete when the rights expire next May.
To add ceiling height, dig down one or two steps below the existing floor level. Or use a pitched roof: the rights restrict this to three metres near boundaries, but allow four metres closer to the centre. In Peckham, southeast London, Juliet and John Baptiste-Kelly achieved this with a sawtooth roof on a larch-clad three-metre extension to their modernist ex-council house. Designed within PD rights by Nimtim Architects, it was shortlisted for New London Architecture’s Don’t Move, Improve! Awards this year.
“It has transformed our family life,” says Juliet, 41, a food stylist. “I now cook and work within sight and earshot of Art, 9, and Agnes, 8, if they’re watching TV, doing homework at the table or playing in the garden. We don’t have to queue for the bathroom now we have a beautiful wetroom downstairs, and the former kitchen in the front of the house is a multifunctional snug/office/guest room that works as a breakout space.”
Yet you shouldn’t be blinded by PD. “I meet so many people who design their building based on what they think they won’t need permission for, when actually they should design the space they need,” says Jason Orme, property expert for the Southern Homebuilding & Renovating Show (June 30 and July 1, Sandown Park, Surrey; homebuildingshow.co.uk/surrey). “Start with what you want.”
Get the design right
“Think about the ratio of inside space to outside space,” says Jo Dyson, of Mae House Design (maehousedesign.com). “If you extend to the maximum allowed amount, you could end up with a large family home, but a garden not big enough for a family.” Extending will also change the way you use the rest of the ground floor. Repurpose other living spaces “or you can end up with a dead room, only used at Christmas”, says Jennifer Hamilton, of the Vawdrey House.
Don’t just plan your living space to connect to the garden on summer days, Orme adds: “For six months of the year, it’s pretty cold, dark and gloomy.” At night, we then crave “a cosy, warm space around the fire. If possible, have both a day and a night option for living.”
In Hampstead, north London, Diane and Phil Turner have added a cutting-edge £250,000 extension, made almost entirely of glass, to the grade II listed Victorian villa they share with their daughters, Leah, 17, and Sofia, 14. “The house has lovely proportions, but the kitchen was always small in relation,” says Diane, 48, a translator. Finkernagel Ross architects designed “a shell of glass so you still see the architectural merit of the house”.
Glazed sliding doors on two sides bring the outside into the new kitchen and dining area, which is shaded from the sun and overlooking neighbours by a crisp Calacatta marble canopy. The dark old kitchen, meanwhile, has become a timber-panelled anteroom where they can read by the fire. The same polished micro concrete flooring extends through both spaces, all the way out to the terrace, tying it all together (finkernagelross.com).
It’s “almost impossible” to perfectly mimic a period house with a period-style extension, Orme says. You’ll have to find not only original bricks to match, but everything down to the mortar colour, the slate and the cast-iron pipework, materials that have been replaced over the past 50 years. “I am of a view, which is shared by most conservation officers, that if you have an old house that’s full of character, you can enhance that by doing a very modern extension. It’s honest and transparent.”
Bring light to the core
The most common mistake with rear extensions, according to the architectural designer Hugo Tugman (tugman.co.uk), is to leave rooms that were previously at the back of the house “gloomy and landlocked”. To retain daylight penetration into what will now be the middle of your house, the openings for doors, windows and points where you have knocked should be as high as possible. “Builders will often make their own lives easier by installing beams or lintels below the ceiling height,” Tugman says, but these low “downstands” block daylight. “While it will cost a bit more to have your beams set within the depth of the floor or roof, it is generally worth it.”
Locate roof lights as far back as possible, for example with a slim strip of horizontal glazing where the house meets the extension. Build Team, a London firm that specialises in side returns, often fits a vertical “inflected skylight” to the original rear wall directly above this point (buildteam.com).
Velux windows start at £286, but an all-glass system — such as the £20,000 glazed box used in a Hût Architecture design for a Victorian terrace in Mile End, east London (hutarchitecture.com) — can be worth it if you plan to live in the house for years to come. Harder to clean (you can build a parapet nest to walk on), they are best suited to areas without trees and facing away from the sun.
Spend on the structure
“Max out on your construction cost and save on the fittings. It will pay dividends,” says Resi’s Alex Depledge. “People cheap out on the box and fill it with expensive stuff — it never looks right.” In the Balham flat where she lives with her husband, John, 36, and daughter, Harper, 3, she spent £16,000 on aluminium-framed glass roof panels — £8,000 more than Velux skylights would have cost — but clawed back the cost by fitting an Ikea kitchen rather than a specialist firm’s equivalent.
Don’t be afraid of structural work, which is often no more than 10% of the total budget. Adding steel beams typically comes to £2,000-£4,000 per opening. To keep costs down, stick to standard sizes for doors, windows, staircases and even ceiling heights — at 2.4 metres, the builders won’t have to cut the plasterboard, says Michael Holmes, property expert at the Southern Homebuilding & Renovating Show.
“A large rear opening is the current trend, but isn’t always the best way to go,” says Claire Holton, of Bradley Van Der Straeten architects (b-vds.co.uk). Last year she added a large kitchen extension to a two-storey Victorian terrace in Stoke Newington, north London, for newly married Sophia Spring and Ed Macdonald on a modest £80,000 budget. A glazed return roof and two sets of french doors let in natural light for Sophia, a portrait photographer, but they used lintels instead of steel. “This kept disruption to a minimum and saved on bespoke glazing and lead times,” Holton says.
French doors are the cheapest type, from about £1,500 a set. Bifolds cost about £900 a metre, but a small courtyard may not have space to stack them, and they can be harder to use. Sliding doors, from £5,000 per four-metre opening, are now available with extremely thin aluminium or timber frames for uninterrupted views. Industrial steel-framed doors are on trend and, like french doors, give you the option of having a window open. But they tend to be the most expensive. At Clement Windows, which specialises in custom-made steel glazing, prices start at £1,200 a square metre, including installation (clementwindows.co.uk).
“Another question to ask is, ‘What am I looking at?’” Jennifer Hamilton says. “Perhaps uninterrupted views are secondary to atmosphere if you have only seven metres of London garden to look at, not the Welsh mountains.”