Have you ever fancied redesigning your hallway? Do you feel your house could benefit from an extra window or door? Perhaps you’re fed up with the botched extension of a previous owner? Most houses could benefit from a little improvement — but how many householders would consider seeking out an architect to give their home a makeover? The annual Architect in the House scheme, run by the Royal Institute of British Architects (Riba), aims to introduce its members to a wider audience. In return for a minimum donation of £20, which goes to the charity Shelter, householders can receive up to an hour’s consultation with an architect with no obligation to act on their advice or plans.

Since its launch in 1997, the initiative has given thousands of people the chance to explore design ideas. Last year, 6,500 people were visited by architects as part of the scheme. Riba’s research suggests a third of consultations turn into jobs.

Lesley Delacourt and husband Stuart Pocock decided to take part to see what suggestions were on offer for their three-bedroom apartment in Bloomsbury, central London, which they bought three years ago. “Originally I wanted advice about what to do with our two grotty bathrooms,” explains Delacourt. The property didn’t have a garden, but that wasn’t even on the agenda. “Architect Paul Archer turned up but it was only as he was about to go that I said, ‘It’s too crazy, but my fantasy is to have a garden’,” she says. Archer couldn’t resist the challenge, and today the leasehold flat boasts an oak-clad roof terrace, designed in such a way that it floods their home with natural light. The 14ft-square terrace, carved out of the roof, cost £40,000 to build.

“The apartment had flat ceilings with a hatch leading into the roof space,” Delacourt explains. “Paul has given us a staircase to the terrace, which is cut into the old sloping roof, with a glass door and window.”

The terrace is a suntrap during the day, and at night thousands of tiny light bulbs placed behind the oak cladding make it glow in the dark. “It’s great,” says Delacourt. “It was worth every penny.”

So why do most architects’ ideas fail to catch on? One reason is a clash of vision and expectation of costs. Charlotte Black, who owns a three-bedroom south London house that is valued at £485,000, was initially delighted with the offer of an hour of an architect’s time for £20 as she wanted help obtaining planning permission for a side kitchen.

“A very personable architect turned up, eager to make his mark in a house left untouched since the war,” she said. “But then he announced that to expand the kitchen to the party wall would cost £110,000.

“Later, another architect, to whom I paid the more usual consultation fee of £100, said: ‘I don’t think the work will cost more than £30,000’.”

Difficulties over costings also beset Dave and Val Scull, whose former farmhouse on the edge of Dartmoor was completely remodelled as a result of the Architect in the House scheme. Although they are delighted with the result, the couple — who retired to Devon four years ago — caution that such projects are generally more expensive than people expect. “Our original budget was £60,000 to £100,000, but the cost has been nearer three times that,” says Dave.

“Also, we were told the work would take six months and it’s taken nearly 18 months to complete.”

The Sculls hired the services of Devon-based architect Stephen Emanuel after meeting him through the scheme six months after moving into the property, which cost the couple more than £300,000.

“The house had an attack of the 1970s; it was last renovated back then,” Dave explains. “We wanted to bring back the character of the old house but have a modern interior.”

Emanuel breathed new life into the property, which he describes as a “series of rooms that didn’t hang together”, by moving the oak staircase, reducing the size of the “cavernous” hallway by converting some of the space into a study and adding a conservatory.

So how much can you expect to pay? An architect’s fees normally amount to 10%-14% of the total cost of a building project, “but for projects under £20,000, they tend to charge an hourly rate,” says Melanie Mayfield of Riba. These are in the range of £55-£95 an hour, although a senior partner would usually charge £95-£180.

According to Jane and Nigel Wright, who hired architect Mark Westcott to replace a “grotty” conservatory at their home in Islington, north London, the financial outlay was worth it. They now have a contemporary garden room attached to their five-storey Georgian villa. Such an extension can cost £50,000 to £150,000. The Wrights paid in the middle of that range, but believe that trying to save money by relying on a builder to do an architect’s job is foolish. “Mark actually found ways to save us money,” said Nigel.

Westcott says: “It’s surprising how often I end up demonstrating how a solution might be achieved by simpler moves.”

There have been occasions when, instead of commissioning him to do the work, people have taken Westcott’s ideas and handed them to a builder, but he is philosophical: “They haven’t got the best they could have, but at least it opens people’s eyes to what architects can do.”

The Riba Architect in the House scheme runs during June 20-29 as part of Architecture Week; www.architectinthehouse.com

Do's and don'ts

• Do be specific: tell the architect your dreams for the house. If you have a little eccentric wish, mention it

• Do open your mind to the possibilities the architect will create for you

• Don’t expect the answer to come at once; you may be offered three or four solutions

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