Property: Ever tried conversion therapy?

Terry Akif was pleased as punch when she bought a small chalet- style house in a desirable corner of suburban Kent in February. Not only was it "frozen in the 1930s" with all its original features, but the garage was perfect for the major plans Terry had in mind. Her mother is disabled and she wanted to provide her with a ground-floor "granny annexe".

The garage seemed ideal to convert to a self-contained flat with its own entrance. "It had to have its own door," said Terry, "or the arrangement would never work." A small passageway between the house and the garage was to be enclosed and become the new front door and hallway.

Plans were drawn up and taken to the council planners to see if the proposals were viable. Terry was totally unprepared for the outcome. "We were told that it was against planning regulations for one property to have two front doors. "I was gutted," said Terry, "and so was my mother.

"My husband is a painter and decorator and was already having to give up the garage as his storage place. He'd have to negotiate me, the children and my mother as he traipsed through the house with his tools every morning." However, Terry's mother is staying put and the Akifs have reverted to a more traditional loft extension.

Janine Maclachlan was looking for a family house a few years ago with an extra room at ground level to accommodate her elderly mother-in-law who had emphysema. She came across a 1947 semi with an integral garage converted into a large room - an unusual find in a very Victorian part of south London. "The house was a smidgin smaller than we'd hoped for, but the extra room overlooked a village-type green with a park beyond."

The room itself was devoid of any features and was 20ft long by 9ft wide, making it tricky for positioning furniture. Janine repainted the dark red walls white and added a small en suite bathroom at the rear for her mother-in-law.

However, since the death of her mother-in-law, Janine has changed the use of the room to a study and guest room. "It means we can get the computer out of the living room, and when guests stay they can potter around without disturbing the household and vice versa. It's an alternative to a loft conversion."

Peter Wood, sales director at Acorn estate agents in Bromley, Kent, has clients on his books specifically looking for properties spacious enough to house grannies, au pairs and nannies. "An extended home in a buoyant market attracts a good price," he says.

It's not only executive-style homes that are popular: "People are settling for terraced properties converted to make four or five bedrooms that they previously wouldn't have gone for, because they can't afford properties in the next price bracket."

In a sought-after area, a loft extension can enhance the value over and above the cost of the work. Buyers are looking for an easy option. If the conversion is of a good standard, they'd prefer to pay a little bit extra to buy a house with the work already carried out rather than suffer weeks of building disruption themselves.

Mr Wood underlines the attraction of a truly self-contained annexe, with its own front door, or a property that lends itself to sectioning off. Acorn is currently selling a six-bedroom house in Queen's Road, Beckenham, Kent, for pounds 285,000. "It could easily be annexed to create a separate flat," says Mr Wood.

Jill Bennett spent more than pounds 30,000 on a loft conversion to provide a "hotel suite" for the live-in nanny who looks after her four children. "We already have five bedrooms but it wasn't fair to expect anyone to start sharing." As they had considerable equity in the west London house they didn't want to skimp on the plans. "The work went on for months longer than the builder said it would," says Jill. "He'd disappear for a couple of days each week once the main construction work was done, but we're really pleased with the results."

When Steve Cohen decided to increase his working hours as a social work manager, he needed to employ an au pair to take over the school run as well as the housework that he shares with his wife, Tracy, a primary school teacher. However, their three-bedroom house, in Essex, couldn't accommodate an extra person comfortably. "We looked at moving, but we like the location and our garden," says Steve. "We'd have to spend at least pounds 30,000 to move to a four-bed house with the same advantages." Expanding into their loft to make a large bedroom and shower room seemed a good compromise.

The Cohens were given quotes ranging from pounds 14,500 to pounds 19,000 from national and local companies selected from the Yellow Pages. "They all came up with similar drawings," says Steve, "but were variable on the information they could give me. Some companies mentioned fire regulations while others didn't."

After several weeks of sitting through the sales patter, Steve and Tracy felt they could only trust one of the companies to do the job. But, like all good craftsmen, he was busy with other work until December, and the Cohens needed their bedroom by the end of the summer, so frustratingly they had to start looking for another company.

"We've found someone else who can start the work shortly," says Steve, "and I've had the money through from the building society. With any luck we'll be enjoying the view from our dormer in a few months' time. Now it's just a question of finding a suitable au pair."

Acorn is on 0181-663 3322.