Mandic and her husband bought the two-bedroom flat in Battersea for £220,000 in 2002 and spent £130,000 removing walls and creating a through living, dining and kitchen space. They then set to work on the loft, lowering the floor and raising the roof, installing a long metal beam so there’s no need for supporting posts, and adding dormer windows. The work cost £55,000, and within a year the flat was valued at £500,000.

Richard and Beverley Beaumont, of Bride Farm near Sandwich in Kent, have added three attic rooms to their home since they bought it seven years ago. One is in the loft of the original building, one is not strictly a loft conversion at all but was purpose-built as part of an extension to the early-18th-century cottage, and one is in a sheep shed in the grounds, which they also converted.

The original attic room was converted with very little cash. The Beaumonts bought Bride Farm for £127,500 and have spent £120,000 updating it, but just £2,000 of that was spent on the first loft conversion. “We put in a staircase, which is like a naval ladder. We converted it for our youngest son to live in and we put in new partitions, so there is an area for a bed, a lounge area with restricted headroom and a storage area,” Richard says. They also added Velux windows and wooden floors. “Although that was a mistake. When anybody walked up there, it reverberated round the house and we had to carpet it.”

Another attic room came almost by accident, he says. “The extension was originally going to be single-storey, but when we were building it we realised that we only needed another four feet and we could turn the loft space into another room, so I ran round to the council to ask for permission.”

Now the family is moving to the other side of Canterbury to be nearer work, Cluttons is selling the house for £499,000. The agent says the conversion of the original attic added up to £25,000 to the price.

However, the Beaumonts’ third attic room serves as a caution to all home improvers. They converted the sheep shed into a single dwelling for another son, with a mezzanine floor in the roof space. It has now taken their home into a higher price bracket. “It’s put us in a different dimension,” says Richard, who is aware they’ve shrunk their pool of potential buyers. “We’re waiting for somebody who needs a house with a separate dwelling.”

Cluttons, 01227 457 441, www.cluttons.com; Gordana Mandic, 020 7352 1092

Next week: bathrooms

TOP TIPS

WHAT GROWS IN THE GARDEN?

An expensive garden renovation is one of the worst investments you can make: a £2,000 project will add just £600 to the price of the property, according to a survey commissioned by the estate agency Knight Frank. It’s true that houses without gardens are hard to sell, but all that’s needed is to make your patch presentable. Just add some decking, for instance, at a cost of £3,000-£10,000, and you’ll get 70% of your money back.

Creating new outside space can add 10% to the price of a flat. Even roof-terrace potential will add thousands.

If you happen to have a spare half acre, converting it into a tennis court can pay off.

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