No job too small: Anyone can create a sleek haven with Ann-Marie Powell's detailed plans

"So lately," says Rob, gazing into the middle distance, "I've been thinking that the problem is that perhaps it needs to have a sort of centrepiece. Like a giant rock." My neighbours and I are having a gin and tonic. There has been some discussion about whether gin and tonic is permitted under their strenuous pre-holiday dietary regime, but caution has been thrown to the wind. So here we are on the terrace, sipping our drinks, sitting in the sunshine, and everything is almost perfect. Almost.

The problem with the garden isn't totally obvious. To the uninformed eye, it's just an average London back garden with a small concrete patio, a big patch of lawn, and a jumbled bit at the end with plants, barbecue and shed. There's a clothes dryer, a sandpit and a number of small plastic vehicles. For some, it'd be a perfect vision of low-maintenance nondescriptness. But for Rob it's a field of broken dreams.

Small-garden owners do have it hard. You've taken out your huge mortgage and just about made it stretch to upgrade the kitchen and bathroom. But there's absolutely nothing left in the kitty for the exterior. Inside, your house is modern and lovely, yet the garden still bears all the visual clues of having been personally designed by Clarence, the previous owner, with all of his glorious and inimitable enthusiasm for bird baths, gnomes and dodgy home-made fencing. And it'll be 2020 before you can afford to do anything about it.

That's why Ann-Marie Powell's new book, Plans for Small Gardens (Pavilion, £16.99), is a bit of a godsend. There have been books about small gardens before, but this one is different: for 10 different garden types you get a detailed plan, a double-page construction brief, and a shopping list that goes all the way down to the number, size and type of screw you'll be needing to do it all yourself. "I suppose I'm doing myself out of a job," she chortles, "but really, it's almost like a cookbook for gardening. And it's also a record of how much work goes into a good garden, because I often think people have no idea."

Powell is no stranger to this sort of project: a Chelsea Gold Medal winner, she nonetheless spends most of the year working on rather smaller designs. In the book there's a slim, sleek urban garden with stone paving and tall bamboo, but also a titchy country garden with a wisteria pergola and a step big enough to sit the evening out on. She knows a dozen different ways to camouflage a petite shed, and she's clear on the merits of a dob of decking, a drip of irrigation and a teeny patch of expensive paving. "In a small garden, everything has to earn its keep. Even in the centre of a town the garden's square metreage can be huge compared with the house, so if you get it right, you expand the usable area for a family by loads."

Yet the modern house-buyer can be a demanding customer, and the book tackles many of the most pressing problems for small-garden owners: "My garden's on a slope", "I only ever go in the garden at night", "I mostly just want to look at it out of the window", "I don't want to have any plants", etc. As a record of Britain's horticultural commitment, it's a bit of a salutary lesson, as it shows what real people want from their real gardens: space to sit, relax, and not think about mowing the lawn.

I especially love the way Powell appreciates and adds value to the tiniest space. A house's side alley is treasured and made beautiful with paving and a miniature planting of Mind Your Own Business; an itty-bitty seating area is raised to James Bond levels of luxury.

"I'm most often asked for 'low maintenance' – it's so hackneyed. But when people think they don't want to maintain their garden, it's often because they've got an ugly garden they don't want to be in. When you put in a garden for them and they're delighted with it, and they find they like being out there, I can't tell you the kick I get out of it when you are turning people into gardeners."