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Here's how to turn your box room into something useful...

When it comes to the smallest bedroom, we're really keen on thinking outside the box. In the last two years 8.8 million British box rooms have been given a new lease of life by homeowners keen to maximise every last millimetre of space, according to research by property portal Zoopla.

'A box room is probably one of the most important spaces in your home and it's not one most people have the luxury just to keep just boxes in,' says Dulux Creative Director, Marianne Shillingford. 'Our box rooms are now our offices, studios and places to retreat to for some much longed-for peace and relaxation, so you need to maximise the potential of the space.'

Of course, one of the easiest ways to do it is with colour. 'Use receding colours like pale blues and greens which will reconnect the room with the sky and nature and add a breezy calming atmosphere. Try colours like Clear Skies and Silver Fern from the Dulux Heritage range,' Marianne suggests. 'You can also split colours with a horizon line to add more interest and a greater sense of depth. Try painting the ceiling and top third of the room in a classic shade like Light French Grey and team it on the bottom two thirds and skirting board with slightly deeper Lavender Grey.'

When it comes to box rooms, the most popular transformation is turning it into a home office (five million, per Zoopla's research), but there are lots of other ways you can box clever – here's our top 10 favourites.

When a small space becomes a functional area and is meant to fulfil multiple functions – keyboard work, reading, Zoom calls and thinking – it's easy for it to feel overcrowded. Well-considered lighting can not only help differentiate between different zones but can create the illusion of more space when proportions are limited.

'With some clever design tricks, you can use your lighting to distribute more light around your space and make it feel much larger than it is,' says Michael Meiser, planning expert at lighting specialists Lumilum. 'Use mirrors or shiny surfaces to help reflect light, too. Place mirrors across from lights or at a 90-degree angle for the best results. LED lights are especially effective to create the illusion of space because they offer a more direct distribution of lights, rather than diffusing it.'

You want your guests to feel as if they are staying over in a boutique hotel. One of the best tricks to pull in a box room is to play with perspective. Bring in an oversized pendant light fitting which will bring immediate focus to the ceiling and take the eye upwards. Deeper jewel shades of paint emit a luxurious opulent feel.

If budget allows (from £200 to £2,300 depending on size, plus fitting, says specialist company Bespoke Frameless Glass), replacing the window with a Juliette balcony won't usually require planning permission but can be installed under easier-to-obtain permitted development rules.

Rich Morgan, head of design at architectural practice Resi, recommends this and says it will really open up a limited space. 'The floor to ceiling glazing of a Juliet balcony not only provides fantastic views but also draws the eye out past the space, creating the illusion of a much bigger bedroom.'

The secret to success when creating a walk-in wardrobe in a box room is getting the storage configurations spot on, says Fabiana Scavolini, CEO of furniture and kitchen company, Scavolini.

Her first tip is to tailor the hanging space. 'Hanging space is the backbone of a walk-in wardrobe,' she says. 'Start by assessing what clothes and accessories you own so you can work out what space you need. For those of you with a penchant for suits, I suggest double-height hanging, with shirts at eye level and trousers below.'

She also likes slide-out racks for footwear, designed with a divider so two tiers of shoes can be viewed at the same time. And she would always add a laundry hamper: 'It may not be high on your list of priorities, but it's a really practical addition to a walk-in wardrobe.'

Drawers should not be underestimated, she adds, including smaller ones for storing jewellery and other delicate items.

And finally, always go for glass: 'Store your clothes behind glass doors so you can see the contents of your cupboards at a glance. Glass will also create a sense of spaciousness, which can be a real bonus in a smaller space.'

The obvious use for a box room in a family home is a nursery. You're aiming to create a peaceful haven for your infant – and you – so consider the colour scheme first and foremost.

'Soft, dreamy colours that help you and your baby feel relaxed are perfect for a nursery,” says Marianne Shillingford, creative director at Dulux. 'Use warm organic neutrals and greys like Gentle Fawn, Egyptian Cotton and Polished Pebble for the predominant background colours, then make it more personal by adding colour to a feature like the door and skirting boards or a band around the room. Try whispered chalky pastels like Blush Pink, Mineral Mist and Tranquil Dawn.'

For furniture, white still tops the popularity list, followed by gender-neutral grey and pale natural woods, adds Marianne.

The key here is flexibility. Turning a box room into a child's room-cum-playroom means multipurpose furniture which can easily be adapted depending on the time of day or night. Platform beds with storage underneath and truckle beds, where storage can be pulled out, are invaluable space-savers.

A mural adds a personal and creative touch, masking the limited proportions of a typical box room. Celebrities including cleaning whizz Mrs Hinch – who created a llama theme for her daughter Ronnie's room – and Stacey Solomon, who went all out to create a stunning pink haven for baby Rose's boudoir, are pushing the trend for a mural wall in children's rooms.

In a busy family home an extra bathroom just for the grown-ups would be both a practical and life-enhancing use of a box room. Banish plastic ducks and toilet training aids and embrace the cult of luxury.

For maximum indulgence, choose the colour scheme carefully, says colour psychologist and founder of wellbeing company Essentialise, Lee Chambers, who has been working with luxury bathroom specialists Big Bathroom Shop. 'Because white brings in light, it can cause an uplift in mood and bring an element of serenity if we are overstimulated. It also can really open a space both physically and in our minds.'

When it comes to soft furnishings, nurturing textures are a must, says Joanna Ross, general manager, product and innovation, at home textiles company Sheridan: 'They are also key to creating a spa-like feel in your bathroom. Nothing says spa quite like a fresh stack of plush towels placed over a towel bar, rolled in baskets or stacked neatly on a shelf.'

A box room doesn't have to be on the ground floor to be turned into a useful utility room. Moving the washing machine, tumble dryer, clothes horse and ironing equipment out of a busy kitchen, crammed under stairs cupboard or draughty outhouse will make laundry management so much easier to deal with. And, the argument goes, if a box room is on the first floor of a house, it's closer to the bedrooms – so you'll cut down the journey of washing from dirty to clean.

A separate utility room makes a hugely convenient central cleaning hub too: 'Organise cleaning supplies by room or task and store them in easy grab baskets so you can take them to the job at hand,' says Sam Hood, co-founder and chief creative officer for homewares company Amara.

A walk-in wardrobe is useful and utilitarian, but a dressing or powder room is all about the glamour. Bring in decadent furniture such a triple-mirrored dressing table and think opulent wall treatments.

'The popularity of dressing rooms is part of a resurgence in focusing on adult spaces in the home,' says Simon Tcherniak, senior designer at furniture company Neville Johnson. 'A master bedroom with dressing room and en suite is high on a list of even family buyers now, adding value to a property, with buyers willing to pay for such a special dedicated space.'

We've all fallen in love with the idea of a designated space to simply read and relax. A narrow box room is the perfect shape for a reading nook; line with simple shelves and paint the whole room a warm and nurturing shade.

And keep it clutter-free, says interior designer Simone Suss at Studio Suss: 'I would advise as uncluttered as possible. Yes, you'll need some good, directional lighting and possibly charging for your devices but apart from that, all you need is a small table with a notepad and pen to take any notes if you're reading something inspirational.'

If your obsession with patchwork or flower-arranging is threatening to take over the house, requisition the box room as your dedicated craft/hobby space.

Your focus should be to maximise natural light to save your eyesight – and electricity bills – and to organise effective storage. 'If possible install large windows in small box rooms,' says architect Ben Ridley, founder of Architecture for London. 'If planning regulations allow, don't be afraid to re-think the size and shape of the existing windows.'

For decor, embrace vivid colours and patterns to reflect your creativity, and to restore calm at the end of a long day, opt for modular storage with baskets so that you can store all your materials neatly away.

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