If you want more space you have to dig deep. Developers have never been slow to do just that, and the results have been spectacular.

Herts Advertiser: Impressive: 25a London Road, Shenley, on sale with Godfrey and BarrImpressive: 25a London Road, Shenley, on sale with Godfrey and Barr (Image: Archant)

With land at premium prices and planning restrictions on building upwards, it’s long been the trend to make the best use of what you can do below ground level.

Some families are even adding them to their existing homes, taking advantage of a growing trend to excavate and build.

And they’re not limited to single storey homes, either. Sub-basements are now very on-trend, thanks to engineering advances that allow developers to drill, and damp-proof more efficiently - and even import natural light from above with the use of fibre-optic cables.

Guest suites, wine cellars, pools, saunas and games rooms are not uncommon either. A property currently on the market in Shenley goes one better than the golf simulator Ricky Gervais had installed under his Hampstead home, incorporating additional shooting and Formula One simulators into its 1,500 sq ft leisure complex.

It’s probably no more than guests would expect, given the sweeping marble staircase that leads to it. Oh, and for good measure, there’s also a sunken snug, bar and billiards room among the buried treasures. It’s on the market with Godfrey and Barr at £3 million.

A far more traditional staircase leads below stairs to a vast space that incorporates a sauna and 23ft by 15ft cinema room at the Victorian retreat that is Northley House in Shillington (£2,375,000; Strutt & Parker). The massive flat screen sits facing rows of tiered leather seats in calming, minimalist surroundings.

Herts Advertiser: Recline in style on these cinema room lounger seatsRecline in style on these cinema room lounger seats (Image: Archant)

There are several under construction in Harpenden’s West Common, offering similar facilities, including gym, cinema and games room, and John Curtis are currently offering one on the fringe of the Avenues that comes complete with a spa room featuring a traditional Finnish sauna and jacuzzi.

Interiors expert Sarah Pritchard says she’s seen a “huge” rise in homes with basements as entertaining spaces and says it’s a chance for both designer and client to “let our creative ideas run wild”.

“You’re not tied down to any particular scheme or creating that ‘flow’ with the adjoining rooms. This is a totally separate area, detached from the rest of the house. The design rule book gets thrown away and we’re free to create something far more daring.”

She tends to discourage clients from thinking they have to make the space light and airy to compensate for the lack of daylight.

Sarah, of Marshalswick, St Albans, said: “That never works. You only end up making the space feel clinical and unwelcoming and highlighting the lack of windows. I suggest embracing the natural habitat of the basement and dare to go dark! Paired with a wide mix of interesting finishes and textures you can create a far cosier, cocoon-like environment and something quite theatrical in the way that’s unexpected and really plays with the senses.

“We recently fitted a leather floor into a basement bar. It’s such a wonderful, luxurious feeling underfoot, not to mention a great sound-proofing material.”

Herts Advertiser: Inside the un-named BAFTA-winning film producer's Hertfordshire homeInside the un-named BAFTA-winning film producer's Hertfordshire home (Image: Archant)

Some of the audio-visual systems currently being installed are fit for the most discerning of ears, including those of a BAFTA award-winning film producer who wanted a state-of-the-art dedicated cinema in his Hertfordshire home.

So what does that look like in a world that has seen so many technical advances spanning laser discs, DVD, blue ray and 4k?

Well, for anyone reclining in one of the 12 luxury reclining cinema seats – the same number George Clooney recently put in the one below his £10m Berkshire home - it means the pictures come via a Vivitek projector, aided by top-of-the-range Denon electronics, Artcoustic’s Spitfire range of loudspeakers, Rako lighting and blinds control and a Crestron iPad system to power it all up.

All, of course, fully calibrated to ensure that what the producer sees and hears from his movies is exactly what his director intended.

Simon Gregory, director of Cinema Rooms, the firm behind the installation, sees cinemas as the new swimming pools in terms of desirability. He said: “This sort of media room is becoming more and more popular. People create cinemas out of lofts or outside in summerhouses but basements are still a big choice.

“They have no light issues and the sound is always good so they are ideal. It’s not cheap to go to the cinema these days and there’s something nice about having it immediately available under your own roof.

Herts Advertiser: This spa room in Harpenden comes complete with sauna and jacuzziThis spa room in Harpenden comes complete with sauna and jacuzzi (Image: Archant)

“Some people prefer cinema seats to get the real cinema experience, others, big comfy sofas where they can chill out together as a family. L and U-shapes work particularly well.”

Home electronics experts agree that screen sizes of more than 100 inches usually mean projector-based systems which themselves have enjoyed technological advances. The projectors themselves can even be lowered on demand from the ceiling or hidden away to transmit images discreetly via mirrored flaps.

Many media rooms these days have access to sources such as Sky HD, Apple TV and Kaleidescape Movie servers and allow the children to simply plug in games consoles.

Other inputs such as Google Chromecast mean the neighbours can pop in and share their holiday videos from their own mobile devices. Some systems even come with age-appropriate filters; good peace-of-mind for parents hosting sleepovers.

There’s even a sound-deadening product called Acoustiblok, a thin layer of which has the same effect as a 12-inch concrete wall, so your peaceful time in the sauna won’t be disturbed by the sound of Glastonbury pounding out next door.

If you really want the full cinema effect, the lighting can even be integrated into the system so it dims when the film starts and rises again at the end.

Herts Advertiser: Sand-black floor lamp, by Sweet Pea and WillowSand-black floor lamp, by Sweet Pea and Willow (Image: Archant)

And if a seat with a motorised back rest and refrigerated drink-holder isn’t enough, seat-mounted actuators can send low-frequency signals through them which match impulses to what’s on the screen, letting you feel the action as well as see and hear it.

All of which means, every time another set of builder’s hoardings are removed and another pristine, palatial property is revealed, just remember: what you’re seeing is just the tip of the iceberg – particularly if someone is watching, hearing and feeling Titanic in 4D two floors below.

Subterranean chic

If your budget - or space - doesn’t run to saunas, bars and surround-sound media rooms, there are some quirky and effective touches you can add to give any basement space an individual look.

Herts Advertiser: Hoxton wine rack, by Harley & LolaHoxton wine rack, by Harley & Lola (Image: Archant)

We asked interiors companies to nominate their suggestions and here are some key themes: Don’t feel the need fuse the design with the more traditional styles you have upstairs, zone them and re-zone them any way you like – and don’t be afraid to go industrial. It is an underground space after all.

There are also some interesting furniture options that may add a style otherwise out of place in the rest off the house. Here are a few of them:

This Hoxton wine rack is crafted from reclaimed mango wood and finished with a steel frame and legs to provide storage with a serious sense of style in a below-stairs, earthy sort of way. (harleyandlola.co.uk, £489.99).

The antique gold leaf surrounding the bulb of this sand-black floor lamp contrasts well with the sleek black design, giving it an elegant and opulent feel. (sweetpeaandwillow.com, £158).

Herts Advertiser: An interesting storage combination from DotdotdotAn interesting storage combination from Dotdotdot (Image: Archant)

And Dotdotdot provide interesting storage combinations that begin with a simple wooden frame structure comprising 96 holes which can be added to or embellished to create interesting combinations of shelving, hanging space and organisers. And they’re all in durable woods such as sapele mahogany and ash. (dotdotdot.com, from £299)