Are you seriously considering living underground? Or maybe you are just intrigued by the idea of a sub-surface home? Either way, this article is for you. We guide you through the various forms of underground dwelling, as well as the benefits and the feasibility of buying or building your own.
Living below ground – a new phenomenon?
Archaeological and historical evidence suggests humans have been living underground for millennia. The earliest human remains come from cave sites, and there is later evidence from around the world of pit-houses, shallow excavations roofed with sticks, mud and thatch, and other semi-subterranean dwellings.
Ethiopia's 13th century monolithic cave churches are an amazing example of rock-hewn, underground spaces, listed by UNESCO as a World Heritage Site. In the Chinese region of Shaanxi, caves burrowed out of the soft, loess soil have been protecting their inhabitants from severe winters and high summer temperatures for thousands of years.
Locals still prefer their cave dwellings to modern, free-standing homes. Similar examples from around the world indicate that underground dwellings are the ideal solution to particular ecological problems and, often, a resource shortage such as a lack of wood or timber which prevents above-ground structures being built.
It seems to have taken modern society a little time to catch on. The potential of underground living was recognised in the West during the oil shortages of the early 1970s. The desire for sustainable building and energy efficiency saw a surge in the number of underground dwellings in the USA and Continental Europe in particular. There are up to 100,000 semi-subterranean or fully underground dwellings in the USA but, right now, Japan seems to be at the forefront of underground innovation.
This overcrowded island has embraced the concept of subterranean living like no other nation. Tokyo's land prices have reached incredible levels – over £4 billion per acre - driving developers underground and giving rise to some ground-breaking, large-scale projects. The Taisei Corporation's self-contained "Alice City" is an underground metropolis, which uses valuable underground real estate to recreate an above-ground office and living space.
The huge cylindrical shaft also incorporates power generation, heating, waste recycling and sewage treatment facilities. Perhaps this is the future of city living? In the meantime, currently subterranean dwellings make up only a tiny fraction of UK housing stock – less than 100 out of the UK's 21 million homes are underground. That's a mere 0.0003%!
Types of subterranean home
In the same way that above-ground houses vary greatly in their construction and appearance, underground dwellings also differ. These are the major types:
These are made by tunnelling or drilling cavities into earth or rock. Essentially the same as a natural cave, constructed caves differ in that they are man-made. Found throughout the world, a famous example is the Australian outback town of Coober Pedy. Most residents in this opal mining town live in caves drilled into the hillside, an effective way to insulate homes from the scorching summer heat. Constructing a cave can be an expensive and dangerous procedure, and is very dependent on suitable geology.
The dwelling is designed as a series of units, made from precast concrete pipes and containers. A pit is then excavated and the prefabricated house lowered into it and covered over with earth. These “cut and cover” dwellings are entirely buried.
Earth Berm Dwellings
A berm is a mound of earth, which offers thermal insulation and protects exterior walls. The house is constructed above ground, with the berms then added on three or four sides, leaving either one wall or simply the roof free for access and light. This type of house is classed as semi-subterranean, and is also referred to as an Earth Sheltered Dwelling.
The same principle as the berm dwelling, except that the house is built into the side of an existing hill. The roof is therefore covered with earth, but the front of the home is left open to the outside. This is one of the most popular forms of underground dwelling and, because of the large amount of natural light and the fact that the house entrance is at ground level, offers something of a transition between conventional, above-ground, and underground living for those who don't want to embrace a totally subterranean lifestyle.
Atrium or Courtyard Homes
These dwellings are built below ground, but have access to outside light via a central courtyard. The whole footprint of the house is excavated before the walls are built around the sunken courtyard or garden. Material excavated is often used in the construction of the dwelling for financial and energy efficiency reasons.
Common questions and misconceptionsHow will outside light enter the house?
No need to invest in any night-vision goggles because living underground doesn't mean living like a badger – in fact a modern subterranean dwelling can be much lighter than a conventionally built home. “Top lighting”, atriums and shafts allow a great deal of light into the dwelling. Earth-sheltered dwellings are often use glass for the whole of the exposed area, giving them a bright, spacious feel.Don't underground dwellings get damp and musty?
There is a common misconception that living underground is akin to living in a natural cave, where you would expect conditions to be cool, dank and earthy. A great environment if you happen to be a bat, but not ideal for modern living. Underground homes incorporate purpose-built ventilation systems to control indoor air quality and humidity, and condensation is never a problem underground.Is fire a risk?
The risk of fire is exceptionally low in an underground dwelling, and reinforced concrete covered by earth offers exceptional fire resistance. Home insurance premiums are substantially lower as a result.Will I get disorientated if I live underground?
Not at all. Imagine your current home – would you get lost there? A subterranean dwelling is no different!
So what are the advantages?
The benefits of living underground are manifold. Here are five top reasons to dig subterranean living:
Energy efficiency – because subsurface temperatures are very stable, underground dwellings benefit from geothermal mass and heat exchange. This means they stay cool in summer (no need for air-con) and remain warm in the winter. Typically, energy costs are only 20% of the average for a conventional house. That means savings of several hundred pounds a year. Solar power can also be incorporated in the roof or atriums, potentially reducing the energy bill to zero, or even generating electricity which can be sold back to the grid.
Low maintenance – with hardly any exterior surfaces, underground dwellings don't require re-pointing, re-painting or other forms of structural maintenance. Mind you, in a culvert or earth berm dwelling, you will have to mow the roof! Underground dwellings are able to store and release heat energy over a long period of time, and as the energy used to heat the house can come from solar power, human body heat and electrical appliances, there is no need for a central heating or hot water system to be installed or maintained.
Money saving – as well as the energy and maintenance savings, insurance premiums are lower for underground dwellings. The excavation itself is a possible source of material (stone, gravel etc.) and build costs can be lower than for a similar conventional house, especially in areas where land is at a premium. Underground homes have a long life expectancy, so they also represent a good investment.
Security – with fewer exterior walls, the number of entry points is reduced, making underground homes much more difficult to burgle. Subterranean dwellings are also much more resistant to storms, earthquakes and even provide more protection against bombing and nuclear fall-out.
Environmentally sound – it's possible to minimise the green footprint of a house by going underground. With a grass-covered soil roof, very little habitat is lost as flora and fauna will return to the site after the build is completed. Visual disruption is minimised – underground homes are virtually hidden from view and blend with the natural landscape. Noise pollution is also much reduced. Their insulating properties make underground homes exceptionally quiet places to live.
The Hockerton Housing Project, a development of earth-sheltered homes, showcases these and other benefits of underground living.
Buying an underground dwelling
With relatively few underground dwellings in existence, finding a suitable house in your area might be difficult. Also consider that most earth-sheltered homes are built by the owner, who is less likely to move than a conventional home owner. There are no specialist estate agents for underground dwellings – it's simply too small a market. However, Green Moves, the UK’s only dedicated eco property selling website, might be a good place to start. Also let your local estate agents know that you are looking for an underground home, so they are aware of your interest if one should come onto the market.
The Hockerton Housing Project, completed in 1998, is a development of five single storey earth-sheltered dwellings. Each house is 6 m deep with a 19 m south-facing conservatory running the full width of each dwelling. The cost of the homes was approximately £90,000 (£485/square metre).
At the other end of the affordability scale is The Burrow, an earth-sheltered home in Harbledown near Canterbury, which went on sale in May 2007 for £2 million. With five bedrooms, indoor swimming pool and sauna, this is a luxury property with a price tag to rival any above-ground equivalent.
Building your own burrow
You have to be committed to see any self-build through, perhaps more so with underground dwellings as they are still a rarity and professional expertise is almost definitely required. For an idea of what you might be letting yourself in for, check out this Grand Designs project to build an underground house in a disused quarry.
Finding a site
To a certain extent the design of an underground home is determined by the conditions of the site. Soil type, topography, precipitation, ground water levels, load-bearing properties, and slope stability all need to be carefully considered. Construction materials need to be waterproof, durable and strong enough to withstand underground pressure (concrete is frequently used). Water is a particular consideration in underground building, and special drainage techniques may need to be implemented around the site, particularly along the roof areas. Climate and topography, soil and groundwater level are all important considerations when picking a site. Ideally, underground dwellings should be sited:
- to take climate and micro-climate into account. If the area experiences harsh, long winters a south-facing slope is best, as south-facing windows allow direct solar heating and plenty of natural light. Less severe winters and hot summers would require a north-facing slope, to keep the building cool.
- with topography in mind. The steeper the slope, the less excavation is required. Contrary to conventional house building wisdom, a flat site is actually the most demanding as it requires extensive excavation.
- above the water table in a location where the water will naturally drain away from the building. This avoids undue water pressure against underground walls.
Like any other major structure, an earth-sheltered or fully subterranean dwelling requires planning permission. In addition, they are required to conform to building regulations, which set standards for the design and construction of buildings to ensure the safety and health for people living in them and the vicinity. Special considerations may be necessary for underground dwellings but in principle planning authorities make no distinction between an application for an underground or conventional development. Employing a planning consultant may help you put together a good case, and improve your chances of obtaining permission. Contact your local planning officer, or visit the Government's Planning Portal for further information.
As with any self-build project you need to do your homework. Read up on sustainable building before you even begin the design stage. Get advice from organisations like The Sustainable Building Association and the British Earth Sheltering Association. This online Encyclopaedia of Alternative Energy and Sustainable Living also has some very useful information about earth-sheltered home construction. It is advisable to use an architect, builder and project manager (if you use one) who is familiar with underground dwellings, or at least with experience in the field of green construction.
It can be more difficult to secure a mortgage for an underground dwelling, so it's worth finding out what your options are at an early stage. Established in 1981 the Ecology Building Society is one of the fastest growing building societies in the country. This West Yorkshire organisation specialises in finance for green homes and sustainable building projects.
Financial assistance may also be available from The Sustainable Development Fund if you live in a National Park. It's a grant scheme funded by DEFRA, which aims to promote sustainable living. You can also contact the Energy Savings Trust who can provide details of grants and awards you may be eligible for.
More information about going underground
As well as the organisations mentioned above, there are several existing underground houses or spaces which you may like to visit, virtually at least, by checking out these websites: The Underground House, Cumbria, Feldon Forest Farm, Warwickshire, Hockerton Housing Project, Nottinghamshire, Caer Llan, Monmouthshire.
Finally, the website of Malcolm Wells is a veritable treasure trove of resources about underground living. Considered by many to be, literally, the architect of the modern earth-sheltered home, his books and designs are inspirational. Essential reading for anyone considering underground living.