Answers to common questions

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Q: Underground spaces are always damp! How do you keep an Earth Sheltered House dry?

A: Keeping moisture from entering the house is a combination of many factors.
It starts with selecting the location on the site that best allows surface water to be deflected away from the house altogether. A ridge rather than a gully is the better choice.
Providing a slight mound to the rear part of the roof further deflects the surface water around the house.
Now we only have to deal with moisture that seeps horizontally through the ground – and rain that falls on the roof.
The underground seepage moisture is controlled by a vertical drainage barrier made up of the latest civil engineering geofabrics that allow the water to drop to the bottom of the rear walls and be carried away by agricultural drains. The whole aim here is to lower the hydrostatic pressure against the rear walls.
The walls themselves are waterproofed with a heavy bodied co-polymer membrane, designed expressly for this job.
The final barrier is the concrete itself. Properly engineered reinforced concrete is virtually waterproof, in fact they use it to build water storage tanks!
Waterproofing is the combination of proper design, appropriate construction techniques and attention to detail.

Q: Caves are dark! Are Earth Sheltered Houses dark too?

A: The front rooms have as much light as an “above ground” house, often more!
The key to getting light into the rear rooms is to design internal courtyards with windows into the rear rooms. These courts are usually only about one or two metres
across, but that is all that is needed to let in plenty of light. They usually have white gravel on the floor to reflect light into the rooms. Hanging and potted plants create a visually softening element to the rooms, and the sky can be seen above, eliminating any feeling of isolation. Many inner-city houses today have similar courtyard layouts with small private courts.

Q: I worry about them being stuffy and airless!

A: The internal courtyards let the house “breath” by creating natural ventilation.
On windy days the airflow over the roof draws air up out of the court. If the windows to the court are opened slightly then airflow is drawn across the room from the front room windows. And it doesn’t matter in which direction the wind is blowing! On hot, still days the air in the courtyard rises as the air in them heats up, again producing cross-ventilation to the house.
The air is never coming in these courtyard windows- always going out.

Q: Are they expensive?

A: Any house built on a sloping site is going to be more expensive than a similar house built on a flat one. An “above ground” house will have to have retaining walls built around the uphill sides and extensive excavation work undertaken to provide a level building platform.
The Earth Sheltered House has these too, but they are part of the house construction costs, not added to them. The main construction cost is in the reinforced concrete floor, walls and roof, and this accounts for approximately half the overall cost.
The majority of an Earth Sheltered House is underground and will not require maintenance.
The savings in heating and cooling throughout the year should also be taken into account when assessing the overall cost.
Each site has it’s own requirements. Some will require bush-fire specific items to be incorporated while others will require major road-works to gain access to the house platform. Some clients require garages and car-ports under the main roof, others will be happy with separate structures. Sites without town water supply will require more rain water tanks. Sites with no power supply will require the integration of photovoltaic solar collection panels and rooms for batteries.
However the cost of an Earth Sheltered House itself should be on a par with a well designed “above ground” house with average facilities on the same site.