Building an Underground House: What Challenges to Expect and How to Overcome Them

1. Waterproofing and drainage

One of the biggest challenges in building an underground house is dealing with water. Moisture from the surrounding soil can work its way into walls and ceilings, leading to problems such as leaks, mould and structural damage.

The solution

The key is to use quality materials: watertight concrete with a crystalline admixture, combined with bentonite seals in the construction joints. On contact with water, bentonite swells and forms a reliable seal. The concrete mix has to be adjusted to the weather during the pour so that no cracks form as it sets. Water can also be led away from the underground house by drainage systems, for example drainage trenches. The soil above the house acts as a natural filter for rainwater, which is led into a well and reused, for instance to irrigate the roof garden.

2. Ventilation and air quality

Ventilation is essential in an underground house, as the circulation of fresh air can be limited. Without the right design, moisture and gases such as radon or CO2 can build up, reducing indoor air quality.

The solution

A well-designed passive ventilation system that does not depend on electricity is essential. The stack effect, with air flowing in naturally through the windows and leaving through roof ventilation pipes, allows an underground house to maintain excellent air quality. Done properly, this system can even be more effective than mechanical ones such as heat-recovery ventilation. Humidity then depends on ventilation and on how the house is used, just as in any other house.

3. Plumbing and drainage

In an underground house, waste water often has to be pumped upwards, which complicates the plumbing.

The solution

Waste water pumps or macerator pumps remove waste water from an underground house safely and efficiently. These systems are energy-saving and environmentally friendly. Besides the conventional options, a reed-bed treatment plant can be installed. This system filters the household waste water through plant roots and natural filtration, removing up to 99% of contaminants. The treated water can then be pumped back for irrigating the roof garden, which makes the whole system sustainable and sparing with resources. Rainwater can also be collected and used for flushing toilets or further irrigation, which increases the efficiency of the underground house still further and minimises water waste.​

4. Energy efficiency and temperature control

Holding a stable temperature in an underground house can be demanding, especially in extreme climates.

The solution

Underground houses naturally make use of the insulating properties of the surrounding soil. The soil acts as a thermal buffer: our measurements showed that the soil just behind the backfilled wall stayed at 13 to 17 °C through the winter instead of freezing, so the house loses heat slowly. This cuts energy use substantially: owners report that heating is needed for only around 90 days a year in Central Europe, compared with around 240 days for a conventional house at an altitude of about 500 m.

5. Natural light

One common concern about underground houses is a lack of natural light, which can affect how good the house is to live in.

The solution

Careful design is the key to bringing sunlight into an underground house. Large windows on the south side let daylight reach deep into the interior. Rooflights or light tubes can bring natural light into areas further from the perimeter walls. Rooms such as living spaces and bedrooms should be placed at the front of the house, where there is the most daylight, while storage and plant rooms go at the back. Sloping ceilings, higher at the front and lower at the back, help distribute light efficiently throughout the house.

6. Structural strength and stability

Underground houses are subject to enormous earth pressure, which can cause cracks and compromise structural stability.

The solution

To withstand these pressures, underground houses should be built of thick, monolithic concrete. This gives exceptional resistance to seismic activity and ground movement. The whole structure moves together with the surrounding soil, which reduces the risk of damage.

7. Fire safety and natural disasters

Fire and other natural disasters are a serious risk for any house.

The solution

Thanks to the concrete structure and the layer of soil around them, underground houses are naturally fire resistant. Even if fire reaches the interior, the damage is minimal and repairs are straightforward. These houses are also highly resistant to strong winds, falling trees, landslides and extreme temperatures.

What we have measured and built ourselves

• Houses: we have built 26 houses in Europe since 2010.
• Soil at one of our houses: 8 to 24 °C over 14 months, air −12 to +35 °C. In a single day the soil changes by about 0.1 °C, the air by about 10 °C.
• Soil just behind the backfilled wall of another house: 13 to 17 °C from late November to early February, not freezing.
• Indoors in late spring: the temperature varied through the day 6 to 9 times less than outside.
• Heating: owners report around 90 days a year.
• Energy costs from our house pages: Zemplín 45 € and Hoblina Košice 40 € per month.

We measured specific houses over specific periods, and all of them were occupied and heated, so please do not take these figures as a guarantee for every house.

Conclusion

Underground houses offer exceptional advantages in energy efficiency, sustainability and resilience to disasters. Their construction does bring particular challenges, yet modern building methods make these easy to overcome. If you are considering an underground house, working with specialists such as Talpa House will keep the build running smoothly and give you a home that is well made, safe, durable and environmentally sound.