Building on a slope: the top 10 questions

A big advantage of a hillside house comes from the location of the house. Because when building on a slope, naturally lit living space can also be created in the basement. With sloping terrain, the basement forms the level necessary for the construction of the house. But there are some challenges you need to factor in when building on a slope. To find out what to expect and how to make the most of your hillside property, read our guide.

What to consider when building on a slope?

When building a house, it is generally advisable to prepare a comprehensive subsoil survey. This is particularly the case with hillside properties. This makes it easier for builders to assess whether and with what effort the area is suitable for building at all. The condition of the building ground must be determined exactly. Here, the load-bearing capacity of the soil, its stability against slipping and water-bearing layers play an important role. Special care must be taken if there are structures on the hillside above your own building site that may be affected by the construction activity.

Tip for building on a slopeMake the most of the view offered by a house on a slope. Orient as much living space as possible to the beautiful, expansive view. This visually enlarges the living space. This view is the priceless quality of your home on a slope!

What special features bring building on a slope?

Regardless of the property situation, you should always have an architect at your side when building a house. It helps you to cope with all the situations you may encounter during construction. When building on a slope can be, for example:

Slope water

Slope water is a special form of seepage water and is strata water that can occur during precipitation. A distinction is always made between HGW (highest water level from groundwater) and HHW (highest water level from floodwater). When building a basement on a slope, the great advantage is that the water can flow downhill past the basement. This is not possible with full basements. However, it is also possible that the water can drain away from the exterior or exterior walls of the building on the slope. -basement walls jams. It is therefore important for builders to observe in particular the regulations of DIN 18533 for waterproofing buildings. DIN regulates the protection of structures against moisture and water. Slope water is a common cause of dispute with neighbors when building on a slope. The homeowner of a lower-lying property must accept that water resulting from natural forces will flow onto his property. This is the case, for example, during heavy rain. But if structural changes cause additional surface or underground water to flow from the higher to the neighbor’s property, he does not have to put up with it.

construction site equipment

The advantage of building on a slope is that part of the excavation pit is practically already in place, since less soil has to be excavated and removed on the valley side. But depending on the property, building site setup on a sloping site can be more complex. In addition, it may be necessary to secure the property against slippage.


With the development one must adapt the house to the property. In general, building a basement on a slope is a good idea, because the backfill here is much more costly when building with a floor slab. As a rule, this requires backfilling on the downhill side or cutting into the slope side.

What to consider when aligning a house on a slope?

The orientation is important for every house and must always be adapted to the property situation. Those who choose to build on a slope find themselves with a more predetermined orientation of the plot and must take into account the associated advantages and disadvantages in the planning process. While a south-facing slope allows the building to be optimally opened up to the sun, houses on north-facing slopes generally lead a shadowy existence. With east or. West slopes you may have to give up the evening or morning sun. The steeper the site, the more extreme the effects are. Before buying, it is best to visit the building site at all times of the day to study the sunlight situation.

Depending on the direction, there are different advantages and disadvantages for building on a slope:

building on a slope_apartment example interior view

It makes sense to build with a basement on a slope, because you can dig it into the ground on the slope side. Towards the valley side, the basement can usually be naturally lit by windows – thus creating another living level. There is space here for an office, a granny apartment or similar. This can also be opened up separately from the outside. This practical example shows how basement construction can succeed even on difficult sites:

What options are there for the basement in the hillside house?

When building on a slope, a residential cellar is the best solution. This represents in any case an increase in the residential value of the house. Even if you don’t initially plan a residential basement, full exterior basement insulation usually pays for alternative uses. This way you are always prepared for changing living conditions: for example, to use the basement as living space for grandparents, adult children or caregivers. Or the cellar gets a new function as a home office. The importance of being able to work from home is clearly shown by the current situation and the generally changing world of work. Renting out the basement apartment is another option. By collecting the rent you profit financially on the side.

Of course, you can also build the cellar as a pure utility cellar when building on a slope. The basement usually houses the building services, so you don’t have to use up living space on the upper floors. Noise-intensive devices and machines find a good place in these rooms.

To bring light into the basement, there are several options: When building on a slope, you can have the exposed part of the basement completely glazed, depending on the property. So the rooms offer a beautiful view into the valley. On the buried side of the slope, windows with light wells bring brightness into the rooms and create a pleasant atmosphere.

When building on a slope, experts advise concrete prefabricated cellars. This prefabricates the basement company in the factory with all the necessary pipes. Manufacturers of prefabricated cellars offer special cellars that are so waterproof that they even "float". Here, for example, is the AquaSafe cellar from Glatthaar. With this type of basement, construction is not dependent on the weather and does not take as much time.

What to consider for a basement and basement apartment?

A granny annexe as well as a residential cellar require an additional permit. The regulations for this can be found in the respective state building code (LBO). Anyone wishing to install living quarters in the basement must generally take the following points into account during planning:

  • Height: at least 2.30 meters. Exceptions in some federal states.
  • Windows and door widthHere there are specifications with regard to the minimum window size. They differ depending on the federal state.
  • Heating/insulationMaximum U-value of 0.283 W/(m²K) according to EnEV 2016. Living cellar needs heating. The regulations of the Building Energy Act (GEG) for K 55, 40 and 40 Plus standards must be complied with.
  • presence of suitable Escape routes.

The granny annexe as such is eligible for subsidies. Since 2021, the subsidies have been awarded as part of the federal subsidy for efficient buildings (BEG). Since the funding amounts within the efficiency house funding are granted per residential unit, you can apply for a house with a granny annexe under certain circumstances double the funding and have it approved. For an efficiency house 40 plus with two dwelling units there is then apart from favorable credits up to 75.000 Euro subsidy. With a Glatthaar basement and its special constructions with core insulation or. You can easily achieve the required values in any case with core insulation and additional exterior insulation: ThermoSafe® and ThermoSafe Plus®.

building on a slope_thermoSafePlus wall

The ThermoSafe Plus wall is made up of many individual layers.

In this 3D view of a basement on a slope, you can see how well living and technical rooms can be realized on the lower level when building on a slope.

Converting a cellar into living space – is that possible??

A basement originally built as a pure utility cellar can only be converted into living space if there is sufficient clear room height and the possibility of lighting through windows. Only then is a use as living space possible under building law. Which room heights must be at least given, regulate the state building codes in the individual states differently. Those who want to retrofit their basement as a residential basement later on must therefore consider the following: the necessary room height and windows must exist or there must at least be the possibility of installing windows later on.

In the case of cellars, room height and daylight incidence are usually lower than in the case of full rooms. In the case of a basement on a slope, the basement floor protrudes from the ground anyway, in contrast to the ground level property. This allows more daylight to enter the rooms. Later conversion is not possible if the room height in the utility cellar is too low and the corresponding external insulation is missing. In an emergency, you can have the latter retrofitted at great expense, but you will have to pay a lot of money for this. And in this case you will also not benefit from a subsidy.

By converting the cellar into a living cellar, the rooms are immediately counted as floor space. The permissible number of square meters on a building plot – i.e. the maximum floor area (GFZ) – is regulated by the building authority. When building out, you must then comply with the regulations of the state building code that applies to the state in question, as already mentioned: Thermal insulation, floor height, width of the entrance door, second escape route for fire protection and the size of the windows.

Are hillside properties more favorable?

In most cases, a hillside plot costs less than a comparable, ground-level building plot in a similar location. But here there are also exceptions. In general, many factors have an influence on building land prices: for example, the chosen region within Germany in which you want to buy a plot of land plays a major role. The price is also determined by whether the plot in question is located near a major city and by its location within the city. It becomes more expensive, for example, if there is a park in the immediate vicinity. If, on the other hand, there is a busy road not far from the property, this usually reduces the costs.

Conclusion Building on a slope

Who decides for a hillside house, is pleased about living with undisturbed view. Before it is however so far, you must consider with the building at the slope some things: let the property examine geologically before the purchase and give a building ground appraisal in order. When planning, it is important to pay special attention to the orientation of the house. Earthworks and development may be more complicated and costly on a slope than on a ground level property. In some cases it is necessary to secure the slope against slipping down.

Since building a house and land cost a lot of money, it is important to make the best use of the available space. When building on a slope, this is best done with a basement, although hillside houses are classic co-basement buildings anyway. Because with a sloping surface, the basement provides the necessary level for the upper floors. The front of the basement is usually above ground. This allows the installation of window areas, so that enough light falls into the rooms. Nothing stands in the way of using the igloo as a fully-fledged living space – for example, as a granny apartment with its own entrance. On the dug-in slope side, there is room for building services and storage rooms. This is how you don’t give away valuable living space on the upper floors when building on a slope.

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