Building a house on a sloping plot

This week we visited a client’s plot to assess whether it is possible to build a house on a slope.

This is a process we carry out regularly, and in this case it was especially important because our client is in the middle of negotiating the purchase price with the owner.

Our visit should not only help you decide—or confirm your decision to buy—if we tell you the plot is suitable for building; it should also provide you with negotiation arguments if we find any shortcomings, such as an excessive slope, poor sun exposure, or subsoil that is unsuitable for building, among others.

Although at first glance we can assess almost everything—the most important factors are orientation and how the sun falls throughout the day, as well as the slope gradient—it is worth noting that, without having carried out the geological survey yet, part of our assessment will lack the technical data needed to determine whether the plot is suitable for construction.

What should we consider to know whether building a house on a slope is viable?

That said, our assessment of whether it is possible to build a house on a slope always starts with a compass, identifying north and south.

The first point to assess when building a house on sloping land is therefore the orientation of the slope. If it faces south, it will be ideal; if, on the other hand, it faces north, you can expect poor sun exposure.

In the example I mentioned, the slope was in the best possible situation, with the access road at the top and fully south-facing.

While it is true that orientation is not the only indicator of sun exposure—once there, you must check for obstacles that prevent the sun from lighting and warming the house for most of the day, such as mountains, vegetation, or neighbouring buildings—in this case the orientation was ideal and there were no obstacles of any kind that would block sunlight throughout the day.

In addition, in this case the main road access is at the top of the slope, so we will not have to climb stairs to reach the house; we will enter at ground level.

How to build a house on a slope?

Although once on site we assess many other factors—water runoff, exposure to radiation from antennas or high-voltage lines, planning regulations, etc.—we also use the visit to evaluate options for building a house on a slope.

In this case, as I mentioned, the house project will start from the upper access to the plot, where the main entrance to the home will be located.

From here, and bearing in mind that the slope requires us to build two storeys (this is not always the case, but in this instance it was clear we needed two storeys to fit the full brief), we have two options:

Although it may seem logical to think that when we arrive home we want to find the entrance hall, the kitchen, and the living room, in this case, with access from above, it is better to reverse the layout.

And why is that? A very common mistake when building a house on a slope is to place the shared living areas on the upper floor because that is where the best views are.

However—and although each case must be assessed individually—most of the time it is worth sacrificing a few metres of view and placing the shared living areas on the ground floor, connected to the garden.

Having the living room and kitchen level with the garden allows us, through porches and covered terraces, to double or triple the usable area of our home in summer.

An outdoor lounge, garden tables, or simply a couple of sun loungers make more sense and are used more if they are placed in immediate relation to the living and dining spaces.

This basic principle is often not followed because the best views are on the first floor; however, you can always leave a study-type room on the upper floor to enjoy the views.

What if the access or main road is at the bottom of the slope?

In that case, unless the views are truly only visible from a certain height, the ideal approach is again to place the garden and shared living areas on the ground floor, which we will access almost at ground level or via just a few steps.

How can you make the most of the slope?

Another common question among people who want to build a house on a slope is what to do with the more internal part of the house, the area that sits beneath the slope. Is it possible to make the most of sloping land? Can semi-buried rooms or spaces be created?

Well, under planning regulations, it is not legal to have a semi-buried bedroom if it does not have a full main opening that allows light and ventilation to enter.

So, we can use the full depth beneath the slope, but if we place rooms in this area we must ensure they have direct ventilation and light from the front façade.

Another option to make use of the semi-buried area, without needing as much ventilation or natural light, would be to place the garage, a wine cellar, or a water tank there.

Pools and outdoor areas

Building a house on a slope is perfect for an infinity pool—one that looks as though the water extends into the distance.

However, to build an infinity pool we would be going against the previous recommendation of keeping the shared living areas on the ground floor connected to the garden, because an infinity pool is more striking when it is placed on a level with some height, allowing for the small cascade that makes it an infinity pool.

So, perhaps the best option, if you want to include an infinity pool, would be to build a single-storey house if you have enough space on the highest part of the plot. However, as we always remind you, based on these premises it is necessary to assess each case individually: building a house on sloping land is complex, and every project is unique.

Be careful with water!

Although building a house on a slope usually ensures that water runoff occurs naturally, this is not always the case.

When building a house on a slope, we must check that water drains properly on days of heavy rain, planning for water collection and drainage routes that carry it away from the house.