How to Design a Home for a Sloping Site – The Key Considerations to Note

Assessing the sloping site’s ground conditions

Before you even contemplate the look of your home, you need to work out how well the land itself will take to being built upon – especially if you are going to construct into the incline of the slope. As a guideline, the drop from the footprint’s front to back should be at least the height of one floor, which is approximately 2.5m. But bear in mind that a steep site could have engineering and logistical complications that may make the total cost prohibitive.

This home by Meisterstueck-Haus features a stepped form to make the most of its position on a sloping site. Large windows and a balcony on the upper storey make the most of the surrounding views, with glazed doors on the ground floor opening out onto the garden

Some sites are considerably easier to construct on than others. This is because ground conditions can cause complications – especially when it comes to foundations. It’s crucial to have the land checked by a structural engineer, ideally before the site is purchased, so that you can budget accordingly without facing unexpected costs at a later date.

The makeup of the ground will have a direct link with the slope incline; this is called the angle of repose. If the ground is made steeper than this and left without support, it will naturally slump down until it reaches this angle. For example, very solid clay can be positioned at a pitch of 35° or 40°, sand-clay 15° and broken rock up to 45°. This means that the soil conditions should influence the design of any retaining walls and possibly the foundations, as well as the landscaping scheme.

Build It readers John and Helen Atkinson replaced a prefabricated bungalow on a sloping plot with an innovative three-bedroom home amid the rolling Devon landscape. From the driveway, the house appears to be a modest bungalow, but the property’s rear reveals a striking two-storey, contemporary home. Photo: Colin Poole

In the worst case, the ground might have to be artificially stabilised, which is likely to be prohibitively expensive unless this has been included in the valuation of the site before purchase. At the other extreme, if there is rock close to the surface it may be very difficult and costly to excavate, requiring the property to be almost entirely built out from the slope.

You will also need to investigate the ground’s moisture content and whether there is any water movement across the plot. Sometimes there is a risk of liquid building up behind any retaining walls that are formed into the slope. This will put pressure on the structure and could cause damp or high humidity inside the dwelling. This can be dealt with by placing land drains behind the affected walls to remove any liquid and by ensuring that the waterproofing layer can withstand high moisture content.

Creating a house design that works for the sloping plot

Moulding the ground into a flat form and placing an unoriginal property on it is the least successful approach. Slicing into the ground and putting in a freestanding dwelling with windows all the way around will probably result in one side of the house facing a retaining wall (which will be there in order to support the slope). It’s a costly solution that takes away the chance for something spectacular.

Deciding on a scheme will require a two-pronged strategy. Firstly, look for features that will trigger inspiration and, secondly, thoroughly test the site conditions to make sure that the building work needed is achievable, both practically and financially.

Maximising views 

Sloping plots often come along with particularly impressive views, so the outlook is generally something worth considering within the design.

This property by Fleming Homes works to make the most of its breathtaking setting by including a balcony on the first floor and glazed doors opening onto the outside from the ground floor

Three-storey setups work particularly well for making the most of a surrounding vista. These schemes generally perform best with the main entrance and living space on the middle floor, sandwiched between bedrooms above and below. This layout will adhere to the cultural preference of keeping bedrooms on the top floor, whilst also providing some of the bedrooms with a good view.

Although the ground floor interiors aren’t likely to benefit from a panorama, they will have access to the outside. If you do opt for this arrangement, introducing a balcony on the middle storey will compensate for the lack of direct access to the garden, as well as offer an outlook across the landscape.

Skyhouse by Baufritz is nestled into the Sussex countryside. The back of the property features less glazing than the front and makes a feature of the slope, by placing entrances on the ground floor at the rear, where the cut-away bank makes a statement

Natural light & ventilation

Daylight and ventilation are important aspects of any scheme and will require careful consideration. If the house has been designed to merge into the slope, there will be some areas of the dwelling left without windows because the retaining walls adjoin the ground – particularly at the back of the lowest storey. Rooms that do not need daylight are best suited to this zone, such as bathrooms or storage areas. Combat the lack of fresh air by incorporating a mechanical ventilation system, which will prevent the rooms from becoming stale and humid. Creative use of artificial lighting and sun pipes will keep the zones bright.

The opposite side of the house will benefit from an abundance of natural light because it will be open to the surroundings. Double-height spaces, open-plan layouts and mezzanines can be used in combination with large spans of glass, rooflights and atria to introduce soft, natural illumination into the heart of the building.

Case study Build It Award-winning oak home on a sloping plot

Chris and Mary Noon replaced a 1950s prefabricated bungalow in Dorset with their beautiful oak frame self build. The site, which offers incredible views of the coast, already had planning permission to build a new home on the footprint of the existing build.

After doing lots of research and visiting various show homes, Chris and Mary fell in love with oak and its inherent character, choosing Westwind Oak to supply and install the oak frame and structural insulated panel (SIP) envelope. The couple also enlisted the help of Nick Wordie at Roderick James Architects, who had plenty of experience working with the unique characteristics of oak.

Photo: Richard Downer

One of the main challenges of the build was the steeply sloping plot. Nick’s solution required digging in major retaining walls to hold back the hill and trees. The proposed scheme consisted of a two-storey, upside-down layout to make the most out of the views. All the key living spaces were placed on one floor to futureproof the home.

Photo: Richard Downer

However, the existing planning consent was for a single-storey house, so the new design faced significant opposition from the local authority. Chris and Mary compromised by removing upper floor from their detached garage design and lowering the pitch of the roof on the main house. Nick worked closely with the case officer and, after several months, the new design was eventually approved. The oak structure was erected in just three days and the SIPs envelope in a further five.

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How to get the house’s exterior scheme right

Outside, the relationship between the property and the sloping ground surrounding affords another opportunity to create interesting effects. There are two main design approaches: either bed the building into the ground or project it out.

If pitched roofs are used, keeping the angle parallel to the main slope will create aesthetic unity and reduce the visual impact of the dwelling on the landscape. A flat roof can create a range of effects, especially if used in bold projecting blocks, through to more subtle elevations, lined with terraces; incorporating turf or sedum roofs are another option that will further reduce its obtrusiveness.

Ray and Ruth Davis were looking to downsize, so turned to the small studio and garage on their sloping site with the intention of knocking it down and building a new home in its place. Cameron Webster Architects helped them develop a design. The build maintains the same height as the previous road-facing garage, while the striking glazed rear extends down into the sloping site. Photo: David Barbour

Due to their nature, these plots are often very visible from all angles of the surrounding area, which could have an impact on what type of scheme will be granted planning permission. It is sometimes easier to persuade your local planning department to approve a low-key design, rather than a more intrusive one.

The elevated position of such landscapes sometimes means that planners will also be concerned about the privacy of neighbours, whose gardens or windows may be overlooked by the new dwelling. This is definitely worth considering before you submit your proposal. Seeking pre-application advice is always a good idea for unconventional builds such as this.

Opportunities for boosting the house’s energy efficiency

Properties positioned on sloping sites generally offer more opportunities for energy efficiency than those on flat land. This is because they tend to be isolated and therefore not overshadowed by surrounding buildings. South-facing roofs are ideal for solar panels and the ground is an excellent insulator, so having external walls sunk into the earth reduces thermal loss. The land also acts as a heat sink, slowing the effects of changing external temperatures and levelling out the conditions inside the house over the course of the days and months.

A potential disadvantage is that the exposed elevations will be vulnerable to strong winds and poor weather, meaning these parts of the abode tend to suffer more thermal loss than a sheltered wall – especially as there is likely to be expansive glazing on the corresponding side of the dwelling. Fitting external shutters to the windows is one way to reduce this effect – they can either be concealed into the wall above the window heads or used as a design feature.