Sloping blocks have a reputation for being difficult and expensive for the construction of a house. However with the correct approach, a sloping block can offer opportunities that a level site cannot.
It is important that the house design be specifically developed for the slope of the land rather than trying to impose a building design that is better suited to a flat site.
Why are sloping blocks traditionally considered difficult to work with?
Sloping blocks have received some bad press over the years – this is primarily due to the costs that can be involved in excavation and the construction of retaining walls to form a level building platform.
These costs can be increased when the excavation abuts side boundaries requiring extensive retaining walls along said boundaries. Excavating into the ground also complicates other building issues such as stormwater drainage, ground water run-off, erosion, landscaping difficulties and the opportunity to gain useful outdoor areas.
How does the degree of slope affect house plans?
Sloping blocks come in a variety of gradients and ground conditions. The sloping site can range from a lot with minimal fall (5 degrees or less) or very steep lots (gradients in excess of 30 degrees).
The ground conditions can also have a substantial impact on construction costs. The ground may be soft soil or sand which presents erosion problems or alternatively may be solid rock which increases the cost of any excavation substantially.
How to make the most of a sloping block
Rather than attempt to determine how to excavate and grade level building platforms, often the best approach on a sloping site is to begin with an assessment of the slope and the possibilities this may offer.
By developing a house plan from the outset which incorporates changes in level (split level or multi-storey), the extent of excavation can be minimised or even eliminated.
A house supported on columns or piers placed above the sloping ground can also minimise any complications due to groundwater run-off and erosion.
Unlike designing on a level site, the first consideration for a house plan on a sloping site is to develop cross sections through the site which shows the slope of the land. These cross sections are developed at the same time as the internal planning of the house. By working back and forth between the floor plan and the site sections, the optimum arrangement for the floor levels of the house can be determined.
Sloping sites can also present other opportunities that are not available on a level site. These opportunities can include:
- The ability to economically incorporate a garage beneath the main floor level of the house
- The ability to develop an elevated floor level (above the street) to obtain views or enhanced privacy.
- More spatially interesting split-level houses (compared to standard houses on a level site)
Examples of sloping block home designs
Examples of sections through our past house projects show how different degrees of land slope have been treated and the building floor levels adjusted to achieve the desired outcomes. The floor plans for all of these examples were developed only after thorough consideration had been given to the Sections.
Example 1 has a site with a relatively gentle slope. This site originally had an older single-storey house with a free-standing garage at the rear – this house was demolished for this project.
The main objective was to gain elevated living spaces and achieve ocean views.
By excavating a half level into the site and raising the floor level above the ground, it was possible to provide a large garage under the house. A rumpus room and bathroom were also located at this lower level.
All the main living spaces and bedrooms were placed on the upper level to obtain water views and easy access to the rear yard.
Example 2 shows a house section with three split levels on a steeper site. The garage and entry are placed at street (middle) level.
As the site falls away towards the rear, the house has two storeys. From the entry, the main living spaces and master bedroom are a half level above. The other bedrooms and a second living space are a half level below the entry.
The section shows how the lower floor opens onto a deck and a raised yard terraced to suit the fall.
The upper level spaces (living 1 and deck 1) enjoy views over the water.
Example 3 shows an unusually steep site which presented some difficult challenges.
The garage was located at the top so a relatively level driveway could be provided. The garage has a suspended, reinforced concrete floor and the large space underneath was used for storage.
The house has two main levels.
The middle floor level (750mm below the garage floor) contains all the main living spaces. These spaces open onto a large deck which is not shown in this section. The highest floor contains all the bedrooms, the bathroom and master bedroom suite.
Both the middle and upper floors gain extensive views over Newcastle.
The lowest floor shown in this section occupies the steepest corner of the site. The footprint of this floor is small when compared to the house above, utilising underfloor space that would otherwise be only a foundation area.
The height of the middle floor was set to enable access to the only level part of the site. This level land serves as the only yard area on this steep site.
In summary, not all sloping sites are difficult and expensive building propositions.
While a very steep site will always present particular challenges, many sites with lesser slopes can be successfully developed with an interesting house provided the correct design approach is adopted from the outset.
Due to their complications, these sites are best suited to the development of a custom design by an Architect. In this way, with the most suitable design, many of the challenges and problems associated with sloping blocks can be eliminated from the outset.