Designing for a sloping block

Posted by on Nov 19, 2012 in Blog, How to/ Tips | No Comments

As an architect specialising in difficult blocks, I’m often presented with the problem of sloping sites. Whilst most sites aren’t flat, it’s those that are steeply sloping that provide both a construction and design challenge. They can also present an opportunity for wonderful views, and if in the country a chance to really engage with the landscape. Within the city there are many areas with steeply sloping properties, however these are more common in the country and in untouched areas, were the topography was formed by nature not people.

It’s impossible to accurately gauge the slope of a site whilst you are on it. Perspective deceives us and any slope always looks less than it really is. People are often caught out when buying a block; it’s only once it’s time to have a house designed, that they are made aware that their steep site is very challenging to deal with, and with that comes additional costs. It is therefore something that needs careful attention and consideration.

What are the difficulties associated with a steep site? Firstly, avoiding all your furniture sliding to one side of the house… no seriously now, the challenge is how flat floors engage with the ground that is sloping. Rather than one continuous floor as on a flat site, a series of floors is required to follow the gradient of the ground. Or put another way, a sloping site will in many cases need to be split-level, to step its way down or up the site. Creating a split-level home adds complexity to the construction. It is much easier to build one continuous level floor and roof, however with a sloping site, you need to create a series of small buildings on different levels connected by stairs. It’s important to understand this adds costs to the project, which can be significant. To avoid being caught out, it is always best to speak to an architect or builder first.

There are two construction approaches to deal with a sloping block. The first is called ‘cutting and filling’, where the site is excavated to create a series of terraced flat sections of ground, as shown below. This keeps the height of the house down, which in the urban context where there are height controls, is usually the only way. The positive to this approach is that you can walk out of the house and straight onto your yard, as you are not raised above it. The negatives however is that this is very expensive.

The second method is to raise the house off the ground and create a series of terraced floor levels. Building above the ground safeguards you from any drainage issues. It also has less impact on the terrain, as plant and wildlife can continue to exist below. In hotter areas, there is the advantage of breezes passing under the floor, which help to cool the house. This is the cheaper of the two options, though still more than building a house on a relatively flat property.

Another great advantage to a steep site is to use the varying levels within the house for zoning. Zoning is the grouping of rooms of similar purpose, so that the different areas have minimal impact on each other; separating noisy living spaces used during the day from the quiet bedroom area. With split-levels required for these sites, you have the opportunity to further physically separate the noisy and quiet zones, by having separate pavilions for each, joined by a small staircase.

Split-level homes create the opportunity for interesting spaces. With the different levels and steps between them, the intersection of volumes create a beautiful composition of shapes, that when seen from inside and out add extra interest to the home. Also I personally feel there is a playfulness, or sense of adventure to split level homes, as it creates a journey of sorts between spaces instead of just corridors or another opening in a wall.

The steep site is another example of why a difficult block, is a chance for you to create a dream home that is unique.

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