Site Costs article in New Home Buyer

Land developers and real estate agents advertise that available blocks are, “flat, easy building blocks” with even more enthusiasm than they declare a site close to shops and public transport. They’re acknowledging that sloping sites can have limited housing options and seemingly unlimited extra costs.

There can be advantages to building on land with a natural fall – an elevated position can make for a more attractive home, for instance, or slope to a natural easement offers a free way for the stormwater to leave your block. At least initially, however, you’ll probably have to pay some extra site costs.

There are very few perfectly flat blocks of land in New South Wales, but there’s also a lot of variance possible between ‘flat as a tack’ and ‘like a cliff face’. Some blocks of land will require homes specifically designed for sloping blocks – whether that means a split-level design, a home built on bearers and joists or a suspended slab. Most home sites, however, will be able to accommodate a standard slab on-ground construction. They might just need a little extra help from one or all of the following methods to ensure the home is as stable as possible.

Cut and Fill is the most obvious way of levelling a site for construction. Quite simply, it involves cutting soil away from the higher areas on the block, and then using this soil to fill the lower areas, therefore reducing the amount of difference between the heights, and creating a flat block. In extreme cases, leftover fill will have to be exported from the site, or additional fill will have to be imported to create the right levels on a block. In newer estates, cut and fill has probably already occurred even before the blocks of land were released on to the market, in order to present the flattest blocks of land possible for sale. As discussed earlier, piers will normally have to extend well past the fill and into the natural soil in order to find a stable spot.

Increasingly, local governments are trying to minimise the amount of cut and fill occurring during development. On Sydney’s Northern Beaches, for instance, Warringah Council’s Local Environment Plan 2000 limits fill to a maximum depth of one metre. This sort of legislation aims to reduce the height and bulk of new dwellings in relation to the existing homes and development around them.

Another problem with building a new dwelling on large amounts of fill is that the fill will need to be contained. One way of containing fill on a site is using a drop edge beam (also referred to as deepened-edge or thickened-edge beam). Whilst most of the slab sits on top of the fill, the slab’s edge is deepened and extended down to the natural (not filled) ground level. This dropped edge effectively contains the fill, and on the finished home will simply appear as a few extra rows of bricks.

Rather than disturb the natural topography of the block, more builders and homeowners are opting for step downs in their designs. Most slabs already have a few steps in them – for instance, most homes step up from the garage into the house. Building a slab on two or even three different levels and providing steps between them means the home will hug the natural contours of the site more, as well as adding visual interest inside the home, and creating higher ceilings in the stepped down sections.