Article 4

'Why do architect houses cost so much?
'Article # 4 - Structural Costs
(in a series of 10)

This is the fourth in a series of Facebook articles which will explore this complex issue. If you would like to follow this series, simply "like" us on Facebook and you will receive these articles as they are published.

Structural Costs

The additional structural costs in our typical sample architect designed house are shown in the chart below. These additional costs generally occur in columns, external wall framing and roof framing, and to a much lesser extent in ground slab costs.

Ground Slabs

As the design of ground slabs is largely driven by size, shape and soil conditions, there is very little inherent difference between volume builder's houses and architect designed houses.
Design and performance features such as below slab insulation, set-downs for floor finishes, polished concrete finishes etc will impact the cost, but these are project specific and not inherently part of the structural design.

On sloping sites, some volume builders may use timber framed floors whereas architect designed houses may have suspended concrete slabs. Again, these are project specific design options available to both types of houses.

Upper Floors

In volume builder's houses, upper floors are almost exclusively designed in timber, whereas some architect design houses may use concrete slabs which are considerably more expensive.

Walls and Roof Framing

The lowest cost wall and roof framing system in a house is a timber truss roof supported by simple load-bearing timber external (and perhaps some internal) wall framing, deliberately designed to reduce or eliminate structural steel. Typically, these houses have smaller windows, maintaining sufficient sized panels of wall faming to provide structural stability. This also reduces the lintel sizes and helps with energy ratings.

Most volume builders tailor their designs towards achieving these simple and low cost structural systems.

The more complex building forms generally found in architect designed houses (such as the one used as our sample project) often require more complex structures. In some instances, this may include a full structural steel frame with the timber wall framing being non-loadbearing infill panels only.

Obviously it is possible to use these simple load-bearing timber structures on architect designed houses, and this will assist in eliminating or reducing this extra cost. However, this may place unpalatable restrictions on the design, which may lead to more structural steel and therefore additional structural costs.

In Article # 5 we will discuss the differences in façade and window costs between volume builder's houses and architect designed houses.