Building costs for Dummies

Q: I have just bought an expensive Fluffy block, am thinking of building a new home and have been getting wildly differing advice on the cost of building houses

TT: Just a quick dip into the internet by anyone shows a range of figures from less than $1000/m2 to over $4,000/ m2 which are bewildering to anyone, particularly if they haven’t built before.

Q: So what are the factors that produce such a large range of cost?

TT: It isn’t really rocket science. The reasons can neatly be put into three categories which all are, once you think about it, just basic common sense. There is correlation between size, complexity, inclusions and the overall cost of buildings.

Q: OK, the first seems fairly straightforward.

TT: Yep, blind Freddy can work that one out, the bigger it is the more it will probably cost.

Q: Complexity; that seems like a broad church?

TT: There is huge range of style of building styles.  At the bottom, with little in the design that deviates from simple standard basic brick veneer construction, on a flat site many project home builders are producing Mc Mansions at under $1800/m2. These types of houses dominate the suburbs and are fine… if this is your cup of tea. Everything about these sorts of homes is generally ‘bog standard’ and requires no specific detailing. These homes can usually be put up by reasonably competent builders and tradesmen with little supervision, they sort of build themselves.

Q: So what is ‘non-standard’ construction?

TT: Every part of a house from the footings to the roof can be designed in a more expensive way. If you are looking at construction methods and aesthetic styles that deviate from that of the brick venereal disease you should be thinking of allowing at least $2,300/2 – $3000/m2 or more. The over 3000/m² category is magazine fodder. Suspended concrete slabs, steep site slopes, articulated building form, cantilevered elements, soaring or complex roofs, exotic cladding materials and custom detailing all contribute to this increased cost but hopefully in a resultant design dividend.

Q: What sort of effect can different inclusions have?

TT: With Project homes it is generally a race to the bottom in regard to the allowances for tiles, taps, windows etc. Good examples of the range in cost of different elements are for example; that you can get a reasonably workable plastic cistern toilet for $300 but a fancy wall hug pan might cost $2,000 ie,  seven times as much. Carpet may cost as little as $60/m2 but a polished hardwood floor would be four times as much at $250/m2. A set of windows in a project home may be as little as $22,000 whereas a reasonably well performing double glazed window would cost more like $45,000 and high-performance thermally-improved windows can be $70,000 or more.  If you think of the relative level of inclusions being like buying different quality cars from say a Kia to a Honda and then up to, say a Beemer you’ll get the idea. You get what you pay for.

Q: Are there any tools to help make sense of this?

TT: I have developed a very simple spreadsheet calculator that I would be happy to make available for free to any readers should they wish to contact me by e-mail.

Tony Trobe is director of the local practice TT Architecture. Is there a planning or design issue in Canberra you’d like to discuss? Email

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