Calculating the costs of a new build

Working out how much a new house build costs is always somewhat subjective and, worse, often a matter of smoke and mirrors from the construction industry, who will almost always try to tell you that a build is cheaper than it really is. It all depends what you include and exclude from your calculations.

Standard measures of cost area ratio (cost per square foot or m2) tend to exclude things like the septic system and water supply, which are not normal costs for most builds. Of course, on Wolfe Island, they are essentials, but it isn’t realistic to include them when advising someone who does have acces to mains services. Most measures also tend not to include personal things like furniture and curtains. However, they do include all flooring and tiling, kitchen and bathroom fitting and appliances etc.

There are also variations based on whether a cost per area is calculated using the basic external footprint of the house multiplied by the number of floors or storeys, or on usuable internal space (and then you’d have to decide whether the floor area of attics and/or basements counts as usable space – we’re excluding it here, even though our attic is pretty usable, because it is not accessible by stairs).

So we’re going to be completely transparent here and give you a range of cost per area estimates in Canadian and US dollars (exchange rates $1 CAN = $0.725 US, as of December 26th 2015).

Basis             Area (sq.ft)      Cost/Area (1)      Cost/Area (2)      Cost/Area (3)

Footprint          1818                 186 / 135                 197 / 143                246 / 178

Usable               1580                 214 / 155                 227 / 165                286 / 207


Basis             Area (m2)       Cost/Area (1)       Cost/Area (2)      Cost/Area (3)

Footprint          169                2100 / 1521           2396 / 1736            2636/ 1909

Usable               147                 2414 / 1749          2755 / 1996            3073 / 2226



(1) Original projections (CAN / US)

(2) Current projections, not including septic and water supply (CAN / US).

This is the standard cost area ratio that will be relevant to most people. The difference between (1) and (2) is largely due to the higher than projected costs of the Cross-Laminated Timber due to the weak Canadian dollar and the fact that we lost an argument with Canadian customs as to whether the shipment should be classified as ‘timber’ as opposed to ‘glulam’ and had to pay import duties.

(3) Current projections, including ecological septic system and water supply (rainwater harvesting system, including larger cistern) (CAN / US).

This is the cost area ratio that will be relevant to those in areas without mains water and sewage.

However, none of these figures include the Solar PV system, which we are going to have to hold off on for a couple of years because we simply don’t have the money. We didn’t end up getting a mortgage or construction loan – the Ontario construction loan rules are ridiculous – and are relying almost entirely on a Line of Credit on our existing house and land, and all of our savings.

Value for Money?

The big question is whether this represents good value for money over other ways of building passive houses. In the beginning, we were thinking that this might be comparable to or even cheaper than the standard North American SIP-based method with an internal stick frame and plasterboard and all that. At the moment, I don’t think we can make that claim: if you had a more local source of high quality factory cut CLT, you could do it. However, it is certainly significantly structurally stronger, more fireproof, and higher quality all round, and looks a lot more beautiful inside than anything you could do with plaster and paint – although aesthetics are even more subjective than cost area ratios.

One thought on “Calculating the costs of a new build

  1. Pingback: Reflections After a Year of Living in Our Passive House | Wolfe Island Passive House Project

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