Designing To Your Budget

Designing to budget is a critical element of any building project.

It’s important to note that, above all, the design and specification of your home sets the price. Yes, you will get some variation on build prices depending on your choice of suppliers and builders but in the greater scheme of things the design of your new home has the most influence on the build price. Your choice of designer and how they operate is critical. The best designers work closely with cost advisers (quantity surveyors or better still the builder) from an early stage.

With regard to design principles, there are some simple things that affect build budgets that are helpful to consider.

Perimeter-to-Area Ratio.

Consider two boxes. Box 1 is 100m long and 1m wide. It has an Area of 100m2 and a perimeter of 202m.  Box 2 is 10m long and 10m wide. It also has an area of 100m2 but it’s perimeter is now only 40m. If the wall was 2.5m high and the full cost of the wall including cladding, lining and installation was $350/m2 the difference is a staggering $141,750. 

 

Length

(m)

Width

(m)

Perimeter

(m)

Area

(m2)

Wall Surface Area

Wall Cost at $350/m2

House 1

100

1

202

100

505

$176,750

House 2

10

10

40

100

100

$35,000

Obviously, this is an extreme example, but the concept works on all types of buildings.

We’re not suggesting you build a square box but be aware that there are ways to enclose a larger space cost-effectively. For example, 2 pavillions will always be more expensive than a single building of the same footprint as they have potentially 2 extra walls.  

 

The Site

Where your house is built can make a big difference. Choosing a hill site may mean your home needs a more expensive foundation system. It may even need to have a retaining wall to allow for the house to go on a flat section of land. But even on the flat, the ground you build on may require a different type of foundation – this is of special consideration in Christchurch where many types of land have been identified. Soft land may require piles or some form of floating foundation that will soon add up in cost. Technically no land “can’t” be built on, but the enormous difference is in the costs of the foundation. The most cost-effective land type is firm, well-drained solid bearing soils where simple standardised foundations can be used.

 

The complexity and size of the building.

Complexity costs money. The more corners you have, the more labour intensive the building will be. Keeping building forms simple can be not only beautiful but cost-effective as well. Size costs money, spans cost money. Simple maxims but true none-the-less. A bigger home will use more materials to build it. Be careful of the $/m2 measurement, it can be very misleading. Instead, focus on whether the house is right for you and your lifestyle and what the overall cost is. 

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