How house shape influences construction costs

Wednesday November 28 2012

By Joy

When evaluating the costs of building a new home, many people commonly use area (Square-metre / square-foot) pricing as a basis for comparison.
The diagrams shown are meant to prove a valuable point, that no accurate pricing can be given on the Area (square meter/ square foot) basis for building a house. The four shapes are; House A = Round, House B= Square, House C = Rectangle, House D = Odd shape, which are all equal in area namely 100Sqm. Their perimeter walls when straightened differ by 42% or 26.74 Metres taken between the House A (round shape) of 36.16meters and House D (odd shape) of 60.93Metres.

Cost analysis
Below is a simple example showing how the quantity of (even) basic materials (bricks, cement and sand) differs for the houses of the same area but of different shapes.
The example given is just for simple comparison and doesn’t reflect the actual or all materials needed to build up each shape; and in this case House B, C and D are compared against House A since it has the shortest linear wall when straightened.

Assuming that it takes 10,000 bricks, 10bags of cement 50 wheelbarrows of Sand to build up the walls of House A, the other houses will cost as follow.
House B; will take about 11,320bricks, 12bags of cement and 57 wheelbarrows of sand.
House C approximately 14,100 Bricks, 15bags of cement and 70 Wheelbarrows of Sand.
House D = 17400 Bricks, 18bags of Cement and 87 Wheelbarrows of Sand.
The example above give when you consider all the remaining materials for finishes, House D costs much more due to its complicated design. Therefore, when on a tight budget, one needs to pay attention to the complexity of the house plan. This gives us an insight that using Areas as a basis for pricing is not a reliable method for determining how much a particular design is going to cost to build.

Below are few tips to consider before getting into a budget creep.
•Much as this article focuses on the walls, it’s important to note that the construction of the roof on House D will cost more due to its complexity.

•The corners cost more and should be kept to the minimum.

•With a little research, square-meter/foot pricing can be a useful tool to get you a particular range but that’s not all.

•Start with a clear idea of the level of finish and quality you expect. Don’t assume that your architect or consultant is in tune with all your ideas about design and finishes; discuss your expectations in detail and whenever possible, (If you’re not the detail-oriented type) Show them samples, Pictures, magazines, videos of the actual designs, finishes and fixtures that are relevant to what you desire.

•Poor quality drawings cause additional unplanned work during construction, and always end up costing money and time.

•Finally, always have realistic expectations about your project budget and communicate that budget to your architect. When everyone understands the project’s financial goals, the chances for success are greatly increased.