How this calculator works
The foundation is a rectangle. Wall area includes the two gable triangles, or the higher wall and sloped end walls of a single-slope shed. Roof surface area is the overhung plan area multiplied by the slope factor. Prices are user-supplied CAD per square metre and are examples, not current construction quotes.
Formula
Floor = W x L; gable run = W/2; slope factor = sqrt(run^2 + rise^2) / run; roof area = (W + 2O) x (L + 2O) x factor. Gable walls = 2(W + L)H + W x rise; single-slope walls = 2(W + L)H + (W + L)rise.
Worked example
A flat-roof shed 3 m by 4 m with 2 m walls and no overhang has 12 m2 floor, 28 m2 walls and 12 m2 roof. Rates of $100, $50 and $200 per m2 respectively total $5000.
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Frequently asked questions
Are doors and windows deducted?
No. Gross wall rates are often used for a shell allowance. Add opening products and any desired adjustments through the fixed material cost field.
Is labour included?
Only if your entered area rates include it. Otherwise this estimates materials for the three shell components and your fixed extras.
Does this size rafters or foundations?
No. Rafter length is geometric. Member sizes, footing design, snow loads, permits and connections need a separate building plan.