Construction cost estimator/calculator
New homes, renovations & additions or extensions

Notes & assumptions

This construction cost calculator only gives an estimate of building costs. It is only suitable for use before any detailed plans are drawn. Note: You will need to adjust the default per-square-foot cost to a value more suitable for your area.

Cost assumptions (which you will have to change):

• A custom designed house on an excellent site using basic finishes will cost $150/square-foot.
• A custom designed house on an excellent site using standard finishes will cost $160/square-foot.
• A custom designed house on an excellent site using luxury bathroom and kitchen fittings will cost $180/square-foot.
• If the site is "good", but not excellent, add 7% to the cost (e.g. a slightly sloping block of land or land that requires some drainage).
• If the site is "difficult", add at least 20% to the cost (e.g. a steep lot or a lot that requires extensive drainage).
• Renovations & additions cost twice as much, per square foot, as new home construction or extensions. Note: This applies more to older houses than new houses.

For accurate construction costs you will require detailed construction plans and the services of a professional estimator or licensed building contractor.

The cost of renovations are often impossible to estimate due to unseen structural issues in the building. However the cost of extensions can usually be determined as accurately as the cost of a new home.

If you speak to a few builders in your area you should be able to get reasonable per-square-foot costs for your own location and requirements.

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