This construction cost calculator is courtesy of the Home Design Directory

>>> START CALCULATOR

The Home Design Directory's construction cost calculator only gives an estimate of building costs. It is only suitable for use before any detailed plans are made. 

Note: You will need to adjust the default per-square-metre cost to a value more suitable for your area.

For those of you who are not building industry professionals, and who are looking for acccurate residential construction costs, will require detailed construction plans and the services of a quantity surveyor or a licensed builder.

Also note: The cost of renovations & additions are often impossible to estimate accurately due to unseen structural issues in the building.

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

The assumptions shown below are based on the author's personal experience building custom homes in NSW - they do not apply to kit homes

Cost assumptions

Cost assumptions built into by the construction cost calculator are as follows:

• Renovations, additions or extensions often cost twice as much, per square metre, as the construction of a new house or building (e.g. a detached granny flat). Please note: Some jobs will cost more than double, and a few jobs will cost the lucky owner less than double; it is best to speak to at least one builder or other construction professional to determine what the case will be for your job. You can then make adjustments to the calculator's settings to account for this.


• A custom designed house on an excellent site using basic finishes will have a base cost of $1500/square-metre.*A custom designed house on an excellent site using standard finishes will cost an extra $300/square-metre ($1800 per square metre).


• A custom designed house on an excellent site using high-end or luxury items such as expensive bathroom or lighting fittings will cost at least $600 extra per square-metre ($2100 per square-metre).*If the building site is "good", but not excellent, add 7% to the base cost of $1500 (eg. a slightly sloping block of land).


• If the building site is "difficult", add at least 20% to the base cost (eg. a steep block of land, or one that requires extra drainage).Outdoor areas such as decks, patios and verandahs cost on average $900/square metre. Use a higher value if the outdoor area will have a roof, or will be high of the ground.


• Garages cost an average of $1200 per square metre. Use a higher value if there are any complications such as a sloping block, poor drainage, etc.