The idea of adding a second storey to your home is exhilarating. Imagine, more living space, more bedrooms, more bathrooms, and a significant bump on the resale value of your home!

For families, having a second storey is a great idea for maximising space and mobility. But with all things in life, cost becomes a concern when thinking about the luxurious things such as a second storey extension. To much surprise, they are more affordable and have a better value than you may think. Plus, you won’t have to say goodbye to your precious yard space or patio.

How much does a second storey extension cost?

The biggest deciding factor when it comes to second storey extension costs is the bottom line. This depends on the extent of the scope of work. For example, a new house ground floor extension can be in the range of $130,000, and $250,000 when adding a second storey. Second storey extensions are more complex than ground storey extensions, which is why they come at a higher price.

Although this figure may seem like a lot, adding a second storey to your home will add significant value to it, and will massively improve your standard of living.

Costs to add a second storey extension per square metre varies dramatically, and depends on the degree of difficulty, the quality of the finish, and the types of rooms to be added. Prices can drastically range from $1,800 to $15,000 per square metre.

It is a common misunderstanding that building a second storey is more costly than adding a ground floor extension. Generally, the cost to remove roof coverings and framework, placing joists and sub-flooring, will offset the costs of excavating, formwork, concrete, and so on.

Nevertheless, every project is unique, and the costs associated with it will be specific to the job requirements.

If the job costs around $2,500 per square metre, the average size for a second storey addition is 100 square metres making the total cost $250,000. You will also need to account for an additional $10,000 to $15,000 for lower ground floor work such as stairway access and plumbing.

With a lightweight timber frame, the cost of building upward can range between $1,800 to $3,000 per square metre. As you won’t normally need any foundations or concrete slab, you save huge costs here. The type of rooms you intend on having in the second storey will impact the costs significantly. Generally, the bigger the addition, the more it will cost. The more complex the requirements - think plumbing - the more costly it will be.

Costs for a second storey luxury home build

For luxury home builds, a basic second storey addition is around $15,000 per square metre. This figure includes an entry level staircase, the roof design, external cladding, and minimal remedial work. The more complex the addition - think ultra modern extensions on an existing property in poor condition, could see costs around $40,000+ per square metre.

Influences to costs of a second storey extension include design and architecture fees, layout, amount of steel required, external cladding, condition of the existing ground floor, internal finishes and inclusions, site access, quality of the builder, and remedial works. For your refutable builder, you can visit Mojo Urban Living.

Additional things to consider

Beyond the costs of the build per square metre, you will have to consider additional cost factors as part of your estimate. These include unforeseen costs such as engineering and building surveyors, council approvals, building permits, planning permits, parking, construction and waste management permits, and so on. As a general rule of thumb, add an extra 15% to your total build costs to cover these fees.

Consulting a building professional building with regards to your intentions to build a second storey extension can help you understand the extent of work involved, as well as costs.