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Cost of Building a Second Floor House Extension

Last updated: 23rd May 2019

For second floor extensions, builders charge around $66/hr. This is only an indicative rate and the actual cost will still change from job to job. Generally speaking, rates range from as low as $60.50/hr to as high as $71.50/hr.

Where does this pricing data come from?

All prices stated in the above article are based on FY 2018 pricing data compiled by The figures resulted from a comprehensive analysis of quotes submitted by Second Floor Extension
Builders on the site from July 2017 to July 2018.

Related: Cost of house extensions

Related: Cost of house building calculator

How do builders determine the cost of second floor extensions?

Adding a second floor to your home is a significant and expensive project. That is why it’s important to understand the things that go into the price that a builder gives you. Professional builders typically consider a number of things including:


This depends on the layout and design of the second floor. The number of rooms and the sizes of these rooms can increase the level of difficulty. Also, prepare a bigger budget if you want a really spacious second floor.


A complete second floor extension will naturally require plenty of materials. This includes timber, cement, concrete, plaster, and other things. If you want to save some money on the cost of materials, make sure to hire a reputable building company because they can usually get discounts from suppliers.

Ease of access

If the area cannot be easily accessed by machinery, you can expect project costs to rise. Areas that are uneven or sloping are harder to reach and will therefore require more work. If it’s a small area that a machine can’t get into, builders might have to manually do the work, making the job more strenuous.

cost of second floor extensions

What are the benefits of adding a second floor to your property?

If you’re still uncertain about adding a second floor, here are some reasons that might convince you:

1. It is more cost-effective in the long run.

Home extension projects are expensive, but that doesn’t mean it’s not worth it. A second floor extension will still be much cheaper than buying a new double-story home.

2. It adds space to your home.

If you want to have more space in your home but don’t have enough area to extend horizontally, you can do so by extending vertically.

3. It is a more flexible option.

You have the ability to control what goes into the project — how big the rooms will be, the number of rooms, the materials used, etc. Whereas if you buy a new home, you’ll have to spend extra to alter any aspects of it that you don’t like, and this added cost will be on top of what you’re already paying for the home itself.

4. It adds value to your property.

A second floor extension is an excellent investment because it is a guaranteed way to add value to your property. If you  ever decide to sell your house, you’ll likely get back what you spent on the extension project plus profits.

5. It is more convenient.

With a second floor extension, you don’t have to go through the hassle of looking for a bigger home and spending valuable time moving into that home. Once the work on the extension is done, that’s it — you can start enjoying it.

Pricing information correct as at February 2018.

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Tons of professional businesses in your area can help with your second floor extensions. Have a look at’s highest-rated tradesmen in these major cities: