How Much Does it Cost to Build a Granny Flat?

The cost of building a granny flat can be as low as $10,000 for pre-fabricated types and can be as high as $120,000 for custom-made designs depending on the project specifics.

Your preferred granny type and design constitute the cost. Whether you are looking to invest in a flat-pack or customised granny flat, consider the expected cost for pre-construction procedures, optional upgrades and council fees.

Consider the method of construction. Is it a home extension or renovation? Building a detached granny flat incurs cheaper costs than attaching the structure to an existing home as less structural work is required.

Granny Flat Building Costs

Generally, a maximum living space of around 60 square metres in size is required for a granny flat.

The total area may vary depending on what your State or local council regulates. In Sydney, there are a few councils that allow a 65m2 granny flat construction. Make sure to clarify the site requirement before hiring a contractor.

For flat-pack construction, expect to pay around:

• $10,000 to $49,000 for transpack granny flats
• $24,000 to $31,000 for a one-bedroom flatpack granny flat
• $31,000 to $79,000 for a two-bedroom flatpack granny flat

Note: Some manufacturers charge an approximate amount of $750 per 100km for delivery. When hiring, clarify GST, delivery and installation fees with your prospective granny flat contractor.

Custom granny flat construction is generally more expensive with indicative costs of:

• 38m2 granny flats could cost around $81,000
• 45m2 granny flats could cost around $86,000
• 60m2 granny flats could cost around $101,000 depending on the roof area
• 64m2 granny flats could cost around $111,000

The standard inclusions are the site preparation, internal and external fittings, kitchen and bathroom fixtures, plumbing and electrical services, roof coverings and flooring, among others.

How Much Granny Flat Builders Charge

On average, granny flat builders charge an hourly rate of $60 to $110. Others may charge a flat fee of 10 to 20% of the total project cost.

If the job is on a per-square-metre basis, costs can be as low as $35 per m2. But be wary of contractors who offer cheap prices. Do your homework and select the contractor that offers the best value, which is not always the lowest cost.

You can ask a local granny-flat builder to give you an overview of the expected costs. Some contractors provide free quotes and help you with planning and budgeting.

Factors that Affect the Cost of Granny Flat Construction

There are defining factors to consider when building a granny flat.

1. Purpose of the residence

Are you building a granny flat to extend your family home? The purpose of construction affects how you will determine the size and quality of the structure which can influence the cost you are expected to pay.

Whether your objective of building an outdoor granny is to increase your property value or generate rental income, it will have an impact on how you will conceptualise a design to suit your needs and preferences.

2. Size and complexity

Are you looking to build a double-storey granny flat with three bedrooms or just a studio granny flat with one bedroom? The size of the structure factors in how much you will be charged for the project.

Likewise, the time required for the builders to complete the building process will incur additional costs in labour.

Another determining cost of building a granny flat is the ground orientation. Sloping blocks or rocky surfaces will influence the price where additional footing installation is required.

3. Type of granny flat

Are you looking to invest in a quality granny flat and have it attached to your existing home? Or are you building a granny flat as a separate structure?

Detached granny flats are more likely to be cheaper than reinforcing the existing structure which may add significant cost.

4. Additional services

Pre-construction works, such as excavation, factor in the overall cost of building a granny flat. Removing obstructions from the job site also incurs additional costs so make sure to clarify these terms prior to construction.

Seek council approval and clarify extra fees to prepare your finances.

Important: Remember to submit a Development Application (DA) to your council. Some granny flat builders cooperate with local councils to submit the necessary requirements and assist you with the approval process.

How much does a granny flat maintenance cost?

Structures that are built with superior materials and energy-efficient properties demand a low level of maintenance. Being small in size, granny flats are easy to clean and maintain. With regular upkeep, you are protecting your investments.

Posting a job on HIREtrades gives you a list of local contractors to have your granny flat professionally built and properly maintained. For accurate pricing, consult your prospective builder.