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Granny Flat Under $20,000? – How it Can be Done

If you want to build a more affordable granny flat, you may have wondered – can you build a granny flat under 20k?


Yes, it is possible – the cost of a fully constructed granny flat can range on average from $20,000 to $200,000-plus.


In today’s article I will discuss how to build a granny flat for under $20,000, and even between 20K – 30K, if your budget allows.

DON'T PAY A FORTUNE FOR YOUR GRANNY FLAT. Find out how to deal with council and build a granny flat for the lowest cost possible. Learn More.


UPDATE: If you are looking at how to put together a granny flat using Bunnings, see my latest article here. For your other budget options however, continue to scroll down below.


You can still get a high-quality granny flat finished for under 20K if you are just willing to wait (I’ll explain below) or don’t want as many rooms.


The examples below cover granny flats that:


  • Only take a few hours to assemble, to save you time and money, and get you under 20K.
  • Are delivered fully constructed but cost you closer to 30K in total. (I’ll explain the hidden costs).
  • Are a very cheap build; but may take more time and effort for modifications required.


The Flatpack Granny Flat


Flatpack, or kit granny flats, is a term for a granny flat that is delivered to you;


  • Fully equipped with everything required for building, in a way that is easily transportable, and
  • In a way that is simple to build, so you can construct it yourself in only 4 hours.


Some options for a flatpack granny flat/cabin are:

  • Cabin #1 – 20 sqm for only $23,000+. However if you wanted to go smaller we could easily make it less than 20K.




  • This price is inclusive of GST
  • There is no additional delivery fee (to metropolitan regions Australia-wide).
  • Delivery takes on average 2 weeks from the time you place your order.


Advantages of this model include:


  • We have a solid steel, termite resistant frame that is easy to transport and won’t warp.
  • Extra kitchens and bathroom pieces can be provided with the relevant models.
  • Construction is easy to do yourself
  • You can modify the layout of the floor to suit your personal preferences.
  • Wiring and plumbing can be handled by your own trades people.
  • They are NBN ready, and are rated 5-star energy efficient.


It looks like a small office or storage container but can easily be made feel like a mini-home.


With a cheaper option, there may be more work to install water, power and extra fittings.


I’ll elaborate how under “additional costs” below.


Or, there are more examples of prefabricated granny flats that you may be able to purchase for under $10K here.


The Transportable Granny Flat


Many companies deliver low cost portable buildings, either fully constructed or in kit form. The only problem these might not meet the building code and it could be a world of hurt in terms of Council finding out and insurance companies not paying out any future claims.


However, please know that with extra costs such as potential Council fees (which I will elaborate on soon), your total price might increase up into the mid to high-20’s.


There are benefits of some types of transportable granny flats and they include:


  • High-quality steel frames.
  • You can add a bathroom, kitchenette, lighting and more.
  • They are water, corrosion, chemical, fire and weather resistant, and most are rated 6-star energy efficient.
  • Their site installation manuals are easy to read, so they are easy to install yourself.


There is also more important information on transporting a granny flat and what to consider, such as saving costs for the installation.


Before going down the route of moving a granny flat onsite, be sure to not be caught out with other Council restrictions.


The Shipping Container


A shipping container can be a great budget build – however there is a fair bit to consider, such as:


  • The type of shipping container.
  • The size of shipping container.
  • Council permits.
  • The modifications required to make it “habitable”.


So, you can expect to purchase a shipping container for roughly $5000.


However, expect to spend a fair bit of time and money before it’s deemed an acceptable place to live.


There are legalities to consider if you are thinking of purchasing a budget option like this.


Don’t Forget About All the Additional Costs


There is more to building a granny flat than the charges for the building itself, mentioned above. Consider all additional costs in your budget, to establish whether it’s possible to build the granny flat you are looking at for under 20K.


These include:


  1. A surveyors report.
  2. Architect or drafts person.
  3. Engineering drawings.
  4. A foundation (piers or a concrete slab).
  5. If you plan on doing the building yourself – the charge to complete the course to get your “owner-builder” certificate.
  6. However, you will still need a licensed plumber and electrician to add water and electricity.
  7. A certifier (either private or local Council) to certify your work.
  8. Additional building materials.
  9. Labour (if outsourced).
  10. Waste removal.
  11. Certification and Council Fees.
  12. Landscaping.


For an overview of these costs, you can read exactly what each of these cost me when I built my own granny flat.


I also strongly suggest that you:


  • Contact your own Council for some of the charges such as their fees, or
  • Gather at least 3 quotes each from engineers, architects or drafts persons, plumbers, electricians, etc.


As these costs do vary between Councils, so I can only give a guideline of what I was changed.


Allocate Your Budget 


It is common to be concerned about blowing your set budget.


In fact, the Home building company GJ Gardner Homes conducted a survey of 500 homeowners who had built their homes in the last decade.


This uncovered research showing that:


  • Almost two-thirds (62.5%) of “owner-builder” projects go over their budget.


Don’t let yourself become one of those figures, just by following this simple trick:


  • Allocating your budget, allowing you to spread your money as far as possible.


How, you wonder? Well, I will help you figure out exactly how you can do so, as this will help you stay under your 20K mark.


Well, the hardest part is already done – you have already determined how much you are willing to spend. Once you have this figure in mind, there is no reason you cannot build a granny flat that meets your requirements.


It will help prevent you from having any big budget blowouts.


Now, it is all about stretching those dollars in the right directions, so you end up with the best possible version of your granny flat.


What I did when building my granny flat, and it worked well, was to write a list of every item needed in each room.


Then I could administer a set amount of money towards each room, and questioned myself when I was:


  • Going over the budget by possibly spending an unnecessary amount of money on a single item.


There are also other ideas on how to save money with a budget option.


I have also found this great article which talks about why developments go over budget, and what else you can do to ensure you stay within yours.




In recent years, the popularity of granny flats has soared – small is the new big!


However, the cost of a building a granny flat can vary significantly, anywhere from $20,000 to $200,000 or more. This all varies depending on your location, the inclusions you choose, the size of the granny flat, its’ materials and more.


You can consider choosing from a:


  • Flatpack granny flat, that comes prefabricated and will only take a few hours to assemble, costing you under 20K, or a
  • Transportable granny flat, which will be delivered fully constructed, but will cost closer to 30K in total.


They are both high-quality granny flats and may include everything you will need, such as:


  • A full kitchen.
  • Energy efficient lighting fixtures.
  • Up to 10 power points.
  • Bathroom with shower and all fittings.
  • Flooring in all rooms.
  • Standard cladding.
  • We can design and make changes to any floorplan to ensure you get what you want.


Inclusions that may affect your quote are:


  • Your choice of cladding (for example, a brick veneer will cost more than your standard cladding).
  • The height and size of your granny flat.
  • Additional plumbing.
  • The materials you chose.
  • Accessibility to your site (quotes are based on having easy access to your site).


Another option is a:


  • Shipping container, which will only cost roughly $5000 to purchase.


However, it will take more time and money for the research and modifications required before it is approved by Council. (And some councils may not let you do this).


Whatever option you choose, I suggest that you:


  • Look at becoming an “owner-builder”, as you can save yourself thousands of dollars just on labour.
  • Do an important, responsible thing – allocate yourself a budget and stick to it.


Every single additional cost must also be taken into consideration, these all add up and become very important.


Please note that costs vary between Councils’, so I also recommend that you contact yours for their exact fees.


If you have a bit more money you are willing to spend, it is also possible to build a granny flat for under $50 000. This (previous link) will explain what needs to be done and where extra costs may catch you out as well.