What You Need to Know Before Building a Granny Flat

What is a Granny Flat?

Granny flats are becoming more popular across Perth and WA, and for a good reason. These compact, self-contained homes are built on the same property as a main residence and can be used in many different ways. Whether you’re looking to accommodate elderly parents, give adult children a space of their own, or generate rental income, a granny flat in Perth could be the perfect solution.

With rising property prices, many homeowners are exploring the benefits of adding a granny flat residents can live in or rent out. But before you dive into construction, there are a few important things to consider.

Why Are Granny Flats So Popular in WA?

If you’ve noticed more people talking about granny flats in Perth, you’re not alone. Homeowners are turning to these secondary dwellings for a variety of reasons. For some, it’s about keeping family close without living under the same roof. For others, it’s a smart investment opportunity, allowing them to earn rental income without buying an entirely separate property.

The rental market in Perth is competitive, and a well-designed granny flat can be an attractive option for tenants looking for affordable housing. Plus, with the ability to rent them out to non-family members, more homeowners are seeing them as a practical way to make the most of their land.

But before you rush into construction, it's essential to understand what’s involved, from granny flat designs homeowners love to granny flat prices and council regulations.

What Are the Rules Around Granny Flats in WA?

When it comes to building a granny flat in Perth, the rules aren’t as simple as just adding a second dwelling to your backyard. Local councils have regulations in place to ensure that these structures are safe, functional, and comply with zoning laws.

In WA, a granny flat is officially known as an ancillary dwelling, meaning it must be located on the same block as the primary residence. The maximum size allowed is 70m², so while it’s a great way to add extra living space, it won’t be as large as a full-sized home.

A few key regulations to be aware of:

  • Your granny flat must comply with the Building Code of Australia (BCA).
  • There are specific setback requirements, meaning the building must be a certain distance from fences and neighbouring properties.
  • Some councils may require additional parking spaces for a second dwelling.
  • You need proper utility connections for water, electricity, and sewerage.

Before you commit to a granny flat builder Perth, it’s a good idea to check with your local council to see if there are any additional requirements in your area.

Planning Your Granny Flat: What to Consider

Where Will You Build It?

The first step in your granny flat project is deciding where to place it on your property. You’ll want to think about privacy, both for yourself and for whoever will be living there. Will the granny flat have its own entrance? Will it be positioned to take advantage of natural light?

Also, consider how easy it will be to connect the granny flat to utilities. If your site requires major excavation or plumbing extensions, the costs could add up quickly.

How Big Should It Be?

Although granny flats in WA are limited to 70m², that doesn’t mean you can’t make the most of the space. Some designs feel open and spacious, while others can feel cramped if not well planned.

Think about who will be using the space. A one-bedroom granny flat might work for an elderly parent, but if you’re planning to rent it out, a two-bedroom design might attract more tenants.

Choosing a Design That Suits Your Needs

The good news is that there are plenty of granny flat designs Perth homeowners can choose from. Some people opt for pre-designed granny flats, which are quicker and more affordable to build, while others prefer a custom granny flat tailored to their specific needs.

A few popular designs include:

How Much Does It Cost to Build a Granny Flat in Perth?

If you’re wondering about Perth granny flat prices, the cost can vary depending on size, materials, and builder fees.

On average:

  • Basic granny flats start from $130,000.
  • Mid-range options cost between $155,000–$200,000.
  • Custom, high-end granny flats can exceed $200,000 plus.

But it’s not just the construction costs you need to budget for. Additional expenses like council approvals, landscaping, and utility connections can increase your overall spend.

To keep costs under control, work with granny flats builders Perth residents trust, and always ask for a detailed quote before starting the project.

Finding the Right Granny Flat Builder in Perth

Choosing the right builder is one of the most important decisions you’ll make. There are many granny flats builders in Perth, but not all of them offer the same level of quality and service.

When researching builders, look for:

  • Experience – Do they specialise in granny flats in WA?
  • Customer reviews – What do past clients say about their work?
  • Transparent pricing – Are their quotes clear and upfront?

It’s also worth asking your builder about the approval process and how long they expect the project to take. Most granny flats in Perth are built within 3 to 6 months, depending on complexity.

Renting Out Your Granny Flat: What You Need to Know

If you’re planning to rent out your granny flat, there are a few things to consider.

First, check the rental market in Perth. Demand is high, especially for affordable housing, but you’ll want to set a competitive rental price. Research similar granny flats Perth landlords are offering to get an idea of potential income.

You’ll also need to factor in landlord responsibilities, such as maintenance and tenancy agreements. A well-maintained granny flat will attract better tenants and ensure a steady income stream.

Final Thoughts: Is a Granny Flat Right for You?

Building a granny flat in Perth can be a great investment, whether you’re using it for family, guests, or rental income. But before you start, it’s important to do your research.

Make sure your project complies with local council regulations, plan your design carefully, and work with experienced granny flats builders Perth homeowners trust. If done right, your granny flat project can add value to your property and provide a comfortable living space for years to come.

Need Help Getting Started?

Looking for a reliable granny flat builder in Perth? Get in touch with professionals who can guide you through the process and bring your vision to life. At Granny Flats by Hallmark we would love to assist you with your granny flat build in Perth. 

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Grannyflats by Hallmark are Perth’s Best Granny Flat Builder. Based in Clarkson (Perth) and building Granny Flats Across Perth’s Northern Suburbs. Locally Owned and Operated by Mark Gethin

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''Perth’s Best Granny Flat Builder''

Here at Granny Flats by Hallmark we are so thankful for the wonderful people we get to work with on a daily basis. Our reviews speak for themselves with our clients always speaking highly of us and the job we have done for them

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Drew & Tamara Coulthard profile picture
Drew & Tamara Coulthard
28 July 2025
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We had a superb experience when Mark and his team built a custom designed garage and upstairs ancillary accommodation from our drafted plans. The project was delivered quite quickly in a very tight access space with minimal disruption to our backyard. Nothing was too much trouble as we changed a few things during the build. The tradespeople were all lovely, trustworthy, quality and professional. We would definitely look to Mark if we were to do a similar build again in the future. Thank you team for a great experience and putting us at ease for what can be a very stressful exercise.
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Elad Feldman
28 July 2025
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+5
Hallmark did a great job building our granny flat. Mark was fantastic to deal with—honest, reliable, and made the whole process easy. The build was high quality and finished on time. Would happily recommend them to anyone!
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belinda o
28 July 2025
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We couldn't be happier with the experience we had with Hallmark Developments for our home addition. From start to finish, their quality of work was outstanding, with every detail handled meticulously. Mark and his team were extremely professional, always keeping us informed and providing honest advice that made the process smooth and worry-free. They were also impressively prompt, completing the project on time without cutting corners. It's rare to find a company that combines such high-quality craftsmanship with transparency and efficiency. We highly recommend Hallmark Developments to anyone looking for a reliable and skilled builder!"
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Fran
26 June 2025
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Had Mark build a large custom granny flat, from start to finish was amazing. Nothing was an issue and easy to work with. Highly recommend build to anyone thinking of putting an addition on their property Thank you mark wonderful job!
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Murray Woodington
2 April 2025
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Outstanding experience. From 1st consultation to handover we've been more than impressed with the first class service and attention to detail delivered by Mark and the team. We now have two amazing spaces to enjoy the wonderful West Oz lifestyle.
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Lolly Evans
2 October 2024
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A personalized, professional experience during these build works from Mark and his team. What we thought would be a nightmare at the back yard with noise, drilling, digging and more, turned out to be a fun experience with his team as we communicated, chatted, drank coffee or tea on the freezing days and just shared opinions about the growth of the works as they happened. Mark and team were always open to suggestions and feedback as works progressed, and this made the entire experience smooth running, to deadline, with a super quality finish, exceeding our expectations.. Thanks Hallmark!. Well done- John and Lauretta.

Ready to Get Started?

Modern house exterior with brick and white walls, large windows, and illuminated lights. A tiled porch leads to glass sliding doors.

Take a look at our range of thoughtfully designed granny flats, made to suit Perth families, investors, and homeowners alike. We specialise in Custom Designed Granny Flats so every design can be personalised to your liking. 

Spacious bedroom with sloped ceiling, large window, and glass doors. Contains a bed, sofa, armchair, floor lamp, and a pendant light. Neutral tones and minimal decor.

See the real results we've delivered across Perth. From sleek finishes to clever use of space, our completed builds show the quality and care that goes into every granny flat we construct. Let these transformations inspire your own backyard project.

Modern single-story house with large glass doors, flat roof, and exterior lighting. A small rectangular garden bed with shrubs is in the foreground, surrounded by a paved patio area.

There’s a lot that goes into building a granny flat but you don’t need to worry about that. We handle the big stuff like council approvals, design, and construction so you can focus on the exciting part! Here's what to expect when building a granny flat with us.