Granny Flats & Home Extensions in Perth metro
Adding space without moving house
Granny flats and home extensions cover a wide range of work: a self-contained ancillary dwelling in the backyard for a parent or rental income, a second storey added over an existing footprint, a kitchen and living area extension out the back, or a bump-out to add a bedroom and bathroom. In Perth metro this category runs from small design-and-build specialists doing granny flats on standard 350-450sqm blocks in areas like Armadale and Rockingham, through to larger renovation builders handling knockdown-style second-storey additions in established suburbs closer to the city. We track 65 businesses working across this space, and their skills and typical project size vary a lot.
Before you commit, ask about council approval experience (granny flats and extensions almost always need a building permit and sometimes planning approval), how they handle existing structural conditions once walls are opened up, whether the quote is fixed-price or has provisional sums for unknowns, and how they manage living on-site during construction. Ask to see completed jobs similar in scale to yours, not just their biggest showcase project.
Our scoring weighs review consistency, responsiveness, how long a business has been trading, and the volume and recency of feedback, so you can compare builders on more than star rating alone. See the full method at methodology, or jump straight to our ranked shortlist at best granny flats and extensions builders in Perth.
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All granny flats & home extensions, ranked by score and relevance
We found 65 businesses offering granny flats & home extensions; 22 met the criteria for the scored directory. The order weighs each business's overall score by how much of its reviewed work is granny flats & home extensions, so a lower-scored specialist can rank above a higher-scored generalist. Filter and sort below, or open the full map view.
Enquiries from contact forms may be shared with partner providers, and we may earn a referral fee from those referrals. Our rankings and scores reflect only our published methodology and are never influenced by referral fees.
Common questions about granny flats & home extensions
- How much does a granny flat or extension cost in Perth?
- A basic one or two-bedroom granny flat typically starts around $120,000-$180,000 depending on finish level and site access, while a single-room extension might run $60,000-$120,000. Second-storey additions and larger extensions with new kitchens or bathrooms often land between $200,000-$400,000+. Site costs (retaining, drainage, sloping blocks), council conditions, and existing structural surprises are the main things that push a quote up.
- Do I need council approval for a granny flat in Perth?
- Yes. Most local governments require a building permit, and some require planning approval depending on lot size, zoning, and whether the granny flat will be rented out separately. A builder experienced in your specific council area (rules differ between, say, Swan and Cockburn) will save you time on this step.
- What should I expect during the build process?
- Expect a design and approval phase of several weeks to a few months before construction starts, then a build period of roughly 8-16 weeks for a granny flat or moderate extension, longer for second-storey work. You should get a written contract with a fixed price or clearly defined provisional sums, a payment schedule tied to construction stages, and regular site updates.
- How do I judge the quality of a granny flat or extension builder?
- Look at how they handle the unknowns: what happens if they find asbestos, rotten framing, or unstable ground once work starts. Ask for recent local references, check how many similar-scale projects they've completed (not just large custom homes), and read recent reviews for mentions of communication and how disputes over variations were resolved.
Guides to choosing granny flats & home extensions
- Granny flat and home extension costs in Perth: what changes the price
Typical cost ranges for granny flats and home extensions in Perth, and the site and design factors that push the price up.
- Building a granny flat for an aging parent in Perth: what to consider
Practical and design considerations for building a granny flat so an aging parent can live nearby, from accessibility to council rules.