Granny Flat Builders Perth

Hallmark is the leading builder of premium quality, Custom Granny Flats in the Northern-Perth region.

Modern single-story house with large windows, flat roof, small front yard, manicured bushes, and flower beds under a clear blue sky.

Granny Flat designs you’ll love...

We have something for everyone.

Select a design from our 'Granny Flats by Hallmark' range or have our Designer work with you to design something custom to suit your individual needs.

Check out our designs, download our design brochure of reach out if you're looking for something more specific.

View All Designs

Custom Designs

One bedroom Granny Flats

Pool House

Two bedroom Granny Flats

Rental Granny Flats

Two-Storey Granny Flats

The Hallmark Difference...

Granny Flats by Hallmark is a family-owned and operated building company that has proudly served Perth and surrounding areas for over 25 years.

You may be familiar with our sister company, Hallmark Developments, known for delivering quality craftsmanship and reliable service.

We specialise in premium custom granny flats designed to suit your lifestyle, with a focus on quality and affordability.

Led by local Perth builder Mark Gethin, our team brings hands-on experience, personalised support, and a commitment to making the building process straightforward and stress-free.

About Us

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.

Our Granny Flat Designs

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.

Our Finished Projects

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.

Our Process

''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

         Posted on Google  
   
   Drew & Tamara Coulthard 
 28 July 2025
 
 
 Trustindex verifies that the original source of the review is Google. 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.
  
 
     Posted on Google  
   
   Elad Feldman 
 28 July 2025
 
 
 Trustindex verifies that the original source of the review is Google. +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!
  
 
     Posted on Google  
   
   belinda o 
 28 July 2025
 
 
 Trustindex verifies that the original source of the review is Google. 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!"
  
 
     Posted on Google  
   
   Fran 
 26 June 2025
 
 
 Trustindex verifies that the original source of the review is Google. 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!
  
 
     Posted on Google  
   
   Murray Woodington 
 2 April 2025
 
 
 Trustindex verifies that the original source of the review is Google. 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.
  
 
     Posted on Google  
   
   Lolly Evans 
 2 October 2024
 
 
 Trustindex verifies that the original source of the review is Google. 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.
  
 
 
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