All of your questions about building a duplex — answered

Let's weigh up the pros and cons, plus some excellent advice on designing a duplex home that you and your neighbour will enjoy.
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A lot of Aussie homeowners today want to make the most of their real estate investment. They want to build a second dwelling in their properties, which they can use to house a relative or earn extra income from long/short-term rental. Some of them build granny flats, while others take the plunge and invest in the construction of a duplex. If building a duplex is a part of your plan, continue reading this blog and you might collect a few golden nuggets that can help you with your project.

Building a duplex vs building a granny flat; which one should I choose?

A granny flat is an accessory, self-contained structure that can be attached or detached from the main house, and is often used as a second dwelling. It was called a granny flat because it is a popular way for families to accommodate aging parents without the need to renovate the main house.

Granny flat on Ruby St in Yagoona. Photo courtesy of realestate.com.au

But, if you’re creating a new house or considering a knockdown rebuild, building a duplex could be a great design solution. A duplex is a structure with two residences sharing a wall but have separate, independent entryways and driveways.

When you build a duplex, you can live on one side and house a relative on the other. If you need another source of income, you can put up the other house for rent. You can also sell the other house and use the money to get out of debt.

Because of the many benefits of building a duplex house, many of our clients who own an ageing house have decided to knock the old house down and build a duplex.

What are the varieties of duplex house plans?

Duplex homes come in various configurations. The most common are single-storey duplexes, where all the rooms of the house are on one level.

Meanwhile, double-storey duplexes allow you to put the common rooms (e.g. kitchen, living area, dining) on the ground floor and the bedrooms on the second floor.

There are up-and-down duplexes where one home is on the ground floor and the other is right on top of it.

There are duplexes where one home is at the back of the other.

Duplex configuration is crucial. With proper design, you can ensure privacy and safety at all times. Talk to a designer and work closely with them to ensure the final duplex design meets your needs and requirements and maximises the size of your property.

Is building a duplex a great investment?

Yes, it is a great investment today because there is an increasing demand for affordable housing. However, you want to avoid daggy designs and cheap, nasty builds. Make it luxurious, with big open plan living spaces, spacious bedrooms, lovely outdoor spaces, and garages. Get help from expert designers and builders, especially when you plan to rent/sell one side.

Should the two houses look the same?

The word duplex came from the word duplicate, so the front facades should look the same. The exterior colours should be uniform across both homes to avoid devaluing the property.

You can change the shape and size of each side (e.g. 60-40% or 70-30%), in case you want more space in your home, then offer the smaller side to renters.

What is the average floor and land space of duplexes?

Most of our clients work with blocks measuring 600-800sqm, meaning each home can have 300-400sqm each. Given that situation, we can build a 440sqm duplex — 220sqm for each house and there's still room for a decent backyard space.

If you are residing in Melbourne and other nearby suburbs, our Melbourne-based designers can help you build a duplex like this. Send us an email and we'll reach out to you about your project.

What is the ideal design of the interior rooms?

There is no rule that says the interior finishes for both dwellings must be the same, so feel free to have some variety.

Let’s say you like polished concrete floors, but you’re not sure if the future renters/buyers will be into it. The safest bet is to go with white interior walls and nice timber floors. This is a basic but pretty look and won’t turn people off.

Be careful not to overspend on your side of the house and skimp on the investment side. You don’t want them to feel like you’ve cut back a lot of expenses. Don’t go overboard, but everything does have to be good quality.

How do you create the feeling of more space in a small duplex?

Two-storey duplexes have a smaller footprint but offer so much design flexibility. You can have an open plan family lounge, kitchen, and dining area that opens to a lovely alfresco on the main floor. A home with a seamless indoor-outdoor flow will feel more comfortable and spacious.

You can install massive windows and skylights so natural light can brighten the space and make it look bigger.

You can also do really high ceilings to induce an airy feel and make your home interiors look massive.

How important is the wall that divides a duplex?

It is very important. Because it’s shared, it must be extremely durable and soundproof. Nobody wants to hear what the neighbour is doing.

What are the current and upcoming design trends to consider?

For the interior rooms, try texture in walls (e.g. painted brick walls and VJ panelling).

If you’re going to use tiles in the bathroom or kitchen, try laying terrazzo tiles in herringbone patterns.

It’s still about stone benchtops, but use thinner marble, Caesarstone, or natural stone slabs for a more streamlined look.

For the floors, opt for polished concrete or timber.

You can also try using small tiles, but lay the same tiles for the floor and walls to create a seamless look that makes the room bigger.

For the garden, level the yard and install a small plunge pool. Use recycle brick on retaining walls and build decks using spotted gum and blackbutt timber boards.

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