Top 5 Things You Need to Know Before Making Structural Changes

20th October 2025

Finance & Budgeting Pre-Construction Design & Trends During Construction First Home Buyer Investor Design & Trends

Planning structural changes to your new home? Explore five practical checks covering builder options, room sizes, wet areas and double-storey designs.

Top 5 Things You Need to Know Before Making Structural Changes

Changing a floor plan can feel like the easiest way to make a new home your own. Move a wall, enlarge a bedroom or swap the bathroom layout, and suddenly the design seems closer to what you want.

But structural changes to a new home can affect much more than the room you are adjusting. Plumbing, structural support, furniture placement and the appearance of the home can all come into play.

In this Home Building Hub Podcast episode, Colin Bischof and Darren Brennan explain five things Australian home buyers should consider before changing a builder's design. Their message is practical: make changes for a clear reason, understand the flow-on effects and listen to the people responsible for designing and building your home.

What do we mean by structural changes to a new home?

In this episode, the hosts use structural changes broadly to discuss modifications to a builder's standard home design. These include changing room dimensions, moving wet areas, extending living spaces and reconfiguring a double-storey layout.

Not every floor plan adjustment affects a load-bearing element. However, even a change that looks small on paper can require updates to other drawings and building details.

Before approving a modification, ask what else needs to change with it.

1. Start with the builder's pre-designed options

Before drawing your own changes onto a floor plan, ask which design options the builder already offers.

Depending on the builder and home design, these might include:

• A larger living area.
• An extended alfresco.
• An alternative kitchen configuration.
• A different room layout.

Colin and Darren explain that pre-designed options often have engineering, pricing and construction details worked through in advance. That can make them easier to document and build than a completely new configuration.

Why an existing option can make the process simpler

A home involves more than the floor plan you see in a brochure. Behind it sit elevations, electrical layouts, cabinetry drawings and construction details.

An established option can help the builder keep these documents coordinated. A custom modification may require extra work to resolve how different parts of the home fit together.

The hosts also explain that pre-designed options can potentially reduce additional costs and delays. That does not mean every option suits every block. Ask the builder to confirm its suitability for your site and any applicable estate requirements.

Ask your sales consultant: Which existing options could achieve what I want, and how do their costs compare with a custom change?

2. Check that the room sizes actually work

A room can look generous on a floor plan and still feel cramped once your furniture is inside.

Before enlarging one area by shrinking another, check the usable space in both.

Look beyond the bedroom dimensions

In the episode, Colin suggests around 3 m x 3 m as a practical starting point for secondary bedrooms, with robe space considered separately. These are the hosts' design preferences, rather than universal minimum requirements or a guarantee that every furniture arrangement will fit.

Think about:

• The size of the bed you intend to use.
• Bedside tables, desks and other furniture.
• Wardrobe depth and access.
• Door swings and walking space.

A bedroom's usefulness depends on its shape and layout as well as its dimensions.

Measure your living and dining furniture

Open-plan kitchen, meals and family areas need particular attention. A single large dimension across a combined space does not tell you whether a dining table and lounge suite will fit comfortably together.

Try marking out the proposed dimensions and measuring your actual furniture. Check whether there is room to pull out dining chairs, walk around the sofa and move between the kitchen and living area.

Do not rely entirely on the furniture symbols shown on a marketing floor plan.

Understand where the extra space comes from

The hosts describe a design where a garage setback requirement reduced an already tight family and meals area. Moving the laundry into the garage as a European laundry allowed space to be returned to the living area.

That was a compromise for that particular design. The broader lesson is to consider how you use the home: gaining space in an everyday living area may matter more to you than keeping a separate laundry.

Ask your consultant: Can we check this layout with furniture dimensions and identify exactly which spaces become smaller?

3. Be careful when changing bathrooms, ensuites and laundries

Moving a shower or toilet may look straightforward, but wet areas need careful coordination.

Colin and Darren highlight problems that can arise when fixtures are squeezed into smaller spaces or moved without considering the surrounding design.

These include:

• Shower doors that cannot open far enough.
• Bathroom doors that clash with toilets.
• Awkward access around fixtures.
• Plumbing locations that do not match the updated layout.
• Drainage and waterproofing details that need further review.

Check the whole room, not just the fixtures

A toilet, vanity and shower might each fit within the room's dimensions, while leaving too little space to use them comfortably.

Check door swings, shower access and circulation space together. Ask the builder to confirm how applicable accessibility and livable housing requirements affect the proposed layout.

The hosts discuss specific circulation dimensions in the episode. For your own home, have the builder or relevant building professional confirm the requirements that apply to your project rather than treating a podcast example as a complete compliance check.

Consider how your household uses the bathroom

Darren prefers a separate toilet to one within the main bathroom. That is a personal layout preference, and different households will have different priorities.

Consider whether someone needs to use the toilet while another person is showering, how guests will use the space and what arrangement suits your family.

Ask your builder: Have the plumbing, slab details, drainage, waterproofing and door clearances all been reviewed for this change?

4. Review both levels before changing a double-storey design

A double-storey home needs to work as one connected design. Moving something upstairs can affect the structure, services and rooms below.

The hosts identify several areas that deserve particular attention.

Stair alignment

Stairs connect two floor levels, so their position affects both layouts. Colin explains that many builders restrict staircase changes because they complicate the design.

Confirm what your builder permits before planning other rooms around a relocated staircase.

Structural support

Changing the position of upper-floor walls can affect how they are supported below. The hosts warn that some changes may introduce additional structural steel and associated costs.

Ask for the engineering and pricing implications before approving the design.

Heating and cooling services

For systems that use ducts between floors, the design needs suitable routes to serve the lower level. Rearranging rooms can remove space previously allowed for those services.

Ask how heating and cooling will reach each area after the change.

Sewer stacks and plumbing noise

A sewer stack carries wastewater down from an upper level. Its route needs to be considered alongside the rooms below.

Colin and Darren warn that poorly considered pipe locations can create unwanted plumbing noise near living spaces. Ask where the pipes will run and how potential noise will be addressed.

Window placement and external appearance

Review the elevations as well as the floor plans. Moving or resizing windows can change the balance of the facade and side walls.

Check window positions, sizes and head heights together. A layout that works internally should also produce an external appearance you are happy with.

Ask your designer: Can we review both floor plans and all elevations together, including the structure and service routes?

5. Make changes for a clear benefit

The final tip is simple: avoid changing a design purely because you feel you should personalise it.

Before making a modification, ask:

• What problem does this solve?
• Will it improve how we use the home?
• What space or feature are we giving up?
• Is the benefit worth the additional cost?
• Could a different standard design suit us better?

A fifth bedroom or an enclosed theatre room might meet a clear household need. Reworking several rooms without a defined goal can leave the home feeling less functional.

If the design is available to inspect, walk through the display home before deciding what needs changing.

Choose a builder suited to the amount of customisation you need

Colin explains that some businesses are set up for custom design, while others operate around repeatable standard plans and established options.

If your needs require extensive changes, discuss that early. Find out whether the builder's design and documentation process can accommodate them, and take their feedback seriously when a proposal creates difficulties.

A checklist before approving floor plan changes

Use these questions to guide your next design discussion:

• Have we reviewed the builder's existing design options?
• Have we measured furniture and checked usable room sizes?
• Do doors and shower screens open comfortably?
• Have wet-area changes been coordinated with plumbing and slab details?
• Have both levels of a double-storey home been reviewed together?
• Have we checked elevations and window positions?
• Have we received written confirmation of the scope, cost and expected timing impacts?
• Does each change deliver a benefit that matters to our household?

Glossary of terms

• Pre-designed option:

  An established variation offered by a builder for a particular home design.

• Wet area:

  A space such as a bathroom, ensuite or laundry where water use requires appropriate design and construction details.

• Circulation space:

  Clear space that allows people to move around and use a room or fixture.

• European laundry:

  A compact laundry arrangement, often enclosed behind doors rather than occupying a separate room.

• Setback:

  The distance between a building or part of a building and a property boundary.

• Elevation:

  A drawing showing an external face of the home, including features such as windows, doors and rooflines.

• Sewer stack:

  A vertical pipe carrying wastewater from upper levels towards the drainage system below.

• Window head height:

  The height of the top of a window relative to a nominated level, usually the floor.

Frequently Asked Questions

Can I change a builder's standard floor plan?

That depends on the builder, the design and the proposed change. Some offer established options, while others accommodate more extensive customisation. Ask about their restrictions and process before committing to a particular plan.

Are pre-designed options cheaper than custom changes?

They can be more cost-effective because the builder may already have the design, engineering and construction details worked out. Compare written pricing for your specific options rather than assuming a particular saving.

Why can moving a bathroom affect other parts of the home?

It can change plumbing routes, drain positions, slab details and waterproofing arrangements. In a double-storey home, it can also affect the location of pipes passing through the level below.

How do I know whether a smaller room will still work?

Check the usable dimensions with your actual furniture measurements, including space for doors, storage access and movement. Marketing furniture symbols alone may not give you a reliable picture.

Should I choose a custom design instead of changing a standard plan?

If a standard plan needs extensive reworking to meet your needs, it is worth discussing a custom design with a business equipped to provide one. Compare the proposed function, documentation process, cost and timing before deciding.

Key Takeaways

• Start with the builder's pre-designed options before requesting custom changes.
• Measure usable room space and furniture rather than relying on how a plan looks.
• Review wet-area changes carefully, including access, plumbing and construction details.
• Check double-storey changes across both levels, including support, services and windows.
• Make each modification serve a clear purpose and listen to your builder's design advice.

Watch the full episode

Before you reach for the red pen, hear Colin Bischof and Darren Brennan explain the common mistakes and practical checks in more detail.

Watch Top 5 Things You Need to Know Before Making Structural Changes on YouTube.

About the Home Building Hub Podcast: The Home Building Hub podcast, hosted by industry experts Colin Bischof and Darren Brennan, is Australia’s premier resource for new home buyers. With weekly episodes featuring special guests, the podcast provides objective, high-quality insights into the home building process - completely free and without sales pitches. From understanding financing options to navigating the complexities of building a new home, each episode is packed with actionable advice and tips. Explore more episodes at http://www.homebuildinghub.com.au and join our growing community of informed home buyers.

Disclaimer: This article was generated by AI based on a transcript of our podcast episode and may contain inaccuracies or omissions. Whilst we’re all about providing value to you, this article should not be considered as legal or financial advice. It contains general information only and is based on the content discussed during the podcast episode. This information is relevant to the episode’s release date and may not be applicable at the time of reading. Always seek independent professional advice tailored to your personal situation before making any legal or financial decisions.