What to Know Before Starting a Double Storey Extension in Melbourne
Before starting a double storey extension, it is worth resolving the major questions that can affect the design, cost and approval process before detailed plans are developed.
This guide is a practical pre-start checklist for Melbourne homeowners considering a second level. It focuses on the decisions and investigations worth completing before committing to the project.
For the complete step-by-step process, see our guide to planning a double storey extension in Melbourne.
1. Be Clear About Why You Need Another Storey
Start with the problem you are trying to solve rather than the number of square metres you want to add.
You may need:
- additional bedrooms
- a parents’ retreat
- another bathroom or ensuite
- a study or home office
- an upstairs living area
- better separation between parents and children
- more storage
Clear priorities make it easier to develop a practical floor plan and avoid adding unnecessary space simply because it fits.
2. Check Whether the Existing House Is Suitable
A second storey adds substantial loads to the existing building. The footings, walls, framing and roof structure therefore need to be considered before the project progresses too far.
Depending on the existing home, additional structural steel, bracing, beams, footing work or changes to load-bearing walls may be required.
Understanding these issues early helps establish whether the proposed extension is practical and gives the design team better information to work with.
3. Understand the Planning Constraints on the Property
Before finalising the size and shape of the upper floor, check the planning controls that apply to the site.
These can include:
- building height
- side and rear setbacks
- overlooking
- overshadowing
- site coverage
- neighbourhood character
- heritage overlays
- private open space requirements
For a more detailed explanation, see our double storey extension planning considerations.
4. Decide Where the Staircase Can Go
The staircase is one of the most important early design decisions because it affects both levels of the house.
Its position can influence:
- the existing ground-floor layout
- structural framing
- circulation upstairs
- bedroom and bathroom positions
- natural light
- how much usable floor area is lost to circulation
A poorly positioned staircase can create unnecessary alterations downstairs, so it should be considered early rather than added after the upper-floor plan has been designed.
5. Establish a Realistic Budget
A double storey extension budget needs to include more than the cost of constructing new rooms upstairs.
Depending on the project, the total budget may need to allow for:
- design and documentation
- structural engineering
- surveying and site investigation
- planning and building approvals
- structural strengthening
- roof removal and reconstruction
- staircase construction
- ground-floor alterations
- bathrooms and plumbing
- scaffolding and temporary works
- internal finishes
- contingency for existing building conditions
For detailed budgeting information, see our second storey extension cost guide.
6. Consider How Much of the Ground Floor Will Change
A second storey addition rarely affects only the upper level.
The staircase, new structural supports, electrical and plumbing services, ceiling work and connection between the existing and new parts of the home can all require changes downstairs.
If you are also considering changes to the kitchen, living areas or existing bedrooms, it is generally better to incorporate these into the overall design rather than adding them later as separate variations.
7. Think About Bathrooms and Plumbing Early
Bathrooms and ensuites are important cost and design considerations in an upper-floor addition.
Where practical, locating new wet areas near existing plumbing can simplify service runs and construction.
The best location should still be driven by the overall floor plan, but plumbing requirements should be considered while the layout is being developed rather than after rooms have been finalised.
8. Check Construction Access
Consider how builders will actually construct the upper floor.
Important site issues can include:
- side access
- driveway access
- neighbouring buildings
- overhead power lines
- established landscaping
- space for scaffolding
- material storage
- crane access where required
Difficult access does not necessarily prevent a second storey extension, but it can influence construction methods, timing and cost.
9. Decide Whether You Can Live in the Home During Construction
Some homeowners can remain in part of the house during sections of the build, while other projects make temporary relocation more practical.
Roof removal, weather protection, electrical and plumbing interruptions, noise, dust and restricted access all need to be considered.
This should be discussed during pre-construction planning so the family knows what to expect before work begins.
10. Understand the Difference Between Planning and Building Approval
A planning permit and a building permit serve different purposes.
A planning permit deals with matters such as the proposed development, neighbourhood amenity, setbacks, overlooking and heritage considerations.
A building permit deals with the technical construction requirements and compliance of the documented building work.
Whether a separate planning permit is required depends on the property and proposed design, whereas structural building work requires a building permit before construction starts.
11. Avoid Designing Too Far Before Checking Feasibility
It is easy to become attached to a particular floor plan before understanding the structural and planning constraints of the property.
A better approach is to establish feasibility first, then develop the design around the information discovered.
This reduces the risk of paying for detailed documentation that later requires substantial redesign.
12. Choose a Builder Experienced in Upper-Floor Extensions
Double and second storey extensions involve a different set of challenges from building on a vacant site.
The builder needs to integrate new construction with an existing occupied building, manage structural strengthening, remove and reconstruct roofing, coordinate temporary weather protection and minimise disruption to the existing home.
Ask to see relevant completed projects and understand how the builder manages design, engineering, approvals and construction.
Ready to Start Planning?
Resolving these questions before detailed design gives you a clearer understanding of what is possible, what the project may involve and where the main risks or constraints are likely to be.
If you are ready to assess your own property, Cameron Construction provides design, engineering, approvals and construction for double and second storey extensions across Melbourne.
