Planning a second dwelling in Bendigo can look simple at first. Then the real site issues start showing up.
The biggest mistakes usually happen before building starts. A block can look perfect on paper, but a planning overlay, poor soil, sewer assets, asbestos, drainage constraints or footing changes can add time and cost fast.
This guide is written to help you spot the real risks early so you can ask better questions before spending money on drawings or permits.
Important: This is general information only, not legal advice. Planning and building requirements vary by site and can change. Always confirm current requirements with the relevant council, water authority, utility providers and your appointed building surveyor before proceeding.
1. Start with the 60 square metre rule, but do not stop there
Victoria’s small second dwelling framework has made many homeowners look more closely at adding a second home on their block.
In plain terms, a small second dwelling is generally a self-contained home on the same lot as an existing house. The key threshold most homeowners hear first is 60 square metres of floor area.
That threshold matters because it can help determine whether a planning permit may be needed at all.
In some cases, a second dwelling that is 60 square metres or less may follow the small second dwelling pathway. In other cases, once you go over that size, the project may move into a more standard two dwellings on a lot pathway, which can mean a different approval process.
But the 60 square metre figure is only the start. You still need to confirm the site-specific requirements for:
- The lot size.
- The planning zone.
- Setbacks and siting.
- Overlays.
- Easements.
- Existing services.
- Any title restrictions or covenants.
- Whether the block can physically accommodate the building.
A block is never approved just because the proposed dwelling is under 60 square metres. That is why it is worth confirming the planning pathway with the relevant council and building surveyor before you commit to full design work.
2. The biggest trap: planning overlays can change everything
One of the most important checks on any Bendigo second dwelling project is whether the property is affected by a planning overlay.
For a homeowner, the big issue is simple: a planning overlay can remove exemptions entirely. A project that might otherwise have had a simpler pathway can suddenly require a planning permit, and sometimes separate demolition consent as well.
That can add significant time, not just paperwork.
This does not mean you cannot build a second dwelling. It means you should not assume the small second dwelling rules will work the same way on every block.
The safe approach is to confirm early:
- Whether a planning overlay applies.
- Whether any exemption is removed.
- Whether demolition approval is needed for any shed, garage or outbuilding.
- Whether the design response will need to change.
If your site is affected, treat this as a regulatory issue to confirm with council and your building surveyor at the start.
3. Soil can change the build cost quickly
Soil is one of the biggest hidden risks in a second dwelling project.
You might think the backyard is ready to go because there is already an old shed slab or a relatively flat area. In practice, that can be misleading. An existing slab is not proof that the ground is suitable for a new dwelling.
A proper soil report helps identify what is really going on below ground. One outcome homeowners need to understand is Class P.
In simple terms, Class P means the site has problem conditions that need special engineering consideration. That might happen because of:
- An old shed slab in the proposed building area.
- Uncontrolled fill that was placed on the site years ago.
- Large nearby trees affecting ground movement.
- Other abnormal ground conditions.
When a site is Class P, the footing system usually needs to be engineer-designed for those conditions. That can change cost, detailing and sometimes the construction method.
This is why it is risky to budget from a rough square metre rate before the soil and site conditions are properly investigated.
4. Footing choice can change the build cost
Homeowners often focus on finishes, but the footing system underneath the building can move the budget significantly.
Depending on the site and the engineer’s advice, a second dwelling might use:
- A stiffened raft slab.
- A waffle pod slab on piers.
- Strip footings with a suspended timber floor.
These are not minor technical differences. The right option depends on the soil conditions, fill, trees, levels, drainage and access. One system may be straightforward on one site and expensive on another.
The key point is that the footing choice can change the build cost.
That is why it is worth asking the engineer and builder whether more than one footing option can be considered and priced where appropriate. Doing that early can save you from locking into a costly solution before you understand the alternatives.
5. Check sewer assets before you get too far
A common backyard problem is a sewer main running through the back of the block.
If that happens, you may need a build-over agreement from the relevant water authority before work starts. Depending on the asset location and the proposed building footprint, the authority may impose conditions, require setbacks, require protection measures or restrict what can be built over the asset.
This can affect:
- Where the second dwelling can sit.
- The footing design.
- The drainage layout.
- The timing of approvals.
It is much better to find this out early than after drawings are finished. If there is a sewer asset anywhere near the proposed building area, confirm the requirements with the relevant water authority before you assume the design will work.
6. Check underground electricity and use BYDA early
Underground electricity is another issue that is easy to overlook on paper.
Before excavation starts, you want a clear picture of what services may already be in the ground. That is where Before You Dig Australia (BYDA) comes in. A BYDA enquiry helps identify the presence of underground infrastructure so your team knows what needs further checking before digging.
For a second dwelling, underground electricity can affect:
- Trenching routes.
- Excavation safety.
- Service connection planning.
- The placement of footings, drainage and external works.
A BYDA response is part of early due diligence, not something to leave until the excavator is booked.
7. Legal point of discharge and council property information matter early
Stormwater and council property information can become a problem if they are left too late.
One item to check early is the legal point of discharge. In simple terms, this is where stormwater from the new dwelling is legally allowed to discharge.
If that point is difficult to access, far from the proposed dwelling, or requires additional drainage work, your costs can increase quickly.
You should also review the available council property information early in the process. This can help flag planning controls, drainage matters and other site constraints before you spend more on design.
These checks are worth doing up front because they affect both feasibility and cost.
8. Older sheds and outbuildings can contain asbestos
If there is an older shed, garage or outbuilding in the area where the second dwelling is proposed, do not assume demolition is straightforward.
Older materials may contain asbestos. If asbestos is present, it must be handled correctly and removed by a licensed asbestos removalist.
This is not something the builder simply deals with as part of normal demolition.
If a structure on site may contain asbestos, treat that as an early investigation item. It can affect demolition timing, cost and the approval pathway, especially if overlays or demolition controls also apply.
9. Energy requirements still need project-specific confirmation
A second dwelling will also need an energy report to show compliance with the current National Construction Code requirements.
The details depend on the design. Items that can affect compliance include glazing, insulation, shading, orientation, sealing and the way the home is serviced.
The important point for homeowners is this: there is no one-size-fits-all answer. Energy requirements should be confirmed for the particular design rather than assumed from another project or an online example.
10. The permit cost-of-works figure is only an early estimate
One of the most honest points to understand at the start is that the cost-of-works figure on a permit application is an early estimate.
Homeowners can get caught out when that early figure changes later. In reality, it commonly rises once the site is properly investigated and the real conditions are known.
That can happen because of:
- Soil classification results.
- Footing changes.
- Sewer or drainage constraints.
- Demolition issues.
- Asbestos removal.
- Service upgrades.
- Design development and specification changes.
The practical lesson is simple: budget for movement rather than assuming the first permit number is the final build cost. That way, you are less likely to be blindsided later.
BOS Construction’s six-step process
BOS Construction uses a clear process to help homeowners navigate second dwellings, renovations, extensions and new builds across Bendigo, Kyneton and Castlemaine.
1. Initial enquiry
Brad answers directly to discuss your plans, property location and what you want to achieve.
2. Site visit
Brad checks existing conditions, levels, access, what is behind walls where relevant, and what the block will realistically allow.
3. Planning
Engineering, soil tests and working drawings get sorted so you know what you are building before anyone prices the construction.
4. Proposal
You receive a real scope and price. Provisional sums are explained clearly as flexible allowances so you understand what may still move.
5. Construction
Brad is on site and on the tools as your one point of contact.
6. Handover
The job finishes with a walkthrough to address anything outstanding.
Why homeowners call BOS Construction
BOS Construction is a Master Builder with Master Builders Victoria membership, backed by 20 years of experience. Brad O’Shea is the owner and builder, and he stays directly involved on site and on the tools. BOS Construction is registered with the Building and Plumbing Commission, DB-U 38574.
BOS focuses on work across Bendigo, Kyneton, Castlemaine and the wider Calder Corridor, along with South Melbourne, with services including renovations, extensions, second dwellings, bathroom and laundry renovations, new builds and occasional commercial fit-outs.
What homeowners get from BOS Construction:
- BOS is the do-it-once-do-it-right option for homeowners who want clear communication, practical advice and solid workmanship.
Ready to talk through your block?
If you are considering a second dwelling in Bendigo, the first step is to look at the block properly before you get too far into drawings.
Call Brad on 0425 808 840 or email info@bosconstruction.com.au to discuss your site and next steps.
Bring whatever information you already have, such as a rough sketch, title documents, site photos or an idea of how you want the second dwelling to be used. From there, Brad can help you understand the practical path forward.
Frequently asked questions
Does a second dwelling under 60 square metres always avoid a planning permit?
No. The 60 square metre threshold is important, but it does not override other controls. Lot size, zone, siting, overlays and other site-specific requirements still need to be checked with the relevant council and building surveyor.
Why is a planning overlay such a big issue?
Because it can remove exemptions that might otherwise apply. A planning overlay may trigger a planning permit and possibly separate demolition consent, which can add significant time. This should be confirmed with council early.
What does Class P soil mean for a second dwelling?
Class P generally indicates problem site conditions such as uncontrolled fill, existing slab issues, nearby trees or other abnormal ground conditions. It usually means the footing system needs specific engineering design.
Can the footing system really change the cost much?
Yes. A stiffened raft, waffle pod on piers or strip footings with suspended timber floor can produce materially different costs depending on the site. It is worth discussing options with the engineer and builder early.
What if there is a sewer main in the backyard?
You may need a build-over agreement from the relevant water authority before work starts. This can affect siting, engineering and timing, so it should be checked early.
Does BOS handle asbestos removal?
No. If asbestos is present, it must be removed by a licensed asbestos removalist. It is not something the builder handles as standard demolition.