Three flood overlays appear in Victorian planning schemes — Land Subject to Inundation Overlay (LSIO), Special Building Overlay (SBO), and Floodway Overlay (FO). Each has different planning controls, different building requirements, and very different effects on insurance and resale. Buyers regularly conflate them, but misunderstanding the overlay you’re buying under can mean the difference between standard insurance and uninsurable, or between freely renovating and being unable to build at all.
This guide covers each overlay’s legal effect, what triggers permits, how insurance treats each, and what every buyer should check.
The three flood overlays — comparison
| Overlay | What it indicates | Planning controls | Insurance impact |
|---|---|---|---|
| LSIO | Land subject to 1-in-100 year flood | Permit for buildings; FFL requirements | Modest premium; some exclusions |
| SBO | Urban stormwater overland flow | Permit for buildings; specific FFL rules | Moderate premium |
| Floodway (FO) | Active floodwater pathway | Generally no new buildings; severe restrictions | Often uninsurable |
Land Subject to Inundation Overlay (LSIO)
LSIO indicates land likely to be inundated during a 1-in-100 year flood event (1% annual exceedance probability). The overlay is applied based on Melbourne Water or local catchment management authority modelling. LSIO controls:
- Building permit required (and planning permit in many councils)
- Finished Floor Level (FFL) must be above the 1-in-100 flood level + freeboard (typically 300–600mm)
- Restrictions on filling and excavation
- Restrictions on subdividing
- Notification on Section 32 (must be disclosed)
LSIO covers significant portions of Maribyrnong, Yarra, Stonnington, Port Phillip, Bayside, and most of metropolitan Melbourne’s creek and river corridors.
Special Building Overlay (SBO)
SBO is similar to LSIO but covers urban stormwater overland flow — water that can’t fit in stormwater pipes during heavy rainfall. SBO is most extensive in inner-Melbourne LGAs:
- City of Yarra (Richmond, Fitzroy, Collingwood)
- City of Maribyrnong (Footscray, Yarraville)
- City of Port Phillip (St Kilda, Port Melbourne)
- City of Stonnington (South Yarra, Prahran, Windsor)
- Bayside (Brighton, Hampton, Sandringham — recently expanded)
- Boroondara (Camberwell, Hawthorn — pockets)
SBO controls are very similar to LSIO — building permits, FFL requirements, restrictions on filling. Many properties carry both LSIO and SBO.
Floodway Overlay (FO) — the severe one
Floodway Overlay applies to land that actively conveys floodwater — the “deepest” flood-prone zones. Controls are severe:
- Generally no new buildings permitted
- Major restrictions on extensions and improvements
- No filling or excavation that affects flow
- Insurance companies often exclude flood cover entirely
- Resale market substantially reduced
Floodway Overlay properties are rare in established residential areas — most floodway land is parks, vacant land, or pre-existing structures with grandfathered status.
Insurance impact
Flood insurance availability and premium depends on overlay:
| Overlay status | Standard cover available | Typical premium loading |
|---|---|---|
| No flood overlay | Yes | Standard |
| LSIO only | Generally yes | 10–30% loading |
| SBO only | Generally yes | 10–25% loading |
| LSIO + SBO | Most insurers | 25–60% loading |
| FO (floodway) | Limited; many exclude flood | 100%+ loading or exclude |
| Recent flood event recorded | Variable; some refusal | 50–200% loading |
Buyer due diligence
- Council planning property report. Confirms which overlays apply.
- VicPlan. Free public planning map; cross-check overlay coverage.
- Melbourne Water flood data. For LSIO/SBO properties, get the 1-in-100 flood level. This sets your minimum FFL.
- Insurance pre-quote. Get a written quote at settlement to confirm availability and premium.
- Recent flood history. Speak with neighbours and check council records for past flooding events.
- Existing FFL vs required FFL.If renovating, confirm whether existing FFL meets current requirements (older buildings often don’t).
Section 32 disclosure
Under section 32C of the Sale of Land Act 1962, vendors must disclose any overlay affecting the property. The Section 32 should include:
- Council planning property report (showing overlays)
- Any flood-related notices or orders
- Past flood history if known
- Any planning permits referencing FFL or flood mitigation
Renovation implications
If you plan to renovate or extend, consider:
- Permit triggers — most works in LSIO/SBO need a permit
- FFL upgrade requirements — extension may need to be at higher level than existing
- Structural assessment — older slabs may not meet current standards
- Drainage and stormwater management requirements
- Insurance review post-renovation — may improve premium
Ready to check your contract? Upload your Section 32 or Contract of Sale at precontractreview.com for a pre-contract check — typically in just a few minutes.