What an overlay is (flood, bushfire, character, koala)

An overlay is a map layer that sits on top of the zone and flags something about the land itself: it floods, it is near bush, the street is pre-1946 character, koalas live there, it is steep, it is next to a highway. The zone says what the land is for; the overlay says what has to be dealt with before building there. For a second home an overlay does two things. It can turn a home that would otherwise be accepted into one that needs a planning application, and it can change what gets built: a higher floor, a bushfire rating on the windows and deck, a design that matches the character of the street.

How an overlay works

Each overlay has a code in the council's planning scheme that lists what a proposal must address inside the mapped area. The overlay applies only to the part of the lot inside the mapping, a lot can carry several at once, and where the overlay code is inconsistent with the zone code, the overlay takes priority. Councils draw many of their hazard overlays from the State Planning Policy mapping, which the state publishes for flood, bushfire, landslide and coastal hazard, and from their own flood studies.

The four that matter most for a second home

Flood. Council maps river, creek and overland flow flooding. Under the Building Regulation 2021 a council can also declare a flood hazard area and a defined flood level for it, and then the building rules in QDC MP 3.5 set the floor height: the defined flood level plus a freeboard, 300 mm unless council says more. On a low block that means taller piers and flood-resistant materials below the line, and sometimes a flood report before the certifier can issue the approval.

Bushfire. Where council has designated land as bushfire prone, Queensland applies AS 3959 to new homes. The block gets a Bushfire Attack Level, from BAL-LOW to BAL-FZ, set by the vegetation, the slope and the distance between them, and the rating decides the windows, screens, cladding, decks and subfloor. A BAL assessment is a report, and the deck material is the line it most often changes. Bushfire ratings explained goes through the levels.

Character. Brisbane's traditional building character overlay maps areas of houses built before the end of 1946. Inside it, demolition and some extensions need an application, and a second home has to fit the streetscape. Other councils have heritage and character overlays of their own. The character overlay rarely stops a second home behind a house; it shapes it.

Koala. In South East Queensland the Planning Regulation 2017 and the koala conservation plan map koala habitat areas. Clearing native vegetation in a koala habitat area needs a development approval, and inside a koala priority area it is prohibited unless an exemption applies. The exemption that matters on a house block is a once-off allowance of 500 m² of clearing per premises, and tree lopping is not clearing. A second home placed on already cleared ground usually never meets the rule.

What to do with a flagged block

• Read which overlay it is and how much of the lot it covers. A flood overlay on the front corner and a home at the back are different things.
• Ask what it triggers: a report, a planning application, or a construction rule. Reports run from about $1,000 for a BAL assessment to several thousand for a flood report.
• Place the home where the overlay is lightest. On most blocks that is the choice that removes the application.

See it for your block

• Check your block for overlays
• What the consultants' reports cost
• Bushfire ratings explained

Questions people ask next