Is my block in a mine subsidence district?
Written by Shea Cullen, architect, for Dudils.
Parts of Newcastle, Lake Macquarie, the Hunter, the Central Coast, the Illawarra, south west Sydney and the Lithgow area sit over old or working underground coal mines. Type an address and the Site Checker reads the mine subsidence district layer that Subsidence Advisory NSW publishes through the NSW Planning Portal, and names the district in the other constraints section of the report if your lot is in one.
NSW addresses only. Free, and no sign up.
Is my property in a mine subsidence district?
The Site Checker tells you, and names the district. Mine subsidence districts are declared under the Coal Mine Subsidence Compensation Act 2017 over land where underground coal mining has happened or may happen, so the ground surface could move. Being in a district does not mean the ground under your lot has moved or will. It means building there is managed so that a house can cope if it does.
The section 10.7 planning certificate in a sale contract also states whether the land is in a district. Subsidence Advisory NSW, the state agency that runs the scheme, can tell you more about the mining history under a particular lot.
What do I need to do before I build?
Get approval from Subsidence Advisory NSW before work starts. It is needed for new buildings, additions, subdivision and other improvements in a district, and it is given under section 22 of the Act. Each district is divided into areas with Surface Development Guidelines, which set what can be built there: limits on the building's size, height and construction type, so the house can flex if the ground moves.
A design that fits the guideline for its area is approved quickly, and the agency aims to decide those within seven days. A design outside the guideline needs an engineer's assessment and takes longer. A development application in a district is integrated development, so council refers it to Subsidence Advisory before approving it. If you are going through complying development, get the approval before you apply to the certifier, and tell your designer the district's guideline before drawing starts, because it can decide the structure.
Does mine subsidence affect insurance or resale?
Mine subsidence damage is generally excluded from home insurance, and is covered instead by the NSW compensation scheme run by Subsidence Advisory NSW. Damage from an active mine is paid for by the mine's operator, and damage from old workings by the Mine Subsidence Compensation Fund, with every claim lodged through Subsidence Advisory. The scheme covers homes inside or outside a district, but a building put up in a district without the approval it needed may not be eligible.
So before you buy a house in a district, ask the seller for the Subsidence Advisory approval for the house and any additions, and have your conveyancer check it. The district is disclosed on the planning certificate attached to the contract, so every buyer of that house sees it too.
How do I check a house I am buying in a mine subsidence district?
Start with the planning certificate in the contract, which names the district. Then ask the seller for the Subsidence Advisory approvals for the house and for anything added since, such as an extension, a granny flat or a pool, because work built without the approval it needed may not be eligible for compensation if subsidence later damages it.
A building inspection is worth having in any district. Cracked brickwork, sticking doors and uneven floors have many causes, from reactive clay to leaking pipes, and an inspector cannot say which one it is. Where the report finds damage that could be ground movement, ask Subsidence Advisory NSW about the mining under the lot before you exchange contracts.
Does building in a mine subsidence district cost more?
Sometimes, and the guideline for your area decides how much. Some guidelines call for articulation joints in brickwork, a stiffer slab, lighter cladding or limits on the size of the building, and a few areas over shallow workings need an engineered design. Others allow an ordinary house with little change. Ask your builder whether they have built under your district's guideline before, and have the guideline in hand before you compare quotes.
What does a mine subsidence district not tell me?
It is a boundary drawn around where mining could affect the surface, not a measurement of the ground at your lot. Some lots in a district have no known workings under them, and the risk varies across a district, which is why the guidelines vary too. Ground conditions such as reactive clay or old fill are covered by the geotechnical investigation for your footings, not by the district. On a sloping block, read the slope on the same report too, and on low lying coastal land the acid sulfate soils class.
Is my block in a mine subsidence district? Check any NSW address, free.
NSW addresses only. Free, and no sign up.
What else do people ask?
How long does Subsidence Advisory approval take?
A design that fits the guideline for its area is decided quickly, with a target of seven days. A design outside it takes longer because it needs an engineer's assessment.
Is every coal mining area a mine subsidence district?
No. Districts are declared where the risk to surface development justifies managing it. Land outside a district can still sit over old workings, and damage there from mine subsidence can still be eligible for compensation.
Who do I contact about mine subsidence?
Subsidence Advisory NSW, which handles development approvals, the guidelines for each district and compensation claims. Its pages are on the NSW Government website.
Where does this information come from?
The Site Checker reads public maps. It is not a section 10.7 planning certificate, a flood certificate, a bushfire attack level assessment or a survey, and a map can be out of date for your lot. Confirm anything you rely on with council or the relevant authority before you buy, design or build. Nothing on this page replaces advice from your certifier, engineer, lawyer or your own designer.