Is my block in a mine subsidence district?

Parts of the northern Central Coast sit above past, present or planned underground coal mining. Where there is a risk the ground could move, Subsidence Advisory NSW declares a mine subsidence district and regulates what can be built there. Type your address below to see whether your block is in one.

What is a mine subsidence district?

It is an area where there is a potential risk of subsidence to buildings from planned, active or non active underground coal mining. Subsidence Advisory NSW declares the districts so it can regulate development and protect homes and other structures from damage.

Subsidence is ground movement over mine workings. It can lower the ground, stretch or compress it, tilt it or curve it. Where old workings are very shallow, it can open a pothole, a hole in the ground, and most of those are less than 5 metres across.

Which parts of the Central Coast are in a mine subsidence district?

Subsidence Advisory's district maps show three districts reaching into the Central Coast council area.

• Swansea North Entrance. The largest, running down from Swansea through Mannering Park, Chain Valley Bay, Lake Munmorah, Doyalson, Colongra, San Remo, Blue Haven, Budgewoi, Buff Point, Charmhaven and Lake Haven.
• Wyong. The rural valleys north west of Wyong, including Jilliby, Little Jilliby, Dooralong, Ravensdale, Wyong Creek, Kiar, Lemon Tree and Durren Durren.
• Hue Hue. A smaller district between Jilliby and Alison.

District boundaries do not follow suburb boundaries, so part of a suburb can be in and part out. Check your own lot rather than the suburb name.

What approval do I need to build in a mine subsidence district?

Approval from Subsidence Advisory NSW before you start work. That covers building or extending a home or other structure, and subdividing land. Some minor works, such as small carports, decks and fences, are on Subsidence Advisory's exempt development list and do not need its approval.

Every property in a district is assigned a Surface Development Guideline. Council and accredited certifiers can approve work that complies with Guidelines 2, 3, 3A, 6 or 8 without referring it to Subsidence Advisory. Properties assigned Guidelines 1, 1A, 4, 5 or 7 need Subsidence Advisory's approval. A development application in a district is integrated development, so council refers it to Subsidence Advisory where needed, or you can lodge directly through the Subsidence Advisory portal.

An application that complies with the guideline is approved within 7 calendar days. One that exceeds it goes to a merit assessment, which is determined within 40 calendar days unless more information is requested.

How does a mine subsidence district affect my design?

The guideline for your lot sets the limits, and neighbouring lots can have different guidelines because one may be mined beneath and the next may not. Guideline 1, for example, applies where there is a pothole risk and allows a single storey brick veneer house or a two storey lightweight house, built on a standard sinkhole footing design or an engineered design.

Where ground movement is the concern, Subsidence Advisory's design advice is to keep foundations shallow or on a slip layer, separate deep footings from the frame above, and add articulation joints in walls so they can move without cracking or jamming doors and windows. Leaving brickwork out above windows and doors helps too. Near creeks and lakes, vertical subsidence can increase flood risk, so habitable floors should sit comfortably above the flood planning level.

Subsidence Advisory needs a full set of architectural plans (site, floor and elevations) to assess an application. I check the guideline before the first sketch, so the footing system and the walls suit it from the start.

Should I worry about buying a house in a mine subsidence district?

Not if the paperwork is right. Every home in NSW, inside or outside a district, can claim compensation for mine subsidence damage, provided the correct development approvals were obtained. So ask your solicitor or conveyancer to confirm with the seller that structures were built with the correct approvals, that there has been no unauthorised work, and whether any subsidence claim has been made. Subsidence Advisory also keeps a searchable register of certificates it has issued. Your section 10.7 planning certificate states whether the land is in a district.

How do I check if my block is in a mine subsidence district?

Use the checker above. Or search your address on the NSW Planning Portal Spatial Viewer and look at the search results on the right. If the property is in a district, it appears there, and clicking the + shows the guideline assigned to it. The Underground Coal Mining Area layer shows whether mining has happened under or near the lot.

For the rest of the maps on your block, run the full Site Checker, or book a free chat and I will go through the result with you.