Lot vs Common Property in a Townhouse — Who's Responsible for What

"That's not my problem — that's the owners corporation's." It's one of the most common questions in strata, and the answer matters because it decides who pays. Here's the plain-English guide for townhouse and villa owners, with the case law that backs it up.

The starting point — Section 106 of the Act

Under Section 106 of the Strata Schemes Management Act 2015 (NSW), the owners corporation has a strict duty to repair and maintain the common property. "Strict" means there's no reasonableness defence — if it's common property and it's broken, the OC must fix it.

Lot owners are responsible for their lot. Everything in the lot, you maintain. Everything that's common property, the OC maintains.

The whole game, then, is working out where the line is.

How the line is drawn

The strata plan for your scheme is the source of truth. Lot boundaries are shown on the floor plan, often with notations about height (the "stratum"). The NSW Court of Appeal in The Owners – Strata Plan No 35042 v Seiwa Australia Pty Ltd [2007] NSWCA 272 confirmed that stratum height notations actually define the lot boundaries — not just guidance.

If your plan doesn't have a stratum notation, the default position under the Strata Schemes Development Act 2015 generally has the lot boundary running through the centre line of common walls, with floor finishes typically being lot property and the underlying slab being common property.

Always check your individual strata plan — there are quirks, especially in older schemes.

Townhouse quick reference

For most modern NSW townhouse and villa schemes, the rough rule of thumb looks like this:

The "check your plan" items vary — some strata plans include garages and courtyards as part of the lot, others mark them as common property with exclusive use by-laws.

The membrane trap

This is the one that catches people out. Even when something looks like it's inside your lot, the structural waterproofing membrane beneath it is almost always common property.

Bannermans Lawyers put it this way in their commentary on water ingress (October 2023):

"The waterproofing membrane, screed, concrete slab, and other structural elements in a scheme are all common property, and failure of these elements is the cause of water ingress in the majority of cases."

So if your bathroom floor is leaking through to the ceiling below, or your balcony tiles have lifted because the membrane underneath has failed, that's almost always the OC's job — even though the surface finish on top is yours.

What about planter boxes and balconies?

A common townhouse situation: a planter box or raised garden bed on the balcony or in a courtyard. Per the principles set out by Bannermans:

1. Check the strata plan — is the planter box shown as lot or common property?
2. Check the registered by-laws — has responsibility been transferred to the lot owner?
3. Even if the planter box itself is lot property, the waterproofing membrane within it is usually common property.

That last point matters because most planter box water problems start with the membrane, not the box itself.

What if you and the OC disagree?

If you've got water damage, mould or other damage and the OC won't accept it's common property, you have options under the Act:

• Mediation through NSW Fair Trading
• An application to NCAT for orders under Sections 232, 241 and 106(5) of the SSMA
• If significant damages are involved, NCAT now has unlimited jurisdiction to award compensation under Section 106(5) — see our separate article on damages claims when the OC fails to repair.