Is fixing the uneven subfloor a lot owner's or OC's responsibility?
Owners corporation’s have a statutory duty to repair and maintain common property under section 106 of the Strata Schemes Management Act 2015 (NSW) (‘the Act’).
The concrete slab forms part of the common property and so too does any levelling compound that is applied to it.
The owners corporation is therefore responsible for the cost to re-level the concrete slab so that flooring can be installed properly on top of it. The concrete slab must be fit for purpose.
Assuming the flooring works (being a minor renovation that must be approved in accordance with section 110 of the Act and clause 28 of the Strata Schemes Management Regulations 2015 (NSW) (‘the Regulations’)) have been properly approved by the owners corporation, a solution could be to ask the installer to quote on re-levelling the floor. Their quotation could then be provided to the owners corporation to consider engaging the supplier directly. This gives the owners corporation the rights to warranties and control over the tradespeople it uses to repair its property.
If an owner wishes to undertake work to common property, approval must be sought under section 111 of the Act. In this article  we explored section 111 in more detail.