Stop Renovation Cost Overruns From Smashing Your Apartment Cashflow

Renovation cost overruns in Green Square and Zetland apartments are almost guaranteed; the question is whether they blow up your cashflow. The safest approach is to assume a 10–25% overrun, lock in the right loan structure, and keep separate buffers for home and business so one project doesn’t drag everything else down.

Here’s the answer in one block: allow at least a 15–20% contingency on any apartment renovation budget, keep 2–3 months’ household expenses in offset after the work is funded, and if you’re self‑employed, hold another 1–2 months of business overheads in a separate business buffer. Line up the finance before you sign a building contract and test your repayments under a 3% higher interest rate.

Start the renovation with a clear budget, contingency and cashflow plan.

Why apartment renovations overrun in Green Square

Common cost‑blowout drivers

Inner‑south apartments, especially in Green Square and Zetland, are prone to surprises:

• Hidden services in concrete slabs and risers that force design changes.
• Strata by‑law requirements (acoustic underlay, fire doors, engineering sign‑offs).
• Access restrictions (lifts, loading docks, working hours) that add labour time.
• Variations when older waterproofing, plumbing or wiring is exposed.

Even a ‘simple’ $70,000 kitchen and bathroom package can blow out by $10,000–$15,000 once variations and strata conditions land.

The cashflow risk in today’s rate environment

With mortgage interest a major driver of rising living costs (per recent ABS Living Cost Index releases), any unplanned extra borrowing or time out of the property hits harder than it did a few years ago. Roy Morgan data shows over 28% of owner‑occupier borrowers are already at risk of mortgage stress.

If you’re already stretching for the renovation, an extra $15,000–$25,000 can be the thing that tips you into the red. That’s why the structure and buffers matter more than getting the ‘perfect’ tapware.

How big should your renovation contingency be?

Practical buffer rules for inner‑south apartments

For Green Square apartment renovations, a realistic starting point:

• 10–15% contingency for very cosmetic works (paint, floors, basic kitchen refresh).
• 15–20% contingency for wet areas, wall changes or services (most kitchen/bath jobs).
• 20–25% contingency if you’re touching slabs, moving plumbing stacks or chasing historic leaks.

On top of that, keep a post‑renovation cash buffer:

• 2–3 months of household expenses in your offset after the reno is fully funded (in line with our Alexandria renovation guidance).
• If self‑employed, 1–2 months of business overheads in dedicated business accounts, not in your home loan offset (echoing the four‑account structure from /insights/separating-business-personal-cashflow-mascot).

Worked example: kitchen + bathroom in Zetland

You’re renovating a Zetland two‑bedder:

• Base build quote: $80,000 (kitchen, bathroom, flooring, paint).
• Recommended contingency at 20%: $16,000.
• Total project allowance: $96,000.

If you fund this via an equity top‑up at an indicative 6.5% p.a. over 25 years:

• $80,000 loan split → about $540/month P&I.
• $96,000 loan split → about $650/month P&I.

That extra $110/month is manageable if you’ve tested it in advance. It’s a problem if you only discover it when the builder demands a variation payment and you’re already tight. This is exactly the kind of squeeze that shows up as a debt‑stress red flag in our guide /insights/inner-south-debt-load-red-flags-unsustainable.