This is the article that would have saved a lot of Perth homeowners a significant amount of money and stress — if they’d read it before demolition started rather than after.
The surprises that renovation companies find inside walls, under floors, and behind tiles in older Perth homes are not rare. They are common, they are predictable given the age of the property, and they can be largely anticipated with the right checks before work starts. What changes when you find them during demolition versus before — is who pays for them and how the discovery affects the project schedule.
This article covers the four most common hidden surprises in Perth renovation projects, how to identify which ones are likely in your home, and how to approach a renovation so that discoveries are managed rather than disruptive.
Non-friable asbestos (bonded asbestos) — where the asbestos fibres are bound within a matrix such as cement — is less immediately hazardous than friable asbestos (loose fibres). Flat sheet fibro, floor tiles, and roof sheeting are typically non-friable. Pipe lagging and some roof insulation materials can be friable.
The distinction matters because non-friable asbestos that is in good condition and not being disturbed carries low risk. The risk arises when it is cut, sanded, drilled, or otherwise disturbed — which is exactly what happens during renovation.
Galvanised steel water pipes were the standard residential plumbing material in Australia from the early 1900s through to the 1960s, when copper became dominant. In Perth, homes built before approximately 1970 frequently retain their original galvanised steel water supply lines — either throughout the home or in sections.
Galvanised steel pipes corrode from the inside over time. The internal bore progressively narrows with rust and mineral deposits, reducing water pressure. In advanced cases, the pipe wall becomes pitted and brittle. When a renovation involves any plumbing work — connecting a new vanity, relocating a shower, adding a sink — the licensed plumber is legally required to assess the existing supply lines. If they are not fit for purpose, they cannot be connected to without replacement.
This is not a bureaucratic technicality. It is a practical and legal requirement that catches Perth homeowners by surprise regularly — because the pipes look fine from the outside and the water flows through them, until the plumber opens the wall and finds a bore the diameter of a pen.
| Indicator | What It Suggests |
| Home built before 1965 | High probability of galvanised supply lines. Assume present until confirmed otherwise |
| Reduced water pressure at taps and showers | Classic sign of corroded galvanised bore. Common in older Perth homes. |
| Rust-coloured water when taps are first run | Galvanised pipe corrosion. Particularly common after a period of non-use. |
| Lead-based solder at copper-galvanised junctions | Sometimes found at transition points. Licensed assessment required. |
| Previous renovations done without replumbing | May have connected new fixtures to old galvanised lines — check the junctions. |
Full replumbing of a Perth home (all water supply lines) typically costs $8,000–$18,000 depending on the size of the home and access difficulty. Partial replumbing of a bathroom or kitchen zone costs $3,000–$7,000. This is not a renovation extra — it is infrastructure work that brings the home to a standard that allows the renovation to proceed correctly.
Electrical standards in Australian residential construction have changed substantially over the past 50 years. Work completed to the standards of 1975 is not necessarily compliant with the standards required today — and when a renovation involves electrical work, the licensed electrician is required to assess the existing installation in the areas they’re working in.
⚠ Watch out — In WA, all electrical work must be performed by a licensed electrician and a Certificate of Compliance issued on completion. There is no legal pathway for homeowners to perform their own electrical work. If you are getting quotes from renovation companies who propose to handle electrical work without a licensed electrician, that is a red flag.
A switchboard upgrade for a typical Perth home costs $2,500–$5,000. Rewiring a bathroom or kitchen zone costs $1,500–$4,000. Safety switch installation across a whole home costs $800–$2,000. These are not optional extras when discovered — they are the legal prerequisite for the renovation work proceeding.
Perth homes that have been extended, modified, or renovated at various points over their lives sometimes carry undocumented structural changes — walls removed without proper beam installation, extensions connected without structural engineering, or load paths that no longer follow the original design. These are discovered when a renovation involves structural work and a licensed builder or structural engineer assesses the existing structure.
Perth’s climate is highly favourable for subterranean termites. Homes without regular termite inspections and barrier maintenance can carry significant structural timber damage that is invisible from the surface. Renovation work that opens wall cavities frequently reveals termite activity or past damage.
Many pre-1970 Perth homes were built on timber stumps with suspended timber floors. Subfloor ventilation requirements were less stringent than today’s standards. Poor ventilation leads to rising damp and timber rot in the subfloor — which is both a structural issue and a health one. A bathroom renovation that exposes the subfloor sometimes reveals that the subfloor itself needs work before new wet area construction can proceed.
For a Perth home built before 1985, a contingency of 15–20% above the base renovation quote is appropriate. This is not pessimism — it is the part of the budget that means a discovery during demolition doesn’t stop the project. A homeowner who enters a bathroom renovation with a budget of exactly the quote price has no room to respond when the wall comes down to reveal something unexpected. A homeowner with a 15–20% contingency has choices.
How to Set a Renovation Budget That Actually WorksWhen a renovation company visits your home, ask directly: what are the likely hidden issues in a property of this age and type, and how are they handled in your quote process? The answer tells you a great deal about the company. A company that says “we’ll cross that bridge when we come to it” is telling you that hidden surprises will come to you as variations after the contract is signed. A company that builds a methodology around identifying likely issues before quoting is telling you something very different.
House & Co conducts a pre-quote assessment of the age and condition of the property before every renovation. Likely asbestos, plumbing condition, and electrical compliance are discussed at the consultation. Where we have significant uncertainty about what we’ll find, we say so — and we build a contingency allowance into the scope rather than treating it as a post-contract surprise.
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