Bathroom strip-outs in older Gold Coast homes routinely uncover issues that were not visible before the tiles came off. Coastal homes and homes 30+ years old are the most affected. The contingency you should budget for at the quote stage depends heavily on the housing age and exposure.
The five most common discoveries
1. Salt-corroded in-wall copper
Where: Beachside homes 25+ years old (Main Beach, Burleigh, Palm Beach, Currumbin and the coastal strips).
What: Original copper pipework running through the walls develops chloride pitting from coastal humidity over decades. By the time the tiles come off and we can see it, the copper often has visible green corrosion at fittings and may be weeks or months from first pinhole leak.
Fix: Replace the affected in-wall copper sections with PEX or new copper during the reno. $400-1,500 additional plumbing cost typically.
How to anticipate: Coastal home over 25 years old, budget $800-1,500 contingency specifically for copper replacement.
2. Drainage with insufficient fall
Where: 1970s-80s homes across all clusters. Some 90s homes too.
What: Original drainage was laid at marginal fall (sometimes well below the AS3500 minimum of 1:60). Over 30-50 years of soap scum and mineral buildup, the effective fall has degraded further, creating permanent slow drains.
Fix: Re-set the affected drainage to proper fall. Often involves slab coring, repositioning the drain, and pouring new screed. $1,200-3,500 additional cost typically.
How to anticipate: Original 70s-80s home, budget $1,500-3,000 contingency for drainage re-set.
3. Absent or failed waterproofing
Where: Pre-1990s homes (before waterproofing standards were really enforced).
What: Original bathroom may have had no waterproofing membrane at all, just cement directly under tiles. Or the original membrane has degraded with age. Often discovered when water-damaged substrate is found behind the toilet, in shower walls, or under floor tiles.
Fix: Standard scope, every bathroom reno includes new waterproofing by a separately licensed waterproofer ($1,800-3,500 typical). The surprise is when substrate damage from old failed waterproofing has spread to areas requiring additional remediation.
How to anticipate: Pre-1990 home, budget $500-1,500 contingency for substrate damage remediation.
4. Asbestos cement sheet behind tiles
Where: Pre-1985 homes (asbestos cement sheet was common in bathroom wall construction until phased out).
What: Asbestos cement sheet (sometimes called AC sheet or fibro) used as the wall substrate behind the tile. Cannot be removed by general trades, requires licensed asbestos removalist for any disturbance.
Fix: Engage a licensed asbestos removalist to remove and dispose. $1,500-5,000 additional cost typically depending on quantity.
How to anticipate: Pre-1985 home, ideally get an asbestos test done before strip-out so the contingency is known. Tests cost $200-500.
5. Tile substrate degraded by leaks
Where: Any home with a history of slow leaks (often unknown to the current owner).
What: Wall substrate (gyprock, plaster, sometimes substrate timber) has rotted or crumbled from years of water ingress at small leak points. Floor substrate (timber subfloor or screed over slab) may also be affected.
Fix: Replace affected substrate before new tiling. $500-2,500 additional cost depending on extent.
How to anticipate: Any home over 20 years old with history of small leaks, budget $500-1,000 contingency.
Other less common surprises
- Lead-based paint on old window frames or door frames. Pre-1970s. Requires lead-safe practices to remove.
- Outdated electrical wiring behind tile substrate. Sometimes original cloth-insulated cable still in service. Electrician will want to upgrade.
- Structural issues termite damage, settled subfloor, cracked slab. Rare but possible, especially in poorly-maintained older homes.
- Galvanised steel water pipes instead of copper. Very old homes (60+ years). Need replacement.
- Original toilet stack connection failures on older two-storey homes. Cast iron stacks sometimes have cracked sections.
How we manage discoveries during the reno
- We strip out methodically and inspect each layer as we expose it.
- We document any unexpected discoveries with photos.
- We tell you straight what we found and what the remediation cost will be.
- We get your sign-off on the variation in writing before doing additional work.
- We coordinate any specialist trades (asbestos removalist, structural engineer) if needed.
Why we recommend contingency
If your reno comes in under quote because no surprises emerged, great, the contingency stays in your pocket. If surprises do emerge and you have no contingency, the reno halts while you find the additional funds. Build the contingency into the budget from the start so the reno keeps moving when something is found.
Recommended contingency by housing age
- New estate home (under 15 years): 5% contingency, low surprise risk
- Inland suburban (1990-2010): 10% contingency, moderate
- Inland suburban (pre-1990): 15% contingency, drainage and waterproofing risks
- Coastal beachside (any age): 15-20% contingency, salt-corrosion and drainage risks
- Pre-1985 home (any cluster): 20-25% contingency, asbestos and other vintage issues
The 1980s Boral block construction problem in Robina, Mudgeeraba and Carrara
Large swathes of Robina, Mudgeeraba, Carrara, and parts of Worongary and Highland Park were built in the late 1970s through 1980s using Boral concrete block construction. Bathrooms in these homes have specific strip-out surprises we see repeatedly. The block walls were often rendered internally then directly tiled with no waterproof membrane installed because the regulations did not require one at the time. When we strip, the render is heavily moisture-damaged behind the shower, sometimes crumbling on touch where decades of small leaks have soaked the substrate. Block cavities can hold years of slow-leak water that pours out when tiles come off, occasionally several litres from a single wall. The drainage layout in these homes used standard 1980s spec which often had the floor waste positioned poorly for a modern walk-in shower, requiring slab coring and redirection at $1,800 to $3,500. The 1980s also predates the consistent use of in-slab conduit for water supply, so the original copper was often run directly through the block cavities rather than in conventional stud walls, making access for any repipe far more invasive than in a timber-frame home. A Robina 1985-build bathroom strip-out we did last year ran $6,800 over the original budget because of compounding block-construction issues: failed render behind two walls, drainage relocation, and partial copper replacement where in-wall pinholes were exposed during strip. Budget realistic contingency on these homes, not the standard 10 percent. We recommend 20 to 25 percent for any Boral block-era home, and recommend a thorough investigation visit before committing to a fixed-price quote.
The high-set Queenslander floor framing rot problem in older coastal homes
Older high-set Queenslander homes (think original 1950s and 1960s timber-framed builds in Coolangatta, Tugun, Bilinga, parts of Burleigh and Currumbin) have bathroom floors framed in hardwood joists with tongue-and-groove flooring under the tile bed. Decades of slow leaks at the shower base, toilet collar, and bath waste rot the timber from above, working downward into the joists. The tiles often look fine because the timber is being held in compression by the tile bed and the joists at the perimeter, even when the structural integrity has been seriously compromised. When we strip, the floor can be unsafe to stand on. We have stepped through bathroom floors during strip-out on three Coolangatta and Tugun jobs in the last two years, on one occasion a section of joist crumbled in hand. Repair scope is significant when this is found: structural carpenter to replace joists ($2,500 to $5,500), new compressed fibre cement sheet flooring rated for wet area use ($800 to $1,400), then standard waterproofing and tiling on top. Total surprise cost $4,000 to $8,000 added to the reno budget. The pre-strip indicator is bounce or springiness in the floor when walked on, particularly near the shower or toilet, sometimes accompanied by visible cracking in the tile grout lines around the shower base or floor waste. If your pre-strip walk-through reveals any of these signs, budget for structural fix as a likely scenario rather than a remote contingency. Sometimes we ask to lift one tile in a discreet area before quote to inspect substrate condition. That five-minute investigation can prevent a $7,000 surprise.
Original tapware buried in cement render with no shut-off access
Pre-1990s bathrooms commonly had wall-mounted bath spouts and shower mixers installed directly into solid cement-rendered block or brick walls with the supply lines buried in the render. No isolation valves at the fixture, no access plate, no flex tail. To remove the original tapware, we have to chisel through the cement render to expose the pipework, isolate at the meter for the whole house (sometimes for hours), and re-rough the supply with modern in-wall valving and flex tails so the new mixer can be serviced without ripping walls open again in future. Adds typically 4 to 8 hours of plumbing labour ($600 to $1,200) plus render reinstatement work before tiling can begin. We see this constantly in original 1970s and 1980s ensuite reno work in Mermaid Waters, Broadbeach Waters, the older Surfers Paradise canal homes, and the original Helensvale and Hope Island estates. The new tapware will often be a quality brand like Phoenix Vivid, Sussex Voda, Astra Walker or Gareth Ashton which is designed for modern in-wall rough-in kits with serviceable cartridges. The mismatch between old buried fittings and new serviceable installations means significant additional plumbing work that is rarely visible to the customer at quote stage unless the plumber specifically inspects existing rough-in conditions. Mention to your quoting plumber that the existing tapware is wall-buried (you can tell by the absence of any access plate or visible isolator) so they can price the rough-in conversion properly. A quote that assumes modern flex-tail tapware will blow out by $800 to $1,500 when the old setup is found mid-strip.
The shower waste under the slab discovery that changes the whole reno
This is the discovery that derails more Gold Coast bathroom renos than any other. In some 1970s and 1980s slab-on-ground builds, the original shower waste was set into the slab during the pour with no provision for future access or relocation. Forty years later, the waste fitting has often degraded, the connecting drainage line has settled or partially blocked, and the original positioning rarely suits a modern walk-in shower layout where waste position dictates the slope of the entire shower floor. To address it properly means slab coring (specialist sub-contractor at $1,200 to $2,500), exposing and re-laying the drainage line to proper AS3500 fall ($1,500 to $3,500), pouring new screed back to finished level ($600 to $1,200), and waiting for cure time, then proceeding with normal waterproofing and tiling. Total impact $3,300 to $7,200 and adds 4 to 7 days to the program. The signs to look for at quote stage are an existing shower that drains slowly even with the strainer cleaned thoroughly, persistent damp smell from the floor when the bathroom has not been used, any visible movement or hollow sound in the shower floor tiles when tapped, or recurring grout failure around the floor waste. If these are present, get a CCTV drain inspection done (we do this for $180 to $320) before signing the reno contract so the slab-coring contingency is built into the budget from day one rather than dropped on you mid-job. The renos that go badly wrong on this issue are almost always the ones where the homeowner accepted the cheapest quote that did not include any pre-strip investigation. The renos that go smoothly are the ones where the plumber spent 30 minutes upfront understanding what is actually under the floor before committing to a price.