A shower leak is almost never a tile problem. Water passes through grout by design, which is why there is a membrane under it, and most membranes fail at 10 to 15 years. Two Cranbourne housing cohorts are sitting in that window right now, which is why this is the most requested job on the site.

The two Cranbourne cohorts failing now

The 1990s western side. Those houses are 28 to 35 years old and were built with sand and cement shower bases, which rely on the screed and the membrane working together. At this age most of them have given up. The usual presentation is a discoloured line along the bottom row of tiles, grout that stays dark for days, and paint bubbling on the other side of the shower wall.

The 2000s estates north of the township. Those houses are around 20 years old, which is past the point where a builder grade membrane can be relied on. Further east the stock is younger, so the more common fault there is an acrylic base that has flexed away from the wall sheeting rather than a membrane that has aged out. Published estimates put the share of Australian showers that leak at 55 to 65 per cent, and age is the single biggest predictor.

There is a third pattern specific to this part of Casey. The old township and the western side sit on the reactive clays at the margin of the drained Koo Wee Rup swamp. The clay swells in winter and shrinks in summer, and the slab and walls move with it. That movement shears silicone and cracks grout on an annual cycle. A shower on this ground that has been regrouted twice does not need a third regrout. It needs rebuilding with flexible movement joints designed in.

Working out what is actually wrong

Repairing the wrong thing is the main way money gets wasted here, so the sequence matters.

Establish where the water is showing: the skirting behind the shower, the hallway carpet edge, the ceiling below in a double storey, or the outside wall.
Check the obvious water paths first: a failed screen seal, perished silicone at the base to wall junction, a leaking tap body or waste connection, and a shower head that sprays past the screen.
Flood test the base with the waste plugged, to separate a base failure from a wall failure.
Moisture meter the adjoining walls and floor to map the extent.
Lift a tile or open a small section of the adjoining wall where the readings say the water is going.

Steps 1 to 4 are non destructive and usually settle it. If the fault is a perished silicone joint, a screen seal or a waste connection, that is a repair. If the membrane has failed, or the screed has broken down, or the base has movement in it, that is a rebuild. Signs to watch for are set out on signs your shower is leaking.

Repair or rebuild

Symptom	Likely cause	Realistic fix
Silicone peeling at the base to wall corner	Movement, wrong sealant, or sealant over grout	Cut out, prepare and reseal with the correct flexible sealant
Water only when the screen door is used	Screen seal or screen not set into the base	Replace the seals or refit the screen
Grout dark and damp for days after use	Screed saturated below the tiles	Rebuild
Skirting or carpet wet in the next room	Membrane failure at the floor to wall junction	Rebuild
Tiles sounding hollow along the base	Debonding over a failed screed	Rebuild
A crack running through tiles and grout in the same line	Structural or slab movement	Rebuild with movement joints, after the cause is assessed

What a rebuild involves

Strip out the base, the screen, and the wall tiles to at least the height the membrane has to reach.
Remove the old screed and membrane back to the slab or the substrate.
Repair or replace any wet area sheeting that has swollen, and any timber that has rotted.
Re form the falls in a new screed, running to the waste with no flat spots or ponding.
Apply the waterproof membrane to AS 3740, current edition 2021, called up by the National Construction Code. Victoria adopted NCC 2025 on 1 May 2026.
Take the membrane up the shower walls to 1800 mm above the floor substrate. That height comes from the National Construction Code, not from AS 3740 itself.
Let the membrane cure for its full stated time before any tile goes on it.
Tile, grout, and install flexible movement joints at every internal corner and at the base to wall junction.
Refit or replace the screen, seal, and test.

Step 7 is where jobs get compromised. A membrane tiled over before it has cured does not perform, and nothing about the finished room will show it until the leak comes back.

Older showers and what is behind the tiles

In a shower built before the 1990s the material to establish is the tile backing board, because it decides how the wall comes off and who is licensed to take it. A sample goes to a laboratory before the first tile is lifted, and the removal cost appears on the quote as its own line rather than turning up as a variation on day two. This affects the township core, Junction Village and Devon Meadows far more than the estates.

What a waterproofing warranty is actually worth

Treat any offer of a legally backed lifetime waterproofing warranty with caution. A guarantee is only as strong as the entity standing behind it, and Victoria already fixes a statutory period for bringing a building action that no tradesperson can extend by printing a longer number on a docket. That period, and the certificates a shower rebuild should generate, are set out on what the law requires.

What it costs

Waterproofing supplied and applied runs $50 to $85 per m2, which is the membrane component on its own and is only part of a rebuild. Wall tiling supplied and laid runs $75 to $165 per m2, and a replacement frameless or semi frameless screen supplied and installed runs $1,200 to $3,500.

A full shower rebuild inside an otherwise sound bathroom typically sits well under a whole room renovation, though once the tiles have to come off three walls and the floor has to be re screeded, the gap narrows. If the room is 20 years old and the vanity, tapware and toilet are original, it is worth pricing a full bathroom renovation at the same time rather than rebuilding the shower now and demolishing it again in three years.

Photograph the shower, note where the water is appearing and how old the house is, then send all three through the quote form.

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Shower rebuilds and waterproofing in Cranbourne