Water through your granny flat in Frankston: what to do in the first hour
Switch the granny flat off at its own circuit breaker before you walk in, and do not stand in water with the power on. If clean water is running and rising, shut the stop tap. Lift bedding, mattresses, power boards and anything with a plug clear of the floor. Photograph and video every wet surface before you mop, because that is what the claim is assessed on. Pull the grate on the overflow relief point near the back door and clear the leaves out of it. If water is coming through the ceiling, put a bucket under the sagging spot and push a screwdriver through the lowest point so it drains in one place instead of the whole sheet letting go.
What you are looking at, how urgent it is, and what it costs to put right
Find your symptom in the left column. The urgency column is the honest one: only four of these eight need somebody on site tonight. Prices are realistic Frankston and Peninsula figures for 2026 and assume a 35 to 60 square metre granny flat.
| Symptom | What it usually means | How urgent | Typical cost to put right |
|---|---|---|---|
| Clean water spreading across the floor from the shower, laundry or kitchen | Blocked waste, failed trap or a split flexi hose under the sink | Now | $450 to $950 to clear and camera. $1,200 to $3,500 if the waste has to be re-run |
| Water rising through the floor at the door threshold during heavy rain | Yard surcharge: stormwater cannot get away and the flat is the lowest opening | Now to contain, this week to fix | $2,800 to $7,500 for a spoon drain and 100mm ag line on the high side |
| Brown stain and a sagging patch in the ceiling | Roof, flashing or box gutter leak with water sitting in the insulation | Now to drain it | $450 to $1,200 make-safe. $900 to $3,500 flashing or gutter repair |
| Sewage backing up through the shower grate or the toilet | Blocked sewer branch or a surcharge from the main. Category 3 water and a genuine health risk | Now, stop using water | $450 to $1,200 to clear. $3,500 to $9,000 if it has flooded the floor |
| RCD trips and will not reset, or buzzing and arcing near a socket | Water has reached a switch, a socket or the sub-board | Now, licensed electrician only | $180 to $320 after-hours attendance plus the repair |
| Damp band along the bottom 200mm of one wall in dry weather | Slab edge damp, a garden bed built up over the slab edge, or a slow pipe leak in the wall | This week | $1,500 to $6,000 depending on whether it is drainage or plumbing |
| Water pooling under a granny flat on stumps, bearers feel damp | Ground falls towards the building and subfloor ventilation is blocked | This week | $1,200 to $4,500 for regrading, vents and a subfloor drain |
| Musty smell and black spotting on the cold south wall, no visible water | Condensation in a small airtight 7-star envelope, not a leak | Can wait | $0 to $450 for a ventilation fix. Up to $1,800 if the lining is affected |
Indicative Frankston and Mornington Peninsula figures for 2026. A firm price needs eyes on the job: call (03) 9022 1391.
What makes the damage worse in the next six hours
Water damage is not really about the water. It is about what the water does to plasterboard, particleboard and insulation while it sits. A wet wall dried inside 48 hours usually gets away with a repaint. The same wall left wet for a week means cutting out the bottom 600mm of lining, replacing the insulation and repainting, which runs $2,400 to $4,500 in a 45 square metre flat. Four things speed that up.
- Leaving carpet, underlay or a mattress on a wet floor. They wick water sideways and hold it against the skirting and the bottom plate. Get them out onto the drive, even if it is raining.
- Closing the flat up. A sealed, unheated 7-star envelope with wet lining grows visible mould in three to five days over a Frankston summer. Open it up, get air moving, keep it above about 18 degrees if you can.
- Leaving wet insulation in the ceiling. Wet batts weigh several times their dry weight, hold water against the sheet and will eventually bring the ceiling down. Drain the ceiling first, then get the batts out.
- Trying to re-energise a flooded circuit. Every reset attempt risks tracking damage in the switchboard, which turns a $400 repair into a $1,600 sub-board replacement.
Safe to do yourself, and genuinely dangerous
We would much rather you did the first list and left the second one alone. Nothing on the second list is worth a hospital visit or a voided insurance claim.
Safe to do yourself
- Isolating the granny flat at its own breaker, from a dry position, in dry shoes.
- Turning the water off at the meter or at the isolating tap on the flat supply.
- Photographing, measuring the water line on the wall, and writing down the time it started.
- Lifting contents, opening windows and doors, towelling and mopping clean water.
- Raking leaves out of gutters at ground level and clearing the overflow relief grate.
- Weighting a tarp over a small roof opening from the ground, if you can reach it safely.
Do not do these
- Do not go up on a wet or steel roof. Colorbond in rain is close to frictionless and the fall from a granny flat roof is still enough to break a back. A professional tarp job costs $450 to $1,200.
- Do not touch the switchboard or a socket in standing water. Isolate at the main switch and call an electrician.
- Do not clean up sewage. Category 3 water carries real pathogens, and the affected lining generally has to be removed either way.
- Do not cut into a wall to look. A gas line, a water pipe or a cable is usually exactly where you would cut, and a hole you made is a hole the insurer did not authorise.
- Do not throw anything out yet. Damaged items are evidence. Our granny flat insurance claim guide has the tick-off list for what to keep and in what order.
Not sure whether it can wait?
Describe what you can see and we will tell you straight whether it is a tonight job or a Monday job. No charge for the conversation.
After hours versus Monday morning: what the difference actually costs
Trades in Frankston, Carrum Downs and across the Peninsula charge an attendance fee plus an hourly rate, and both change outside normal hours. The 2026 pattern is fairly consistent: $90 to $150 attendance and $95 to $130 an hour Monday to Friday between 7am and 5pm, then $180 to $320 for the first hour after 6pm or on a weekend and $110 to $160 an hour after that. Sunday and public holidays sit at the top of those bands. On a two-hour job that is a difference of roughly $200 to $400.
That money is worth spending when water is still arriving, when power is involved, when sewage is involved, or when a ceiling is holding water. It is not worth spending on something already contained. If you have stopped the source, lifted the contents and got air moving, the damage curve flattens right out and waiting nine hours changes almost nothing. The one exception is timber flooring, which starts cupping within about a day: if you have engineered or solid timber down, treat it as a tonight job.
One more honest note about after-hours work. Nobody replaces plasterboard, re-runs a waste line or repairs a roof properly at 9pm on a Saturday. What you buy after hours is a make-safe: the water stopped, the power made safe, a tarp on, drying equipment running. The actual repair happens in normal hours regardless. Paying the premium for a make-safe is usually right. Paying it in the hope of a finished repair is not.
When it is not an emergency, and waiting saves you real money
Roughly a third of the after-hours calls we take about granny flats on the Peninsula could safely have waited until the morning. The common ones:
- Condensation, not a leak. Black spotting in the corner of the coldest wall, worst in July, worst on the side that never sees sun. A small, well-sealed dwelling with one occupant showering daily and no exhaust fan running produces a surprising amount of moisture. Run the bathroom fan for 20 minutes after every shower, crack a window, and see whether it comes back before you spend anything.
- A stain that is not growing. Draw a pencil line around it and write the date on the wall. If it has not moved in 48 hours, book a normal-hours inspection.
- A dripping tap or a leaking flexi hose you have already isolated. Once the tap is off, it is a Monday job.
- Damp along the slab edge in winter. Almost always drainage and garden levels, which is a daylight job with a shovel rather than a 10pm job. Our page on backyard drainage for Frankston granny flats covers the permanent fixes and what they cost.
We will tell you on the phone if we think it can wait. We would rather do the proper repair on Tuesday than charge you a premium on Saturday to look at something we cannot fix until Tuesday anyway. It is also worth saying plainly what we do not do: we are granny flat builders, not a 24-hour restoration company. We attend, make safe, diagnose and quote the repair. If a job needs industrial drying or sewage decontamination we will say so and point you at the right people rather than pretend otherwise.
If the flat is one we built, the fix may be a warranty item rather than a bill. Victorian domestic building work carries statutory warranties, and domestic building insurance responds to structural defects for six years and non-structural defects for two years from completion. Raise that before you pay anybody. If the flat was built by somebody else without a building permit, be aware that an unapproved structure changes both the repair options and the insurance position: the Victorian granny flat permit rules page explains what approval your build should have, and the build process page shows where the inspections sit.
Send us the photos and get a written repair price
Tell us what you are seeing and we will call you back the same working day with a plan and a realistic number.
Questions people ask at 9pm
What should I turn off first if water is through my granny flat?
How much does an after-hours emergency call-out cost in Frankston?
Should I mop up before I photograph the damage?
When is water in a granny flat not an emergency?
Why does water come up through the floor at the door after heavy rain?
Can I dry the granny flat out myself with fans and a heater?
More reading: the Frankston granny flat maintenance schedule covers the gutter and drainage jobs that stop most of this happening, site costs explains what drainage work costs at build time, and our 2026 pricing guide has the full build ranges.