Should You Get a Waterproofing Inspection Before You Buy?
Yes, and the reason is the one most buyers get backwards. Because the membrane in a finished home is already under the screed and the tiles, the inspection is not about seeing it. It is about recording everything that still can be seen and measured, and asking the seller for the one set of documents that proves the rest. Both are worth most before you exchange; after exchange, a cooling-off period, where one applies, may be the last chance to walk away.
Why a standard building inspection stops at the tiles
A pre-purchase building report is a broad visual survey. Where it reaches a bathroom, an ensuite, a laundry or a balcony, it will usually note that the waterproofing could not be assessed, or recommend a specialist inspection. That is not a failure of the inspector. Waterproofing is formed at a construction stage that no longer exists, and a general report is not written to measure what is left of it. The gap is real, and it is where most of the expensive problems in apartments and townhouses sit. If you are looking at a new build rather than a finished home, the pre-tile inspection is the counterpart to this one.
What a pre-purchase waterproofing inspection records
The inspection is an observation exercise: what is there, what can be measured, and what the documents say. In practice:
- Documents first. The waterproofing certificate, any construction-stage photographs or video, and the building report are reviewed before the visit, so that what is measured on site can be checked against what was claimed.
- Falls to each floor waste, measured with a digital level in the frame of the photograph. Water has to reach the waste. A floor that falls away from it is visible today; the consequence is not, until it is.
- Doorways and shower recess edges, photographed from both sides. These are the junctions where a membrane most often stops short.
- Grates lifted and the waste recorded, and water run to each waste to see where it goes.
- Balconies: the visible threshold detail (sill, any exposed flashing, sealant, staining) and the fall toward the drainage point.
- Evidence of previous repair at any wet area: patched grout, replaced sealant, new tiles among old, staining on the ceiling of the room below.
What it cannot see, and why that is not a reason to skip it
The water stop and the membrane itself were formed before the screed and tiles went down. The top edge of a water stop can often be seen at a doorway or shower edge; its seal to the membrane, and the membrane itself, cannot. What remains is still the useful part: the falls, the junctions, the wastes, the thresholds, and the paperwork. A membrane that was installed correctly usually leaves a floor that measures correctly. One that was not, often does not.
The one thing to ask the seller
Ask for the waterproofing certificate and any construction-stage photographs. A builder who has them produces them. The request costs nothing, and the response often tells you more than the documents themselves. Where they exist, the record shows whether what can be measured is consistent with them. Where they do not, the inspection becomes the only record of the wet areas you will ever have. How that bears on your contract is a question for your conveyancer, not for an inspector.
Timing when there is a deadline
Buyers are usually working to a cooling-off period or a seller's deadline. An inspection can typically be arranged within days, and the written report usually follows the same or next business day once the inspection is complete. Two things need to be in place for the visit: water connected and running to the wet areas, and access to every wet area and to the rooms directly below or beside them, because that is where the evidence of a leak appears.
What the standards say
AS 3740 governs waterproofing of domestic wet areas, including the minimum fall to the floor waste; on a finished shower floor the standard's finished-surface fall is the one that can still be measured. AS 4654 governs external above-ground membranes such as balconies. The record notes what was measured against what each standard requires. It does not decide whether the work complied; it gives you, your conveyancer, or a later engineer the measurements to do so.
Practical takeaway
Before you pay for anything, ask the seller for the waterproofing certificate and the construction-stage photographs. Then have the wet areas measured and photographed while you still have the right to walk away. If the documents exist, the record shows whether what was measured is consistent with them. If they do not, it is the only independent record of what the wet areas showed when you bought, and it should be kept with the contract file for as long as you own the property.
If you are buying and the building report has flagged the wet areas, get an independent evidence report before you exchange.
Certified Waterproofing prepares independent waterproofing evidence records across Sydney.