Should You Get the Waterproofing Membrane Inspected Before Tiling on a New Build?
Yes, and it is the only window in which it can be done. Once the tiles go down, the membrane, the falls in the substrate beneath it, the upturns behind the wall tiles and every junction where two products meet are covered for the life of the building. Anything not recorded before tiling cannot be recorded afterwards. It can only be inferred, usually after water has already found the gap. For a finished home the question is different, and covered in the pre-purchase inspection.
Why this stage is the one that matters
A waterproofing membrane is a system with several parts that have to be right at the same time: the substrate it sits on, the falls that carry water to the waste, the membrane itself and the number of coats, the height it turns up the walls, and the way it is finished at floor wastes, penetrations and corners.
At the pre-tile stage all of that is visible and measurable. AS 3740 sets a minimum fall of 1:100 in the substrate (cl 2.3.1) and 1:80 on the finished surface of a shower (cl 2.3.2). The first of those can only be measured before tiling. After tiling, the finished-surface fall is the only one anyone can still check, and if the substrate beneath it was wrong, the tiler has been asked to fix with tile bed what should have been fixed in the screed.
The builder and the waterproofer will have their own hold point here. An independent record is a different thing: it is made for you, by someone with no stake in the sign-off, and it exists whether or not the building ever leaks.
What an independent inspection records at this stage
The inspection is an observation exercise. It records what is there, measures what can be measured, and references what the manufacturer's sheet requires. Room by room:
- The membrane system, as stated and as labelled. The applicator names the product; the tub on site confirms it. Where the two disagree, the label is recorded as the fact and the difference is noted.
- Coats applied, as stated by the applicator, against the number the product's data sheet requires.
- Falls, measured with the instrument in frame. Each wet area is read on more than one axis toward the waste. A common finding at this stage is a shower floor that falls correctly on one axis and not the others. That is recorded as a measurement, not an opinion.
- Upturn and termination heights, measured above the screed surface and, in shower areas, up the walls, against the heights the standard and the sheet require.
- Bond breakers and fillets at wall-to-floor junctions: present or absent, and their approximate size where it can be seen.
- Floor wastes and puddle flanges: installed, recessed, and how the screed meets them.
- Penetrations through the membrane and how each is sealed.
- Where two membrane systems meet. New builds sometimes finish one area in a different product from the rest. The record notes the location and whether either product's data sheet addresses contact with the other. Often neither does. See membrane compatibility.
- Cure and tiling-readiness windows. Each sheet states a minimum cure before tiling, and some state a minimum screed cure before the membrane goes on. The record notes the dates against those windows.
What it does not do
It does not certify the work, direct the builder, or decide whether the membrane complies. Those decisions belong to your certifier, and to the builder who is responsible for the work. The value of the record is precisely that it is not a judgement: it is a set of measurements and photographs, indexed by room, that any of those parties can act on.
What you receive
A photographic record organised by room, with each measurement shown with the instrument in the frame; the product sheets referenced against what was observed; and a written report, usually the same or next business day once the inspection is complete. It is written to be handed straight to the builder or to your certifier without explanation.
When to book it
After the last coat has cured for the period the product sheet requires, and before a single tile is laid. In practice that means asking the builder for the date the membrane will be finished, then confirming the stage with a photo before the visit. A membrane that turns out to be primer only, or one coat short, on the day of the inspection is still recorded, but as an earlier stage than the one booked.
What the standards say
AS 3740 governs waterproofing of domestic wet areas, including minimum falls to the waste and the heights the membrane must turn up walls and around fixtures. The manufacturer's Product Data Sheet governs the product itself: primers, number of coats, cure times and the surfaces it may be applied over. Where the standard and the sheet both speak to the same item, the record notes both. Where the applicator's account differs from either, the record notes that too.
Practical takeaway
The pre-tile stage is the last point at which the waterproofing can be seen. If you want a record of it, that record has to be made now; it cannot be recovered later. Ask the builder for the membrane completion date, book the inspection for after the cure window, and keep the report with the building's documents. If it is never needed, it cost a visit. If it is, it is the only evidence of what was under the tiles.
If the membrane is on and the tiles are not, record the visible waterproofing details before they are covered. Book a pre-tile waterproofing inspection.
Certified Waterproofing prepares independent waterproofing evidence records across Sydney.