Which applies to my bathroom: Specification 26, AS 3740 or the Housing Provisions?

It depends on the building class. Class 2 to 9 buildings use NCC Volume One: F2D2 requires wet areas to be waterproof or water resistant in accordance with Specification 26 and to comply with AS 3740. A Class 1 house uses Volume Two: H4D2 points to Housing Provisions Part 10.2, which repeats the Specification 26 requirements and lets you build to its own clauses 10.2.7 to 10.2.32 or to AS 3740.

Does Specification 26 require the shower walls to be waterproofed to 1800 mm?

Yes: S26C3(1)(b) requires the shower walls to be waterproof not less than 1800 mm above the floor substrate (NCC 2025; NCC 2022 measured from the finished floor level). AS 3740:2021 clause 4.6.3(c) adds 50 mm above the shower rose where that is higher, and full height where the rose is ceiling mounted.

Where does the 1500 mm unenclosed shower area come from?

Not from the NCC. Specification 26 and the Housing Provisions only distinguish enclosed from unenclosed showers. AS 3740:2021 clauses 2.1.1 and 4.8.2 put the waterstop of a Type 2 unenclosed shower (a curtain or nothing) 1500 mm from the shower rose connection, which sets the extent of the shower area.

Does a floor waste change what has to be waterproofed?

In Volume One only where the floor waste is required by F2D4, a Class 2 or 3 bathroom or laundry above another unit or a public space: S26C6(4) then makes the whole floor, its wall/floor junctions and its floor penetrations waterproof. In Volume Two the Housing Provisions go further: 10.2.1(d) makes the floor waterproof wherever a floor waste is provided for drainage of a bathroom or laundry floor.

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NCC Specification 26 vs AS 3740 vs the Housing Provisions: who says what about wet area waterproofing

Published 18 October 2026. Written for designers, certifiers, builders and waterproofers who have to say which document a wet area detail answers to, and what that document actually says.

Three documents govern the waterproofing of an Australian bathroom, laundry or WC, and they are routinely confused with each other. NCC Specification 26 (Volume One) says what has to be waterproof and what need only be water resistant in a Class 2 to 9 building. AS 3740:2021 says how that is achieved: membranes, falls, waterstops, hobs, junctions and terminations. The ABCB Housing Provisions, Part 10.2 (Volume Two) carries the same what for a Class 1 house, with its own how in clauses 10.2.7 to 10.2.32, and lets you use AS 3740 instead.

Below is the element-by-element matrix of what each one requires, the places where they genuinely differ, and a link into our free checker so you can test your own room against all three. This is the reading of the documents we apply in our waterproofing designs and inspections; it does not replace the documents or a project-specific design.

Open the Specification 26 checker →

In this article How the three documents fit together Which edition applies, and when The matrix: element by element Where they differ Construction practice: Housing Provisions vs AS 3740 Check your room against all three

How the three documents fit together

The NCC is the law. Volume One applies to Class 2 to 9 buildings (apartments, hotels, offices, hospitals, aged care), Volume Two to Class 1 and 10 (houses, townhouses, sheds). AS 3740 is a standard; it only binds a project because the NCC calls it up.

Volume One, F2D2(1): in a Class 2 or 3 building or a Class 4 part, building elements in wet areas must be water resistant or waterproof in accordance with Specification 26, and comply with AS 3740. F2D2(2) applies the same to the bathrooms, shower rooms, laundries and sanitary compartments of Class 5 to 9 buildings.
Volume Two, H4D2: wet areas comply with Housing Provisions Part 10.2. Clause 10.2.1 repeats the waterproof / water resistant requirements of Specification 26 as clauses 10.2.2 to 10.2.6, and for construction practice offers two routes: the Housing Provisions' own clauses 10.2.7 to 10.2.32, or AS 3740.
AS 3740:2021 defines the terms the NCC uses loosely (Type 1 and Type 2 unenclosed showers, the 1500 mm shower area, waterstop heights), sets the falls, the membrane terminations and the material requirements through AS/NZS 4858, and describes the junctions.

So a Class 2 bathroom answers to Specification 26 and AS 3740 at the same time; a house answers to the Housing Provisions, and to AS 3740 only if the builder chooses that route. Where the documents are silent the others fill in, and where they overlap the stricter reading is the safe one.

Which edition applies, and when

NCC 2025 was published by the ABCB on 1 May 2026. Victoria adopted it on that date. New South Wales adopts it on 1 May 2027 and applies NCC 2022 until then; other states and territories set their own dates and transition periods. For wet areas the 2025 changes are small but real: the shower wall height is now measured from the floor substrate rather than the finished floor level, fibre-cement sheet flooring joins concrete and compressed fibre-cement in the water-resistant floor list, and a new clause S26C6(3) deals with WCs that have a hand-held bidet spray. AS 3740:2021 is the current edition of the standard in both NCC editions.

The matrix: element by element

WaterproofWater resistantNo requirement— the document is silent

Element	Specification 26 (NCC 2025 Volume One)	AS 3740:2021	Housing Provisions 10.2 (Volume Two)
Shower floor, including a hob or step-down	WaterproofS26C3(1)(a)	Membrane to the floor, falls 1:80 min to the shower waste; hob of masonry, concrete or metal with the membrane over it and 50 mm onto the floor2.3.2, 4.6.2, 4.7	Waterproof10.2.2(1)(a)
Preformed shower base	Floor clause does not apply; walls, junctions and penetrations still must beS26C3(2)	—	Same as Specification 2610.2.2(2)
Shower walls	Waterproof not less than 1800 mm above the floor substrateS26C3(1)(b)	1800 mm above the finished floor or 50 mm above the shower rose, whichever is higher; full height for a ceiling-mounted rose4.6.3(c), (d)	Waterproof not less than 1800 mm above the floor substrate10.2.2(1)(b)
Wall junctions and joints in the shower	WaterproofS26C3(1)(c)	Junction types and bond breakers4.11	Waterproof10.2.2(1)(c)
Wall/floor junction in the shower	WaterproofS26C3(1)(d)	Membrane up the wall 150 mm above the finished tiles (hob or step-down: or 25 mm above the retained water level); hobless: 150 above the highest tile4.6.3(a), (b)	Waterproof10.2.2(1)(d)
Penetrations in the shower	WaterproofS26C3(1)(e)	Sealed to the membrane4.10	Waterproof10.2.2(1)(e)
Extent of an unenclosed shower area	"Enclosed and unenclosed" only; no distanceS26C2(1)(a)	Type 1 (frameless panel, 900 fixed panel over a bath): waterstop under the panel and across the opening. Type 2 (curtain or nothing): 1500 mm from the shower rose connection2.2.2, 2.1.1, 4.8.2	As Specification 2610.2.2
Floor outside the shower: concrete, compressed FC or FC sheet	Water resistantS26C4(1)	— (construction only)	Water resistant10.2.3(1)
Floor outside the shower: timber, particleboard, plywood	WaterproofS26C4(2)	—	Waterproof10.2.3(2)
Wall/floor junctions outside the shower	WaterproofS26C4(3)	Junction types4.11	Waterproof; a flashing needs a 40 mm horizontal leg10.2.3(3)
Bathroom or laundry with a floor waste	Waterproof floor, wall/floor junctions and floor penetrations, only where F2D4 requires the waste (Class 2 or 3, above another unit or a public space)S26C6(4), F2D4(1)	Membrane into the floor waste flange4.3.2	Waterproof floor, floor/wall junctions and penetrations wherever a floor waste drains the floor10.2.1(d)
Falls to the floor waste	— (F2D4(2): 1:80 min, 1:50 max where the waste is required)	Shower floor 1:80 min; floor beside the shower 1:100 min; substrate under the membrane 1:100 min; whole bathroom as an unenclosed shower 1:802.3.1 to 2.3.5	— (SA 10.2.33: 1:80 to 1:50)
Freestanding bath, more than 75 mm from every wall	Floor as the room; Waterproof tap and spout penetrations in horizontal surfaces; no wall requirementS26C5(1)	—	Same10.2.4(1)
Bath within 75 mm of a wall	Water resistant walls 150 mm above the lip for the extent, exposed surfaces below the lip; Waterproof wall/floor junction behindS26C5(2)	Walls around a bath water resistant to 150 above the edge; recessed baths with an integral upstand and a waterproof bath/wall junction4.13	Same10.2.4(2)
Inset (drop-in) bath	Waterproof shelf with a waterstop under the lip; walls 150 mm above the lip; No requirement under the bath or beneath the lipS26C5(3)	—	Same10.2.4(3)
Shower over a bath	Shower requirements applyS26C2(2)	Walls around the bath waterproof to 150 above the rose; 900 fixed panel = Type 1, curtain = Type 24.13, 2.2.2	Shower requirements apply10.2.2 Note
Basin, sink or tub within 75 mm of a wall	Water resistant 150 mm above the vessel for its extent; Waterproof wall junction where fixed to the wall; Waterproof tap penetrationsS26C6(1)	—	Same10.2.5(1)
Laundry or WC floor	Water resistant floor and wall/floor junctionsS26C6(2)	—	Water resistant10.2.5(2)
WC with a hand-held bidet spray	Waterproof floor; walls Waterproof to 150 and Water resistant to 1200 within 1500 mm of the spray; junctions and penetrations waterproof (NCC 2025 only)S26C6(3)	—	Same10.2.5(3)
Waterstop at a hobless enclosed shower	—	Vertical leg 5 mm above the finished floor outside the shower, under the screen rail4.8.3, 4.8.4	Construction clauses10.2.7 to 10.2.32
Shower within 200 mm of an exit	—	Must be enclosed, with a waterstop, hob or 15 mm step-down at its extremity4.8.5	—
Door threshold	—	Waterstop at floor level openings flush with the finished floor; frames not embedded in tiles; 2 mm sealed gap under the architrave4.9.1, 4.9.2	Construction clauses10.2.7 to 10.2.32
Membrane materials	—	AS/NZS 4858 membranes, compatible systems2.1.2, Section 3	Materials nominated for waterproof and water-resistant systems10.2.6, 10.2.8 to 10.2.10

Clause numbers are NCC 2025. The Housing Provisions numbers are the Volume Two equivalents. AS 3740 numbers are from the 2021 edition. Where a cell says "same", the Housing Provisions reproduce the Specification 26 wording.

Where they differ

1. A floor waste changes the floor, but not the same way.In Volume One the whole bathroom floor only becomes waterproof when F2D4 requires the floor waste: a Class 2 or 3 bathroom or laundry above another sole-occupancy unit or a public space. A floor waste that is merely provided leaves S26C4 in charge, and a concrete floor outside the shower stays water resistant. In a house, Housing Provisions 10.2.1(d) makes the floor waterproof the moment a floor waste is provided for drainage. Check a Class 2 bathroom with a floor waste that is not required, then the same room in a house.

2. The 1800 mm has three datums.NCC 2025 measures it from the floor substrate; NCC 2022 from the finished floor level; AS 3740 from the finished floor level or 50 mm above the shower rose, whichever is higher, and full height for a ceiling rose. Design to the highest of the readings that apply. See the NCC 2022 reading.

3. Only AS 3740 sizes the unenclosed shower.Specification 26 and the Housing Provisions say "unenclosed" and stop. AS 3740 2.2.2 splits it into Type 1 (a splash-restricting panel) and Type 2 (curtain or nothing) and puts the Type 2 waterstop 1500 mm from the rose connection. In a typical bathroom that reaches the vanity and the door, which is why AS 3740 4.8.5 then demands an enclosed shower near an exit. Check a Type 2 shower.

4. Waterstops, hobs and thresholds live in the how, not the what.The 5 mm waterstop under a hobless screen, the hob construction rules, the flush waterstop at the doorway and the 2 mm gap under the architrave are AS 3740 (4.7 to 4.9) and the Housing Provisions' construction clauses. Specification 26 never mentions them; it only says the floor including any hob or step-down is waterproof. Check a hobless enclosed shower.

5. The bidet spray exists only in NCC 2025.S26C6(3) and Housing Provisions 10.2.5(3) are new: a WC with a hand-held bidet spray gets a waterproof floor and a 1500 mm radius of treated wall. Under NCC 2022 the same WC is an ordinary water-resistant WC. Check a WC with a bidet spray.

6. The Housing Provisions add a flashing dimension.For wall/floor junctions outside the shower, 10.2.3(3)(b) asks for a 40 mm horizontal leg where a flashing is used. Specification 26 has no equivalent sentence.

7. Baths split three ways in the NCC, one way in AS 3740.Specification 26 treats a freestanding bath (no wall requirement), a bath within 75 mm of a wall (water-resistant walls 150 above the lip, waterproof junction behind) and an inset bath (waterproof shelf and waterstop under the lip) differently. AS 3740 4.13 speaks of walls around a bath and recessed baths with an integral upstand. The NCC split is the one certifiers apply. Check an inset bath, a freestanding bath.

8. Laundry and WC floors are water resistant whatever the substrate.S26C6(2) does not repeat the timber-floor exception of S26C4(2). A timber laundry floor is water resistant under Specification 26; most specifiers waterproof it anyway. Check a timber laundry floor.

Construction practice: the Housing Provisions' own route vs AS 3740

The matrix above is about what must be waterproof. A house has a second choice to make about how: Housing Provisions 10.2.1(b) lets the builder follow the Housing Provisions' own construction clauses 10.2.7 to 10.2.32 or AS 3740. Those two rule books disagree in places that matter on site:

Construction item	Housing Provisions 10.2.7 to 10.2.33	AS 3740:2021
Floor waste flange	A drainage flange with the membrane terminated at or in it; may be cast in, set into the slab top or set into the tile bed10.2.29	A leak control flange recessed into the substrate, not protruding, sealed to the riser, matching its diameter, clear of bond breakers4.3.1
Step-down	At least 25 mm10.2.15	No general minimum; 15 mm allowed at a shower within 200 mm of an exit4.8.5
Hob materials	Masonry, concrete, AAC, extruded polyurethane foam; no fall stated10.2.16	Masonry, concrete, corrosion-resistant metal; AAC only primed with an internal membrane; top falls to the shower4.7
Unenclosed showers	Waterstop 1500 mm from the rose, or the whole floor waterproofed and drained10.2.18	Type 1 (frameless panel): waterstop under the panel. Type 2 (curtain or nothing): 1500 mm from the rose2.2.2, 4.8.2
Baths	Every non-freestanding bath has an upturn lip and is recessed into the wall10.2.20	Insert baths without a lip allowed with the walls waterproofed 150 above the edge; freestanding baths treated as a Type 2 shower area4.13
Bond breakers	At all junctions and movement joints for bonded membranes; compatible with the membrane class10.2.27	Width by membrane class: 100, 35 or 12 mm4.10, Table 4.10
Substrate moisture, inspection, testing	—	Moisture content measured; visual inspection before tiling; optional flood test or electronic leak detection4.4.3, 4.5.3, 4.5.4
Water-resistant substrates	No structural plywood; concrete, render and masonry treated to resist moisture movement10.2.9	Structural plywood accepted for walls and floors3.3.2
External flashing overlap	32 mm10.2.24	30 mm, no fastening through the flashing4.11.2

The full clause-by-clause comparison, with 34 items filtered by topic and flagged for who is stricter, is in our AS 3740 vs Housing Provisions construction tool.

Check your room against all three

Our free Specification 26 checker takes the room, the floor material, the shower type and edge, the bath, the basin, the WC and the floor waste, and lists every floor, wall, junction and penetration with what Specification 26 says, what AS 3740 says and what the Housing Provisions say, side by side, with the clause quoted. Switch between NCC 2025 and NCC 2022 and between Volume One and Volume Two. The summary downloads as a stamped PDF. Then pull the matching generic junction details from the detail generator.

For which pathway your building is on, and who has to sign what, read Internal waterproofing compliance pathways by building class.

Need the wet areas designed, specified and inspected to all three? Talk to our waterproofing engineers. We prepare the design, the specification, the membrane inspection and the NSW design declaration for apartments, houses and commercial buildings.