E3/AS1 Internal Moisture
What internal moisture puts on a set of drawings: the impervious finishes and the evidence for one the document does not list, the thermal resistance and condensation control of Section 1.0, containment and floor wastes where an overflow could reach somebody else, and the shower.
- E3/AS1Second Edition Amendment 75 Nov 2020
- E3/AS2First Edition5 Nov 2020
- G13/AS1Second Edition Amendment 102 Nov 2023
- WMAI Code of Practice
- GIB Wet Area Systems
- Building Act 2004
E3 requirements
Every requirement E3 states, numbered, so one can be pasted onto a sheet as it stands. Where the document states a condition, N/A answers that it does not hold here; the answer prints, so the sheet says what was left out and why. The reading and the guidance do not print.
Finishes, and the evidence a finish outside E3 needs
The question that arrives at consent is usually not what the Code says but what has to be submitted. E3/AS1 lists three floor finishes and four wall finishes, and most designs use something else.
- Floor finishes E3/AS1 accepts Integrally waterproof sheet material with sealed joints, sealed or coved at edges where watersplash may occur. Or ceramic or stone tiles of no more than 6% water absorption, waterproof grouted joints, bedded with an adhesive the tile manufacturer specifies for the tiles, the substrate and the environment, edges sealed or coved where watersplash may occur, laid on a continuous impervious substrate or a membrane the manufacturer specifies as suitable.
3.1.1 a), 3.1.1 b)
- Sealed concrete, in two places only A slab-on-grade concrete floor with a steel trowel or polished finish, sealed at edges where watersplash may occur, satisfies 3.1.1 in a domestic laundry within a garage or in a building containing only sanitary facilities. Nowhere else.
3.1.1 c)
- Wall finishes E3/AS1 accepts Integrally waterproof sheet with sealed joints; or ceramic or stone tiles of no more than 6% water absorption on a specified adhesive; or sheet linings with a semi-gloss or gloss coating, or a hard-wearing low-sheen latex paint containing mould inhibitors; or water resistant sheet linings finished with decorative high pressure laminate or factory-applied polyurethane or resin, with impervious joints.
3.1.2 a), 3.1.2 b), 3.1.2 c), 3.1.2 d)
- Where the impervious floor extends to Throughout any space containing sanitary fixtures or sanitary appliances, and in an open plan space at least 1500 mm (1.5 m) from every one of them. Tiles in that band bring 3.1.1 b)'s substrate or membrane with them.
3.1.1
Section 1.0: thermal resistance, ventilation and condensation
E3.3.1 reaches only Housing and Communal Residential; Sections 2.0 and 3.0 reach every building. A detached house, a flat and a boarding house are all on this side.
where the building is Housing or Communal ResidentialClause E3.3.1, limits on application
- Minimum R-values No less than R1.5 for a framed wall with a cavity, R0.6 for a single-skin normal-weight masonry wall without a cavity, R0.6 for a solid timber wall no less than 60 mm thick, and R1.5 for a roof or ceiling of any construction.
1.1.1
- How the R-value is determined By the methods in NZS 4214. A laboratory test sample must be truly representative of the wall, roof or ceiling system, including any provision for reducing thermal bridging.
1.1.2, NZS 4214
- Building paper Extends from the upper side of the top plate to the underside of the bearers or wall plates supporting the ground floor joists.
1.1.4 a)
- Insulation fit No perimeter gaps between the insulating material and the framing members.
1.1.4 c)
- Thermal break to steel framing Where steel framing is used, a thermal break with a minimum R-value of R0.25 at the outside face of each steel framing member. EPS strips 10 mm thick provide it; other materials or methods may, if they provide the same minimum.
1.1.4 d)
- Foil insulation Where foil insulation is used, it is placed on the lining side of the studs, not the cladding side.
1.1.4 e)
- Ventilation Provided naturally or mechanically to comply with G4/AS1.
1.2.1, G4/AS1
- Condensation channels Metal-framed windows with single glazing, in a building that is not air conditioned, have a means of condensation disposal: a collection channel of clear dimensions no less than 10 mm wide by 5 mm deep, which either drains to the outside or holds the water until it evaporates.
1.3.1, 1.3.3
- Channel ends and outlets Channels have closed ends and no openings that let ponded water reach building elements susceptible to moisture. Drainage outlets can expel all condensed water and prevent it being blown back by wind pressure.
1.3.2
- Cleaning Channels and drainage outlets can be cleaned.
1.3.3
Section 2.0: overflow
A detached house on its own lot has nowhere for an overflow to reach. Anything with a household unit above, below or beside another, or a fixture near a boundary, has. The requirement follows the fixture, not the room.
where a sanitary fixture is located where an accidental overflow could damage an adjoining household unit or other property2.0.1
- Overflow, Section 2.0 Containment and a floor waste are required at any sanitary fixture located where accidental overflow could damage an adjoining household unit or other property. The requirement follows the fixture's position, not the room it is in.
2.0.1
- Containment An impervious floor covering, continuous and coved or with sealed joints where it meets the wall, extending to the doorway and all walls of the room, or at least 1500 mm (1.5 m) from every sanitary fixture and appliance in an open-plan room.
2.0.1 a), 2.1.1, Figure 1
- Floor waste A floor waste complying with Clause G13, at each of those fixtures. A graded floor is not essential in this situation.
2.0.1 a), 2.2.1, G13/AS1 3.4
- Floor waste diameter The floor waste, and its water trap if it has one, no less than 40 mm in diameter.
G13/AS1 3.4.2
- Grating A removable grating, flush with the floor.
G13/AS1 3.4.1
- How it discharges Trapped, discharging above a gully trap grating and vented; or trapped, charged to keep its water seal, and discharging to the foul water plumbing; or (where its only purpose is accidental overflow) untrapped, discharging to the open air within the property boundary at a safe location, with a means to keep out birds and vermin.
G13/AS1 3.4.3
- Sinks and laundry tubs are exempt on a condition A household kitchen sink or laundry tub with an integrated overflow of no less than 0.25 L/s needs no containment or floor waste, provided the taps cannot outrun it: either the maximum tap flow is lower, or the supplies carry proprietary flow restrictors that make it so. The overflow is tested and verified to BS EN 274. Where several tubs or sinks share one tap, each has its own complying overflow, or a secondary one has a controlled overflow path into a main one that does. The exemption is that fixture's. A basin or WC beside it is still 2.0.1's.
2.0.1 b), 2.0.2, 2.0.2.1, BS EN 274
- Appliance hoses are not an overflow Containment and a floor waste are not required solely for the failure of a dishwasher's or washing machine's component or hose, where the flexible discharge hose is directly connected into the plumbing system: mechanically fastened to a fixture trap spigot, or inserted into an open standpipe or a laundry tub waste hose connection port.
2.0.3
The wet-area build-up: surfaces, joints and membrane
- Fixture to floor Where a sanitary fixture abuts the impervious floor finish, the base of the fixture is sealed to it.
3.2.1
- Fixture to wall Where a bath, basin, tub or sink abuts an impervious lining, the joint between fixture and lining is sealed so water cannot reach concealed spaces or get behind the lining.
3.2.2, Figure 3
- The membrane system Selection, design and installation to sections 1 – 4 of the Code of Practice, as modified.
E3/AS2 1.1
- The finish over the membrane The membrane is installed with an over-surface finish that is easy to clean, forming the floor and wall surfaces at the fixtures. The finish itself (tiling, say) is outside E3/AS2, so its compliance is shown another way; E3/AS1 3.1 is the usual route.
E3/AS2 1.1, E3.3.3 – E3.3.5, E3/AS1 3.1
Showers, and showers over baths
where there is a shower3.3.1
- Lining height Impervious wall linings or finishes to 1800 mm (1.8 m) above the shower floor, and to 300 mm above the shower rose, whichever is higher.
3.3.1, Figure 5(b)
- On the membrane route the height is the Code of Practice's E3/AS2 1.2 d) says the IWAM Code of Practice takes the membrane higher above the shower rose than the Building Code requires. E3/AS1's 50 mm is the Code minimum; the membrane is built to the Code of Practice's figure.
E3/AS2 1.2 d)
- Top edge The top edge of the impervious shower wall lining or finish is sealed to the wall behind, or to the ceiling if full height, so condensation cannot get behind it.
3.3.1
- Penetrations Tapware, mixers and roses through the shower wall are waterproofed with a proprietary flange system or with sealant, installed so they stay accessible for replacing washers, ceramic discs and o-rings.
3.3.1, Figure 6
- Where the shower materials apply Within the shower enclosure; or, where there is no enclosure such as a wall, screen, door or curtain, within a 1500 mm (1.5 m) horizontal radius of the shower rose.
3.3.1.1, 3.3.1.2, Figure 5
- Shower floor A plastic or stainless steel shower tray; or integrally waterproof sheet material with sealed joints, coved at edges; or ceramic or stone tiles of no more than 6% water absorption on a specified adhesive, laid within a tray the manufacturer specifies for tiles or on a membrane it specifies as suitable. A tiled shower floor must have tiled walls.
3.3.1.1 a), 3.3.1.1 b), 3.3.1.1 c)
- Shower walls Plastic shower wall liners, jointless or with waterproof joints; or integrally waterproof sheet with sealed joints; or tiles of no more than 6% water absorption laid on a specified membrane; or water resistant sheet linings finished with high pressure laminate or factory-applied polyurethane or resin, with impervious joints.
3.3.1.2
- Tray to wall Where a shower tray is used, the junction between tray and wall linings is detailed so the lining laps into the tray.
3.3.2.2, Figure 4
- Shower over a bath The bath rim is no less than 15 mm high, and the shower wall lining laps over and is sealed to it. Either the rim is recessed into the wall framing or the lining is packed out to suit it. No bath mould or flashing.
3.3.1.3
- Enclosure Where a wall, screen, door or curtain is used, it is continuous from floor level or the top of the upstand to no less than 1800 mm (1.8 m) above floor level, and to 300 mm above the rose on these drawings; 3.3.2.1 states 50 mm above the rose.
3.3.2.1
- Floor fall Where the shower floor has no upstand, or a wall, screen, door or curtain is omitted, the floor falls no less than 1:50 towards the floor waste, across the area within a 1500 mm (1.5 m) radius of the point vertically below the rose, or from any wall within that radius.
3.3.2.3, Figure 5
- Threshold A shower installed for use by people with disabilities has a level threshold.
3.3.2
Urinals
where there is a urinal3.3.3
- Urinal Impervious wall extending horizontally at least 300 mm beyond each side of the urinal, and vertically from floor level to 1500 mm (1.5 m).
3.3.3
Taking the E3/AS2 route
Usually yes: E3/AS1 governs the finished surface and E3/AS2 the membrane behind it, and a tiled shower wall needs a membrane under 3.3.1.2 c) whatever route is claimed. An acrylic liner over a vinyl floor may have none.
where a membrane system is built to the Code of Practice, under E3/AS2E3/AS2 1.1
- What it does not cover E3/AS2 cannot show compliance with E3.3.1. Thermal resistance, ventilation and condensation control are shown separately, and Section 1.0 above is E3/AS1's.
E3/AS2 Supporting information, E3/AS1 1.0
E3 requirements to show on the drawings
What has to be drawn or named for each requirement to be checkable. It follows the answers on Requirements. Tick as you go; the ticks print, the guidance does not.
Show on the drawings
- 1.1.1, 1.1.2
- 1.1.4 a), 1.1.4 c)
- 1.1.4 d)
- 1.1.4 e)
- 1.2.1, G4/AS1
- 1.3.1, 1.3.2, 1.3.3
- 3.1.1, 3.1.2
- 3.1.1 COMMENT, 3.1.2 COMMENT, Building Act s 49(1)
- 2.0.1, 2.1.1
- 2.2.1, G13/AS1 3.4
- 2.0.1 b), 2.0.2.1, BS EN 274
- 3.2.1, 3.2.2
- E3/AS2 1.1, E3/AS2 References
- E3/AS2 1.1, E3.3.3 – E3.3.5, E3/AS1 3.1
- 3.3.1, Figure 5(b), E3/AS2 1.2 d)
- 3.3.1.1, 3.3.1.2, Figure 5
- 3.3.1, Figure 6
- 3.3.2.2, Figure 4
- 3.3.2.1
- 3.3.2.3, Figure 5
- 3.3.1.3
- 3.3.2
- 3.3.3
Terminology
The words the requirements lean on, defined where the document defines them.
- Sanitary fixture, sanitary appliance3.1.1 COMMENT, 2.0.1
- A kitchen sink is a sanitary fixture; a dishwasher and a washing machine are sanitary appliances. 3.1.1's impervious floor extends from both, 2.0.1's overflow test is asked of a fixture, and 2.1.1's containment measures from a fixture or an appliance.
- Adjoining household unit, other property2.0.1
- 2.0.1's trigger: a sanitary fixture located where an accidental overflow could damage an adjoining household unit or other property. True of anything with a household unit above, below or beside another, and of a fixture near a boundary; a detached house on its own lot has nowhere for an overflow to reach.
- Classified useClause E3.3.1, limits on application
- The Building Code's seven uses. E3.3.1 (thermal resistance, ventilation and condensation control) applies only to Housing and Communal Residential; Sections 2.0 and 3.0 apply to all seven.
- E3/AS1 and E3/AS23.1.1 b), 3.3.1.2 c), E3/AS2 1.1
- Two Acceptable Solutions that are halves of one job, not alternatives. E3/AS1 governs the finished surface and treats the membrane as a component it names and never describes; E3/AS2 governs the membrane and says the finish over it is outside its scope. Neither reaches E3.3.1.
- Membrane systemE3/AS2 1.1
- A wet-area membrane selected, designed and installed to sections 1 – 4 of the Code of Practice, as E3/AS2 2.0 modifies it. That installation is what E3/AS2 accepts as compliance with E3.3.2 to E3.3.6.
- Code of PracticeE3/AS2 References
- The Code of Practice for Internal Wet-area Membrane Systems, the Waterproofing Membrane Association Inc.'s document, which E3/AS2 cites at its August 2020 edition. Nothing of it is reproduced here.
- Registered product certificate (CodeMark)Building Act 2004 s 19(1)(d), s 272A
- A current product certificate registered under the Building Act: what MBIE's CodeMark scheme issues. One of the things a building consent authority must accept as establishing compliance, provided every condition in it is met. Building Act 2004, as at 30 June 2026.
- AppraisalBuilding Act 2004 s 49(1)
- A BRANZ Appraisal or the like: evidence towards the test every consent is granted on (that the authority is satisfied on reasonable grounds the Building Code would be met) rather than something the Act makes an authority accept. Building Act 2004, as at 30 June 2026.
Reading E3
Why the document says what it says: the anomalies, the scope statements, and what an authority must accept. Screen only; none of it is a requirement.
Finishes, and the evidence a finish outside E3 needs
- Why sealed concrete, in two places only3.1.1 COMMENT
- The COMMENT gives the reason: those are the places where small imperfections such as microcracking do not matter.
- Which rooms, and why containment does not decide it3.1.1 COMMENT
- 3.1.1's COMMENT: the spaces are kitchens, bathrooms, laundries and toilets, and the impervious floor is required whether or not Section 2.0 asks for containment. A kitchen sink and a dishwasher each count; see Terminology.
- The 6% has no test method3.1.1 b), 3.1.2 b), E3/AS1 References
- E3/AS1 sets a maximum water absorption for tiles in four paragraphs and names no way of measuring it. Its References list only NZS 4214, BS EN 274 and the BRANZ House Insulation Guide, and no other standard is designated anywhere in the document. So the figure on the supplier's data sheet is the only evidence there is, and which test produced it is the consent authority's judgement rather than the document's. Get the data sheet at specification, not at inspection.
- A finish outside those lists3.1.1 COMMENT, 3.1.2 COMMENT
- Anything else is outside this Acceptable Solution, and most designs contain one. The COMMENTS to 3.1.1 and 3.1.2 say what such a finish still has to do (no gaps or cracks within the finish or at any part of its perimeter exposed to watersplash, and a suitable durable sealing coating where needed), but meeting that description is not compliance by Acceptable Solution, and the element becomes an Alternative Solution for E3.3.3 to E3.3.5.
- What that means at consent3.1.1 COMMENT, E3/AS2 Supporting information, Building Act s 49(1)
- E3 asks for none of this. It follows from the Building Act: a consent is granted only when the building consent authority is satisfied on reasonable grounds that the Building Code will be met (Building Act s 49(1)), and a finish outside 3.1.1 and 3.1.2 is not met by Acceptable Solution. 3.1.1's COMMENT and E3/AS2's Supporting information point at it, but both are informative, so it is not listed as an E3 requirement. It is the one line on Show on drawings with no requirement behind it: the finish, its substrate and its edges drawn, and the evidence the consent relies on named.
- CodeMark: the product evidence the Act makes an authority acceptBuilding Act s 19(1)(d), s 272A
- A current registered product certificate (what MBIE's CodeMark scheme issues) is one of the things a building consent authority must accept as establishing compliance with the Building Code, alongside compliance with an Acceptable Solution or a Verification Method, provided every relevant condition in the certificate is met. Check that it is registered and has not been suspended or revoked, and that its conditions cover this use. Building Act 2004, as at 30 June 2026.
- A BRANZ Appraisal is evidence, not a must-acceptBuilding Act s 49(1), s 19(1)
- The Building Act does not mention appraisals, or BRANZ, anywhere. An appraisal is evidence towards the test every consent is granted on (that the authority is satisfied on reasonable grounds the Building Code would be met), so an authority may rely on it, and usually does, but may also ask for more. That is the difference from CodeMark. Check the appraisal is current and that its scope covers this use. Building Act 2004, as at 30 June 2026.
- The rest of the evidence
- Around a certificate or an appraisal: the manufacturer's specification and installation instructions, test data, and a producer statement. E3 names none of these and requires none of them; they are the customary ways of satisfying an authority. Read what the system's manual says it covers, too: a wet-area manual generally addresses the wall and floor surfaces and says so, leaving E3's ventilation, condensation control and overflow to the rest of this list.
Section 1.0: thermal resistance, ventilation and condensation
- H1 is not E31.1.5, 1.1.5 COMMENT
- Insulation that satisfies H1 Energy Efficiency cannot be assumed to meet these R-values: H1 is met by the building as a whole, and a building with heavily insulated floor and ceiling and no insulation in its walls can pass H1 and fail 1.1.1. Under H1's calculation method a framed wall is held to E3's R1.5 rather than H1's own R1.0 floor.
- The BRANZ House Insulation Guide1.1.1, E3/AS1 References
- The Guide gives constructions that meet 1.1.1; the R-values chosen from it are the ones that satisfy E3, not H1's.
- Foil alone does not reach 1.1.11.1.4 COMMENT 1
- 1.1.4's COMMENT 1: framing with 10 mm plasterboard linings and a single layer of foil comes to about R0.9, short of 1.1.1's wall value. Foil placed where 1.1.4 e) puts it is not by itself an insulated wall.
- A wider channel1.3.3 COMMENT 2
- 1.3.3's COMMENT: a 10 mm channel is normally wide enough not to overflow but awkward to clean, and 20 mm is more practical. The requirement stays 10 mm.
- Specific design1.1.4 COMMENT 2
- A building enclosing a very warm or wet area (a spa pool, sauna or swimming pool) or in a very cold environment such as a ski lodge or mountain hut is not covered by this Acceptable Solution. Vapour barriers and surface condensation there need specific design.
The wet-area build-up: surfaces, joints and membrane
- A membrane is E3/AS1's requirement too3.1.1 b), 3.3.1.1 c), 3.3.1.2 c), E3/AS2 1.1
- This is why both are ticked, and it is the ordinary case. E3/AS1 requires the membrane (tiles on a continuous impervious substrate or a membrane the manufacturer specifies, and a tiled shower wall on a membrane outright), but describes nothing about it. E3/AS2 governs the membrane's selection, design and installation and excludes the finish over it. Each supplies the half the other leaves out. An acrylic or plastic shower liner needs no membrane under E3/AS1; putting one behind it is E3/AS2 1.2 c)'s own example of the Code of Practice going past the Building Code.
- How to read the Code of PracticeE3/AS2 1.3
- Text that is WMAI commentary, italic on a grey background, is non-mandatory and is not part of the Acceptable Solution.
- What E3/AS2 changesE3/AS2 2.1
- Section 1.2.4's requirement that the applicator and installer be certified by the supplier, and that a PS3 be provided, is deleted. E3/AS2 does not make certification a condition of compliance, though the authority must still be satisfied on reasonable grounds that the installation meets the Code.
Showers, and showers over baths
- Why 300 and not 50Figure 5(b), 3.3.1, 3.3.2.1, 3.3.1.1, 3.3.1.2, 3.3.2.3
- E3/AS1 gives two numbers. Paragraphs 3.3.1 and 3.3.2.1, as amended in November 2020, say 50 mm above the rose; Figure 5(b), on a page still dated 1998, dimensions 300 mm. The figure is not an outside source (3.3.1.1, 3.3.1.2 and 3.3.2.3 all point at Figure 5), so both numbers are this document's and it does not reconcile them. These drawings carry 300 mm, which satisfies either reading and ends the argument. 50 mm above the rose is the enforceable minimum if you are assessing something already built.
- Tapware with its own instructions3.3.1 COMMENT
- 3.3.1's COMMENT: some tapware manufacturers set installation requirements of their own, additional to the sealant around the penetration.
- Recessing the rim3.3.1.3 COMMENT
- 3.3.1.3's COMMENT: notching the framing to recess a bath rim may need over-sized framing members, so the notches do not weaken the wall. That is B1's question, raised by E3.
Taking the E3/AS2 route
- What E3/AS2 coversE3/AS2 1.1
- A membrane system installed to sections 1 – 4 of the WMAI Code of Practice for Internal Wet Area Membrane Systems, as modified by E3/AS2 2.0, complies with E3.3.2, E3.3.3, E3.3.4, E3.3.5, E3.3.6.
- Which edition is citedE3/AS2 References
- E3/AS2's References fix the Code of Practice for Internal Wet-area Membrane Systems at its August 2020 edition, and say the referenced documents must be the editions listed. The WMAI has published later editions since. Building to a later one is not E3/AS2 as written, and a consent relying on it needs the authority to accept the newer edition.
- Where the Code of Practice goes further than the Building CodeE3/AS2 1.2 a)
- It provides floor wastes where the Building Code does not require them: anywhere an overflow could not damage an adjoining household unit.
- Where the Code of Practice goes further than the Building CodeE3/AS2 1.2 b)
- It provides overflows within plumbed cabinetry units, which the Building Code does not require.
- Where the Code of Practice goes further than the Building CodeE3/AS2 1.2 c)
- It puts a membrane behind impervious secondary shower linings, including showers over baths, and beneath and behind impervious fixtures sealed to walls and floors. The Building Code does not, where that sealing keeps water out of concealed spaces.
- Where the Code of Practice goes further than the Building CodeE3/AS2 1.2 d)
- It takes the shower membrane higher above the rose than the Building Code requires.
- Outside E3/AS2 altogetherE3/AS2 Supporting information
- Membranes installed with specialist systems such as underfloor heating or sound insulation; industrial processing areas; and the surrounds and changing facilities of internal swimming pools and spas.
Where the rest is
What this page reads, and what it points at rather than reads.