BUILDING CODE UPDATES 2020-2021 - INTERNAL MOISTURE

On the 4th November 2021, the changes to NZBC E3/AS1 and addition of E3/AS2 become the Acceptable Solutions for Internal Moisture. This article looks at the changes to E3/AS1 and reviews the new E3/AS2, how they work together and how it might affect you.

E3 INTERNAL MOISTURE: NZBC E3/AS1 amendment 7

The new amendments have made NZBC E3/AS1 a bit more complicated and in some cases confusing.  New clauses and altered existing ones have complicated when to waterproof and what surface materials to use. They, along with new definitions, have also increased restrictions of what you can use and when.

DEFINITIONS

Sanitary Appliances: new added definition - appliance used for sanitation (washing machines, dishwashers etc) but not a sanitary fixture.
Sanitary Fixtures: existing altered definition - Sinks and Tubs have been added to the list of the "comment" to the definition. Previously sinks and tubs were not thought of as Sanitary Fixtures.

SECTION 2.0 - OVERFLOW

This section deals with what to do if there is a possibility of accidental overflow under certain conditions.  The key parameters are:

• Applies to Sanitary Fixtures only (not Appliances, more on this later)
• Applies if accidental overflow could damage adjoining household unit or (any) other property
• If it applies then requirements are for:
• Containment and floor waste or
• Integrated overflows for household kitchen sinks and laundry tubs
• Does not seem to apply to a stand alone house or any other type of stand alone building (under a single ownership).  Although for multiple rental/leased household units in a standalone building it would probably apply (based on the terminology). This is less clear for other types of multiple rentals/leases.

Provision of overflows

If compliant integrated overflows are provided for household kitchen sinks and laundry tubs, then containment is not required (although an impervious floor may still be required for Watersplash?).
An overflow shall comply with BS EN 274.2, which is a new Standard added to E3/AS1 for testing of overflows.

Containment and floor wastes

This is the provision of impervious floor or floor finish, and a floor waste. The floor is not required to have falls to the waste. Extent of containment is at least 1.5m from possible source or the full extent of the room. 

SECTION 3.0 - WATERSPLASH

Watersplash is not really defined, but in some cases it seems to be closer to a good hosing down than a few stray drips.

3.1 Lining Materials - Floors

Spaces with Sanitary Fixtures and Sanitary Appliances are to have impervious and easily cleaned surfaces.  Extent of the impervious and easily cleaned surfaces is at least 1.5m from the source or the full extent of the room. These are required regardless of containment requirements.

Satisfactory floor materials listed are:

• Integrally waterproof sheet (like vinyl sheet flooring), edges sealed or coved
• Ceramic or stone tiles on impervious substrate (e.g. on waterproof membrane), edges sealed or coved
• Slab-on-grade concrete floor in very limited circumstances

As you can see this is a very limited range of materials.  An E3/AS1 Comment does admit there may be other materials that can satisfy requirements, but they would be Alternative Solutions.

It is worth noting what materials were removed by amendment 7 and no longer satisfy:

• Plaster/concrete (not limited)
• Cork tiles
• Monolithic coatings (Terrazzo)
• Sealed timber or timber based materials

3.1 Lining Materials - Walls

Spaces with Sanitary Fixtures and Sanitary Appliances, adjacent linings or linings which are likely to be splashed, are to have impervious and easily cleaned surfaces.  This is still quite a vague concept which could lead to some interesting discussions with your BCA?
Satisfactory wall materials listed are:

• Integrally waterproof sheet (like vinyl sheet flooring), sealed joints
• Ceramic or stone tiles (Note, waterproof membrane not required)
  
• Sheet linings coated with specific paint types (could be wet area plasterboard painted)
• Water resistant sheet lining pre-finished with high pressure laminate or polyurethane, with impervious joints

It is worth noting what materials were removed by amendment 7 and no longer satisfy:

• Plaster/concrete
• Cork tiles
  
• Monolithic coatings (Terrazzo)
• Sealed timber or timber based materials
• Vinyl wallpaper

 3.2 Joints

Joints between a Sanitary Fixtures and an impervious floor finish must be sealed.

Joints between a bath, basin, tub or sink and an impervious wall finish must be sealed.

Remember that frequently any tops (vanities, sink benches, bath surrounds etc) may also need sealing to fixtures and to wall finishes.

3.3 Showers and Urinals

3.3.1 Showers

Showers to have impervious floor/floor finish and impervious wall/wall finish (does not mention easily cleaned surfaces?). Extent of the impervious surfaces is:

• For floors at least 1.5m from the rose or the full extent of the room/enclosure (includes shower curtains)
• For walls at least 1.5m horizontally from the rose or the full extent of the room/enclosure, and at least 1800mm above the floor and 50mm vertically above the rose (this is reduced from 300mm)

In clause 3.3.1 and 3.3.2.1 the height of an impervious wall lining above the shower rose has been changed from a minimum of 300mm to 50mm. However Figure 5 has not changed and still shows 300mm, we assume this is an oversight?

Satisfactory shower floor materials listed are:

• Plastic or Stainless Steel shower tray
• Integrally waterproof sheet (like vinyl sheet)
  
• Ceramic or stone tiles on impervious substrate (e.g. on waterproof membrane), or impervious tray.  If tiled floor then walls must be tiled.

Satisfactory wall materials listed are:

• Plastic shower wall liners
• Integrally waterproof sheet (like vinyl sheet flooring), sealed joints
• Ceramic or stone tiles on waterproof membrane
• Water resistant sheet lining pre-finished with high pressure laminate or polyurethane, with impervious joints

All impervious linings are to be sealed along the top.

Penetrations like tapware, mixers, roses etc are to be waterproofed with sealant or proprietary flange systems (see new figure 6) for showers and showers over baths.

Note; proprietary shower enclosure requirements under 3.3.2 remain mostly the same, except for the lining being at least 50mm above the rose (this is reduced from 300mm).

3.3.1.3 Shower over baths

Basically the same as for shower walls and penetrations. The bath to shower lining junction is different to a standard bath, the bath must have a minimum 15mm high rim and the shower lining must lap over and be sealed to the rim. Bath flashings/mouldings are not to be used. This will seriously limit the range of baths that can be used with showers over, and provide some tricky detailing.

3.3.3 Urinals

Although the clause has not changed, it requires the use of an "impervious wall" behind the urinal. As we have seen the range of impervious walls has changed. Even though this clause comes under part 3.3 Showers and Urinals, impervious wall in this case seems to be covered by wall linings under part 3.1 Lining Materials.

Masterspec

Masterspec has updated effected sections, which mainly involves sections related to sanitary fixtures and tapware.

E3 INTERNAL MOISTURE: NEW NZBC E3/AS2

E3/AS2 - A new Acceptable Solution

This new Acceptable Solution cites the Waterproofing Membrane Association Inc's, Code of Practice for Internal Wet-areas Membrane Systems, as an Acceptable Solution for substrate waterproofing. The new E3/AS2 of course slightly modifies the Code of Practice (CoP).

E3/AS2 only requires the use of sections 1 - 4 of the CoP, which cover materials, design and details.  However, this does not include installation, site practice, specialist systems or finishes. AS2 also deletes the requirement for the installer/applicator to be certified by the supplier.

E3/AS2 clause 1.2, also identifies items in the CoP that may exceed the NZBC clauses E3.3.2 - E3.3.6.  If you are using E3/AS2, then it is important to understand that exceeding NZBC is optional not mandatory.

Items in the CoP that may exceed NZBC in relation to:

• Floor wastes located in areas not required by E3/AS1 for accidental overflow
• Provision of overflows within plumbed cabinets (vanities etc)
• Membrane behind impervious shower linings (other than tiles) and beneath impervious sanitary fixtures
• The height the membrane must go above a shower rose

One area of the CoP that is worth noting is the requirements for substrates under waterproof membranes.

Allowable substrate materials are:

• Concrete (floors/walls), cementitious screeds (floors) and concrete blocks, AAC panels, cement plaster (walls)
• Plywood H3 CCA
• Fibre cement, compressed for floor
• Reconstituted wood panels, non-oriented strand board (not OSB and not particle board)
• Water-resistant gypsum board (walls only)

Sheet substrate minimum thickness is:

Note: check the CoP for further detail requirements on substrates.

Masterspec

Masterspec has updated a considerable number of sections related to wet area membranes and membrane substrates.

Download the CoP in AS2