Timber Flooring and NZBC E3 Internal Moisture
Clause E3 of the New Zealand Building Code governs internal moisture. It is the reason most conversations about timber flooring stop at the bathroom door.
E3 does not prohibit timber. It requires that surfaces about sanitary fixtures be impervious, which E3 defines as not allowing the passage of moisture. That is a performance standard. How it is achieved is open.
In July 2026 we had both our flooring and our wall and ceiling boards independently tested to establish exactly that.
What was tested
An IANZ accredited laboratory, tested assembled board joints to ISO 4760:2022(E), the international method for topical moisture resistance of an assembled joint.
The method was modified to reflect how the product is actually installed. Rather than testing a floating locked joint, planks were adhesive-fixed at 100 percent bond coverage and the test applied across a T joint, where three boards meet and where water would find a way through if it were going to.
What the testing found
20mm engineered oak flooring
Report 1622873.6, 13 July 2026
No migration of water along the upper surface. No migration of water to the underside. Neither during the test nor on disassembly, in any of the three specimens.
Every specimen returned a qualitative rating of 1, “no change”, the highest rating available on the five-point scale, for both wet swell and recovered swell. Maximum wet swell across all specimens was 0.17mm, recovering to 0.07mm.
12mm wall and ceiling boards
Report 1622876.9R, 15 July 2026
The same result. No water migration on any surface, in any specimen, at any stage. A rating of 1 throughout. Maximum wet swell 0.11mm, recovering to 0.09mm.
In plain terms: dye solution stood over a board joint for a full day and did not get through.
What this means, precisely
This is independent evidence supporting an Alternative Solution under the Building Act. It is not a certification, because none exists. E3/AS1 itself records that no specific methods have been adopted for verifying compliance with the performance of E3, which is exactly why an evidence-based Alternative Solution is the appropriate route.
Our Alternative Solution has been submitted for building consents across the country and accepted, with no further information requested.
Compliance is determined by local councils for each project on its own facts. We supply the full documentation with every specification so it can be submitted with the application rather than requested afterwards.
Where Marchand can be used
| Space | Position |
|---|---|
| Living areas, bedrooms, hallways | Yes. E3 provisions not engaged |
| Kitchens | Yes, with E3 moisture management provisions met |
| Laundries | Yes, with E3 moisture management provisions met |
| Powder rooms | Yes, with E3 moisture management provisions met |
| Bathroom floors | Conditional. Impervious coating and sealed joints for a minimum of 1.5m from any sanitary fixture. Refer to the Alternative Solution |
| Bathroom walls and ceilings | Conditional. The 12mm board carries the same test evidence. Refer to the Alternative Solution and confirm the detail with us |
| Showers and continuously wet zones | No |
| Exterior and permanently damp conditions | No |
Installation conditions
E3 performance is a property of the installed system, not of the board alone. The following are requirements.
| Condition | Requirement |
|---|---|
| Joints | Glued, per the tested assembly |
| Adhesive | Bona R848T or Ardex PU30, or another approved system, at full bond coverage |
| Substrate moisture | Below 75 percent RH. Above that, a vapour barrier is required. Exceeding it voids the warranty |
| Substrate flatness | ±2mm over 2m |
| Sealing near fixtures | Impervious coating with joints sealed for a minimum of 1.5m from any sanitary fixture |
| Ambient conditions | Interior only, RH 40 to 65 percent, 15 to 25°C |
| Installer | Experienced installer working to the Marchand Installation Manual |
Not covered
Flooding, moisture ingress through the building envelope, subfloor moisture above 75 percent RH, steam mops and over-wet cleaning. Standing water left on any timber floor will eventually find a way in. The testing shows what a correctly assembled joint resists over 24 hours. It is not a licence to leave water sitting.
Questions
Has Marchand flooring been independently tested for moisture resistance?
Yes. an IANZ accredited laboratory, tested assembled board joints to ISO 4760:2022(E) in July 2026. Dye solution held over a joint for 24 hours produced no migration of water to the underside in any specimen, and every specimen returned a qualitative rating of 1, no change, the highest on the scale. Reports 1622873.6 and 1622876.9R are published in full.
Can you put timber flooring in a bathroom in New Zealand?
Conditionally. Marchand engineered oak may be used in powder rooms, kitchens and laundries where E3 moisture management provisions are satisfied, which requires an impervious coating and sealed joints for a minimum of 1.5m from any sanitary fixture. It cannot be used in a shower or any continuously wet zone. Our Alternative Solution, supported by independent ISO 4760 testing, has been accepted for building consents across the country.
Can engineered oak go in a kitchen or laundry?
Yes. Both are normal applications where E3 moisture management provisions are met. The UV-cured lacquer gives an impervious, readily cleanable surface, and independent testing showed no water penetration through a glued board joint after 24 hours of standing liquid. Avoid standing water and do not use steam mops.
Can timber wall or ceiling boards be used in a bathroom?
The 12mm wall and ceiling board carries the same independent moisture test evidence as the flooring, achieving a rating of 1 with no water migration in any specimen. This supports use in bathrooms outside the shower enclosure, as an Alternative Solution, with the detail confirmed for the specific project. It is not suitable inside a shower.
Does Marchand flooring comply with E3?
Compliance is a property of the installed system and is determined by the Building Consent Authority. What we hold is independent ISO 4760 test evidence supporting an Alternative Solution, which has been submitted for consent and accepted with no further information requested. E3/AS1 itself records that no specific verification methods have been adopted for demonstrating E3 performance, which is why an evidence-based Alternative Solution is the appropriate route.
What is an Alternative Solution, and will a council accept it?
Both Acceptable Solutions and Alternative Solutions are valid means of compliance under the Building Act. An Acceptable Solution is prescriptive and deemed to comply if followed. An Alternative Solution demonstrates that the same performance requirement is met, supported by evidence. Ours has been submitted for building consent and accepted with no further information requested. Consent authorities assess each application on its own merits, so we supply the full documentation with every specification.
Do steam mops damage timber floors?
Yes. They force hot moisture into board joints under pressure and are excluded from our warranty and from most others in the category. Use a damp mop with a pH neutral timber cleaner.
Documentation
NZWTA report 1622873.6, flooring. NZWTA report 1622876.9R, wall and ceiling boards. E3 Alternative Solution. BPIR technical statements. All available from Resources, or see Specification and Compliance for the full technical library.
Last reviewed August 2026.