Slab moisture testing & asbestos checks for NZ flooring installers

Is flooring a licensed trade in NZ?

No. There is no flooring-specific trade licence in New Zealand, unlike electricians, plumbers, gasfitters and drainlayers. Laying carpet, vinyl, LVT, engineered timber or solid timber is unregulated work. That does not mean it is unregulated risk. Your obligations come from three directions instead: health and safety law (asbestos is the big one on renovation work), the Building Act 2004 when your job touches the structure beneath the floor, and your own contract, where a failed floor is argued over using the manufacturer’s installation instructions and the relevant Australian/New Zealand standard. In practice the question a customer, builder or insurer asks after a failure is “what did you check before you laid it, and where is the record?” The rest of this guide is about having a good answer to that.

Testing a concrete slab before you lay: AS 1884 and RH probes

Most floor failures over concrete come down to moisture: adhesive that lets go, boards that cup, vinyl that blisters, mould under a covering. A floor that looks dry and sounds dry can still be well above what the adhesive or covering tolerates. The installation standard for resilient floor coverings, AS 1884:2021, makes the in-situ relative humidity (RH) probe test the normative method, following ASTM F2170, with the probes sealed in the slab for at least 24 hours before they are read. The older hood-style method (ASTM F2420) has been withdrawn, so a surface moisture meter or a taped-down plastic sheet is not a substitute for a proper probe reading. The pass mark is not set by the standard. It is set by the flooring or adhesive manufacturer, and a commonly quoted figure is 75% RH (from overseas practice, not a limit in AS 1884), but you must read the limit from the data sheet for the product you are actually laying. Record several readings across the slab rather than one, including near external walls, plumbing penetrations and any area that was poured or patched last.

• Read the manufacturer’s RH limit for the covering and the adhesive, and use the lower one.
• Drill to the depth the method requires, seal the probe, and leave it a full 24 hours before reading.
• Log each probe location, depth, RH, slab temperature and the hours sealed.
• If a reading is over the limit, wait and re-test, or use a manufacturer-approved moisture barrier system. Do not lay and hope.
• Keep the record with the job, signed and dated. It is your evidence if the floor lifts a year later.

Asbestos in pre-2000 vinyl, lino, backing and black mastic

If you are lifting flooring in a building from before 2000, assume the old covering may contain asbestos until a test says otherwise. Sheet vinyl, vinyl tiles, linoleum, their paper or felt backing, and the black bituminous adhesive underneath them are all known risks. Under the Health and Safety at Work (Asbestos) Regulations 2016 you must not dry-sand, dry-scrape or power-cut material that may contain asbestos. WorkSafe’s licensing rules then decide who may do the removal. Without a WorkSafe removal licence, a competent person may remove no more than 10 m² of non-friable asbestos, counted cumulatively across the whole removal project, not per room or per day. More than that needs a Class B licence, and any amount of friable asbestos needs a Class A licence. Because the 10 m² is a whole-project figure, a house you lift in stages is still one project. The practical routine is to sample or presume before quoting, price testing and any licensed removal as separate lines, and put the result on file before a crew member touches the floor.

Floors in wet areas: the membrane comes first

In a bathroom, laundry or ensuite the floor finish is the last layer on top of a waterproofing system, not the waterproofing itself. Wet-area membranes are covered by AS/NZS 4858:2004, and the Building Code route for wet-area surfaces runs through clause E3 and its acceptable solution. Your job is to make sure the finish is compatible with the membrane that has been installed (adhesive chemistry, primers, how you finish at the floor waste and the shower hob) and to avoid puncturing or compromising the membrane with fixings, trowel notches or sanding. There is no official “flooring certificate” for this, but a short record of the product you used, the membrane it sits on and the installation method protects the membrane warranty and shows you did not cause a later leak. If the membrane installer or builder has not left you their product details, ask before you start, not after the first complaint.

Where flooring ends and consented building work begins

Replacing floor coverings does not need building consent. The line is crossed when the work moves under the covering. Replacing or re-blocking bearers and joists, adding underfloor supports or altering the structural subfloor is building work that may need a consent, and on a home it can be restricted building work that has to be carried out or supervised by a Licensed Building Practitioner. That is a separate scope from laying the floor, so quote it separately and name who is responsible. Underfloor insulation is the other trap. If you disturb perimeter or underfloor insulation to prepare a subfloor, reinstate it. On a new build, insulation is part of the consented energy-efficiency design (clause H1), and on a rental the Healthy Homes insulation standard applies, so a floor job that leaves a gap is a defect you have created. The current H1 acceptable solution is the 6th edition, in force since 27 November 2025; see our H1 6th edition explainer for what changed.

Keeping the records without chasing paper

None of the checks above is difficult. They fail because they happen on site, on a phone, and never make it into the job file. Toolie’s flooring pack includes a slab moisture register where you enter each probe reading with its depth, temperature and hours sealed, plus the manufacturer’s RH limit that you type in from the data sheet. Toolie never assumes a limit for you. It then flags any reading over your limit and any probe read before 24 hours, and produces a printable test record you can hand over. The same pack carries an asbestos check for pre-2000 jobs, so the “test or presume” decision and the licence thresholds sit on the job beside your quote instead of in your head, and a wet-area compatibility record for bathroom floors. Use whatever system you like, but make sure the record exists and is dated before the first square metre goes down. If you want it built into your quoting, see Toolie for flooring businesses.

Sources

Official sources this guide relies on. Rules change, so check the current version before relying on a date or threshold.

• WorkSafe NZ: asbestos removal licensing FAQs
• Health and Safety at Work (Asbestos) Regulations 2016
• MBIE: H1/AS1 6th edition (Energy efficiency)
• Tenancy Services: insulation standard
• MBIE: Restricted building work

Related: flooring business software · H1 6th edition explained · Healthy Homes calculator · LBP Record of Work. Back to flooring installers software · software for every trade.