Fibre cement is stable, predictable, and entirely about the joints.

Plank — Hardiplank and its equivalents

Horizontal boards laid like weatherboard. Dimensionally stable and easy to coat. The vulnerable points are the cut ends, which are far more absorbent than the factory face and must be sealed; the butt joints, which need a flashing or soaker behind them rather than a bead of filler; and the bottom edge, which takes the splash. On plank, look at the ends and the joints — not at the middle of the board.

Plank is also frequently mistaken for timber weatherboard by both owners and quoting painters. The difference matters, because plank does not need the timber-specific primers, does not rot, and does not need the moisture-content test that governs a timber weatherboard job.

Sheet — flat and textured

Large panels, usually with joints either expressed and flashed, or stopped to disappear. Sheet is where the cracking complaints come from, and the pattern gives it away: a crack that runs dead straight for the full height of the wall in a repeating grid is a sheet joint moving, not a substrate failure. It needs the joint system rebuilt — reinforcing tape and the correct compound, or a properly sized flexible sealant joint — not filler skimmed across it.

Textured sheet with a coating over it behaves as monolithic cladding for practical purposes, and should be read on that page instead.

Chalking, which is the one that ruins repaints

Ultraviolet light breaks down the binder in the old coating and it releases pigment as a fine powder. Rub your hand across a north-facing wall: if it comes away dusty, that is chalk. Paint over chalk and the new film is bonded to loose powder, which is why some fibre-cement repaints fail within two seasons. It has to be washed off and the surface stabilised with a bonding primer. This one step is worth more than an upgraded topcoat.

Asbestos-cement sheet was used extensively in New Zealand buildings — as wall cladding, as soffit and eaves lining, as roofing, and as backing board — and the importation of asbestos-containing products was only prohibited in 2016. As a working assumption: fibre-cement sheet installed before the mid-1980s may contain asbestos, and you cannot tell by looking at it. Neither can a painter, and neither can this page.

The important distinction is between the material and the dust. Sound, coated, undisturbed asbestos-cement sheet is generally regarded as low risk — the fibres are bound in the cement matrix. The hazard is created when the sheet is disturbed: dry sanding, grinding, high-pressure water blasting, cutting, drilling, or breaking it. Those are, unfortunately, precisely the ordinary preparation steps for repainting fibre cement. Which is why identification has to come first.

What to do: stop and leave it alone. Get the material identified by testing a sample at an accredited laboratory, taken by someone competent to take it. Then work to WorkSafe New Zealand’s requirements, which cover when a survey is needed, what work is restricted, and when a licensed asbestos removalist is required. WorkSafe is the regulator and the right source. A painter’s reassurance is not.

Coating rather than removing is sometimes the recommended approach, exactly because it leaves the material undisturbed. Whether that applies to your building, and what preparation is permissible, is a question for a competent assessor, not for a quote.