Until you know, leave it alone
Don't drill, cut, sand, water-blast or walk on a roof that might be asbestos cement. Old cement sheets can give way underfoot, and it's damaged or disturbed asbestos that releases fibres. Snapping off a corner to check counts as disturbing it.
How the answer is worked out
It weighs two things. WorkSafe says a home built before 1 January 2000 may contain asbestos, and so may extensions or renovations done before then. On the roof, the usual suspect is grey cement sheeting, which Resene says was most often sold as corrugated Super Six.
Choose tiles or metal and the checker rates the roofing itself as lower risk, but WorkSafe lists ridge capping, spouting (gutters), downpipes, gables and eaves as other places asbestos turns up. Some cement roof tiles and shingles contain it too, Health NZ says, so if you can't tell what your tiles are, pick "not sure".
If your roof is decramastic
Pick the metal option and the checker says the roof itself is unlikely to be asbestos. Decramastic is the exception. Gerard says stone-chip metal tiles made before the early 1980s often had small amounts of asbestos in the bitumen or mastic coating, and Resene advises testing or assuming it's there. WorkSafe's guidance for cleaning these roofs is a low-pressure sprayer, never water-blasting.
If the answer is to treat it as asbestos
Leave it be for now
Bonded asbestos in good condition that's left alone generally doesn't release fibres, so there's no need to rush.
Get a sample tested
Use a reputable asbestos contractor. Health NZ suggests talking to a health protection officer at your public health service before a sample is taken.
Plan the work around the result
If it's positive, a business removing more than 10 square metres needs a Class B licence for bonded sheeting, or Class A for crumbly, friable material. Check their licence shows as Current on WorkSafe's register.
Tell every tradie
Give the result to any roofer or painter before they quote, so they plan safe methods from the start.
What we'd do first
If the checker says test, we'd get the test done before asking for quotes. The result decides whether you need a licensed removalist, a roofer or both, and it stops anyone quoting the wrong job. Our guide is my roof asbestos? covers the signs, and asbestos roof removal explains what replacing it involves.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.