Is it time to stop patching the tiles?
Resene describes decramastic wearing out in stages: the stone chips erode, the bitumen under them is exposed, then the galvanised steel, which eventually rusts. When rust shows at tile edges over most of the roof and leaks appear in several spots, a recoat buys little time.
If only a few tiles are bad, repair still makes sense. See decramastic roofs for that route.
Get an asbestos test before a single tile comes off
Gerard says asbestos went into decramastic coatings up to 1981, so roofs laid as late as 1982 could have it, and a roofer will want a test before stripping. You can't tell by looking. Until the result is back, nobody should water-blast, cut or grind the tiles. If it's positive, see asbestos roof removal.
How the switch usually goes
Test and plan
Asbestos result back, consent position confirmed in writing, product and colour chosen from a real sample.
Strip the tiles
Tiles, battens and old flashings come off, by a licensed removalist if asbestos was found.
Purlins and underlay
Longrun is fixed to purlins across the rafters, so the roofer fits them and replaces rotten timber. Underlay follows, which E2/AS1 requires under profiled metal longrun.
Sheets and flashings
Dimond says sheets should run in one length from ridge to spouting where possible. NZ Steel says lead can degrade COLORSTEEL, so flashings use soft zinc or aluminium instead.
Will it need a building consent?
Possibly not. MBIE's exemptions guidance treats a lighter roof going on in the same position as generally exempt under Schedule 1: its example is an old clay tile roof replaced with longrun or pressed metal tiles. Consent comes in when the roof gets heavier, such as iron replaced with concrete tiles. Decramastic to longrun is steel for steel.
Some councils read a change of roofing type more strictly. Wairoa's, for one, lists corrugated iron to pressed metal tiles as a change of system needing consent. Check with your council, or get the roofer's view in writing. Where consent is needed, an LBP does or supervises the roofing and gives you a Record of Work.
Pitch is rarely the problem: E2/AS1 sets 12 degrees as the minimum for pressed metal tiles, and RANZ gives 8 for standard corrugate. Have it measured anyway.
MAXAM or ALTIMATE?
COLORSTEEL is two products now: MAXAM for most of New Zealand, inland and coastal, and ALTIMATE, a marine-grade aluminium, for extreme spots like breaking surf. ENDURA and MAXX are retired, so a quote naming either is out of date.
NZ Steel warrants by its own environment categories, Mild to Extremely Severe, and doesn't recommend MAXAM in Extremely Severe. Within 100 metres of salt water, it asks you to contact COLORSTEEL to confirm the warranty. Genuine sheets carry the brand on the back, so ask for it by name on the quote.
Questions to ask before you say yes
- Has the roof been tested for asbestos, and who's licensed to remove it if needed?
- Will you put the consent position in writing, and who applies?
- Which COLORSTEEL product and profile, and what warranty applies at my address?
- Are you an LBP with profiled metal roofing among your areas of practice?
- How will rotten timber under the tiles be handled?
What's yours to do, and what isn't
You can
- Look for stone chips collecting in the spouting or at downpipe outlets
- Photograph rust streaks and lifted tiles from the ground
- Find out when the roof went on, for the asbestos question
- Hold a COLORSTEEL sample against the house in daylight
Leave to a roofer
- Asbestos sampling and testing
- Foot traffic on the tiles, which can badly dent them
- Stripping, purlins, underlay and sheeting
- Consent paperwork and the Record of Work
If it were our decramastic roof
We'd book the asbestos test before anything else, because the result shapes the whole job. If the steel is rusting through across the roof, we'd stop paying for patch repairs and go to COLORSTEEL longrun, with the product, the warranty category for the address and the consent position all written into the quote.
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.