What you've got up there
BRANZ notes that corrugated steel and concrete tiles were New Zealand's commonest roofs in the first half of the 20th century, and that heavy tiles fell out of favour in the decades before 2012. Monier's New Zealand range today is flat Horizon and raised Tudor and Hacienda, made across the Tasman.
They're heavy. A Horizon tile weighs 5.2 kg, or 57.2 kg per square metre of roof. The colour is a surface coating that fades, Monier says, and Resene adds that weathered concrete tiles turn porous and grow moss and mould readily.
Keep the tiles, or change to metal?
| Keep and maintain the tiles | Re-roof in metal | |
|---|---|---|
| Weight on the house | Stays heavy | Gerard says pressed steel tiles weigh about a tenth of a concrete tile roof |
| In an earthquake | Tiles can shake off battens if they aren't tied down | Damage in Christchurch was mostly from falling chimneys, and minor |
| Consent | Repairs with a comparable product can be exempt | A change of roofing system can need consent, and extra bracing is sometimes needed |
| Ongoing upkeep | Ridge bedding and pointing, moss, cracked tiles | Washing unwashed areas, fixings and flashings |
Earthquakes, wind and the coast
Weight matters most when the ground moves. In Christchurch's hill suburbs, BRANZ found concrete and clay tile roofs often lost tiles off their battens because they weren't tied down or the ties had corroded. The Natural Hazards Commission says one roof tile can weigh up to 4.5 kg, and suggests lighter roofing in place of concrete or slate tiles, or making sure they're well secured to the framing.
Wind brings underlay into it. E2/AS1 insists on underlay beneath tiles in Very High and Extra High wind zones, and tile roofs with underlay need anti-ponding boards.
By the sea, it's the fixings that count. For masonry tiles, E2/AS1 calls for 304 or 316 stainless steel fixings, with hot-dip galvanised allowed only in Zones B and C.
How long they last
Monier warrants its New Zealand concrete tiles against manufacturing defects for 30 years from purchase. The warranty excludes weathering and colour fade, efflorescence (a white, salty bloom), damage from people walking on the tiles, and cleaning with the wrong chemicals or too much pressure.
A warranty isn't a lifespan, and we haven't found a published service life for concrete tiles we'd stand behind. Roofers judge it tile by tile: sound tiles with tired ridges are worth keeping, while tiles that crumble or crack at a touch are telling you something.
Looking after a concrete tile roof
Monier suggests a roofing professional inspects the roof ideally every five years, with spouting cleaned at least yearly. It recommends homeowners don't clean their own tiles, because of the risk of falls and broken tiles, and strongly advises against pressure washers.
Ridge bedding (the mortar under the ridge caps) and pointing (the seal on top) crack and loosen over time, and Monier wants repairs done with modern flexible compounds by a roofing professional.
Painting is optional. Resene says there's no reason to paint concrete tiles other than looks, and Monier says it needs redoing about every five years and doesn't improve waterproofing. See painting a tile roof.
What makes the job bigger or smaller
How many tiles are cracked, how much ridge needs rebedding, the roof's height and pitch, and whether scaffolding is needed. Matching an old profile can be the fiddly part, so keep any spare tiles you find in the garage.
Changing material is the bigger call. MBIE says going heavier, from corrugated iron to concrete tiles, needs consent because of the extra load. Going lighter is kinder to the house, but ask your council first.
What a good tile repair quote spells out
- How many tiles will be replaced, and with what
- How much ridge will be rebedded and repointed, and with which compound
- Whether moss treatment is included, and how it's cleaned without high pressure
- Access and edge protection
- What happens if more broken tiles turn up on the day
From the ground, and from the roofer
You can
- Look for slipped tiles and crumbling ridge mortar with binoculars
- Check the roof space with a torch after heavy rain, stepping only on joists
- Keep spare tiles somewhere dry
Leave to a roofer
- Replacing tiles and rebedding ridges
- Moss treatment and cleaning
- Checking tile ties and fixings
If it were our roof
Sound tiles with tired ridges and a bit of moss? We'd repair and keep them. If tiles are cracking across the roof, or the weight overhead in a big quake worries you, we'd ask a roofer about a lighter re-roof and talk to the council early about consent.
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.