Metal vs tile roofing in New Zealand conditions: the upkeep each roof needs, why more homeowners are converting, and what a tile-to-metal conversion involves.
If you're reading this, it's likely you're asking yourself one question: should I replace my tile roof with a long-run metal roof?
This post covers the maintenance a concrete or clay tile roof needs compared with a metal roof, why more homeowners are converting, and what has to happen to the roof structure when they do.
Short answer: both roofs can last a long time. Our view is that concrete and clay tiles will outlast a metal roof, for one reason: concrete and clay don't rust, and steel eventually breaks down. But what really decides how long either roof lasts is the maintenance it gets over the years. Where long-run metal comes out ahead is weight, upkeep, and how well it works with solar panels, skylights and anything else that goes through the roof.
| Concrete or clay tile | Long-run metal | |
|---|---|---|
| Weight | 45–57 kg/m² (concrete tile) | About 5.6 kg/m² (0.55 mm corrugate) |
| On a 150 m² roof | About 7 to 8.5 tonnes | Under 1 tonne |
| NZS 3604 class | Heavy roof (over 20 kg/m²) | Light roof (20 kg/m² or less) |
| Typical life | 50–60 years with maintenance | 30–60 years, depending on the product, your distance from the sea and maintenance |
| Main upkeep | Wash, re-coat, re-bed and re-point every 10–15 years | Wash unwashed areas every 6 months, or every 3 months in severe coastal areas |
| Sits on | 25 mm battens | 45 × 70 mm H1.2 purlins |
| Rust | Tiles don't rust (flashings and fixings can) | Steel eventually breaks down; the product must suit the site |
| Solar and skylights | Possible, but harder to seal, install and walk on for repairs | Screw-fixed with sealing washers; easy to add or remove, and custom flashings can be made to suit |
| Rain noise | Quieter | Louder, but ceiling insulation helps reduce the sound |
| Building consent to switch | Metal to tile: usually needed, because of the extra weight | Tile to metal: usually exempt under Schedule 1 |
Sources: concrete tile weights from Monier's New Zealand technical statements; corrugate weight from Dimond's product data; tile lifespan from BRANZ's Good Repair Guide; washing intervals from NZ Steel's maintenance recommendations; screw embedment from the NZ Metal Roof and Wall Cladding Code of Practice.
A tile roof needs regular work to reach its full life:
As a rule of thumb, that's needed roughly every 10 to 15 years.
One caution on coatings: they only make sense on a roof that's still sound. Be wary of membrane products sold to “seal up” an old tile roof. They don't fix what's wrong underneath, and they can trap moisture.
Concrete and clay are porous. Once the coating has worn, water soaks into the tile, especially through winter. On cold nights that water can freeze, and as it turns to ice it expands, splitting and cracking the tile from the inside. That's why tiles crack even when nobody has been up on the roof, and why owners are often surprised to find loose or broken tiles.
Wind is the other problem. Tiles are heavy, but strong winds can still lift them and shift them out of place, and they need to be put back before water gets in behind them.
Pressed steel tiles, such as Decramastic, look like tile but behave like metal, and they have problems of their own.
Steel tiles rust and concrete tiles don't, but they're maintained in much the same way. Steel tiles can be re-coated with new chips or painted, and concrete tiles can be painted too.
Less, and most of it is straightforward.
On older metal roofs, the usual work is replacing the old lead-head nails with screws and profile washers, and repainting the roof to extend its life. Over time you may need to replace some ridge flashings or other flashings, or the pipe flashings (often called Dektites) around penetrations once they fail.
On any metal roof, keep the gutters clear and wash the areas the rain doesn't reach, such as under overhangs. NZ Steel's maintenance guide for COLORSTEEL® asks for that every 6 months in moderate conditions and every 3 months in severe coastal ones. It's part of keeping your warranty valid.
We're seeing more homeowners make the switch. It usually comes down to a few things.
A concrete or clay tile roof is heavy. Concrete tile weighs around 45 to 57 kg per square metre, so on a 150 m² roof that's roughly 7 to 8.5 tonnes sitting on the frame. The same roof in 0.55 mm corrugate weighs under a tonne. NZS 3604 treats anything over 20 kg per square metre as a heavy roof.
Over time, that weight can make the roof sag between the rafters and distort the fascia boards. Once the fascia moves, the spouting no longer sits at the right fall, so it overflows or drips. From the street it shows as a wavy roofline. All that weight is also carried down through the walls to the foundations, and in an earthquake it's mass the walls have to hold. That's why NZS 3604 asks for more bracing under a heavy roof than a light one.
We've written more about why spouting overflows.
You can absolutely put solar panels, skylights and other penetrations on a concrete tile roof. But you can't seal and rivet to tiles the way you can to steel, so the waterproofing around them isn't as thorough. Tile roofs are also much harder to walk on, so once panels or skylights are in place, getting to a leak becomes a bigger job.
Long-run metal is far more forgiving. Solar brackets screw straight through the roofing, with an EPDM rubber washer between the bracket and the steel to seal it. If the panels ever come off, the brackets unscrew and a screw goes back into each hole. If you need a new penetration, or want to remove an old one, a single sheet can be replaced, or a back tray flashing added to cover the area or take the new penetration.
Long-run is lighter and quicker to install, and it comes in a wide range of colours. Current roofing products also generally carry longer warranties and perform better than the steel that went onto older roofs.
There are profiles to suit different buildings, too. If a roof is walked on a lot, a stronger profile such as BB900 is less likely to dent and much easier to walk on, which suits commercial buildings that see regular maintenance. Our roofing materials page explains the options.
Changing material doesn't mean changing the look of the house as much as people expect. The Westmere houses at the top of this post went from red tile to Scoria, and the Morningside house below went from green tile to Mist Green. See the COLORSTEEL® and COLORCOTE® colour range.
Going from a heavy roof to a light one isn't just a change of material. The structure underneath has to suit the new roof.
Concrete, clay and steel tiles sit on 25 mm battens. Long-run steel needs 45 × 70 mm H1.2 treated timber purlins, fixed to the framing with fixings to suit your wind zone. Depending on the zone, that might be purlin screws, bugle screws or 90 mm galvanised nails.
The reason is simple. The screws holding the roofing down have to bite into the timber, and the NZ Metal Roof and Wall Cladding Code of Practice generally calls for 30 mm of embedment in a timber purlin. A 25 mm batten can't give that, so new roofing can't be fixed to the old battens.
A tile roof was built to carry weight. Its framing and fixings were designed for downward load, not for wind trying to lift the roof off. Once the tiles are gone, wind uplift becomes the main load.
A new metal roof also has ventilation paths, with air coming in at the bottom of the roofing and out at the ridge. In a storm, that means pressure pushing up from inside the roof space as well as suction over the top, both working to pull the roof off.
So the framing needs extra fixings to tie it down. That can mean 150 mm bugle screws from the rafters down into the top plates and lintels, connectors and ties around the ridge board, screws from the top purlin into the rafters, and cross bracing where it's needed. BRANZ sets out what needs checking when a tile roof is replaced, and we've written about why your roof needs to breathe.
New underlay goes on as part of the job. And as with any reroof, the condition of the timber can't be seen until the tiles are off. Here's what happens if they find rot when your roof comes off.
In most cases, no. Replacing a tile roof with long-run metal usually falls under Schedule 1 of the Building Act as exempt building work. MBIE's guidance on exempt building work uses replacing a clay tile roof with profiled metal as one of its examples, and flags wind uplift as the thing that has to be dealt with.
It's still worth checking before work starts, because a change of roofing material can trigger consent requirements. The Roofing Association of New Zealand or Auckland Council can confirm it for your house.
Exempt doesn't mean anything goes. The work still has to meet the Building Code, so treat it as though it were consented work: the structure strengthened to suit the new roof, as described above. More on that in most reroofs don't need a building consent, so who checks the work?
Going the other way is different. Swapping a metal roof for concrete tile adds load the framing may not have been designed for, and MBIE's guidance generally treats that as needing a consent.
A vague answer to any of these is worth following up before you sign.
Next: what should a roofing quote include?
Which lasts longer, a tile roof or a metal roof?
A well-maintained concrete or clay tile roof will generally outlast a metal one, because concrete and clay don't rust. How long either roof lasts comes down to the maintenance it gets.
How often does a tile roof need maintenance?
Roughly every 10 to 15 years: washing, re-coating, and re-bedding and re-pointing the ridge and hip lines.
Why are my roof tiles cracking when nobody has been on the roof?
Concrete and clay are porous. Water soaks in, and when it freezes it expands and cracks the tile. Strong winds can also lift and shift tiles.
Can new metal roofing be fixed to the old tile battens?
No. Tile battens are 25 mm, and roofing screws generally need 30 mm of embedment in the timber. Long-run steel goes onto new 45 × 70 mm purlins.
Do I need a building consent to change from tile to metal?
Usually not. It generally falls under Schedule 1 exempt building work, but the Building Code still applies in full and the roof framing usually needs extra fixings to hold the roof down in high wind. Check with RANZ or Auckland Council if you're unsure.
Can I put solar panels on a tile roof?
Yes, but the waterproofing around the brackets isn't as thorough as on metal, and leaks are harder to get to once the panels are on.
Is a metal roof noisier than tile?
Yes, in heavy rain. Ceiling insulation softens it considerably.
Technically reviewed by Impact Roofing Solutions.
This article is general roofing information based on our experience working on Auckland properties. Every building and roofing system is different, and requirements can vary depending on the existing construction, location, product specification and proposed work. Project-specific requirements should be confirmed before work begins. Building Code and consent information can change, so check the current requirements with Auckland Council or the relevant project professional where required.
