How long does a roof last in NZ? Lifespan and maintenance by roof type

The roof is the part of the house that gets the least attention and does the most work. It is also the one buyers almost never look at properly, because you cannot see much from the driveway. I climb onto every roof I can safely get onto, and I look at the underside from the roof space, because the underside usually tells the truth first.

How long each roof type lasts

• Long-run steel. The most common roof in the Waikato. Thirty to fifty years depending on the coating and how close you are to the coast. The sheets usually outlast the fixings, so rusted screws and lifted washers are where it starts.
• Concrete tiles. Fifty years and more for the tiles themselves, but the pointing on the ridges and the underlay beneath fail well before that. A concrete tile roof with perished underlay leaks into the roof space without a single broken tile.
• Clay tiles. The longest lived of the lot, up to a century if they are looked after. They need very little beyond checking for cracked or slipped tiles and cleaning off moss and lichen so water sheds properly.
• Membrane and butynol. Flat and low-pitch roofs. Fifteen to twenty-five years, and ponding water is what shortens them.

What actually kills a roof early

It is rarely the material. It is the small things nobody does. Gutters that have not been cleared so water backs up under the sheets. Tiles that have been walked on and cracked by an aerial installer. Fixings that have rusted and let go. Moss holding moisture against the surface all winter. Standing water on a flat roof because the fall was never right.

On the house behind our sample report, the gutters on three sides held standing water. Nothing dramatic, but that is how a fifty year roof becomes a thirty year roof.

What I check on an inspection

• From on top: the sheets or tiles, ridges, flashings around chimneys and vents, gutters and downpipes, and anything that penetrates the roof
• From the roof space: the underside of the roofing, the underlay, the framing, insulation, and any staining that says water has been getting in
• The age and coating of steel roofs, and whether the fixings are original
• Moss, lichen and debris, because they are the cheapest fix and the most common cause of trouble

Each finding is graded red, orange or green in the report, with photos, so you can see whether the roof needs a clean, a repair, or a budget line for replacement.

What to budget for

If a roof is near the end of its life the report will say so, and that belongs in your offer. Replacing a long-run roof on a typical Hamilton home is a significant cost, and a roof that only needs new fixings and a clean is a weekend job. The difference is worth knowing before you buy.