Salt Air and Steel Roofs on Wellington's South Coast
Living near the water on Wellington's south coast is hard on a house. Spray carried in on southerly gales settles on roofs in Island Bay, Owhiro Bay, Houghton Bay, Lyall Bay and Seatoun, and salt attacks steel. Roofs here can show corrosion years earlier than the same roof a few kilometres inland.
When it is time for repairs or a new roof, it pays to talk to a roofer who knows long-run and corrugated steel roofing in Wellington and the coastal requirements in the NZ Building Code. The grade of steel, the coating, the fixings and the flashings all need to suit the exposure, or the weakest part will fail first.
Where corrosion starts
- Laps between sheets, where salt and moisture sit
- Fixings, especially if they are not matched to the roofing
- Cut edges at the gutter line and ridge
- Areas sheltered from rain, such as under eaves and overhangs
- Spots where different metals touch, such as copper pipes on steel
Rain washing matters
It sounds odd, but the parts of a roof that get rained on often last longer than sheltered parts. Rain washes salt off exposed surfaces, while salt builds up where water does not reach. Some coastal owners gently hose down sheltered areas of the roof and spouting a few times a year to help with this, where it can be done safely from the ground.
Spotting trouble early
Look for white powdery deposits, rust spots at fixings and bubbling paint along laps. Inside, check the roof space for rust stains on the underside of the iron. Small areas of corrosion can often be treated and touched up before they spread.
Choosing replacement steel
If you are replacing a roof near the coast, ask what corrosion zone your property sits in and which product and fixings are suited to it. Getting this right at the start is what lets a new steel roof stand up to decades of salty southerlies.
More on this site: Restore or Replace? Deciding on a 1970s Roof in Lower Hutt and Ponding Water on Wellington Flat Roofs and Decks.