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Roof Restoration
Metal roofs · corrugated sheet · the rules around it

Restoring a metal roof, crest by crest

How far from the sea a metal roof can sit before its coating has to change, what its colour does to the heat inside, why it can drip on a clear night, and what it adds to the water in your tank. A guide published by Dotto from the official sources linked on each page.

Corrugated metal roof sheets in low sunlight, laid in overlapping planes with rows of roofing screws along the crests
Corrugated metal roofing in low sun. Photo by sandid on Pixabay
Profile 1 · The sheet in section

Five places the rules meet a metal roof

The National Construction Code (NCC) sets out its rules for metal sheet roofing on a house in the ABCB Housing Provisions. They are “deemed-to-satisfy” provisions: other methods may be used if they meet the code’s performance requirements. The drawing marks five places where the code, or the board that writes it, has something to say.

A corrugated metal roof sheet in section A wavy corrugated sheet runs across the drawing. A roofing screw with a washer passes through one crest into a batten below. Droplets hang from the underside of the sheet in the valleys and fall onto a sheet of sarking, which slopes down to the right towards the gutter. The sun shines on the top of the sheet, and rain runs off it to the right. 1 2 3 4 5
Drawing not to scale, numbered to match the list below.
  1. 1The metal coating. The sheet must be protected from corrosion to the level the code sets for its location, which depends on its distance from breaking surf, sheltered bays and aggressive industrial areas. Coastal corrosion, by distance
  2. 2Screws, flashings and gutters. Where different metals are used together, including flashings, fasteners, guttering and downpipes, they must be compatible with each other.
  3. 3The underside. The Australian Building Codes Board’s condensation handbook says condensation under a metal deck roof is probable, and that sarking can collect the drips and drain them to the gutter. Condensation under a metal roof
  4. 4The colour. In climate zones 1 to 5, the solar absorptance of a roof’s upper surface must not be more than 0.64. Not in NSW: its own version of this clause, NSW 13.2.3, sets no colour limit, only the thermal break, and BASIX applies to new homes and larger renovations there. Roof colour and heat
  5. 5The water that runs off. The National Construction Code says “no lead materials can be used on roofs that form part of a drinking water catchment area”. Rainwater from a roof

Which edition of the code applies depends on where you live. NCC 2025 was published on 1 May 2026 and took effect in Victoria that day; NSW and Queensland adopt it on 1 May 2027, according to the ABCB’s adoption table, so the 2022 edition still applies there for now. Rules 1, 2 and 5 read the same in the 2022 edition, and so does rule 4 everywhere except NSW, where the 2022 edition’s NSW variation has no colour limit.

Profile 2 · Six guides

Six guides, laid side by side

Each one answers a single question about metal roofs from official sources, and says which state or which edition of the code it speaks for.

Profile 3 · Distance from the sea

How far from the surf is your roof?

The NCC grades a roof’s surroundings from low to very high corrosion, and for ocean beaches the measure is distance from breaking surf: salt water where waves break on an average of at least 4 days a week. A summary of the code’s categories for surf coasts only, read on the NCC’s sheet roofing page:

  1. 0 to 100 mVery highNone of the metallic coatings in the table is listed as suitable.
  2. 100 to 200 mVery highOnly coated sheet that also has an organic coating is listed.
  3. 200 m to about 1 kmHighGalvanised sheet drops out of the table.
  4. Beyond about 1 kmMediumCan reach about 10 to 50 km inland, depending on wind and the lie of the land.
  5. Remote inlandLowMany areas at least 50 km from the sea, with many exceptions.

Sheltered bays and industrial areas have their own distances. The coastal corrosion guide sets them out, with the coatings each category accepts.

Profile 4 · Before work starts

Three things to know before anyone goes up

  • Approval is the owner’s question. Queensland’s building regulator says it is the home owner’s responsibility to make sure the right approvals are in place before work starts, even with a builder hired. Consumer Affairs Victoria says the same of planning and building permits, and NSW Planning says it is the property owner’s obligation to find out whether approvals are needed. Approvals and licences, state by state.
  • Older roofs can hold lead. NSW Health lists lead-based household paints used before 1970 among the places lead is found, and advises against collecting rainwater from roofs with uncoated lead flashing or lead washers on roofing screws. Lead and older roofs.
  • Older roofs can hold asbestos, too. The national asbestos agency says a home built or renovated before 1990 might contain it. If asbestos roof sheeting is in good condition, the agency’s advice is not to disturb it. It also says it is “not recommended that you handle or remove asbestos yourself”, and in some places the law goes further: in the Australian Capital Territory any removal needs a licensed removalist, unless it is part of minor routine maintenance or other minor work, and in Queensland a home owner must be trained before taking out more than 10 square metres of non-friable material, and only a removalist holding a Class A licence may remove friable material. The agency adds that asbestos waste must go to a landfill licensed to accept it. What the rules say before any of it is disturbed is in the approvals guide’s section on asbestos.