Metal Roofing Sheets
A colour coated sheet is galvanised or galvalume steel with a baked paint system applied over it on a continuous coil line. The steel carries the load, the metallic coating resists corrosion, and the paint handles weather and appearance. Because the paint is applied and cured before the coil is profiled, the finish is far more consistent than anything sprayed after forming.
The trade uses PPGI for paint over galvanised and PPGL for paint over galvalume. Both arrive as patra in everyday site conversation.
Standard polyester suits most inland industrial buildings and is the usual specification where the roof is not closely looked at. SMP holds colour longer under strong sun. PVDF is the most durable of the three against fade and chalking and is chosen where the building is visible or where a longer appearance warranty is wanted.
Paint thickness matters as much as paint type. A thin coat on a cheap sheet chalks within a couple of summers, and once chalking starts it cannot be reversed without recoating.
The paint does not stop corrosion on its own. The metallic coating under it does, and it is quoted as AZ70 or AZ150 for galvalume, where the number is grams of alloy per square metre across both faces. AZ150 carries roughly twice the coating of AZ70. For a normal inland shed AZ70 is usually adequate; near the coast or beside a plant putting acid or ammonia into the air, AZ150 earns the difference.
Most damage happens before the sheet is fixed. Bundles left in the rain trap water between sheets and cause white rust on the coating, which shows through the paint later. Sheets dragged off a stack scratch through to bare steel, and every scratch is a corrosion line for the life of the roof.
Cut edges are the other weak point. A guillotine leaves a clean edge; an abrasive disc burns the coating back for several millimetres either side and throws hot particles onto the sheet that embed and rust.
The covered area, the profile, the purlin spacing, the thickness, and the colour or brand if the specification names one. If you are matching an existing roof, a photograph of the profile is usually enough for us to identify it.
Both are painted steel. PPGI is paint over a zinc galvanised base; PPGL is paint over a galvalume base, which is an aluminium-zinc alloy. Galvalume generally holds up better against corrosion for the same coating mass, which is why PPGL is common on industrial roofing.
We stock JSW, Tata, Essar, AM/NS, Jindal and Prabhat coil, including the branded lines buyers ask for by name such as Durashine, Coloron+, Pragati+, Prisma, Indradhanush and Sabrang. Tell us the brand your specification calls for and we will quote against it.
It depends far more on the coating mass and the environment than on the paint colour. An inland roof on AZ150 with a good paint system commonly stays serviceable well beyond a decade. Coastal and chemically loaded sites age faster, and unsealed cut edges or mismatched fasteners shorten life more than anything else.
Usually yes. Send a photograph and, if you have it, the original shade code. Colour is batch dependent, so matching an older roof exactly is not always possible, and it is worth ordering sheets and accessories together so they come from the same batch.
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