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Metal roofing is the standard across Papua New Guinea for good reason: it sheds heavy tropical rain fast, it is quick to install, and it stands up to the sun. But near the coast the salt air is hard on steel, and the wet-season downpours will find any badly-fixed sheet. Getting the coating, the fixings and the fall right the first time is what decides whether a roof lasts five years or twenty-five.

What you'll need

Everything here is stocked across our branches.

Step by step

  1. 1

    Pick the right coating for how far you are from the sea

    The closer to the coast, the more corrosion protection you need. As a rule of thumb, plain (unpainted) galvanised sheet is the cheapest but corrodes fastest in salt air; a heavier zinc/aluminium-coated or pre-painted (Colorbond-style) sheet costs more up front but lasts far longer near the water. If you are within sight of the sea, do not buy the thinnest, cheapest sheet — ask the branch for the marine-grade option.

  2. 2

    Match sheet profile to your roof pitch

    Corrugated sheet suits steeper roofs; low-pitch roofs need a Trimdek/klip-lok style profile with deeper ribs so water does not pool and back up under laps. Very low pitches need longer single sheets (fewer end-laps) to stay watertight in heavy rain. If in doubt, tell the branch your roof's rise and run and they will steer you to a profile.

  3. 3

    Use the correct roofing screws, not nails

    Fix with self-drilling roofing screws that have a bonded EPDM sealing washer, driven into the ridge of the rib (not the valley) so water runs past the hole. Use the fixing spacing your sheet supplier specifies — more screws along the edges and at the ends, where wind lift is strongest. Cheap unsealed screws or plain nails are the number-one cause of leaks and rust streaks.

  4. 4

    Lay sheets away from the prevailing wind and seal the laps

    Start laying from the end away from the prevailing wind so side-laps face downwind and driving rain cannot be pushed under them. Overlap side-laps by one full corrugation, and give end-laps a generous overlap with sealant between them. Flash around every penetration — vent pipes, chimneys, skylights — and turn the flashing up under the sheet above.

  5. 5

    Finish clean and protect against rust from day one

    Sweep every steel filing and off-cut off the roof before you leave — left on the sheet in the rain, they rust and stain the new roof permanently. Touch up any cut edges and scratches with a matching cold-galv or roofing paint. Fit gutters with enough fall to clear wet-season volumes.

Tips for the PNG climate

  • Near the coast, corrosion is the enemy, not the rain. Spend the extra on a marine-grade coating — replacing a rusted-through roof costs far more than the coating ever did.
  • Never mix bare steel off-cuts, swarf or steel tools left lying on a new coated roof — they set off rust spots that spread.
  • Work on the roof early morning before the steel gets too hot to handle, and never in the afternoon wet-season storms.
  • Rainwater off a clean metal roof is a genuine asset in PNG — size your gutters and downpipes for the heaviest downpour, not the average.

Common questions

Galvanised or Colorbond-style pre-painted — which should I buy?
For an inland shed on a budget, galvanised is fine. For a house, and especially anywhere near the coast, a pre-painted or zinc/aluminium-coated sheet lasts much longer and looks better. Ask your branch which grades they currently stock.
Can I screw straight through the sheet anywhere?
Fix into the top of the rib with a sealing-washer roofing screw, following the sheet supplier's spacing. Screwing into the valley, or using unsealed screws, will leak.
Do you deliver roofing sheet to site?
Yes — delivery is arranged from every branch. Add the sheets to an enquiry, choose your branch, and we confirm length options, price and delivery before you commit.

Ready to start?

Add what you need to an enquiry and choose your nearest branch. We confirm the price and what is in stock before you travel — fourteen branches in ten locations.

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