What is Galvanized trapezoidal sheet?
A galvanized trapezoidal sheet is trapezoidal profile rolled from continuously hot-dip galvanized coil to EN 10346 — steel strip passed through a zinc bath so that both faces carry a metallurgically bonded zinc layer whose mass is the zinc class: Z100 (100 g/m² total, about 7 µm per side), Z140 (10 µm), Z200 (14 µm) and Z275 (20 µm per side). The zinc protects the steel twice: as a barrier, and sacrificially at cut edges and scratches, where it corrodes instead of the steel; the roof\'s life is simply the zinc thickness divided by the corrosion rate of the site — 10–15 years for Z100 inland, 20–25 for Z275, half that within a few kilometres of the sea or in an industrial atmosphere — after which rust appears and the sheet is painted or replaced. Because the profile is rolled after galvanizing, the zinc is continuous over ribs and pans; only the cut ends are bare, and they self-protect for the width of a millimetre or so. The sheet is silver-grey with the spangle pattern of the zinc (minimised spangle on request), reflects heat well (SRI around 50–60 when new) and dulls to a matt grey over the years. We roll GI in our three trapezoidal profiles — 27/150 for walls and liners, 38/151 for roofs, 45/333 for long spans — and the corrugated 18/76, from DX51D (0.40–0.50 mm, walls and standard roofs) or S280GD (0.50–0.70 mm, roofs designed to a span table), in Z100 for dry inland and interior use, Z140 as the export standard, Z275 for coastal, Gulf and agricultural (ammonia) atmospheres. Galvanized flashings, closures and zinc-flake screws complete the roof.
Grades, standards and tolerances
| Grade / standard | Yield (MPa) | Note |
|---|---|---|
| DX51D+Z100 (EN 10346) | ≈ 140 (not guaranteed) | interior, liners, dry inland — 10–15 yr |
| DX51D+Z140 | ≈ 140 | export standard roofs and walls — 15–20 yr |
| DX51D / S280GD+Z275 | 140 / 280 | coastal, Gulf, farms — 20–25 yr inland |
| S280GD+Z275 | 280 | designed roofs, long spans |
| ZM (zinc-magnesium) ZM120–175 | — | coastal alternative, better cut edges, to order |
Zinc mass per EN 10346 is the total of both faces (triple-spot minimum); life estimates for ISO 9223 corrosivity classes C2–C3.
Zinc class and expected life
| Zinc class | µm per side | C2 rural / dry | C3 urban / inland industrial | C4 coastal (> 1 km) / heavy industry | C5 marine splash / Gulf shoreline |
|---|---|---|---|---|---|
| Z100 | 7 | 15–20 yr | 8–12 yr | 4–6 yr | 2–3 yr |
| Z140 | 10 | 20–30 yr | 12–17 yr | 6–8 yr | 3–4 yr |
| Z200 | 14 | 30–40 yr | 17–25 yr | 8–12 yr | 4–6 yr |
| Z275 | 20 | 40+ yr | 25–35 yr | 12–17 yr | 6–8 yr |
| ZM140 (zinc-magnesium) | 10 (≈ Z275 performance) | 40+ yr | 25–35 yr | 12–17 yr | 6–8 yr |
| PPGI PE on Z100 (for comparison) | 7 + 25 µm paint | 15–20 yr | 10–15 yr | 5–8 yr | 3–5 yr |
Roofs in agricultural buildings (ammonia) and near cement or fertiliser plants behave like C4. For C4–C5 sites specify Z275 or PVDF-painted sheet and stainless or zinc-flake screws.
Profiles, gauges and weight
| Profile | Cover width | Gauges | kg/m² (0.50 mm) | Purlin spacing (0.50 mm, 0.75 kN/m²) | Use |
|---|---|---|---|---|---|
| Corrugated 18/76 | 1 000 mm | 0.40–0.70 | 4.5 | 1.2 m | sheds, fences, curved roofs |
| 27/150 (T27) | 1 050 mm | 0.40–0.60 | 4.7 | 1.5 m | walls, liners, light roofs |
| 38/151 (T38) | 906 mm | 0.40–0.70 | 5.5 | 2.1 m | industrial roofs |
| 45/333 | 1 000 mm | 0.50–1.0 | 4.8 | 2.6 m | long-span roofs, decks |
Weights per m² covered, Z140; add ≈ 0.1 kg/m² for Z275.
Lengths and stock
GI T38 and T27 in 0.40 and 0.50 mm Z100 / Z140 are rolled continuously and available within a week in any length to 14 m; Z275, 0.60–0.70 mm and 45/333 in 1–2 weeks. Galvanized ridge, eaves and verge flashings, closures and zinc-flake screws ship with the sheets; VCI paper and desiccant for sea freight on request.
Fixing, storage and painting later
Fix through the rib crests with zinc-flake or stainless self-drilling screws and EPDM washers at every purlin (see the profile pages for patterns); cut with shears or nibbler and touch up cut edges with zinc-rich paint on coastal sites. Store packs dry, sloped and ventilated — wet-storage stain (white rust) forms when packed sheets get wet; open packs that arrive damp. A galvanized roof can be painted after 6–12 months of weathering (or after etch priming) to extend its life once the zinc dulls.
Where it is used
- Warehouse, workshop and factory roofs and walls
- Agricultural buildings, stores and stables
- Camps, markets, temporary and relief buildings
- Liner sheets and ceilings
- Fences, hoardings and enclosures
- Re-roofing on a budget
Galvanized vs PPGI vs aluzinc
PPGI trapezoidal adds 25 µm of paint and a colour for 15–25 % more, with roughly the same life inland and a better one coastal; aluzinc (to order) lasts longest bare. Galvanized is the price leader and the right choice for utilitarian buildings, liners and dry climates — and it can be painted later. The roofing overview compares all materials.
Price
Galvanized trapezoidal is the base price of the roofing list — per m² by gauge and zinc class (Z140 adds about 0.10 USD/m², Z275 0.25) — and follows the galvanized coil price; the bands below are the month\'s indicative FOB Istanbul ranges for 0.40 and 0.50 mm. Flashings per metre, screws per hundred.
Bands from our weekly export list (September 2026), FOB Istanbul, full-container quantities, excluding freight and certificates. Firm price per project on RFQ within one working day.
Export and packing
Galvanized sheets ship in packs of 30–60 on timber bearers, strapped with edge boards, PE-wrapped and — for sea freight — with VCI paper and desiccant to prevent wet-storage stain; packs are labelled with profile, gauge, zinc class, length and count. A 40' HC holds 2 400–3 200 m² of 6 m sheets depending on profile (≈ 12–14 t); 12–14 m sheets on flat-rack from Derince. HS 7210.41 / 7308.90.
| Term | Detail |
|---|---|
| MOQ | 300 m² per profile and gauge |
| Incoterms | FOB Istanbul · CIF / CFR Gulf, Africa · DAP EU, Balkans, Iraq, Caucasus · DAP Aktau |
| Lead time | Z100 / Z140 0.40–0.50 mm: 3–7 working days; Z275 and 0.60–0.70 mm 1–2 weeks |
| Packing | Packs of 30–60 sheets on timber, strapped, PE-wrapped; VCI paper for sea freight |
| Container / truck | 40' HC ≈ 2 400–3 200 m² of 6 m sheets by profile; long sheets on flat-rack |
| Documents | Invoice, packing list, EN 10204 3.1 (coil), CE DoP (EN 14782), certificate of origin; SASO / SONCAP on request |
| Payment | 30% advance, balance against B/L copy; L/C at sight above 100 t |
Certificates
Supplied with the coil mill\'s EN 10204 3.1 stating grade and zinc mass (triple-spot / single-spot) and our CE declaration of performance under EN 14782 for the profile; SASO, SONCAP and third-party inspection certificates on request for Gulf and West African destinations.
How to order
Specify profile, thickness, zinc class (Z100 / Z140 / Z275), grade if designed (S280GD), sheet lengths and quantities or the roof m² and slope, flashings and screws, and the destination climate so we can confirm the zinc class.
Standards
- EN 14782 — self-supporting metal sheet for roofing and cladding
- EN 10346 — DX51D / S280GD + Z100–Z275 substrate
- EN 10169 — coil-coated (PPGI) substrate
- EN 1993-1-3 — cold-formed design; EN 10204 3.1
Grades
Grade data sheets (chemistry, mechanicals, equivalents) are on our reference site: DX51D · S280GD · S320GD
Frequently asked questions
What is galvanized trapezoidal sheet?
Trapezoidal roofing and cladding sheet rolled from hot-dip galvanized coil (Z100–Z275 zinc) without paint — silver, the cheapest metal roof, 10–25 years of life inland depending on zinc class.
Z100, Z140 or Z275 — which zinc class?
Z100 for interiors, liners and dry inland sites; Z140 as the export standard for roofs and walls; Z275 for coastal, Gulf, agricultural and industrial atmospheres.
How long does a galvanized roof last?
Z140: 20–30 years rural, 12–17 urban, 6–8 coastal; Z275 roughly double — see the life table. It can be painted when the zinc dulls.
What causes white rust on new sheets?
Wet-storage stain: packed sheets that got wet in transit or storage. Store packs dry, sloped and ventilated; light staining is cosmetic.
Galvanized or coloured (PPGI) sheet?
Galvanized for cost and utilitarian buildings; PPGI where colour, heat reflection or a longer coastal life matter — 15–25 % more per m².
What is the price of GI roofing sheet?
Per m² FOB Istanbul by gauge — see the bands above; it follows the galvanized coil price.