A farm building concentrates everything that attacks steel: moisture that cycles every day, fertiliser and feed dust, manure gases inside livestock housing, and a maintenance budget that assumes the building will be ignored for years at a stretch. The catalogue answers that with three families - corrugated coated sheet for roof and walls, structural sections for the frame, and stainless products for the parts animals and cleaning water actually touch. What matters is matching the coating and the form to each zone, not buying one grade for the whole farm.

The roof decision: aluminium-zinc or zinc

The roof is the largest steel surface on any farm building, and it is where the 55% aluminium-zinc coating earns its keep. A galvalume steel sheet carries 55% aluminium, 43.4% zinc and 1.6% silicon, and the product pages put its corrosion resistance at two to six times that of a galvanized sheet of the same thickness, with a listed service life of around 25 years. It also reflects up to 80% of sunlight, which keeps an open-sided shed workable through summer, and it stands up to 315 °C, against roughly 230 °C for hot-dip galvanized sheet - relevant wherever a dryer or flue passes near the roof. The galvalume corrugated roof panels are quoted at 0.151 to 1.2 mm thick in 914, 1000, 1200, 1220 and 1250 mm widths, which covers the common farm spans; the same range appears on the corrugated galvalume panels and galvalume roofing sheet listings.

Plain galvanized corrugated sheet still has a place, mostly on price. The galvanized corrugated steel plate page lists applications that read like a farm order - farm vehicles, agriculture greenhouse, steel structure - with 0.19 to 2 mm thickness, 200 to 2500 mm width, a 5 t minimum and delivery within 10 days. The DX52D galvanized corrugated plate page shows what corrugation does to width: a 1000 mm blank leaves the line at 915, 910, 905, 900, 880 or 875 mm depending on the profile, carrying 60 to 275 g/m² of zinc at a ±0.02 mm tolerance, in containers of 25 t. The galvalume versus galvanized comparison comes down to this: at equal thickness the aluminium-zinc coating lasts several times longer, so on a roof meant to be forgotten, the coating difference is the whole decision.

Coating mass, and where the service-life order comes from

Coating mass is the number to argue about on any farm roof. The Z275 galvanized steel coil spans 30 to 275 g/m² in 0.12 to 2.0 mm thickness and 600 to 2000 mm widths, with 3 to 5 t reels and a 5 t minimum. For roofing specifically, the Z80 roofing galvanized coil page exists to decode the designation: Z80 is the same coating written as Z08 and Z080 across GB/T 2518, JIS G3302, EN 10327 and ASTM A653M, and the same table shows Z275 matching G90, with the grade row reading SGCC, DX51D+Z or CS Type A/B/C depending on the standard. The service-life ranking on the coated-sheet pages runs rural, industrial, general marine, then severe marine - a farm in dry inland air sits at the generous end of that order, a piggery or a coastal feedlot does not, and the coating mass should move up accordingly.

Painted walls and the visible elevations

Where the sheet is seen, washed or asked to match a brand colour, painted coil replaces bare coating. PPGL coil is offered in PE, SMP, HDP and PVDF paint systems, with the high-durable polyester rated for 16 years outdoors; top coats run 10 to 25 µm and back coats 5 to 20 µm. The TDC51D+Z PPGI coil covers 0.12 to 2 mm in 600 to 1250 mm widths to a RAL colour. For shed cladding that takes knocks from machinery and handling, the wrinkle-finish PPGI roofing page names agricultural buildings in its own application list: the fishnet texture hides scuffs and dust that would show on a smooth gloss panel, it runs 0.12 to 4.0 mm at Z40 to Z275, tensile 200 to 550 N/mm² with 16 to 30% elongation, in 15 t minimums per colour and about 30 days.

The frame: sections, purlins and pipe

The steel structure building system page sets out the standard farm-shed skeleton: Q235B or Q355B welded H-section columns and beams, Q235B C and Z purlins, and roof and wall cladding in steel sheet or sandwich panel with EPS, PU, glass wool or rock wool cores. The ASTM A36 hot-rolled H-beam carries flange widths of 50 to 400 mm and web depths of 100 to 900 mm in 6 to 12 m lengths, with a 1 t minimum and delivery inside 7 days - the column-and-truss answer for machinery sheds and grain stores. For greenhouses, livestock tunnels and small animal sheds, a pipe frame is usually cheaper to erect: the ASTM A53 galvanized pipe page bills the product outright as greenhouse steel pipe, from 1/2 to 36 inch nominal bore in SCH 40, 80 and 160, Grade B at 60,000 psi tensile and 35,000 psi yield, in lengths of 3 to 18 m.

Fittings the animals and the washdown touch

Two catalogue items earn their place in the farm specification. The first is enclosure: the stainless steel wire rope netting is built from 7x19 rope at 3.2 mm carrying 7.38 kN with 120x208 mm mesh, down to 7x7 constructions at 1.6 mm and 2.17 kN with 80x140 mm mesh, in 201, 304, 304L, 316 or 316L, or in hot- and cold-galvanized rope where budget rules - the same zoo-net construction that keeps large animals in and birds out of feed stores. The 304 and 316 stainless wire rope covers gates, hoists and tensioned lines. The second is the wet zone: in parlours and feed kitchens, square stainless tube from 10x10 to 100x100 mm and 304 stainless sheet - the grade page lists commercial food processing equipment among its applications - survive the washdown that eats painted carbon steel. The steel plate bending service, with knife, 180° and double-layer bends on CNC presses, is how troughs, gutters and chutes get formed from the same plate.

Minimums, lead times and the order itself

The minimums shape small farm orders. Galvanized coil starts at 5 t; corrugated and painted programmes run 25 t per container and 15 t per colour; the stainless lines start at 1 t, which is what makes the wet-zone fittings practical to buy alongside a coil order. Lead times follow the same ladder: 7 to 14 days on galvanized coil, 15 to 20 days on corrugated plate, 30 days on textured painted coil, 1 to 7 days on beams. Browse the roofing sheet category and the GI and PPGI corrugated sheet listings to see the full profile range before fixing a specification. Put the zone, the coating mass and the finish on the order together, and the building's steel becomes a 25-year decision instead of a first-cost one.