Technical

Material Selection for Outdoor Furniture

Material choice decides how a bench looks in year one and whether it is still there in year fifteen. It is the first specification decision, not the last.

Buyers in this category almost always choose the material before the model. That is the opposite of indoor furniture, and it is why we keep a material reference separate from the product catalogue.

This page compares the six materials we build in, states what each one fails at, and sets out how the choice changes with climate. Dimensional and anchoring data lives in the specifications hub instead of here, so the two pages do not compete.

For a tender that has to hold up across all four seasons, the short answer is this: there is no single all weather outdoor furniture material — there is a right pairing for each exposure. Hot-dip galvanized steel with a powder coat carries temperate, wet and freeze-thaw sites; stainless carries high-touch and high-humidity locations, with the coastal grade named per project at quotation stage; corten carries the inland landscapes where the patina is the design intent and runoff staining is acceptable. The table below is arranged so you can read down the exposure column first and the cost column second, because a material that fails at year three is not cheaper than one that does not.

As a street furniture supplier we buy these materials as sheet, tube and board and process them in-house, so what follows is written from the workshop side of the decision rather than from a catalogue.

Six materials at a glance

Material Suited to Maintenance Typical failure mode Cost band Watch out for
Corten steelInland signature landscapes, planters as edge definitionNone — no coating to maintainRunoff staining; patina may not stabilise near the coastMidNot recommended within about 1 km of the shoreline — chlorides prevent the patina from stabilising
Powder-coated steelGeneral-purpose public furniture inland, any RAL colourTouch-up of scratches; repaint after long exposureCorrosion starting at a scratch through to bare steelLowBarrier coating, not sacrificial
Hot-dip galvanized steelWet, coastal, high-exposure sites; duplex with powder coatMinimal; zinc sacrifices at scratchesWhite rust if stacked wet before coatingMidISO 1461: 85 µm mean over 6 mm steel, 70 µm at 3–6 mm
Stainless 304 / 316Coastal frames, high-humidity sites, high-touch surfacesRoutine washing; tea-staining under neglectTea-staining and pitting under sustained chlorideHigh316 near the coast and in de-icing-salt zones; 304 inland
Hardwood (teak, ipé)Premium landscapes where grain and cool seat surface matterOiling on a 12–18 month cycleSplitting and surface degradation if left unoiledHighService life at public-use intensity pending factory confirmation
WPC / recycled plasticMaintenance-light municipal fleets and campusesNone — no rot, no oilingLower structural strength; hotter in full sunMidService life pending factory confirmation

Service-life figures for hardwood, WPC and recycled plastic are pending factory confirmation and are confirmed per project at quotation stage.

Corten steel

Corten is specified for inland signature landscapes where the rust-orange patina is part of the design intent. It forms a stable, self-repairing oxide layer through repeated wet and dry cycles — typically within 12–24 months in a temperate urban site, and possibly never within about a kilometre of the shoreline, where salt interrupts stabilisation.

Two practical consequences: it stains light paving during the first year through runoff, and it is not a coating — there is nothing to repaint, but there is also nothing to touch up when a section is scratched. Read the patina timeline before specifying it near buildings or pale surfaces.

Powder-coated steel

Powder-coated steel is the general-purpose baseline: any RAL colour, repairable in the field, and the lowest cost band of the metal options. It is the right answer for most inland public sites, and the wrong answer for coastal sites where the coating is likely to be breached.

Powder coating is a barrier, not a sacrificial layer — where it is scratched through to bare steel, corrosion starts at the scratch. That is why the coating specification matters as much as the colour: film thickness and surface preparation decide whether the barrier survives. See touch-up and repair for field practice.

Hot-dip galvanized steel

Hot-dip galvanizing protects by sacrifice rather than by barrier: the zinc corrodes in place of the steel, so a scratch does not become a corrosion site. ISO 1461 sets the minimum mean coating at 85 µm for steel over 6 mm thick and 70 µm for 3–6 mm.

Combined with a powder coat — a duplex system — it is our specification for wet, coastal and high-exposure sites. The galvanizing guide carries the standard coating table and the environment-by-environment service intervals.

Stainless steel: 304 and 316

304 (18% Cr, 8% Ni) is the default for inland and general outdoor use. 316 adds 2–3% molybdenum, which is what extends service life under chloride attack — the reason it is specified within roughly 10–15 km of the coast and wherever de-icing salt is used.

Neither grade is maintenance-free: both tea-stain under long neglect, and 316 is not a licence to skip cleaning in a beachfront location. The 304 vs 316 comparison sets out the trade-off, including the cost index.

Hardwood, WPC and recycled plastic slats

Slat material is a separate decision from frame material, and it is where most maintenance budgets are won or lost. Documented teak and ipé give the warmest appearance and the coolest seat surface, with an oiling cycle of 12–18 months in temperate climates per our hardwood slat maintenance guide. Service life at public-use intensity is Pending factory confirmation. WPC gives no rot and no oiling, with lower structural strength and a hotter surface in full sun; its service life is also Pending factory confirmation.

Recycled plastic lumber is specified where rot resistance matters more than stiffness. Service-life figures for recycled plastic are not published here — Pending factory confirmation — and we will not quote a number we have not verified.

The WPC vs hardwood question is usually about maintenance capacity rather than purchase price. Hardwood needs an oiling cycle of 12–18 months and a crew that will actually carry it out; WPC needs no oil and no finish, but it deflects further under load and runs hotter in full sun. Municipal fleets tend to settle on hardwood where seating is a design feature with grounds staff on site, and on WPC for promenade and transit seating where the maintenance programme is thin. The WPC vs hardwood slats comparison sets out the trade-offs criterion by criterion.

How to specify all weather outdoor furniture by climate

Four climate profiles drive most specifications. In each case the material decision precedes the model decision:

ExposureCorrect defaultAvoid
Coastal, salt air, within 1 km316 stainless frame, or duplex galvanized + powder coatCorten (patina may never stabilise); plain powder-coated steel
High UV, hot summersPowder-coated steel or anodized aluminium frame; hardwood or light-coloured slats — see our aluminium grades guideDark WPC in full sun — surface temperature is noticeably higher
Freeze-thaw, de-icing saltHot-dip galvanized + powder coat; 316 where salt is applied directlyUntreated mild steel; 304 in direct de-icing contact
Urban, high vandalismWelded steel frame with steel-bar slats, tamper-resistant fixingsTimber slats in unlit locations; removable seating

Climate guidance is qualitative. Material service life depends on coating class, maintenance regime and airborne chloride load, and is confirmed per project.

Frequently asked questions

Which material should I choose for outdoor public furniture?+

There is no single right material — the answer depends on exposure. Powder-coated steel is the general-purpose baseline inland; duplex galvanized steel or 316 stainless for coastal sites; corten only for inland landscapes where the patina is intended.

Is corten steel suitable for coastal areas?+

Generally no. Salt air can prevent the oxide layer from stabilising within about a kilometre of the shoreline, so the surface keeps shedding rather than settling. Use duplex-coated steel or 316 stainless instead.

Should I choose 304 or 316 stainless?+

316 within roughly 10–15 km of the coast and wherever de-icing salt is used; 304 inland and in general outdoor conditions. 316 contains 2–3% molybdenum, which is what resists chloride attack.

Do WPC slats get hot in the sun?+

Yes, noticeably hotter than hardwood in direct sun. In unshaded plazas, hardwood or a light-coloured WPC is the more comfortable choice.

Do recycled plastic slats last longer than wood?+

They do not rot or need oiling, which is their advantage. We do not publish a service-life figure for recycled plastic because the data has not been verified for our specific profiles.

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