Steel vs Timber Solar Canopy: Which Should You Choose?

The frame under a solar canopy is roughly 45% of what you pay, so the material you choose for it drives your whole £/kWp — and the aesthetic and planning outcome too. For UK car-park and forecourt projects the choice comes down to galvanised steel or timber (usually engineered glulam). This guide compares the two honestly on cost, span, lifespan, planning and heritage fit, maintenance and appearance, using verified UK 2026 figures, and ends with a plain “choose steel if / choose timber if” framework.

Two quick clarifications before the detail. First, “timber” in commercial canopies almost always means glulam (glued laminated timber) — engineered beams that behave predictably under load, not sawn softwood. Second, the material choice is separate from the structural layout — cantilever/single-post versus multi-bay/back-to-back — which you can read about on our cost page. Here we’re only comparing the frame material.

The comparison at a glance

Factor	Galvanised steel	Timber / glulam
Typical cost (£/kWp)	£900–£1,400/kWp at commercial scale; toward the lower end on larger, simpler layouts	Higher — sits in the £1,200–£3,000/kWp “smaller/complex” band even at scale
Cost per parking bay	Lower end of the £6,000–£12,000/bay range	Upper end, or above it
Column-free span	Wide — comfortably spans a full parking bay or double row; best for cantilever/single-post designs	Shorter practical spans for the same section depth; more columns or deeper beams needed
Lifespan	25+ years; hot-dip galvanising gives decades of corrosion protection with no coating upkeep	Long if detailed and maintained well, but needs periodic inspection/treatment
Maintenance	Effectively zero on the frame for the design life	Periodic — checks for moisture ingress, connection integrity, occasional re-treatment
Appearance	Industrial/engineered; slim members; neutral	Natural, warm, “architectural”; suits sensitive settings
Planning / heritage fit	Fine on standard sites; can look intrusive near listed/conservation settings	Favoured by planners in conservation areas and near heritage assets
Foundations	Ground screw (~90% of sites), ballasted or driven pile	Same options; heavier beams can increase loads
Best-fit projects	Volume car parks, retail, industrial, NHS/public-sector at scale	Schools, campuses, heritage/conservation sites, flagship frontages

Cost: steel wins on £/kWp, and the gap shrinks at scale

Across all elevated solar canopies and carports, expect £900–£1,400/kWp at commercial scale and £1,200–£3,000/kWp for smaller or more complex jobs — roughly £6,000–£12,000 per parking bay. (For reference, an equivalent rooftop system is £700–£1,050/kWp, and open-land ground-mount solar is ~£700–£900/kWp; both are cheaper, but neither leaves you usable parking underneath.)

Galvanised steel is the default because it’s the cheapest way to hit those numbers. It’s the most common canopy material, spans wide, and delivers the lowest £/kWp at scale. Timber/glulam is a premium/architectural choice — even on a large project it tends to sit in the higher band rather than dropping to £900/kWp.

Because the frame plus foundations is about 45% of total cost, your £/kWp falls as bay count rises — you amortise the fixed design and grid-connection work over more panels. That scale benefit applies to both materials, but steel starts lower, so a 100-bay steel scheme (≈180–270 kWp at ~2 kWp per standard bay, from four to six 450W modules) will almost always beat the same scheme in timber. Full worked numbers are on our cost page.

Payback follows cost: 8–12 years solar-only, 7–11 with EV charging — the same range for both materials, but timber’s higher capital cost pushes you toward the longer end. (We never claim a 5-year solar-only payback for a canopy; that’s a rooftop figure, at 4–6 years.)

Span and structure: steel spans further for less

Span is where steel’s engineering advantage shows. Galvanised steel spans wide for a given member size, which makes column-free bays — cantilever or single-post designs that keep parking easy and door-swings clear — far more economical. Timber can be engineered to span too, but for the same clear span you generally need deeper glulam beams or more columns, which adds cost and can complicate the parking layout.

Both materials are designed to the same rules: Eurocode 1 (BS EN 1991) for wind and snow loads, CDM 2015 for construction safety and BS 7671 for the electrical installation. Foundations are the same menu for either — ground screw on roughly 90% of sites, with ballasted or driven-pile alternatives — though heavier timber sections can raise foundation loads slightly.

Lifespan and maintenance: steel is fit-and-forget

Hot-dip galvanised steel is essentially fit-and-forget — decades of corrosion protection with no coating upkeep across a 25+ year design life, which comfortably outlasts the panels’ performance warranty. That’s a real total-cost-of-ownership advantage that rarely shows in the headline quote.

Timber is durable when detailed and installed correctly, but it is a natural material in a UK outdoor environment. Expect periodic inspection and occasional treatment — checking connections and end-grain details for moisture, and maintaining protective finishes. Budget for that upkeep over the canopy’s life; it’s manageable, but it isn’t zero, and steel’s is.

Planning and heritage: the one area timber can win

For most English sites, canopies now use Class OA permitted development (in force 21 December 2023) for non-domestic, off-street parking. That means prior approval — the council assesses siting, design and glare — not full planning permission. The conditions: no more than 4m high, at least 10m from any dwelling, a SuDS (drainage) condition, and you must start within three years. It excludes listed buildings and scheduled monuments, and it is England only — Wales, Scotland and Northern Ireland still need standard planning.

This is where material choice can matter. On an ordinary retail or industrial car park, galvanised steel sails through prior approval on design grounds. But near a listed building, in a conservation area, or on a sensitive campus or civic frontage, planners often respond better to timber/glulam because it reads as a natural, less industrial material. On those sites — exactly the kind excluded from permitted development and pushed into full planning — a timber canopy can be the difference between approval and refusal, and the premium buys you a consentable scheme. Schools and public-sector estates frequently fall into this category; see our pages on solar canopies for schools and NHS and public-sector car-park canopies.

Appearance: engineered versus natural

Steel gives you slim, engineered members and a neutral, industrial look — ideal where the canopy is functional infrastructure and nobody’s judging it aesthetically. Timber gives warmth and a natural finish that suits campuses, visitor-facing frontages and heritage settings where the structure is part of the public realm. Neither is “better” — it’s a fit-to-context decision, and on a flagship entrance the look may justify timber’s cost on its own.

The decision framework

Choose galvanised steel if:

• You want the lowest £/kWp and the best return — especially on larger schemes where scale drives the cost down.
• The site is a standard car park, retail, industrial or logistics setting with no heritage or conservation constraints.
• You need wide column-free spans — cantilever or single-post bays for easy parking.
• You want a fit-and-forget frame with effectively zero maintenance over 25+ years.
• You’re in England on a site that qualifies for Class OA permitted development and design isn’t a sticking point.
• You’re doing high bay counts (e.g. 100+ bays / 180–270 kWp) where amortising fixed costs matters most.

Choose timber / glulam if:

• The site is a conservation area, near a listed building or scheduled monument, or a sensitive civic/campus/heritage frontage where a natural material aids consent.
• Appearance is a genuine project driver — a visitor-facing or flagship location where the look justifies the premium.
• You’re in a full-planning jurisdiction or scenario (Wales, Scotland, NI, or an England site excluded from permitted development) and want to maximise approval odds.
• You accept a higher capital cost (upper end of £1,200–£3,000/kWp) and periodic maintenance in exchange for the aesthetic and planning benefits.

For the large majority of UK commercial car parks, galvanised steel is the right answer — it costs less per kWp, spans further, lasts longer with no upkeep, and passes prior approval on ordinary sites. Reserve timber for the specific cases where heritage, planning sensitivity or a flagship look genuinely require it.

What doesn’t change between the two

Whichever frame you pick, the rest of the project is identical. You’ll want a turnkey MCS-certified installer delivering the structure, PV, electrical and DNO connection under one contract — not a bare frame with the wiring left to you. Grid connection is G98 up to 3.68kW/phase, G99 above (most commercial jobs, ~4–8 weeks), and MCS is required to claim SEG. The funding picture — SEG export payments, the £1m Annual Investment Allowance, the 50% First-Year Allowance (solar is special-rate, so no full expensing), business-rates exemption to 31 March 2035, and the Workplace Charging Scheme — is the same regardless of material; see our grants and funding page for the current position. And if you’re pairing the canopy with 7–22kW AC charging, the structure choice makes no difference to the EV side — see EV charging solar canopies.

Not sure which frame suits your site, planning context and budget? Tell us the location, bay count and any heritage constraints and we’ll spec both options honestly. Request a quote or call +44 7707 970661.