Galvanised Steel Greenhouse · 6mm Polycarbonate, Walk-In

SteelRoot's frame and glazing are engineered for typical UK wind and snow exposure when correctly anchored. The 0.67 m arch spacing, closed RHS galvanised steel section, screw-fixed 6 mm twin-wall polycarbonate and included ground anchors are the four mechanisms doing the work — not "stormproof" marketing.

Damage caused by wind gusts above 50 mph during a Met Office Named Storm is excluded from the warranty. That threshold is published before checkout, not in the post-purchase small print. Below that envelope, panel and frame defects are covered — see our warranty page for the full terms. If your plot is on the Pennine spine, the Outer Hebrides or a Shetland coastline, email us before ordering — we'd rather discuss your exposure than have you discover the limit the hard way.

Panel deflection scales with the cube of unsupported span. Reducing arch spacing from 1.00 m to 0.67 m means a 4 m greenhouse has 7 arches instead of 5, a 12 m has 19 instead of 13 — roughly 40% more frame-to-panel intersections. That cuts panel flutter under wind load and stiffens the whole structure against racking.

At 0.67 m spacing, SteelRoot's snow load rating sits at approximately 140 kg/m² — equivalent to 55–60 cm of fresh snow on the roof. That's a 1.5× safety margin against design snow loads for Scottish Highland exposure. We don't retail the 1 m spacing in the UK because it doesn't carry that margin.

Two adults, no specialist tools. The frame is pre-drilled and bolt-assembled — components arrive numbered and grouped by build stage. Realistic build times working at a comfortable pace:

4 m 1–2 days · 6 m 2 days · 8 m 2–3 days · 10 m 3 days · 12 m 3 days.

What you need: a cordless drill, a spanner set, a spirit level, a step-ladder. That's it. No concrete pour, no specialist install. A QR-code-linked build-along video covers every step. Build-support line open weekday and Saturday mornings during install season.

Ground anchors are included as standard — one bent-L galvanised steel anchor per 1 m of length, so 4 anchors on a 4 m model, 6 on a 6 m, scaling up to 12 on a 12 m. They drive into prepared ground and pin the arch base. Correct anchoring is required for the 10-year frame anti-corrosion warranty to remain in force.

Most UK competitors sell ground anchors separately at £60–£110 per screw — at a 6 m length that's a £360–£660 add-on after the headline price. We made the decision to include them because a greenhouse without anchors isn't a finished product, it's a sail.

The frame is hot-dip galvanised 40 × 20 mm rectangular hollow section steel with a ZAM coating (zinc-aluminium-magnesium). ZAM gives self-healing edge protection at scratches and drill points — the coating chemistry passivates exposed steel surfaces as the structure ages. The 10-year anti-corrosion warranty covers through-corrosion penetration, not surface oxidation or edge spotting, which are cosmetic and normal.

Practical care: avoid grinding or drilling new holes after the build (every hole is pre-drilled at the factory for this reason). If a bolt-head gets scuffed during assembly, a touch of cold-galvanising spray from any DIY store closes the gap. No annual treatment, no oiling, no painting required.

6 mm twin-wall polycarbonate carries about 33% better thermal retention than 4 mm twin-wall and roughly 50% better than single-pane horticultural glass. The cellular flutes are larger, the panel is stiffer between supports, and impact resistance against hailstones and falling debris steps up substantially.

6 mm physically requires a steel arch to mount — the cross-section is too thick and heavy for a hobby-tier aluminium extrusion or a timber frame to carry safely. Our wooden NORDIC range stays at 4 mm for that structural reason. On SteelRoot, 6 mm closes the bowing-under-wind failure pattern documented on every UK greenhouse forum at the cheap-tier end.

Roof vents are fitted as standard with automatic wax-cylinder openers calibrated to open around 18°C and close around 12°C. By length: 1 auto vent on the 4 m, 2 on 6 m and 8 m, 4 on 10 m and 12 m. Both gable doors are two-part stable doors — the upper section opens independently as a cross-flow door window, giving you two additional opening points on every model.

For Cornish or Mediterranean-style heat exposure, side-louvre or gable-vent kits are a planned Y2 accessory. Most UK plots are fully served by the standard configuration; if your site is south-facing and gets baking sun from June through September, a roll-down shading kit (sold separately) covers the gap.

SteelRoot 3.14 m wide footprints, in real growing language:

4 m / 12.56 m² — two full-size raised beds plus a working path; quarter-allotment scale.
6 m / 18.84 m² — three raised beds, year-round salad and tomato programme.
8 m / 25.12 m² — small-allotment scale; tomatoes, beans, cucumbers and brassicas under one roof. The most-ordered SteelRoot length.
10 m / 31.40 m² — serious-grower volume with overwintering capacity.
12 m / 37.80 m² — commercial-domestic scale; cut-flower microbusiness viable.

If you're between two lengths, take the longer one — the £150–£200 step is small money compared with rebuilding 18 months in.

Usually no. The 3.14 m line has a ridge height of 2.02 m, comfortably under the 2.5 m UK Permitted Development cap for outbuildings on most domestic plots. Check with your local council if any of these apply: conservation area, listed building, plot under an Article 4 Direction, structure closer than 2 m to a boundary, total outbuildings already covering 50% of your garden.

SteelRoot is classified as a greenhouse, not a polytunnel — useful where allotment councils ban polytunnel covers on aesthetic grounds. The plain-language Permitted Development checklist ships in your order pack so you can verify before delivery.

3-4 weeks from order for UK mainland — included in the price. Every SteelRoot is made-to-order; production typically takes 2-3 weeks at the workshop, plus 5 working days UK pallet transit. You receive an "In production" email within 5 working days of order, then an "On its way" email with tracking when the pallet leaves our warehouse.

The pallet arrives on a tail-lift truck and is dropped kerbside. SteelRoot pallets are 1.2 × 0.8-1.0 × 2.1 m and weigh 65-105 kg depending on length. The 2.1 m height is worth checking against any access constraints (low garage doors, narrow side gates) before ordering. You'll receive an SMS the day before with a 4-hour delivery window. Scottish Highlands, the islands and Northern Ireland have surcharges or limited service — calculated at checkout or quoted by email. Full carrier terms on our shipping policy.

You have 14 days from delivery to start a return — unused, in original packaging. We arrange the collection through our carrier. SteelRoot pallets are large; you pay the carrier collection cost, typically £75–£175 depending on length and your region. We'll quote the exact figure on request before you commit. Full terms on our refund policy.

If the structure has been built and you're stuck on something specific — a wrong size, a delivery damage that surfaced during the build, a missing part — talk to us first. Most problems sort out short of a full return.

SteelRoot uses standardised component SKUs that the supplier has produced for 20+ years. Panels are 6 mm twin-wall polycarbonate, fasteners and brackets are commodity stainless or zinc-plated hardware, and we hold UK stock specifically so we can despatch replacements quickly rather than re-importing each time.

Replacement parts go through our customer-service team at customer-service rate. SteelRoot is a sub-brand of Waldenhaus — a multi-product UK operator, not a single-line outfit that disappears when one product underperforms. If you bought a SteelRoot in year 1, you can still buy parts for it in year 10.

Yes. Two options at checkout:

V12 Retail Finance, 0% APR over 12 months — a soft credit check, a decision in minutes, no impact on your credit file unless approved. Typical monthly payment on a 3.14 m SteelRoot: £100 (4 m entry) to £162 (12 m flagship).

PayPal Pay Later — split the cost into monthly instalments via your PayPal account, no credit check at our end.

V12 is the UK garden-finance category standard. For commercial buyers or smallholders, longer-term finance (24–36 months at 0–9.9% APR) is available on request — book a 15-minute spec call to discuss.

Polytunnels cost less upfront — typically £400–£1,000 for an equivalent footprint. Over a decade, the cost picture rebalances: the polythene cover needs replacement every 5–7 years at £200–£400 plus a weekend of re-trenching, and a torn cover in a winter storm is a documented pattern, not an edge case. Tensioned-film systems are also banned at many allotment sites and in most conservation areas on aesthetic grounds.

SteelRoot is one capital purchase with screw-fixed 6 mm polycarbonate that doesn't perish, an architectural arch silhouette that councils accept, and roughly 33% better thermal retention than a single-skin film. If you love your polytunnel for the growing but you're tired of the film cycle, this is the next step. If you want absolute lowest £/m² for a dedicated growing-only space, polytunnels remain a sensible answer.

Different category, not the same product cheaper. Entry-tier aluminium polycarbonate kits (£170–£800) use open C-section extrusion that racks under moderate UK wind, spring W-clip glazing that pops out before the first winter, and warranties that exclude "extreme weather" — the named-storm scenarios that define a British year. review-site reviews are full of customers who lost budget twin-wall kits in the £400-900 bracket during named UK storms.

SteelRoot uses closed RHS galvanised steel, screw-fixed 6 mm polycarbonate, included ground anchors and a published warranty position on named storms. The customer who's already lost a cheap-tier greenhouse to a storm is the customer SteelRoot is built for. You're paying roughly 2–3× the entry-tier price once, instead of replacing every two or three winters.