Galvanised Steel Arch Greenhouse, Twin-Wall Polycarbonate, Walk-In | SteelRoot by Waldenhaus

Both are offered, and you pick at checkout. 4 mm is the base specification: lowest cost, lightest, and it grows a full crop. 6 mm is stiffer between supports, holds about 33% better thermal retention than 4 mm, and steps up impact resistance against hailstones and falling debris. The cellular flutes are larger and it flexes less in strong wind.

Choose 4 mm if you want the lowest entry price. Choose 6 mm when extra stiffness, impact resistance or thermal retention matters more than the lowest price.

Cross-ventilation is standard on every SteelRoot: both gable doors are two-part stable doors, and the upper section opens independently as a cross-flow door window, giving two opening points on every model. Wax-cylinder roof auto-vents are an optional add-on (£99 each) that open around 18°C and close around 12°C on their own.

For Cornish or Mediterranean-style heat exposure, side-louvre or gable-vent kits are a planned accessory. If your site is south-facing and bakes from June to 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 rather than a polytunnel, which helps 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.

1–4 weeks from order for UK mainland, included in the price. Every SteelRoot is made to order. Production typically takes 2–3 weeks, 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 is despatched.

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'll arrange the collection through our carrier. SteelRoot pallets are large, so 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, say a wrong size, a delivery damage that surfaced during the build, or a missing part, talk to us first. Most problems sort out short of a full return.

SteelRoot uses standardised component SKUs produced to a fixed spec. Panels are 4 or 6 mm twin-wall polycarbonate, fasteners and brackets are commodity stainless or zinc-plated hardware, and we keep them documented and coded so we can source replacements rather than re-engineering 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 that maintains a living parts catalogue. If you bought a SteelRoot in year 1, you can still buy parts for it in year 10.

If provider-backed finance is available for your order, it will be shown at checkout by the payment provider before you commit.

We do not publish manual monthly payment estimates on the PDP because the final offer depends on provider approval and the selected build.

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 day of re-trenching, and a torn cover in a winter storm is a documented pattern rather than 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 twin-wall polycarbonate that doesn't perish, an architectural arch silhouette that councils accept, and better thermal retention than a single-skin film. If you love your polytunnel for the growing but the film cycle has worn thin, this is the next step. If you want the lowest £/m² for a dedicated growing-only space, polytunnels remain a sensible answer.

Entry-tier aluminium greenhouses and SteelRoot serve different requirements. Compare the published frame profile, panel-fixing method, anchoring, glazing options and warranty terms rather than the starting price alone.

SteelRoot uses 40 × 20 mm closed RHS galvanised steel, screw-fixed twin-wall polycarbonate and included ground anchors. The base specification uses 4 mm glazing and 1 m arch spacing; 6 mm and 0.67 m close-arch options are available.