Freestanding garden greenhouse
Apex-roof kits from about 1.8 × 1.2 m (6 × 4 ft) up to 3 × 4 m and more, glazed with toughened glass or twin-wall polycarbonate, with a sliding or hinged door and roof vents.
Outdoor structures
Aluminium Greenhouse Kits, Frames & Profiles
Aluminium is the standard frame material for glass and polycarbonate greenhouses because it does not rust in a warm, humid growing climate, and because thin, strong extrusions shade less of the crop than timber or steel. Metline supplies greenhouse frame profiles such as glazing bars, gutters, ridge sections and panel channels, cut and drilled to drawing, to garden-product brands, greenhouse builders and growers worldwide.
- Profile alloy
- 6063-T5 / T6, 6005A-T6
- Coverings
- Glass, polycarbonate, film
- Finish
- Mill, anodised, powder coat
- Design code
- EN 13031-1 · local codes
Why greenhouses are built in aluminium
A greenhouse frame lives in the harshest climate of any building component: constant humidity, condensation running down every bar, fertiliser and pesticide sprays, and daily temperature swings. It also has to be as slender as possible, because every square centimetre of frame is a shadow on the crop.
Aluminium meets both demands. Its natural oxide film protects it in humid air without paint, so frames stay sound for decades and do not stain glass with rust. Extrusion lets one profile combine a structural web, a glazing rebate, a condensation channel and a screw port, which a rolled steel section cannot do. And at a density of 2.70 g/cm³ the frame is light enough to ship as a flat-packed kit and assemble with hand tools.
For small garden greenhouses aluminium is almost universal. In commercial horticulture, the classic Dutch Venlo greenhouse combines a galvanised steel truss and column structure with aluminium gutters, ridges and glazing bars, while all-aluminium and hybrid structures are used for retail garden centres, research glasshouses and conservatory-style buildings.
Types of aluminium greenhouse
Lean-to greenhouse
A single-pitch structure fixed against a house or garden wall. The wall stores heat, which helps in cooler climates; the wall plate and flashing details matter most.
Mini and wall greenhouses
Compact frames for patios and balconies, where light weight and easy assembly are the main requirements.
Commercial Venlo glasshouse
Multi-span houses with small roof pitches, aluminium gutters spanning between columns and aluminium glazing bars carrying horticultural glass.
Wide-span and polycarbonate houses
Larger arched or peaked spans clad in multi-wall polycarbonate, often with aluminium end walls, doors and vent frames.
Film greenhouses
Steel hoops covered in polyethylene film, using aluminium wire-lock channels, roll-up bars and door frames for fastening and ventilation.
Aluminium profiles used in a greenhouse
A greenhouse kit is a set of extrusions that each do one job. The table lists the main profiles and what each one does, so you can match a parts list or drawing to the right sections.
| Location | Profile | Function |
|---|---|---|
| Roof | Glazing bars (rafters) | Carry the roof glass or panels and drain water and condensation to the eaves |
| Ridge | Ridge profile | Joins both roof slopes, carries vent hinges and seals the top edge |
| Eaves and valleys | Gutter / eaves beam | Collects rain, stiffens the roof line and, in multi-span houses, spans between columns |
| Walls | Side and gable bars, corner posts | Vertical framing and panel support |
| Base | Base frame or sill | Anchors the structure to a slab, sleeper or footing |
| Panel joints | H channel | Joins polycarbonate or panel edges on roofs and walls |
| Panel edges | U channel and end caps | Close and protect the open flutes of multi-wall sheet |
| Openings | Door, sliding-door track and vent frames | Access and ventilation |
| Film houses | Wire-lock channel, roll-up bar | Clamp film and drive side-wall ventilation |
Most profiles are extruded from 6063 aluminium in T5 or T6 temper, which gives clean, thin sections with good surface quality. Gutters and long-span beams that carry snow and crop-hanging loads are often made in 6063-T6 with deeper webs, or in 6005A-T6 or 6061-T6 where higher strength is needed. Fasteners are stainless steel or zinc-plated with plastic isolation.
Glass, polycarbonate or film?
| Covering | Typical thickness | Approx. light transmission | Insulation | Notes |
|---|---|---|---|---|
| Horticultural float glass | 3 – 4 mm | About 89 – 90 % | Low (single layer) | Classic look, long life, breaks into sharp pieces |
| Toughened safety glass | 3 – 4 mm | About 89 – 90 % | Low | Safer near children; standard for garden kits |
| Diffuse / anti-reflective glass | 4 mm | Up to about 95 % or more | Low | Spreads light deeper into the crop; commercial use |
| Twin-wall polycarbonate | 4 – 10 mm | About 80 % | Good | Light, virtually unbreakable, diffuses light |
| Multi-wall polycarbonate | 16 mm and up | About 60 – 70 % | High | Cold climates, heated houses |
| Polyethylene film | 150 – 200 µm | About 85 – 90 % new | Low (single) or moderate (double, inflated) | Lowest cost; replaced every few years |
Transmission values are indicative for new, clean material and vary with product and coating. Check the covering supplier's data for your selection.
The aluminium profile must suit the covering. Glass sits on glazing tape or gaskets and is held with clips or caps; polycarbonate needs H and U channels and room to expand, because it moves about three times more than aluminium with temperature. Film is clamped with wire-lock channels so it can be re-tensioned and replaced.
Structural design: wind, snow and crop loads
Even a small garden greenhouse is a lightweight structure with a large surface area, so wind is usually the governing load; in cold regions snow on the roof and in valleys takes over. Commercial greenhouses also carry hanging crops, thermal screens, lighting and irrigation, which the gutters and trusses must support.
| Design point | What to check |
|---|---|
| Code | EN 13031-1 for commercial production greenhouses in Europe; local building codes and manufacturer design guides elsewhere |
| Wind | Uplift on the roof and suction on walls; anchorage of the base frame to the foundation |
| Snow | Ground snow load for the site and drift in valleys of multi-span houses; roof pitch and glazing bar spacing |
| Glass sizing | Pane width and thickness for the bar spacing and loads; EN 13031-1 includes rules for horticultural glass |
| Deflection | Limit bar and gutter deflection so glass does not crack or slip and gutters do not pond |
| Thermal movement | About 2.3 mm per metre of frame over a 100 °C range; allow at panel joints and long gutters |
Mill finish, anodising and powder coating
Mill finish
The lowest-cost option. The frame weathers to a dull grey and stays structurally sound. Common on commercial glasshouses where appearance is secondary.
Anodised
A clear or bronze anodic layer, typically 10 – 20 µm, improves corrosion resistance and keeps the frame looking clean. Popular for premium garden greenhouses.
Powder coated
Green, black, grey or any RAL colour, 60 – 80 µm. Gives a furniture-like look for garden and orangery projects; specify a durable coating for strong sun.
Reflective white
A white coating reflects light back into the crop and reduces frame heating; often used on commercial gutters and bars.
Fertiliser solutions and some crop-protection chemicals can attack bare aluminium if they collect in crevices. Good drainage in the profile, regular rinsing and an anodised or coated finish all extend service life in intensive growing.
Aluminium compared with galvanised steel and timber
| Factor | Aluminium | Galvanised steel | Timber |
|---|---|---|---|
| Corrosion / decay | Self-protecting oxide film | Protected by zinc; rusts where coating is cut | Rots unless treated and maintained |
| Weight | Light | About three times heavier for the same volume | Light, but sections are bulky |
| Shading | Slim profiles, low shading | Slim but needs bracing | Thick bars, more shading |
| Maintenance | Washing only | Repair coating damage | Regular treatment or painting |
| Strength for large spans | Good with deep sections | Highest; preferred for trusses and columns | Limited |
| Integrated features | Drainage, glazing rebates, screw ports in one extrusion | Separate parts | Machined rebates |
| Best use | Kits, glazing bars, gutters, retail and research houses | Primary structure of large commercial houses | Traditional garden houses |
Many commercial projects use both: a galvanised steel primary structure for columns and trusses, and aluminium for the gutters, ridges, glazing bars, vents and doors where corrosion, light and precision matter most.
What Metline supplies
- Profiles for garden-product brands that pack their own greenhouse kits, cut, drilled and labelled to the brand parts list
- Frame profiles: roof, wall, gable, door and vent sections for local builders to assemble, glaze and erect
- Individual profiles: glazing bars, gutters, ridges, H and U channels, wire-lock channels and base sections
- Replacement parts matched to drawings or samples for repairing or extending existing houses
- Processing: cutting to length, punching, drilling and CNC machining of profiles, with labelling by part number
- Custom extrusions developed to your cross-section drawing, or matched to an existing die where possible
Each order is checked for profile dimensions, lengths, hole positions and finish against the approved drawing, and shipped with material certificates and a detailed packing list.
How to order greenhouse aluminium
- Share the designGreenhouse size or layout drawing, cross-section drawings or samples, and the parts list.
- Confirm covering and loadsGlass, polycarbonate or film, panel thickness, and the wind and snow conditions at site.
- Select alloy and finishUsually 6063-T5/T6; mill finish, anodised or powder coated in your colour.
- Approve sample or first articleFor new profiles, a sample length or first-article check before full production.
- Pack and shipProfiles sleeved and bundled or packed by part number, in export cartons or crates, on EXW, FOB, CIF or DAP terms.
References and standards
- EN 13031-1 – Greenhouses: design and construction, Part 1: commercial production greenhouses
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 755-2 – Aluminium and aluminium alloys: extruded rod/bar, tube and profiles, mechanical properties
- EN 1999-1-1 (Eurocode 9) – Design of aluminium structures
- International Society for Horticultural Science (ISHS) – Acta Horticulturae papers on greenhouse light transmission
Aluminium (aluminum) greenhouses: FAQ
Is an aluminium greenhouse better than a wooden one?
For durability and light, usually yes. Aluminium does not rot, needs no treatment and uses slimmer bars, so more light reaches the plants. Timber insulates slightly better and suits traditional designs, but needs regular maintenance.
Will an aluminium greenhouse frame corrode?
Aluminium forms a protective oxide layer and resists humid greenhouse air very well. Problems arise only where it touches dissimilar metals, sits in standing fertiliser solution, or is in permanent contact with wet concrete; use stainless fixings, good drainage and an anodised or powder-coated finish for intensive growing.
Which is better for an aluminium greenhouse: glass or polycarbonate?
Glass gives the highest light transmission and a long life; toughened glass is safest. Twin-wall polycarbonate insulates better, is almost unbreakable and diffuses light, at the cost of some transmission and a shorter surface life. Many growers use glass in mild regions and polycarbonate where heating costs or hail are a concern.
What alloy are greenhouse profiles made from?
Mainly 6063 in T5 or T6 temper, because it extrudes into thin, complex sections with a good surface. Gutters and long-span members may use deeper 6063-T6 sections or 6005A-T6 and 6061-T6 for extra strength.
Can you supply replacement greenhouse parts?
Yes. Send a drawing, sample or clear photographs with dimensions, and we can supply glazing bars, H and U channels, gutters and connectors to match, or develop a new die if no existing profile fits.
Can greenhouse profiles be supplied pre-cut?
Yes. Profiles can be cut, drilled and labelled by part number to your parts list, so the greenhouse brand or builder can pack its own kits or assemble on site. We do not supply complete greenhouse kits.
Building or supplying greenhouses?
Send drawings, parts lists or samples, the covering type, finish and destination to sales@metline.in for a profile quotation.
