Aluminium pergolas: alloys, structure and finish

An aluminium pergola is an outdoor structure of powder-coated aluminium posts, beams and rafters, with the load-bearing frame usually in EN AW-6082 T6 and the trim and slats in 6063 T6 or 6060 T6, carrying a fixed, slatted or louvred roof over a terrace or garden. The aluminium is chosen because it does not rust, needs no repainting and stays light enough to span wide openings on slim sections. This guide covers the alloys and finish, the posts, beams and roof, the fixings and foundations, and how wind and snow loading decide the section sizes, so the finished pergola is both good-looking and structurally sound.

What an aluminium pergola is made of

A pergola is a post-and-beam frame: uprights carry perimeter beams, and rafters or slats bridge between the beams to form the roof. In an aluminium pergola every one of those members is an extruded aluminium profile, powder-coated to a single colour, and bolted or bracket-fixed rather than welded on site. The result reads as one clean, maintenance-free structure. The same profile-and-coating logic sits behind the modern fence range, so a pergola and a matching boundary can share the alloy family and one RAL colour. For the extrusion side see our guide to aluminium profiles.

Why aluminium rather than timber or steel

Timber greys, splits and needs regular treatment, and untreated steel rusts, so both demand ongoing maintenance outdoors. Aluminium forms a thin self-healing oxide the moment it meets air, which is why an uncoated aluminium profile does not corrode in the way steel does, and a powder coat on top locks in the colour for decades. Aluminium is also about a third the weight of steel for the same volume, so a pergola frame stays easy to handle and to fix down without heavy footings. For the corrosion behaviour see our guide to whether aluminium corrodes.

The alloys: 6082 T6 for the frame, 6063 and 6060 for the trim

Pergolas use the 6000-series alloys, which combine good strength with the fine surface finish that powder coating needs, and they split the frame between two roles. EN AW-6082 T6 is the load-bearing alloy, with a proof strength around 250 MPa and a tensile strength around 290 MPa, so it carries the structural posts and beams of a carport or pergola frame. EN AW-6063 T6, with a proof strength around 170 MPa, and EN AW-6060 T6, around 150 MPa, are the softer architectural tempers used for trim, slats, rails and cladding, where surface finish matters more than load, and 6060 is the alloy ULAMEX uses for carport roof and cladding profiles. All are fully weldable with 4043 or 5356 filler where a fabricated joint is needed. For hollow members such as posts and beams see our guide to aluminium tube and box section.

Powder-coated finish and colours

The finish that makes a pergola weatherproof is a polyester powder coat, applied to a minimum 60 micron thickness over a pre-treated surface, giving UV stability and colour retention for twenty years and more. The standard palette is RAL 7016 anthracite grey, RAL 9005 jet black, RAL 7035 light grey and RAL 9006 white aluminium, with any RAL shade available on wholesale orders. Anthracite RAL 7016 dominates the European market for its neutral, contemporary look. Aluminium also anodises well and gives its brightest anodised finish on 6063, which ULAMEX can advise on, though the aluminium itself is supplied mill finish or powder coated.

Posts, beams and rafters

The frame divides into three jobs. Posts are the uprights, usually a square hollow section such as 100 x 100 mm in load-bearing EN AW-6082 T6, sized to carry the roof load and the wind on the structure down to the foundations. Beams run along the tops of the posts to tie them together and to carry the roof members, and take the same structural temper. Rafters or slats span between the beams to form the roof surface itself, in the lighter 6063 or 6060 architectural tempers. Each member is an extruded profile designed so that brackets, end caps and fixings locate cleanly, which is what lets a pergola be assembled on site with hand tools rather than welded.

Roof options: fixed, slatted and louvred

The roof is where pergola styles diverge. A fixed roof carries solid infill panels or polycarbonate for full shelter, and behaves like a light canopy that must shed rain and snow. A slatted roof uses fixed aluminium blades for permanent, filtered shade and free airflow. A louvred, or bioclimatic, roof uses rotating blades so the shade and ventilation can be adjusted, closing to shed rain and opening to let heat escape. ULAMEX supplies the aluminium profiles and blades for these roofs; where a louvred roof is motorised, the aluminium is supplied for the automation to be fitted into.

Fixings and galvanic isolation

The fasteners are stainless and matched to the exposure: A2 (1.4301) in sheltered positions and A4 (1.4404) outdoors and near the coast, so they resist corrosion and do not stain the aluminium. The rule to hold onto is to avoid a wet joint between dissimilar metals, because that drives galvanic corrosion of the less noble part. Aluminium against stainless is a benign pairing, but aluminium bolted directly to a bare carbon-steel bracket in a wet detail needs an isolating washer or a coated interface. Correctly specified fixings are a small line on the order that protects the whole structure.

Foundations and fixing down

A pergola is light, but it presents a large roof to the wind, so it must be anchored properly. Freestanding pergolas are fixed to concrete pads or footings through base plates at the foot of each post, with the pad sized to resist both the downward load and the uplift and overturning that wind produces. Wall-mounted or lean-to pergolas take one edge on a wall bracket and the outer edge on posts. In colder parts of continental Europe the footings reach below the local frost line so that freezing ground water cannot heave them. The base detail is set out at the planning stage, not improvised on site.

Wind and snow loading

The loads a pergola must resist are set by the Eurocode for the country and the site: EN 1991-1-4 for wind and EN 1991-1-3 for snow. Wind is usually the governing case for an open structure, because the roof acts as a sail and the uplift on a light canopy can exceed its own weight. A closed or louvred-shut roof catches far more wind and snow than an open slatted roof, so it drives larger posts, beams and footings. Sizing the members and foundations to the correct Eurocode loads for the exposure, before fabrication, is what keeps a pergola standing through storms and winters.

Sizing, spans and modular bays

Pergolas are built to a bay, so a large structure is made from repeating spans rather than one impossibly long beam. Keeping the post spacing within the span the beam section can carry, and adding an intermediate post where a run gets long, keeps the roof flat and the deflection small. The same modular thinking lets a pergola be extended later by adding a bay. Because the actual section sizes depend on the span, the roof type and the local loads, they are confirmed against the Eurocode for each project rather than taken from a fixed table.

Matching a pergola to fencing and screens

Because a pergola and a modern fence use the same 6000-series aluminium, the same powder coating and the same RAL palette, they can be specified as one coordinated scheme. A terrace can be enclosed with slatted aluminium side screens in the pergola colour, and the garden boundary can carry the same anthracite finish, so the whole outdoor space reads as one design. Ordering the pergola profiles, the screens and the fence together also keeps the colour batch consistent. For the boundary side see our guide to modern aluminium fencing systems.

Maintenance and lifespan

A powder-coated aluminium pergola is close to maintenance-free. The aluminium does not rust, the coating does not rot or need repainting, and periodic washing with water keeps the colour looking new. There are no annual oiling or staining routines as there are with timber. The points worth an occasional check are the fixings, which should stay tight, and any cut end from an on-site adjustment, which is simply deburred and tidied because aluminium does not need a sacrificial coating to resist corrosion. Over a twenty-year-plus life this is by far the lowest-effort outdoor structure to own.

Aluminium pergola components from ULAMEX

ULAMEX has supplied the metals and structures trade since 1988 and manufactures under EN 1090-1 EXC2 and ISO 3834-2.

Planning a pergola project? Send the size, roof type, colour and quantities, and ULAMEX will return a non-binding quotation with lead time and availability. Browse the aluminium profiles range, see the matching modern aluminium fencing systems, read about steel and aluminium carports for a covered-roof structure, or view our supply capabilities. Contact the export desk at [email protected] or +48 504 424 761.

Frequently asked questions