Design codes
EN 1999 (Eurocode 9) or the Aluminum Association's Aluminum Design Manual set design strengths, including reduced strengths in heat-affected zones of welds.
Guide
Architectural Aluminium: Material Requirements Guide
In windows, doors, curtain walls and façades, aluminium has to do two jobs at once: carry structural and wind loads, and look right for decades. Most disputes on building projects come from appearance and tolerance requirements that were never written down. This guide explains which alloys and tempers to specify, which standards govern dimensions and finishes, and what to agree with the supplier before the first profile is extruded.
Alloys and tempers for architectural work
| Alloy and temper | Min. Rm / Rp0.2 (MPa, EN 755-2, thin sections) | Strengths | Typical use |
|---|---|---|---|
| 6060-T6 / T66 | 190 / 150 ; 215 / 160 | Excellent surface, easy extrusion, best for decorative anodising | Window and door profiles, trims |
| 6063-T5 | about 160 – 175 / 110 – 130 | Good finish, economical (press-quenched) | Window and door frames, light sections |
| 6063-T6 / T66 | 215 / 170 ; 245 / 200 | Higher strength while keeping a fine surface | Curtain-wall mullions and transoms |
| 6005A-T6 | about 255 – 270 / 215 – 225 | Structural strength in more complex hollow shapes | Heavy mullions, balustrade posts, structural sections |
| 6061 / 6082-T6 | about 290 – 310 / 240 – 260 | Highest 6xxx strength; harder to extrude, rougher anodised finish | Brackets, fixings, structural members |
| 5005-H14 / H24 sheet | about 145 / 120 | Anodises to match 6060/6063 profiles | Cladding panels, flashings, soffits |
| 3003 / 3105 coil | varies by temper | Formable, economical for coil-coated products | Composite-panel skins, rainwater goods, roofing |
Minimum properties depend on wall thickness and temper; the values summarise EN 755-2 for thin sections. ASTM B221 gives equivalent minimums for North American orders.
Dimensional tolerances: which standard to quote
Architectural profiles are usually ordered to the precision tolerances of EN 12020-2 (for 6060 and 6063 and similar alloys), which are tighter than the general EN 755-9 tolerances. North American orders follow the Aluminum Association's Aluminum Standards and Data / ANSI H35.2 tables. Critical features such as glazing pockets, thermal-break grooves and hardware slots should be dimensioned with their own tolerances on the drawing.
- Quote the tolerance standard on the drawing and the purchase order
- Mark critical dimensions (gasket and thermal-break grooves, screw ports) and their tolerances
- Define straightness, twist and flatness requirements for long visible members
- State cut-length tolerance and end squareness if profiles are supplied cut to size
Anodising and powder coating: what to specify
| Finish | Main quality standards | Key specification items |
|---|---|---|
| Anodising | QUALANOD; EN ISO 7599; AAMA 611 (North America) | Film class (e.g. 15, 20 or 25 µm for exterior work; AAMA 611 Class I ≥ 18 µm), colour and colour range, sealing quality, pre-treatment (etched, brushed, chemically brightened) |
| Powder coating | QUALICOAT (class 1, 2, 3); AAMA 2603 / 2604 / 2605 | Powder class for the climate, film thickness, pretreatment (chrome or chrome-free), gloss and colour, seaside-class pretreatment where needed |
| Liquid PVDF | AAMA 2605; QUALICOAT | Coat system (2- or 3-coat), colour, warranty basis |
| Mechanical finishes | Project samples | Brushing direction, grit, and protection film |
Anodised colour depends strongly on the alloy and on the metal's history, so profiles and sheet that must match should come from controlled alloy compositions (for example 6060 profiles with 5005 "anodising quality" sheet) and, ideally, from the same production batches. Agree limit samples showing the acceptable colour range before production. QUALICOAT and QUALANOD distinguish approved products from licensed coating plants; check both when a project specification names the label.
Structural design and compliance
An alloy designation alone does not prove that a façade or window complies with building regulations. The structural adequacy of the assembly is demonstrated by calculation and testing of the complete system.
Execution
EN 1090-3 covers the fabrication of aluminium structures; structural extrusions and sheet for construction products fall under EN 15088.
Thermal performance
Thermally broken profiles use glass-fibre-reinforced polyamide strips; shear strength of the composite is tested to EN 14024.
Weather and fire
Air, water and wind tests (e.g. EN 12152/12154 for curtain walls) and fire classification of panels are system properties, not alloy properties.
Architectural aluminium enquiry checklist
- Drawing and alloyProfile drawing with alloy and temper, tolerance standard and critical dimensions.
- Exposed facesMark visible (decorative) faces on the drawing; surface defects are judged on these faces only.
- FinishFinish type, colour reference, film class or thickness, and approved limit samples.
- ProtectionProtective film or interleaving on visible faces, and packing that prevents rub marks during transport.
- Lengths and quantitiesMill lengths or cut lengths, quantities per profile, and delivery schedule by building phase.
- DocumentsMill certificate for alloy and temper, finish test reports (film thickness, adhesion, sealing) and any project-specific certificates.
Common mistakes on architectural projects
- Specifying 6061 or 6082 for decorative anodised profiles, then rejecting the streaky finish
- Mixing sheet and profile alloys that anodise to visibly different shades
- Leaving exposed faces undefined, so every handling mark becomes a dispute
- Using interior-grade powder on coastal façades instead of a higher QUALICOAT class with seaside pretreatment
- Ordering by catalogue section without checking the system's tested structural and thermal data
References and standards
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
- EN 12020-2 – Extruded precision profiles in alloys EN AW-6060 and EN AW-6063: tolerances
- QUALICOAT – Specifications for a quality label for coatings on aluminium
- QUALANOD – Specifications for the quality label for sulfuric acid-based anodizing of aluminium
- EN 1999 (Eurocode 9) – Design of aluminium structures
Architectural aluminium (aluminum) requirements: FAQs
Which alloy is best for window and door profiles?
6060 or 6063, in T5, T6 or T66 temper. They extrude into complex thin-walled shapes with a smooth surface and anodise evenly. Heavier structural members may use 6005A.
What anodic film thickness should be used outdoors?
Exterior architectural work typically uses at least 20 µm (QUALANOD class 20) or AAMA 611 Class I (18 µm minimum); 25 µm is common in aggressive or coastal environments.
What is the difference between QUALICOAT class 1, 2 and 3?
They are powder classes with increasing weather resistance. Class 1 is standard architectural durability, class 2 is super-durable, and class 3 offers the highest long-term colour and gloss retention.
Why do anodised sheet and profiles sometimes not match?
Colour after anodising depends on alloy composition and metal processing. Use alloy pairs designed to match, such as 5005 anodising-quality sheet with 6060/6063 profiles, and approve limit samples.
Does using 6063-T6 guarantee code compliance?
No. Compliance is shown by structural calculation of the assembly and by system testing; the alloy and temper are inputs to that design, not proof of it.
Planning an architectural aluminium package?
Send profile drawings, finishes and quantities. We will confirm alloy, tolerance and finish options and quote delivered to site.
