Scaffold load classes and width classes explained
Load class and width class are two short codes on the scaffold tag that decide what may happen on the deck. They tell the user how much weight a working area may carry and how much room there is to work. Both are defined in EN 12811-1, the European standard for the performance requirements of working scaffolds, and both are frequently misread on site.
What a load class means
A load class states the uniformly distributed service load that a working area may carry, in kilonewtons per square metre. It covers people, tools and material together. EN 12811-1 defines six classes:
| Load class | Uniform load | Approx. kg per m² | Typical use |
|---|---|---|---|
| 1 | 0.75 kN/m² | 75 | Inspection and access only, no material stored |
| 2 | 1.50 kN/m² | 150 | Painting, cleaning, light maintenance; one or two workers with hand tools |
| 3 | 2.00 kN/m² | 200 | Render, external wall insulation, general facade work with working material |
| 4 | 3.00 kN/m² | 300 | Brickwork, natural stone, heavy tiles |
| 5 | 4.50 kN/m² | 450 | Heavy masonry and industrial work |
| 6 | 6.00 kN/m² | 600 | Special heavy loads, plant and machinery assembly |
Besides the uniform load, the standard also sets concentrated loads and partial-area loads for each class, which matter when a heavy item sits on a small spot. These values are built into the system's design; the user needs to know the class and the rules in the manufacturer's instructions.
Load class 3 is the everyday standard on housing and facade work. Classes 5 and 6 are rare and usually involve a design by a structural engineer.
Working out the class you need
Take the worst realistic situation on one bay of one lift:
- Add up the loads. As a practical figure, one person with tools is about 1.0 kN (about 100 kg). Material converts at roughly 1.0 kN per 100 kg. Include buckets, bags, boards and small machines such as mixers or cutters.
- Divide by the deck area of the bay. Bay length × deck width gives the area in m².
- Compare with the table and choose the next class up.
Example: a renderer and a labourer on a 3.07 m bay with a 0.73 m deck, with six 30 kg bags of render on the boards. People 2.0 kN, material 180 kg ≈ 1.8 kN, total 3.8 kN. Deck area 3.07 × 0.73 = 2.24 m². Load: 3.8 ÷ 2.24 ≈ 1.70 kN/m². Class 2 is exceeded, so the scaffold needs load class 3. Add a pallet of insulation boards and the answer can move towards class 4.
Width classes
The width class says how much clear deck width is available, measured between the uprights or rails. EN 12811-1 defines classes from W06 upwards in steps of 0.3 m:
| Width class | Minimum clear width | Typical system width |
|---|---|---|
| W06 | 0.6 m | frame scaffolds of about 0.70–0.73 m |
| W09 | 0.9 m | frame scaffolds of about 1.0–1.09 m |
| W12 and above | 1.2 m, 1.5 m … up to 2.4 m | modular scaffolds and wide working platforms |
A narrow W06 scaffold is enough for painting and inspection. Where material is stacked and people still need to pass, W09 is more practical. For external wall insulation, where board stacks, adhesive and tools share the deck, many contractors choose W09; see scaffolding for external wall insulation. Widening with brackets is covered in inside and outside brackets.
Rules that are often overlooked
- The class applies per working area, not per scaffold. Load class 3 does not mean every lift can carry 2.00 kN/m² at the same time. The instructions state how many lifts may be loaded simultaneously.
- The class depends on bay length and deck type. The same system may reach class 4 at 2.07 m but only class 3 at 3.07 m. Check the instructions for the bay you are using; see the manufacturer's instructions.
- Stacked material counts in full. A pallet of blocks put down in one corner concentrates its load on a small area.
- The tag must show it. Load class and width class belong on the scaffold tag or handover notice at each access point, together with the date of inspection and any restrictions.
- Brackets have their own limits. An outside bracket often carries less than the main deck.
Load class, inspection and regulations
The load class is part of the scaffold's design and is checked at handover. In Great Britain, a competent person inspects under the Work at Height Regulations 2005: once before the scaffold is used, then weekly at the latest and whenever something could have compromised it; tube and fitting designs follow NASC guidance such as TG20. Across the Atlantic, OSHA 29 CFR 1926 Subpart L puts the check at the beginning of each shift, again by a competent person. In other countries, national rules decide; when unsure, involve a safety adviser.
Whatever the jurisdiction, the user is responsible for keeping within the posted class. If the work changes, for example from painting to brickwork, the scaffold must be checked for the new load before it is used for it.
Practical guide by trade
| Work | Load class | Width class | Note |
|---|---|---|---|
| Inspection, surveys | 1 | W06 | No material on the deck |
| Painting | 2 | W06 | Paint tins and hand tools only |
| Window and gutter work | 2–3 | W06 | Depends on what is stored |
| Render and plaster | 3 | W06–W09 | Bags and mixing on the deck |
| External wall insulation | 3 | W09 recommended | Board stacks need room |
| Brickwork, natural stone | 4 | W09 | Plan material storage carefully |
| Industrial, heavy assembly | 5–6 | project-specific | Engineered design |
When buying, choose a system that reaches the class your typical work needs at the bay length you prefer. Used frame scaffolding and modular scaffolding are listed with their system, and the scaffolding calculator helps with the quantities.