Falsework and shoring towers: EN 12812 design classes A, B1 and B2
Falsework is the temporary structure that carries a concrete slab, beam or other permanent element until it can support itself. In Europe its requirements and design are governed by EN 12812, which sorts falsework into design classes. Class A is reserved for simple cases within fixed limits, as summarised in standards overviews: slabs with a cross-section of up to 0.30 m² per metre of width, beams up to 0.50 m², a clear span of no more than 6.00 m and a height below 3.50 m. Anything beyond that falls into Class B, which comes in two variants, B1 and B2. Both require all details to be shown and the structural system to be captured precisely; they differ in the design method used. Prefabricated shoring towers have their own product standard, EN 12813. This guide explains the classes from the viewpoint of someone buying or planning formwork and shoring, not as a substitute for the design itself.
Falsework is not a working scaffold
On site, a birdcage of props under a slab and a facade scaffold can look like close relatives. Their jobs are quite different.
| Working scaffold | Falsework | |
|---|---|---|
| Purpose | a safe place for people, tools and materials | temporary support for a permanent structure under construction |
| Main load | people and materials on the platform | fresh concrete, reinforcement, formwork, plus construction loads |
| Key standard | EN 12811-1 (with EN 12810 for prefabricated facade systems) | EN 12812, with EN 12813 for prefabricated shoring towers |
| Typical loading figures | load classes from 0.75 to 6.0 kN/m² | derived from the element being cast and its construction stages |
| Consequence of failure | falls of people or materials | collapse of the structure being built, often with people underneath |
The separation also shows up in national guidance. In Germany, for example, the accident insurers' guidance on working and protective scaffolds expressly excludes falsework, which is covered by a separate rule. The point for buyers is simple: a scaffold system's load class tells you nothing about its suitability as falsework, and props or towers cannot be judged by facade-scaffold logic. Working-scaffold loads are explained separately under scaffold load and width classes.
Class A: the simple cases
Class A covers routine situations where the loads and geometry are modest. According to standards summaries, these limits apply:
- Slabs: cross-section up to 0.30 m² per metre of width.
- Beams: cross-section up to 0.50 m².
- Clear span: no more than 6.00 m.
- Height: falsework height below 3.50 m.
Treat the limits as a package. A case that fits three of them but breaks the fourth is no longer a Class A case.
Reading the slab limit
“Cross-section per metre of width” sounds abstract, but for a solid slab it is simply the thickness. A strip of slab one metre wide and 0.25 m thick has a cross-section of 0.25 m². So the Class A slab limit of 0.30 m² per metre corresponds to a solid slab up to 300 mm thick. For beams, multiply width by depth: a beam 400 mm wide and 1,000 mm deep has a cross-section of 0.40 m² and lies within the beam limit; one 500 mm wide and 1,200 mm deep has 0.60 m² and does not.
Worked examples
| Element | Check | Class A? |
|---|---|---|
| Residential floor slab 220 mm, clear span 5.4 m, storey height 2.8 m | 0.22 m²/m, span and height within limits | yes |
| Slab 320 mm thick, otherwise as above | 0.32 m²/m exceeds 0.30 | no |
| Downstand beam 300 × 600 mm under the 220 mm slab | 0.18 m², within the beam limit | yes, if the other limits also hold |
| Beam 500 × 1,100 mm | 0.55 m² exceeds 0.50 | no |
| 220 mm slab in a hall, falsework height 4.2 m | height not below 3.50 m | no |
| 220 mm slab, clear span 7.2 m | span exceeds 6.00 m | no |
Class A does not mean that no thought is required. Someone competent still has to choose the props or towers, check the ground or the slab below, set spacings within the manufacturer's load tables and make sure the falsework is braced. Class A simply marks the range in which the standard considers the case simple enough for that approach.
Class B: full design with B1 or B2
Once any Class A limit is exceeded, the falsework needs a design in Class B. Summaries describe two variants, B1 and B2. Both require all details to be represented and the structural system to be modelled accurately; the difference lies in the design method. Some short descriptions of EN 12812 speak of two classes, A and B, rather than three; the two ways of counting refer to the same structure, with B subdivided into B1 and B2. Which variant suits a project is a decision for the falsework designer.
For the contractor or buyer, Class B has practical consequences:
- Drawings and calculations exist before erection and show every relevant detail: tower positions, prop spacings, heads and bases, bracing, foundations and connections.
- The falsework is built as drawn. Substituting a different prop, extending spacings or swapping a tower for a stack of props on site breaks the design.
- Equipment data must be available. The designer needs reliable load values for each component used. Without manufacturer data for the exact product, the component cannot be designed in.
- Construction stages matter. Pour sequence, intermediate states and when supports may be removed belong in the design, and changes need the designer's agreement.
Situations that typically lead into Class B follow directly from the limits: thick transfer slabs, deep beams, double-height spaces and long spans.
Shoring towers and props
Prefabricated shoring towers are covered by EN 12813. They are assembled from frames or modular elements and carry heavier or higher loads than single props, with heads and bases that can be adjusted to the formwork level. In a falsework design they appear as components with defined capacities; EN 12812 governs the falsework as a whole, while EN 12813 deals with the towers as products.
Single floor props are the everyday tool for slab formwork in buildings, often in Class A situations. Their capacity depends on the extension length, so the same prop carries a different load at a short and at a long extension. Read the load table for the actual height rather than quoting a single figure for the prop. Used floor props and shoring towers are among the items available on this site.
From slab drawing to propping plan
Whatever the class, the route from the structural drawings to falsework on site follows a similar pattern. Knowing it helps a buyer order the right equipment at the right time.
- Collect the facts: slab thickness, beam sizes, clear spans, storey or falsework height, and what the falsework will stand on, whether ground, an existing slab or a basement deck.
- Classify: compare those figures with the Class A limits. If one is exceeded, a Class B design is needed and a falsework designer should be involved before equipment is ordered.
- Select the equipment: props for straightforward slabs, shoring towers where loads or heights are greater, plus beams, heads and bracing as the formwork system requires.
- Set out the arrangement: positions and spacings according to the manufacturer's load tables (Class A) or the design drawings (Class B).
- Check the support below: ground conditions and the capacity of any slab underneath, which may need back-propping through several floors.
- Inspect before the pour: a competent person compares what has been built with the plan before concrete arrives, and records the result.
The last step is where many problems are caught: a missing brace, a prop standing on a loose offcut, a tower head not fully in contact with the primary beam. A short, structured check against the plan costs far less than a failure under wet concrete.
Questions to put to the falsework designer
- Which design class have you used, and which assumptions about loads and pour sequence does it rest on?
- Which exact products and versions does the design assume, and may alternatives be used?
- What bearing capacity is assumed for the ground or the slab below?
- Who confirms on site that the falsework matches the design before the pour, and who releases it for striking?
What formwork buyers should check
- Manufacturer documentation: load tables and instructions for the exact product and version, ideally in English. Without them, a designer cannot use the equipment in Class B, and even Class A work becomes guesswork.
- Condition: damaged components must not be used. Look for bent tubes, cracked welds, worn threads, deformed heads and base plates, and corrosion that has eaten into the wall.
- Completeness: towers need their bracing, couplers, heads and bases; a pallet of frames without these is not a usable tower.
- One system: keep components of different systems apart unless the designer has confirmed the combination.
- Quantities from the design: buy to the propping plan, plus reserve for damaged items found on site, rather than to a rule of thumb.
Our used formwork overview lists slab formwork and shoring equipment, and every used item is checked before sale.
Typical mistakes
- Assuming everything is Class A. The thickness limit is exceeded faster than many expect; a 320 mm slab is already outside.
- Ignoring the height limit. A slab that is simple in plan becomes a Class B case in a tall space.
- Treating a facade scaffold as falsework. Working-scaffold load classes describe platform loads, not support for concrete.
- Changing the propping on site. Wider spacings or substitute props without the designer's approval.
- Forgetting the ground. Soft subgrade or a young slab below can fail before any prop does.
Sources
- Baunetz Wissen: Traggerüste, Heinze GmbH (undated)
- Baunetz Wissen: Gerüstnormen, Heinze GmbH (undated)
- DGUV Information 201-011, edition 2023