Scaffolds an work at height: practical guide
The scaffold is a type of equipment widely used to provide a stable platform but at the same time to move quickly. It is normally used to deal with some work at height that does not take much time and that must be carried out at a height not particularly high, less than 12 meters.
UNI EN 1004:2021
The use of mobile scaffolding defined by Legislative Decree 81/08 as a bridge equipped with wheels is regulated by UNI EN 1004:2021, in force since December 2021. The standard provides a complete overview of the use of the trabattello and in particular is the reference for:
- definitions (scaffolding, component, installation, maintenance, etc.);
- safety requirements for the design, production and use of mobile prefabricated scaffolding. These include load requirements, stability, weather resistance, safe access, fall prevention, etc.;
- design and production: you will find the specifications of the materials, dimensions and workloads allowed;
- requirements for installation and dismantling, including assembly procedures, stability checks, protection against electricity hazards, etc.
- maintenance and inspection: cleaning procedures, stability and operation checks of components, etc.
Then it is necessary to distinguish the scaffolds from the small scaffolds defined and regulated by UNI EN 11764:2019.
Both scaffolds and small scaffolds are classified according to the following factors:
- Load class: For bogs the load classes can be 2 and 3 respectively with a uniformly distributed load of 1,50 and 2,00 kN/m2. For small scaffolds the maximum load is 150 kg including a single worker, equipment and material.
- classes of use: there are only two or inside or in the sternum and in turn imply respectively the absence or presence of wind.
- height classes :
- scaffolds can have class H1 ≥ 1,85 m or H2 ≥ 1,90 m;
- small scaffolds h < 2 m o 2 m ≤ h < 4 m.
- access classes:
- access type A: ramp staircase,
- type B access: staircase,
- type C access: inclined ladder,
- type D access: vertical ladder.
- Access mode: for normal trabattelli you can access it from the outside or from the inside. Outside access is allowed if the highest height is less than 2 m. For the small scaffolds the modalities of access are classified as follows:
- Type E access: outside,
- Type I access: inside,
- EI type access: outside and inside.
Designation and label
Scaffold in accordance with UNI EN 1004:2021 must have its designation in which the following information and indications are indicated:
- the product: scaffold,
- the reference to the standard: UNI EN 1004:2021,
- the load class: 2 or 3,
- the maximum height outside and inside: 8 and 12 m,
- access classes: A, B, C or D for trestles with a single type of access; ABCD if there are four types of access; or if there are two accesses, the missing ones must be indicated interspersed with an X (for example if the accesses are B and D with XBXD),
- height classes: 1,85 m (H1), 1,90 m (H2).
The label of scaffold visibly placed must indicate the designation, the name of the manufacturer, the words “read the instruction manual”.
The small scaffold similar to the scaffold must have in its designation the same indications according to UNI EN 11764:2019. The label is also similar.
Once mounted or transformed the scaffold must be equipped with a visible sign with some essential minimum information:
- name of the supervisor,
- assembly date ,
- load class,
- if the scaffold is ready for use,
- if the scaffoldis exclusively for indoor use.
The scaffold choice must be made considering different aspects such as the dimensions of the scaffold, whether the work is to be done indoors or outdoors, whether there is wind or not, the load class, the type of access, if the loads are horizontal or vertical as they can destabilise the trap itself, the conditions of the ground, the possible use of stabilizers, external projections, ballast or if there is a need for anchorages.
the greatest risks
The greatest risk is represented by the fall of the operator, who can fall both during the assembly or disassembly phase, and during the work at height, but also during the ascent and descent between the various bridges.
During assembly/disassembly, the risk of manual handling of loads is present because these phases require the handling of prefabricated frames and boards for assembly.
Accidental dropping of material such as tools or other objects can occur while performing work. The presence of tools or other obstacles on deck planes can cause the worker to slip or stumble and fall with the risk of accident.
Risks associated with moving the scaffold
There is also the investment risk: you have to pay attention also in the displacement of the scaffold to avoid investing any other workers on the path. Shocks can occur with electrical cables or structural elements such as beams, bridge cranes or other suspended elements, causing the possibility of electrocution or damage to the worker involved.
Overloading or incorrect positioning or the absence of stabilizers or anchoring can cause the overflow to overturn and workers to fall.
The oscillation of the scaffold can be due to an ineffective locking of the wheels; oscillation that would be amplified by the presence of load on top.
Accurate inspection of the metal components allows optimal maintenance. It must be carried out by qualified personnel and in particular it must monitor:
- surface layer,
- state of wear and corrosion,
- state of the welds,
- status of moving parts,
- state of screws, pins, nuts, bolts, rivets.
While for the maintenance of the wooden components you must check:
- presence of cuts or abrasions,
- damage caused by heat or aggressive substances,
- deterioration caused by sunlight.
These checks must take into account the frame, the diagonals, the currents, the intermediate and thermapidal protection, the access openings, the decks, the wheels, the stabilizers and the feet.
Documentary aspects and training
The mandatory instructions must be provided by the manufacturer and are indispensable for the correct assembly, disassembly and transformation of the scaffold. For this last phase, the transformation, we mean the transition from one configuration to another, if allowed by the manufacturer for the single model.
Before proceeding with the installation of the scaffold, it is of fundamental importance to carry out an inspection of the site chosen from the assembly to verify the soil conditions, the slope, any obstacles, weather conditions, possible presence of overhead power lines.
Scaffolds should not be marked CE because there is no product directive.
Often when we speak of scaffolds we also speak erroneously of PIMUS (Assembly Plan, Use and Disassembly), but it refers exclusively to the scaffolding itself and not to the scaffolds.
Finally, a mention of the training that is not necessary in itself for the use of the scaffold, but for the type of work that takes place in it or work at height as required by Legislative Decree 81/08. In any case, the workers in charge of the assembly, disassembly and transformation of the scaffold must be trained to the task in accordance with Legislative Decree 81/08.