SOA category OS21
Special structural works
OS21 relates to specialised structural works: interventions that transfer loads onto soils with low bearing capacity, stabilise the ground, prevent landslides and retrofit existing structures to make them earthquake-resistant. It is one of the most technically demanding categories within the SOA system. It entails one key requirement: the workforce must include operators holding a licence for complex machinery (drilling rigs), issued by construction training colleges. It is strategic for the seismic bonus scheme, hydrogeological instability and the foundations of structures.
SOA certification OS21: areas of application
OS21 covers subsoil engineering and consolidation. The main sectors:
- Deep foundations: bored piles, driven piles, micropiles and CFA piles, when the ground cannot bear the loads.
- Anchored retaining walls: typical of large urban excavations for car parks, underground railways and tall buildings.
- Ground consolidation: jet grouting, grout injection, ground freezing and deep drainage.
- Slope stability: soil nailing, cable nets and anchors to secure embankments and slopes.
- Underpinning: reinforcement of the foundations of historic or damaged buildings. OS21 only covers the subsoil, not the above-ground parts.
- Foundation-level seismic upgrading: micropiles and ties to improve seismic response, a fast-growing segment.
- Wells: water wells, drainage wells and underground water intakes.
In short: OS21 is the category of the subsoil at work: a technical and protected market, reserved for genuinely well-equipped companies.
SOA categories related to OS21
carries out subsoil surveys (boreholes and tests); OS21 the works that follow.
covers passive protection (rockfall nets and barriers); OS21 active anchoring such as tie-backs and soil nails.
builds structures above ground; OS21 everything below.
is needed for the above-ground consolidation of protected heritage; OS21 only for their foundations.
is the category of transport infrastructure; OS21 builds its special foundations.
uses “green” techniques for slopes (timber, geosynthetics); OS21 structural ones (tie-backs, micropiles).
reinforces above-ground structures; OS21 works at foundation level.
Why it pays to qualify in OS21
OS21 has high barriers to entry: SIOS constraints, mandatory qualification and the complex machinery licence keep improvised companies out. Demand is growing:
· hydrogeological instability, affecting over 80% of municipalities;
· the seismic bonus and post-earthquake reconstruction;
· special foundations for major works.
If you work on special foundations, micropiles, tie-backs or jet grouting, OS21 opens up major contracts, reconstruction and the consolidation of public buildings.
SOA category OS21: frequently asked questions
What is the complex machinery licence?
What is the difference between OS21 and OS12-B?
Does OS21 include reinforcement of the above-ground parts of buildings?
Which works count as CEL for OS21?
Your next move?
Demonstrate your requirements and turn this knowledge into action: make sure you have the right SOA qualification and don’t hesitate to invest in training and innovation.
