Detailed design (EXE): what goes into a set of formwork and reinforcement drawings?

Formwork drawings, reinforcement drawings, bar schedules and calculation notes: what a detailed design package contains and what to check before issue.

Detailed design studies, known in France as EXE studies, turn a design into documents that can be built from. For a reinforced concrete structure, they mainly consist of formwork drawings, reinforcement drawings and calculation notes. Their quality has a direct impact on site: an incomplete or inconsistent drawing is paid for in stoppages, rework and non-conformities.

Where detailed design fits in a project

In the French organisation of design assignments, detailed design comes after the project design stage (PRO) and the tendering of contractors. It is most often carried out by the contractor or the engineering firm it appoints, then submitted to the design team for approval (VISA) before any use on site.

The EXE package does not simply reproduce the design: it incorporates the contractor's choices (methods, sequencing, any precast elements), the openings required by building services and the actual constraints of the site.

Formwork drawings

The formwork drawing defines the geometry of the concrete to be cast. It is the reference document for formwork crews and for the other trades. It generally includes:

• dimensioned plans, sections and elevations, with levels;
• thicknesses of walls, slabs and rafts, and sections of columns and beams;
• openings, sleeves and cast-in items resulting from coordination with building services;
• joints (expansion, shrinkage), construction joints and the casting sequence;
• concrete strength classes, exposure classes and the associated covers.

Reinforcement drawings

The reinforcement drawing describes the steel to be placed. It must be readable both by the bending yard and by the fixing crew. It shows:

• the mark of each bar or welded mesh panel, with diameter, number and spacing;
• anchorage and lap lengths, mandrel diameters and shape codes;
• links, stirrups and pins, as well as shear and construction-joint reinforcement;
• the bar schedule (developed lengths, weights per diameter);
• nominal covers and the position of spacers.

Detailing must comply with Eurocode 2 (EN 1992-1-1) and its national annex, but must also remain buildable: an area that is too congested with reinforcement makes concreting and vibration difficult and becomes a risk for the quality of the structure.

The calculation note

The calculation note justifies the choices shown on the drawings. It must be possible for a third party (design team, technical inspector) to read and check it. A well-structured note presents:

1. the assumptions: materials, exposure classes, geotechnical data, reference documents;
2. loads and their combinations according to Eurocodes 0 and 1 (and Eurocode 8 where seismic action applies);
3. the structural model: geometry, support conditions, stages considered;
4. ultimate and serviceability limit state checks: resistance, cracking, deflections;
5. a summary of the reinforcement areas adopted, directly linked to the drawings.

What to check before issue

• Consistency between formwork, reinforcement and openings: every opening must be dealt with in the reinforcement (trimmer bars).
• Interfaces with building services: openings must come from an approved coordination model, not from assumptions.
• Sequencing and construction joints: starter bars and joint reinforcement must match the actual sequence.
• Contractor methods: precast planks, precast elements or system formwork change the detailing.
• Revision control: every revision must be identified and tracked through the approval process.

In short

An effective EXE package is consistent, justified and designed for the site. ROKENG produces formwork drawings, reinforcement drawings, construction details and calculation notes adapted to site constraints, supporting construction companies and engineering firms.