BTS Bâtiment common mistakes
BTS Bâtiment · Understand the traps and how to avoid them.
Reading the CCTP/descriptive specification as if it were a plan set, then answering design questions with dimensions taken from the written document instead of from the drawings and the scale.
Candidates conflate the written technical clauses (CCTP) with the graphical design documents (plans, coupes, façades) and assume any figure found in the dossier is authoritative.
What to do instead
Before answering, classify each document in the dossier (pièce écrite vs pièce graphique) and state which document governs the quantity or dimension you are about to use; when a written and a drawn value conflict, look for the coordination clause and note the discrepancy explicitly.
Applying a load or span formula without checking the units and the support conditions (simple span vs continuous, encastrement, porte-à-faux) implied by the sketch.
Exam sketches are schematic; candidates pattern-match to the formula they memorised last and skip the boundary-condition check, mixing kN/m, daN/m and kg/m in the same calculation.
What to do instead
Write the boundary conditions in one line before computing (appuis simples, nombre de travées, charges permanentes vs variables), convert all inputs to a single unit system at the top of the calculation, and sanity-check the result against an order of magnitude (e.g. flèche admissible L/300 to L/500).
Producing a planning exercise (réseau, Gantt) with links that ignore real construction logic, such as starting la pose des cloisons before les dalles are cured or scheduling the grue without its montage/démontage.
Candidates optimise the diagram for a tidy critical path rather than for physical sequencing, and forget the prerequisite tasks that carry duration but no obvious quantity.
What to do instead
Build the task list from the lot structure first, then state the predecessor for each task with a reason (séchage, cure, décoffrage, livraison); add the installation/removal of major equipment and the intempéries/attente tasks explicitly before computing the chemin critique.
Sizing installations de chantier (base vie, aires de stockage, grues, bennes) from a generic ratio instead of from the actual phasage and quantities of the project.
Under time pressure, candidates reproduce a rule of thumb seen in a corrigé without checking whether the project's phasage, site area or delivery frequency makes it valid.
What to do instead
Derive each installation need from an explicit quantity (effectif de pointe, tonnage livré par semaine, surface de stockage par lot) and show the phasage assumption behind it; if the data is missing, state the hypothesis rather than defaulting silently.
Writing a mode opératoire or a sécurité note that lists PPE but omits the specific risk of the task (coffrage en hauteur, tranchée, levage, travaux en présence de réseaux).
Candidates treat the safety section as a generic checklist to fill rather than as a task-specific analysis, and do not connect the risk to the means de protection and the ordre des opérations.
What to do instead
For each major task, name the dominant risk, the protection adopted (étaiement, blindage, garde-corps, plan de levage) and the control point before the next phase starts; tie each measure to the phase of the mode opératoire where it applies.
Answering a conduite de chantier scenario by describing what should ideally happen rather than by reacting to the concrete event given (retard de livraison, malfaçon, intempérie, ordre verbal du MOE).
Candidates default to a textbook description of good practice and skip the immediate actions, the traceability and the contractual consequences that the scenario is testing.
What to do instead
Structure the answer as: constat factuel, action immédiate sur le chantier, information écrite aux parties (compte rendu, OS, réserve), conséquence planning/coût, puis mesure préventive; always name who writes what to whom.
Confusing the roles and contractual levers of MOA, MOE, entreprise and bureau de contrôle when answering a question about an ordre de service, a réserve or a réception.
The actors overlap in everyday speech and candidates use them interchangeably, so the answer attributes the decision to the wrong party.
What to do instead
For each scenario, write one line identifying who decides, who executes, who controls and who pays before drafting the answer; check that any OS or reserve is issued by the party actually empowered to do so.
Building a devis or a budget with a forfait global instead of a décomposition (sous-détail de prix) that separates main-d'œuvre, matériaux, matériel and frais généraux.
Candidates jump to the total price and skip the sous-détail, so they cannot justify the figure or adjust it when a quantity or a rate changes in the scenario.
What to do instead
Always produce the sous-détail first (temps unitaire × taux horaire, quantité × prix matériau, matériel, frais), then aggregate; keep the unit and the source of each rate visible so the total is auditable.
Ignoring TVA, retenue de garantie, actualisation, révision de prix or délais de paiement when computing a marché amount or a situation de travaux.
Candidates focus on the HT works total and treat the financial and contractual clauses as decorative, forgetting that the exam scenario deliberately includes them.
What to do instead
Use a fixed checklist for any financial calculation: HT → TVA → TTC, avance/retenue de garantie, révision (index, formule), then the net à payer at the situation date; tick each line even when the value is zero.
Writing a note or a compte rendu without a clear addressee, a decision requested and a traceable reference, so the answer reads as a description rather than a professional communication.
Candidates reproduce course content instead of adopting the role and the register of the writer, and omit the object, the reference and the expected action.
What to do instead
Impose a fixed frame: émetteur/destinataire, objet, référence, faits, analyse, décision ou action attendue avec échéance; reread to confirm a reader could act on it without further information.