Regulatory risks in construction: accessibility, fire, environmental and seismic

The table gives, for each major requirement, the cost according to the stage at which it is discovered, from design at zero to construction, where it is catastrophic.

The table reveals a fundamental asymmetry: every requirement built in at concept stage costs nothing or next to nothing, being part of normal design. Discovered on site, most trigger costs of 30 to 150 k€, or a stoppage. Appointing a specialist engineer at outline stage costs 3,000 to 15,000 € according to complexity, a return of ten to fifty times if a single non-conformity is avoided.

Accessibility for people with reduced mobility is governed by the 2005 act and its implementing decrees. It imposes different obligations by programme: 100 % of social dwellings must be accessible, 20 % of new private dwellings, 100 % of buildings open to the public in the first four categories, and the common parts of every new residential building.

• The forgotten lift: any building above two upper floors must have a lift. If the shaft is not planned at outline stage, adding it at developed design forces the whole layout to be reconsidered. The cost of an unplanned lift shaft at developed design: 25 to 60 k€ in structural work alone.
• Insufficient turning circles: wheelchairs need turning spaces of 1.50 m by 1.50 m in the common parts, the bathrooms and the WCs. Corridors slightly too narrow, or 80 cm doors instead of 90 cm, can require a complete redesign of the layout.
• Larger public buildings: big retail units, performance venues and substantial schools carry reinforced requirements, external routes, adapted parking, signage, which can represent 5 to 10 % of the total budget if not built in from the design stage.

ℹ The rule of 90 centimetres In the great majority of accessibility non-conformities discovered during construction, the error comes down to 10 centimetres: an 80 cm door instead of 90, a 1.30 m corridor instead of 1.40, a shower of 0.90 by 1.20 m instead of 1.20 by 1.20. Those 10 centimetres, unnoticed on a 1:100 drawing, become a major problem on site. Systematically checking the accessibility dimensions on the 1:50 drawings at developed design, package by package, is the most profitable investment against this risk.

The environmental regulations, applicable to new construction since 1 January 2022, introduce a double requirement generating two distinct risks for clients and design teams.

The bioclimatic indicator measures the efficiency of the building envelope independently of the energy systems. An insufficient figure requires either revisiting the envelope, reinforced insulation, triple glazing, or compensating with higher-performance systems; both cost money. The risk: designing the outline without thermal modelling and discovering at developed design that the envelope does not meet the thresholds.

The construction carbon indicator measures the greenhouse gas emissions of the materials used. It is the least known risk and potentially the most blocking: if it exceeds the regulatory threshold, which tightens progressively to 2031, the project cannot obtain planning permission. The choice of structural materials, concrete against timber against steel, at outline stage is decisive for that indicator, and changing structural system at developed design is very expensive.

ℹ Thresholds that tighten The thresholds harden in steps: 2022, 2025, 2028, 2031. A project designed with the 2022 thresholds in mind whose application has slipped past a step must meet the new ones, which can force a revision of materials or systems mid-design. The best protection: model the construction carbon from outline stage with the materials envisaged, and check compliance with the thresholds of the step foreseeable at the date of the application.

Fire regulation distinguishes two bodies of rules by the use of the building: the labour code for workplaces such as offices and warehouses, and the safety regulation for buildings open to the public. The two have very different requirements, and their interaction, on a mixed office and retail building, for instance, is a frequent source of anticipation errors.

• Smoke control: every common circulation longer than 30 m and every room above 300 m² must have smoke control. The system, natural or mechanical, must be sized from outline stage; the air inlets and smoke outlets impose constraints on the façade and the structure.
• Sprinklers: mandatory in first-category public buildings and warehouses above 6,000 m². The sprinkler network represents 15 to 30 € excluding VAT per square metre according to the density required. If not planned at outline, adding it at developed design means revisiting the service distribution in the ceilings, with a cascading effect on the other technical packages.
• Fire compartmentation: fire-resisting compartments impose specific construction whose unit cost can be two to three times that of ordinary partitions. Forgetting them at outline can significantly under-state the partition packages.

Mainland France is divided into five seismic zones. Zones three and four, the Alps, the Pyrenees, the Caribbean, part of Alsace, impose seismic requirements that generate a premium of 5 to 15 % on the structural cost. In the overseas territories, in the highest zones, that premium reaches 15 to 25 % of the structure.

The frequent error is to apply standard provincial ratios to projects in a seismic zone without the correcting coefficient. On a 3 M€ programme, forgetting a 10 % seismic premium is a 300,000 € gap between the outline estimate and the developed-design reality.

Preventing all these risks rests on a single discipline: doing the complete regulatory checklist at the right stage, with the right party.

The table confirms the rule stated at the outset: the ratio between the cost of a non-conformity found on site and the cost of the same requirement built in at concept stage is between eight and fifty times, according to the regulation. For seismic and environmental requirements the ratio is no longer calculable at all, late discovery can make the project technically impossible without partial demolition.

Regulatory risks follow an implacable law: found at concept stage, their cost is nil or marginal. Found on site, they cost from 30 k€ to the total stoppage of the project. The four most frequent traps are the forgotten accessible lift or ramp, the carbon thresholds not modelled at outline, sprinklers built in too late, and the seismic coefficient not applied outside the Paris region. The ten-point checklist, verified by the right party at the right stage, is the most profitable preventive investment in this cocoon: for a specialist engineering cost of 3,000 to 15,000 €, it avoids corrections of 30 to 200 k€.

The nature of the figures quoted

The percentages and amounts quoted on this page are orders of magnitude for framing, not measurements. They illustrate mechanisms and proportions, and they substitute neither for a tender exercise nor for an estimate prepared on drawings.

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