In short
When do offices become an ERP (building open to the public)?
As soon as they receive members of the public, meaning outside people admitted freely or by invitation, whether or not they pay. Offices that only receive employees fall under workplace rules; if they receive the public, they become a type W ERP (building open to the public), with their own accessibility and safety rules and a works authorisation even without a building permit.
- 5th category for type W: public headcount below 100 people in basements, 100 on upper floors and 200 in total (only the public is counted).
- Public headcount: one person per 10 m² of the areas receiving the public, or one per 100 m² if the interior layout is not known.
- Works authorisation in an ERP: four months' processing time.
Offices and ERPs
A building open to the public (établissement recevant du public, ERP) is a building or premises to which outside persons are admitted, freely or by invitation, whether or not they pay. ERPs are classified by type of activity and by category according to the number of people admitted. Administrations, banks and offices fall under type W.
Offices that do not receive members of the public are not an ERP: they fall under the rules for workplaces.
The 5th-category thresholds
For type W, the establishment falls into the 5th category when the number of members of the public stays below the following thresholds: 100 people in basement levels, 100 people on upper floors, 200 people in total (ERP safety regulations, article PE 2). Only the public is counted for these thresholds. The public headcount is calculated at one person per 10 m² of the premises fitted out to receive the public, or one person per 100 m² when the interior layout is not known.
An authorisation, even without a permit
Works in an ERP are subject to a works authorisation (autorisation de travaux), even when they do not require a building permit: interior fit-out, partitions, change of activity. The processing period is four months. When the works require a building permit, the permit serves as the authorisation, with a specific file on accessibility and safety.
Accessibility
ERPs must be accessible to people with disabilities, whatever the disability. In an existing building, exemptions are possible on grounds of technical impossibility, heritage preservation or manifest disproportion, after the opinion of the competent commission.
The same architect publishes detailed guides, in French, on buildings open to the public: architecte-erp.fr and, for Paris, dossier-erp-paris.fr.
Frequently asked questions
Does receiving a few clients a day make my offices an ERP?
The notion of an ERP concerns the admission of outside persons. It is assessed case by case: the nature of the reception, the number of people admitted, the layout of the premises. Receiving clients occasionally may be enough; it is one of the first points we check.