Drawing a plaster faux ashlar in Versailles: when render imitates cut stone
Updated: Oct 27
In brief: in Versailles, some plinths that look like cut stone are in fact lime-free plaster render, divided into courses by drawn joints. A flat arch (plate-bande) usually has an odd number of voussoirs around a central keystone, and its joints are neither vertical nor parallel: they point towards a spot on the axis of the opening. A correct layout is judged at first glance. In a remarkable heritage site, this kind of work falls under the authorisation regime of the French Heritage Code, with the possible approval of the Architecte des Bâtiments de France (ABF).
Updated on 25 October 2026.
On some classical façades in Versailles, what looks like a cut-stone plinth is only plaster render. It is laid flat, then divided into courses by joints drawn into the fresh material. Making this imitation convincing takes more than a straightedge: you have to understand the logic of the stone being imitated.
Plaster, a stone of illusion in the Île-de-France
Imitating stone with plaster render is a well-documented Île-de-France tradition. The research programme of the French Historic Monuments Research Laboratory on plaster façade renders in the Île-de-France gives an example: at the Château de Méréville, remodelled in 1784, a classical decor was applied over older walls using plaster renders, with rustication lines drawn into the fresh render and plaster window surrounds and cornices.
Plaster made it possible to give a ground floor the visual weight of stone without massive stone blocks. On the material and what the ABF expects, see our article on plaster façades in Versailles.
The flat arch: geometry before decoration
Viollet-le-Duc defines it as a lintel built of voussoirs, that is, cut stones set on two jambs. It is therefore not a stone beam: it is an assembly whose strength comes from the shape of its pieces.
To draw its imitation, three principles guide the design, the details depending on the type of flat arch and the setting-out chosen:
the number of voussoirs is generally odd, so that a keystone sits at the centre;
the joints are neither vertical nor parallel: they point towards a spot on the axis of the opening;
the keystone is symmetrical and centred on the axis of the bay.
This art of the line belongs to stereotomy, the science of cutting stone. Long a guarded mason’s knowledge, it was set down in drawings in treatises from the Renaissance onwards. Frézier, in his Treatise on Stereotomy (1754-1769), devotes a problem to the height of the voussoirs of a flat arch.
On a site on boulevard du Roi
During a façade renovation led by the Atelier on boulevard du Roi in Versailles, the street-side ground floor was stripped back entirely. The flat surfaces were reworked set back from the retained stone plinth, with crisp plaster arrises. The joint drawings of the ground floor were then carried out, and the window surrounds and mouldings were restored to their original design.
The flat arch over the carriage entrance needed particular attention. At site inspection, it was asked to be redone so that it fans out more than before, and the design of its keystone was to be refined in relation to the finished face of the façade.
Why this precision matters
Poorly drawn faux ashlar is noticed at first glance: vertical joints above a window, lopsided voussoirs or an off-centre keystone spoil the elevation. Conversely, correct geometry makes the imitation disappear. This is where the role of the architect as project manager lies: designing the coursing, then overseeing its execution on site.
The City of Paris recommendations for façade renovation advise, for renders imitating stone, repairs in the same kind of material and prior trials. In Versailles, the choice of material and finish must be based on a diagnosis of the existing building and the heritage requirements that apply to it.
Frequently asked questions
Are drawn false joints original?
Often, on classical and nineteenth-century façades. Only examining the render layers and the archives can establish it for a given building.
How can you tell plaster faux ashlar from real cut stone?
In raking light, the joints of faux ashlar appear as shallow incisions in the thickness of the render, without the depth of a joint between two blocks.
Is authorisation required to redraw faux ashlar?
In a remarkable heritage site, work likely to change the exterior appearance of a façade is subject to the authorisation regime of the French Heritage Code. Depending on the protection that applies, the approval of the Architecte des Bâtiments de France may be required. Check the procedures with the local planning department before any work.
Conclusion
Plaster faux ashlar is a stone of illusion that demands the rigour of real stone. On a Versailles façade, preserving or restoring it keeps the original architecture legible.
On this site: the Atelier and your questions
Antoine de Gironde
Architect DESA — Registered with the Ordre des Architectes no. 084305
Atelier d’Architecture Antoine de Gironde
10 rue de Fontenay, 78000 Versailles
Going further
Sources
Laboratoire de recherche des monuments historiques, newsletter no. 4 "Les enduits de façade en plâtre d’Île-de-France", January 2018 (Château de Méréville): museeduplatre.fr
Viollet-le-Duc, Dictionnaire raisonné de l’architecture française du XIe au XVIe siècle, 1864, entry "Plate-bande", p. 207.
Frézier, La théorie et la pratique de la coupe des pierres et des bois, ou Traité de stéréotomie, 1754-1769, volume III (appendix): archive.org
Bibliothèque nationale de France, "Pratique et théorie de la coupe des pierres": passerelles.essentiels.bnf.fr
City of Paris, Urban Planning Department, façade renovation recommendations, sheet 10 "Façade in mortar or render imitating stone": cdn.paris.fr
French Heritage Code, article L632-2 (approval of the Architecte des Bâtiments de France in remarkable heritage sites).
