Le Marquis de Versailles: 130 m² across two levels.

The starting point.

A 130 m² duplex in Versailles, to be fully renovated. On paper, a modest surface next to our other residential projects — half the size of Le Vénitien and its 240 m². In practice, a project that mobilised twelve craftsmen over six months, against nine over seven months for the apartment twice its size.

That single gap sums up the whole subject. Surface area is the figure clients look at first when sizing up a renovation; it is also the one that tells them the least. What drives the duration and complexity of a project is not the number of square metres — it is the number of interfaces: between rooms, between levels, and between trades.

What a second level really changes.

A duplex is not a bigger apartment: it is two apartments that have to work as one. Four consequences, none of which a floor area reveals.

• Every trade comes in twice. The electrician, the plumber, the plasterer, the painter: all of them work the lower level, then the upper one. These are not the same hours twice over — they are two mobilisations, two set-ups, two strip-downs. On a schedule, that translates into a density of people the surface does not justify: twelve craftsmen here, for 130 m².
• The staircase dictates the order of the works. It is both an item to build and the only route to the upper level. Until it is in place, supplying the upper floor is constrained; once fitted, it becomes a finished element that has to be protected while the rest of the works keep passing over it. That contradiction is settled in the schedule, not on site.
• The services cross a slab. Plumbing risers, supplies, waste, data cabling: in a duplex they no longer run horizontally alone but pass through a level. Every crossing is a technical point — and an acoustic one.
• Acoustics become an internal matter. In a single-level apartment, you insulate yourself from the neighbours. In a duplex, you also insulate yourself from yourself: footsteps, the staircase, water running between two levels occupied by the same family. It is dealt with in the invisible phases — insulating the intermediate slab, decoupling it, choosing the finishes — or it is never dealt with at all.

To all of this, this project added a work package rarely seen in an apartment renovation: structural works. As soon as a project touches the structure — slab, floor opening, load-bearing wall — it changes category. It calls for a prior study, an approval period, and often the consent of the co-ownership. It is the kind of decision settled in the first month of a project, never in the fourth.

Six months, twelve craftsmen: the mechanics.

Every work package was renewed: demolition, structural works, plastering, electrical, plumbing, painting, floor finishes. This is an all-trades renovation in the strict sense — nothing of the existing interior was kept as it was. The sequence:

Six months for 130 m² often comes as a surprise at first. It becomes logical as soon as you think in interfaces rather than surface: five phases, two levels, twelve trades to be crossed without getting in each other's way. We set out this arithmetic of timelines, format by format, in our article on renovation timelines.

Renovating in Versailles rather than Paris.

The planning rules are of the same nature on both sides: prior declaration or permit depending on the works, consent of the general meeting as soon as a common part is touched. Two differences are nonetheless worth anticipating.

Heritage. Part of Versailles falls within heritage protection perimeters: works visible from the outside — windows, façade, roof — may there be subject to the opinion of the Architecte des Bâtiments de France, with the corresponding approval period. For a purely internal renovation the constraint generally does not apply, but it is checked before costing, never after. We set out all these formalities and their real timelines in our guide to renovation permits.

Logistics. Access, parking for deliveries and permitted working hours govern the supply rhythm — and therefore the schedule. It is a parameter that appears on no quotation and yet weighs on the duration. It is anticipated during the technical survey, at the same time as the measured drawings.

What order of magnitude for 130 m²?

We do not disclose the budgets of our clients' projects. Our observed ranges, however, make it possible to situate an operation of this nature. For a full quality renovation, the works budget sits between €1,800 and €2,500/m², averaging around €2,000/m². Applied to 130 m², that gives an order of magnitude between €234,000 (130 × €1,800/m²) and €325,000 (130 × €2,500/m²), excluding furniture.

On a duplex, that rate per square metre pulls towards the top of the range rather than the bottom: the double mobilisation of the trades, the staircase and the treatment of the intermediate slab are items that do not dilute across the surface. The item-by-item breakdown of a full renovation budget is set out in our guide to renovation prices.

What this project taught us.

• Surface is a poor indicator of complexity — 130 m² across two levels called for more people than 240 m² on a single floor. What costs, in renovation, are the interfaces: those between rooms, between levels and between trades.
• Structure is decided first or never — a structural package moved mid-project does not only cost its own price: it costs the services already run, the partitions already built, and the weeks already spent.
• A duplex is designed as one whole — treating the upper level as a second phase, to be decided later, is the most common false good idea on this format. The two levels share their services: they must share their decisions.

Frequent questions.

How long does a full duplex renovation take?

On Le Marquis de Versailles, 6 months on site for 130 m² spread over two levels, with 12 craftsmen. A duplex generally takes one to two months longer than a single-level apartment of the same surface: every trade comes in twice, once per level, and the staircase dictates the order of the works.

Can the staircase of a duplex be moved during a renovation?

It depends on the nature of the floor opening and the slab. Moving or rebuilding a staircase touches the structure: the work falls under structural trades, requires a prior study and, in a co-owned building, the consent of the general meeting whenever a common element is involved. It is a decision to settle at the very start of the project, never mid-way through the works.

Renovating in Versailles: how does it differ from Paris?

The planning rules are of the same nature — prior declaration or permit depending on the works, co-ownership consent for common parts — but part of Versailles falls within heritage protection perimeters, which can make anything visible from the outside subject to the opinion of the Architecte des Bâtiments de France. Indoors, the difference is mainly logistical: access and parking for deliveries. W.A.R.D works across Paris and the Île-de-France region.

See the full project page and its gallery: Le Marquis de Versailles — 130 m², duplex. For other residential projects, browse our portfolio or our page on apartment renovation in Paris, and discover the work of our interior architecture studio.