Heavy refurbishment costs: ratios by building type and level of intervention

Costing a refurbishment is not costing new build made more complicated. The difference runs deeper: on new build the brief is defined and the economist can foresee every element. On refurbishment part of the work is unknown until the walls are opened, and that unknown part can represent 15 to 30 % of the final budget.

The uncertainty shows at several levels. The real condition of the structure is known only after opening up and surveys. Hazardous materials such as asbestos and lead may not have been fully identified before the works. Existing services may be in worse condition than estimated. The interfaces between old and new generate costs that are hard to foresee.

That is why refurbishment ratios systematically carry higher contingencies than new build, 12 to 25 % according to the level of intervention, against 5 to 8 % on standard new build, and a systematic recommendation for surveys before any binding estimate.

The rule on prior surveys

Any refurbishment estimate produced without the following surveys must carry an explicit statement about its reliability: a pre-works asbestos survey for any building constructed before July 1997, a lead exposure report for dwellings before 1949, an inspection of the roof structure where it is not visible, and an energy audit where a thermal refurbishment is envisaged.

An estimate produced with those surveys is reliable to ± 15–20 %. Without them the band of uncertainty is ± 30–40 %.

Refurbishment is not one category but a continuum from simple redecoration to near-complete restructuring. Defining the level precisely is the first step of any refurbishment estimate.

These levels are not mutually exclusive. A programme can be light on finishes and heavy on the thermal envelope; the economist then builds a hybrid estimate, package by package, rather than applying a single global ratio.

The table crosses the levels of intervention with the principal uses. The ratios are per square metre of habitable area for housing, per room for hotels, and per square metre of usable area for the others. They include demolition and strip-out but exclude fees, land and external works.

Note: listed or protected buildings attract specific premiums arising from the requirements of the heritage architects: substitute materials, traditional methods, longer approval times. These can double the ratio of a standard refurbishment. For protected buildings a specialist estimate from an economist experienced in heritage work is indispensable.

The age of the building is the principal risk factor not visible in a refurbishment estimate. The older it is, the higher the probability of finding hazardous materials, degraded structure or obsolete services.

Asbestos: the most financially significant risk

Buildings constructed between 1950 and 1975 have the highest probability of containing asbestos in many materials: sprayed fire protection, pipe lagging, vinyl tiles, tile adhesives, external renders, movement joints.

Removing friable asbestos is carried out in a sealed enclosure by certified contractors, at a cost of 310 to 820 €/m² of area treated. Removing asbestos from an apartment building of the 1960s or early 1970s can represent 100,000 to 500,000 € of unanticipated cost if no survey was carried out before pricing.

On refurbishment, demolition and strip-out is not an incidental item; it is often the second or third largest by value, representing 8 to 15 % of the total according to the level of intervention. It covers careful removal of elements to be reused, demolition of partitions and floors to be rebuilt, removal and sorting of waste, and any asbestos or lead removal.

Managing demolition waste is governed by the French environmental and circular-economy legislation, which requires a waste survey before demolition for buildings above a certain size. That survey identifies recoverable materials and hazardous waste, and its cost of 1,000 to 5,000 € is amply recovered in savings on sorting and recovery.

Unlike new build, where the economist measures the works on the project drawings, refurbishment requires the existing and proposed drawings to be superimposed in order to identify what is to be demolished, what is to be retained and what is to be created. That differential method is longer and more complex than standard measurement, which is why a refurbishment estimate takes more time than a new-build estimate of the same area.

The contingency on a refurbishment is not a comfort margin, it is a provision statistically founded on the frequency of discoveries during construction. On the refurbishment sites monitored, unforeseen risks average 12 to 18 % of the original contract on heavy refurbishment. Presenting a refurbishment estimate without an explicit contingency is a professional fault.

The question arises regularly on badly degraded buildings. The answer depends on several economic and regulatory parameters.

• Comparative cost: a complete restructuring costs 1,530 to 2,550 €/m² of habitable area, close to new build at 1,630 to 2,550 €/m² of floor area. If the refurbishment exceeds 70 to 80 % of the cost of rebuilding, demolition and reconstruction often becomes the more rational solution.
• Regulatory constraints: an existing building often carries acquired rights on height, footprint and density that a new building could not fully recover under the current local plan. Those rights can economically justify a dearer refurbishment.
• Programme and occupation: refurbishing an occupied building is more constrained but avoids mass rehousing. Demolition and reconstruction implies rehousing everyone, a cost and a complexity to include in the comparison.
• Carbon footprint: refurbishment retains the carbon embodied in the existing structure, a strong argument for clients committed to a low-carbon approach. The carbon value of a kilogram of concrete retained against a kilogram of new concrete is increasingly built into decisions.

You have better things to do. Submit your refurbishment project on quostra.com; estimate with levels of intervention and contingencies within 72 working hours.

Refurbishment ratios run from 260 €/m² of habitable area for light redecoration to more than 2,550 €/m² for the complete restructuring of a heritage building. Four parameters structure every refurbishment budget: the level of intervention, the use of the building, its age and the hazardous materials that go with it, and the quality of the prior surveys. A contingency of 12 to 25 % is not optional, it is the financial translation of refurbishment's structural uncertainty. The question of demolition and reconstruction arises systematically once the refurbishment cost exceeds 70 % of the cost of rebuilding.

Reference basis of the figures

These bands are orders of magnitude for framing, and their reference market is the Paris region. They serve to place a budget at the earliest stages and to compare building types with one another. They replace neither a tender exercise nor an estimate prepared on drawings, and they are not a record of prices actually charged.

The ratios per square metre and per item on this page are stated in January 2026 values. They were updated from January 2025 values, the basis adopted for the whole cocoon, using the BT01 all-trades index published monthly by INSEE on its 2010 base: 132.0 in January 2025, 134.7 in January 2026, a rise of about 2 %.

The global amounts quoted as examples, and any rents, charges or receipts expressed per year or per night, remain on their own basis: a building cost index does not apply to them.

To bring the ratios forward, apply the usual revision formula: updated value = page value × (BT01 for the month in question / 134.7). The index has kept rising since: it stood at 138,3 in June 2026, the last value published when this page was checked, that is 2,7 % above the reference base. BT01 measures contractors' input costs, wages and social charges, materials, plant and energy, not the prices actually tendered.

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