The construction economist on refurbishment: what changes and which deliverables adapt

The refurbishment column reveals a single thread: uncertainty. It is present in every dimension of the work — measurement, ratios, risks, contingencies. This is not a weakness of method: it is the physical reality of a building whose true condition is unknown until the walls are opened. The economist's role is to quantify that uncertainty, document it, and propose realistic contingencies rather than hide it behind falsely precise figures.

On new build the economist can produce a reliable outline estimate without visiting the site; the drawings and the brief suffice in most cases. On refurbishment that is impossible.

The visit establishes the real condition of the fabric, identifies visible defects, makes sense of the existing spatial organisation and the constraints it places on the project, distinguishes what is to be kept from what is to be demolished, and assesses access difficulty and site conditions. Without a visit, any refurbishment estimate rests on assumptions that can prove very far from reality.

ℹ Visit before or after the surveys? Ideally the economist's visit follows the mandatory or advisable technical surveys: the pre-works asbestos survey, the lead survey, the infestation report, and an inspection of the roof structure where needed. Those documents let the economist build the constraints of asbestos or lead removal into the estimate from the outline stage. Where no surveys exist, the economist must say so explicitly and increase the contingency accordingly.

Refurbishment ratios are generally expressed in euros excluding VAT per square metre of habitable area, or per dwelling, rather than per square metre of floor area as on new build. They vary widely with the level of intervention: a light refurbishment — redecoration, replacement of equipment, bringing the electrics up to standard — costs quite differently from a heavy one involving external insulation, restructuring of the layout, a new lift and accessibility compliance.

The economist systematically distinguishes three levels: light refurbishment at 310 to 710 €/m² of habitable area, intermediate at 710 to 1,220 €/m², and heavy at 1,220 to 2,040 €/m². These bands are only starting points; the reality of any given project can depart from them significantly.

Measurement on a refurbishment means superimposing two states: what is in place and what is proposed. From that superimposition comes a third: the work to be carried out — demolition, creation, modification. Every element must therefore be classified as demolished, retained, created or modified.

That triple reading — existing, proposed, work — is more complex than measuring a new-build project, and it demands a level of detail in the drawings and a knowledge of the existing fabric that only accumulates through the studies and the opening up.

On refurbishment, demolition and strip-out form a package of their own and can represent 5 to 15 % of the total budget. It covers removing existing fittings — sanitary ware, joinery, finishes — masonry demolition, taking down partitions and suspended ceilings, managing and removing waste, and any asbestos or lead removal.

The package is particularly exposed to risk: asbestos found in materials the original survey did not identify, a partition that turns out to be load-bearing, buried services nobody recorded. The economist allows a contingency specific to this package, generally higher than for the others.

Refurbishment is the field where risks on site are the most frequent and the most costly. The table lists the principal sources of surprise, their frequency and their budget effect, together with ways of anticipating them.

The table illustrates a simple reality: on refurbishment, risks are not rare accidents, they are structurally frequent. The recommended contingency of 12 to 20 % is not pessimism, it is the statistical reflection of what refurbishment sites reveal systematically.

ℹ The classic error of optimistic pricing Using a contingency of 5 %, standard for new build, on a refurbishment exposes the client to recurrent overruns. Contractors themselves know the unforeseen is near-certain on refurbishment, which is why some load their prices accordingly while others bid low counting on recovering through variations. An economist who prices a refurbishment on a 5 % contingency does their client a disservice.

It must separate demolition and strip-out, safety and compliance work, energy improvement work, comfort improvement work and finishes. That breakdown lets the client make trade-offs family by family if the envelope is constrained.

The measure on a refurbishment is produced on what is called a differential basis: only elements modified or created are measured, those retained being simply listed and valued at their cost of maintenance. That approach requires precise existing drawings and proposed drawings that can be superimposed on them — a condition often hard to meet on older buildings that have never been surveyed.

Refurbishment specifications must carry clauses specific to the presence of the existing fabric: protection of what is retained, how to work in occupied premises where the building is inhabited, management of the interfaces between old and new, and traceability of hazardous materials discovered during the works. A refurbishment specification written as if it were new build guarantees dispute.

The frequency of variations justifies more intense cost monitoring than on new build: endorsement of the monthly valuations with particular attention to remeasured items, rapid assessment of variations arising from discoveries, an update of the budget dashboard at every finding. The economist must be responsive — a refurbishment variation not assessed quickly can hold up the whole site.

Quostra treats refurbishment as a speciality in its own right, with ratios calibrated on real refurbishment sites, a documented site-visit methodology, specifications carrying the clauses specific to the existing fabric, and contingencies sized to the condition of the building. The site visit — or, for remote projects, analysis of the surveys and photographs available — forms an integral part of every outline or developed-design assignment on a refurbishment.

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The construction economist on a refurbishment works under structural uncertainty: the real condition of the fabric emerges only as the studies and the works progress. That reality translates into ratios different from new build, differential measurement, higher contingencies — 12 to 20 % against 5 to 8 % on new build — specifications adapted to the presence of the existing, and reinforced monitoring on site. A refurbishment priced with the same tools and the same assumptions as a new-build project is a price that systematically under-states the real risks.

Reference basis of the figures

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 coefficient of 1.0205.

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 BT01 measures contractors' input costs, labour at 44.9 % and materials at 36.5 %, not the prices actually tendered.