1. Refurbishment against new build: the eight differences that change the economics
The first error in a refurbishment estimate is to apply the methods and rates of new build to an existing building. The two exercises share the names of the trades and sometimes the materials, but their economic logic differs on eight fundamental points.
| Dimension | New build | Refurbishment | Economic impact |
|---|---|---|---|
| Knowledge of the fabric | Ground investigated, drawings precise | Existing fabric only partly known; surprises behind the render, in the floors, in the services | Contingency of 5–8 % in new build against 10–20 % in refurbishment |
| Basis of the quantities | Complete drawings, quantities reliable to ± 5 % | Drawings often partial or absent, quantities to ± 15–25 % at outline design | An outline refurbishment estimate is a wide range, which is normal and has to be said |
| Specific items | No strip-out or demolition | Strip-out, selective demolition, clearing, asbestos and lead removal: 5 to 15 % of the budget | Items routinely missing from do-it-yourself estimates |
| Regulatory constraints | The environmental regulations for new build | Energy requirements plus the energy performance certificate, accessibility, and public-access rules if the use changes | Bringing the building into compliance is an unplanned extra if it surfaces late |
| Hazards during the works | Rare; ground and drawings well known | Frequent: old masonry, decayed roof timbers, non-compliant services, residual asbestos | More instructions and variations, a more complex final account |
| Contractual regime | Standard contract, standard conditions | Reinforced conditions: unforeseen works clauses, unforeseen site conditions, explicit provisions | Without adapted clauses, every hazard becomes a dispute |
| Phasing | Free phasing in an empty building | Often occupied, constrained phasing, tenant interfaces, reinforced safety planning | Cost of phasing: 8 to 15 % above works in a vacant building |
| Duration of the appointment | Standard, one estimate per major stage | Longer, with frequent revisions as things are discovered, and many variations | Refurbishment fees exceed new build fees for the same area |
The most structural difference is the contingency. In new build, 5 to 8 % is standard. In refurbishment, 10 % is a minimum, and 15 to 20 % is advisable on heavy refurbishment or on older buildings, from before 1945, whose structure is only partly known. That provision is not a sign of poor work by the economist: it is an honest quantification of the uncertainty that remains in an existing building.
2. Benchmark rates in refurbishment
Refurbishment rates vary more than new build rates, because they depend heavily on the initial condition of the building, on the level of specification and on the exact scope. The ranges below are orders of magnitude for projects in France outside the Paris region, to which 15 to 25 % should be added inside it.
| Type of work | Range per m² | Conditions | Warning sign |
|---|---|---|---|
| Light refurbishment, finishes only | 200 – 400 €/m² | Paint, floors, sanitary fittings, structure retained | Below 200 is understated; above 400, check the scope |
| Intermediate refurbishment | 400 – 700 €/m² | Plus partitions, electrical, plumbing, internal insulation | A wide range; a breakdown by package is essential |
| Heavy refurbishment | 700 – 1 200 €/m² | Plus roof structure, covering, façades, partial structure | Close to new build; the demolition trade-off arises |
| Complete refurbishment | 1 000 – 1 800 €/m² | Structure retained, everything else renewed | Has to be justified against demolition and rebuilding |
| Energy retrofit alone | 80 – 250 €/m² | Insulation, windows and services, depending on ambition | Varies with the target rating and the grants available |
| Asbestos removal plus refurbishment | + 50 – 200 €/m² | The extra depends on the nature and quantity of asbestos | An asbestos survey is compulsory before any estimate |
| Common parts in an apartment block | By package | Façades 150–400 €/m², roof 100–250 €/m² | Apply rates by package, never a global rate |
ℹ The heavy refurbishment trap: when to compare against demolition When a complete refurbishment exceeds 1 200 €/m², the comparison with demolition and rebuilding becomes unavoidable. On a scheme of 1 000 m², the difference between the two options can be 200 000 to 500 000 €, and rebuilding may offer better energy performance and greater durability. The economist should produce that comparison systematically whenever the refurbishment estimate exceeds 80 % of the cost of an equivalent new building. It is not an architectural judgement, it is an economic decision the client must be able to take on the strength of a costed comparison.
3. The eight families of tools
This cluster covers the eight families of economic questions specific to refurbishment.
| Family | Key questions |
|---|---|
| Economic survey | How do you produce a reliable budget with no drawings? Which surveys should be commissioned, and at what cost? |
| Apartment block economics | How do you budget works on common parts? Who is the client? How is the work voted and financed? |
| Refurbishment measurement | What measurement rules apply to strip-out, demolition and retained fabric? Are the units the same as in new build? |
| Energy regulations | Energy requirements, performance certificates, poorly rated dwellings, grants: how do the obligations and the subsidies enter the budget? |
| Accessibility | What obligations apply in refurbishment by building type? What does compliance cost? What exemptions exist? |
| Refurbishment contracts | How do you write conditions of contract that protect the client against the unforeseen? Unforeseen conditions, hidden work, provisions. |
| Site control | How do you handle discoveries, issue instructions to vary, value the variations? The five commonest surprises. |
| Retrofit payback | How is the return on investment calculated? Energy saved against the cost of the works, payback period, grants. |
4. The items specific to refurbishment
The preliminary surveys
Before any estimate, several compulsory or advisable surveys determine how reliable the budget can be. Their cost belongs in the overall envelope, and their findings can move the works estimate significantly.
Asbestos survey before works: compulsory for any building whose planning permission predates July 1997. Cost: 500 to 2 500 € depending on the area. It can trigger an asbestos removal contract adding 50 to 200 €/m².
Lead survey: compulsory before works on dwellings built before 1949. Cost: 300 to 1 500 €. Lead removal can represent 30 to 100 €/m² depending on the nature and quantity of material affected.
Energy audit: advisable before any significant energy retrofit, and compulsory before selling a poorly rated property. Cost: 500 to 1 500 €. It is indispensable for calculating the payback and for claiming the grants.
Structural survey: advisable on buildings from before 1948, where there is cracking, doubtful floors, or structural change in prospect. Cost: 500 to 3 000 € depending on the scope. It can reveal strengthening work nobody had allowed for.
Measured survey of the existing building: on projects with no drawings, a precise measured survey is indispensable before any tender. Its cost, 1 000 to 5 000 €, is negligible against the measurement errors it prevents.
Strip-out and demolition
Strip-out and selective demolition are specific to refurbishment and are routinely understated, because they precede the visible works and produce nothing tangible. They nonetheless represent 5 to 15 % of the total budget depending on the scope.
Removing finishes, tiling, flooring, linings: 2 to 8 €/m² depending on the material and on access.
Demolishing partitions: 8 to 25 €/m² depending on the material, plaster, brick, concrete, and on how the debris is removed.
Removing windows and doors: 80 to 200 € each depending on type and height.
Removing services, plumbing, electrical, mechanical: usually taken as a lump sum per trade; allow 15 to 25 % of the cost of reinstallation.
Removal and disposal: an item often forgotten, at 80 to 200 € a tonne depending on the waste stream; asbestos waste costs five to ten times that.
Phasing and working in an occupied building
Works in an occupied building, a let block with tenants remaining, a block of flats with constrained access, a public building still in use, add 8 to 15 % to the packages concerned. Those costs have to be written explicitly into the tender documents and carried in the estimate as a dedicated line for working in occupation.
5. The economic chain of a refurbishment project
The economic chain follows the same broad stages as new build, with additional milestones tied to the surveys and to progressive discovery.
Stage 1, feasibility: an envelope budget from overall rates at ± 25 %, carrying the high contingency from the outset.
Stage 2, surveys: commissioning the surveys and reflecting them before outline design; their findings can move the envelope by 10 to 30 %.
Stage 3, outline and developed design: a detailed estimate by package with quantities taken from the measured survey, accurate to ± 15 % against ± 8 % in new build at the same stage.
Stage 4, tender: conditions of contract adapted with unforeseen works clauses, a specification carrying the occupied-building constraints, and a priced bill with explicit strip-out items.
Stage 5, tender assessment: analysing the tenders in the light of the assumptions about the existing fabric, and checking that the contractors have allowed for the specific constraints.
Stage 6, construction: close tracking of discoveries, frequent instructions to vary, a variations dashboard kept continuously up to date.
Stage 7, final account: price adjustment reflected, unforeseen works accounted for on the basis of the instructions, and the residual contingency released.
6. The regulatory specifics of refurbishment
Refurbishment carries a denser regulatory stack than new build, because it has to satisfy both the obligation to bring the existing building into compliance and the requirements applying to the new work. Three regimes have a direct economic impact.
Energy requirements in refurbishment: the performance obligations differ from those for new build and apply package by package according to the work undertaken, replacing windows, insulating, renewing the services. Both the trigger and the level of requirement vary with the nature and scale of the intervention.
Accessibility in refurbishment: the obligations depend on the type of building, on the nature of the works, and on whether the use changes. Compliance can represent 3 to 8 % of the budget depending on the starting deficit.
Heritage protection: listed buildings, and those within the setting of a historic monument, are subject to technical constraints and consent procedures that can raise costs by 15 to 40 % depending on what the heritage architect requires.
The nature of the figures quoted
The percentages and amounts quoted on this page are orders of magnitude for framing, not measurements. They illustrate mechanisms and proportions, and they substitute neither for a tender exercise nor for an estimate prepared on drawings.
Articles liés
- How to produce a reliable refurbishment budget with no drawings
- Works in an apartment block: budget, vote and financing
- Energy requirements and grants in refurbishment: obligations and budget
- Refurbishment contracts: unforeseen works and unforeseen conditions clauses
- The payback on an energy retrofit: how the economist calculates it
- Asbestos, lead and the works budget: reflecting the surveys in the estimate
- Structural risks in refurbishment: assessing the unforeseen before you start
- Measurement rules specific to refurbishment
- Accessibility in refurbishment: obligations, costs and exemptions
- Unforeseen works on a refurbishment site: instructions, variations and provisions
- Outsourcing the cost work on a refurbishment: the real calculation
- Construction costs in France: rates per m², building types and the factors that move them
- The economic risks of a construction project: the complete picture
Sources: the BT construction cost indices published monthly by INSEE on its 2010 base, used to update the figures · construction cost statistics from SDES, the statistical service of the ministry responsible for construction · regulatory texts published in the Journal officiel and consolidated on Légifrance for the requirements cited.