Bands by intervention level
| Level | Cost per m2 | 150 m2 house | Content |
|---|---|---|---|
| Complete interior, envelope retained | EUR 800 - 1,100 | EUR 120,000 - 165,000 | Services, finishes, windows; no structural work |
| Full with envelope | EUR 1,100 - 1,600 | EUR 165,000 - 240,000 | Adds external insulation, roof, facades |
| Full with structure | EUR 1,600 - 2,200 | EUR 240,000 - 330,000 | Adds strengthening, floor slabs, structural openings |
| Premium | EUR 2,200 and above | EUR 330,000 and above | High-end materials and services |
As always, professional fees (12-15 per cent, higher than in apartments because of the structural component), VAT and a contingency reserve must be added, and here the reserve should be taken to 15-20 per cent: in a detached building the surprises are more numerous and more expensive. On a detached house those items weigh more than on an apartment.
The packages an apartment does not have
The roof. Recovering, insulation, possible replacement of the timber frame, rainwater goods: EUR 120 to 250 per m2 of roof slope, with significant jumps if the roof structure is decayed.
Facades and external insulation. Insulation systems, render, scaffolding on every side: EUR 90-160 per m2 of vertical surface, plus the cost of the scaffolding itself, which in a detached building is an item of its own.
Structure. Floor strengthening, framing for new openings, seismic improvement works: these are the trades with the greatest estimating uncertainty, because they depend on checks that only complete with opening-up works and surveys.
Whole-building services. Boiler room, distribution across several levels, external drainage, connections: larger in scale and length than an apartment's at equal usable area.
The typical extra costs of existing buildings
| Extra cost | When it emerges | Order of magnitude |
|---|---|---|
| Floor slabs needing strengthening | after structural opening-up | EUR 80 - 200 per m2 of slab |
| Rising damp in the walls | when stripping plaster | EUR 3,000 - 15,000 |
| Removal of hazardous materials | in the roof or pipework | by quantity, from EUR 3,000 |
| Bringing services up to code | at design stage | already included if properly estimated |
| Inadequate foundations | with structural verification | a significant intervention |
Hence the operating rule that distinguishes successful projects: surveys before the estimate, not during the works. Structural opening-up, verification of the foundations, damp testing, roof inspection: a survey package costs a few thousand euros and moves the estimate from hope to measurement.
Renovate or demolish and rebuild
Above a certain threshold of decay, rebuilding becomes competitive. The comparison, on a 150 m2 house. The comparison is made at equal floor area and equal level of finish.
| Item | Full renovation with structure | Demolition and rebuild |
|---|---|---|
| Works | 150 × 1,800 = EUR 270,000 | 150 × 1,800 = EUR 270,000 |
| Demolition and disposal | partial, EUR 12,000 | total, EUR 35,000 |
| Contingencies | 18% (EUR 48,600) | 8% (EUR 21,600) |
| Final performance | limited by the existing fabric | new-build level |
| Indicative total | EUR 330,600 | EUR 326,600 |
At nearly equivalent costs, rebuilding delivers new-build energy and seismic performance with halved contingencies. But the decision is not only economic: planning constraints (rebuildable volume, distances, possible landscape protections), longer permitting timelines and the applicable tax regime can reverse the comparison. It is an assessment to make with the designer on a preliminary design, using the new-build references in the article on residential construction costs.
Note: the figures shown are 2026 orders of magnitude for the Italian market, for guidance only. Every project requires preliminary surveys and a specific estimate based on a bill of quantities.