The effect is multiplicative, not additive
This is the point estimates most often understate. The amplitude between economy and high-end finishing exceeds double.
A change of range on one item is not a lump-sum extra: it applies to a quantity. A standard floor finish at around 25 euros per m² and solid oak parquet at around 100 euros per m² produce, on an 80 m² apartment, a difference in the order of six thousand euros for that item alone.
The same mechanism applies to kitchen, sanitary ware and joinery. Three or four simultaneous upgrades do not add up; they compound across different quantities, and the total far exceeds what each decision appeared to commit.
The items that carry the difference
| Item | Nature of the gap |
|---|---|
| Floor finishes | ratio of one to four between common ranges |
| Kitchen | most elastic item, no real ceiling |
| Sanitary ware and taps | wide gap between standard and designer ranges |
| External joinery | PVC, timber or aluminium, with performance effects |
| Internal joinery and stairs | frequently understated in comparisons |
| Lighting and accessories | low unit cost, high quantity |
The kitchen deserves separate treatment. It is the item with the widest amplitude and the only one without a natural upper bound. It is also the item most frequently excluded from offers, which distorts comparisons.
What distinguishes finish from quality
A costly confusion deserves clearing.
A high level of finish does not mean a better-built building. Structure, insulation, weathertightness and services belong to shell and second fix, not to finishes.
A building can be excellently built and finely finished, excellently built and soberly finished, or the reverse. The two dimensions are independent.
That distinction is useful when deciding: lowering the range of floor finishes does not degrade the construction, whereas reducing insulation or joinery touches performance and durability. The first decision is reversible, the second is not.
External joinery is a special case
It appears in the list of finish items but belongs there only half. External joinery in fact belongs to the closed shell.
The choice between PVC, timber and aluminium concerns appearance, but also thermal performance, weathertightness, durability and maintenance. An upgrade may be an aesthetic or a technical decision, and the two are not weighed alike.
It also represents a significant share of the closed shell, in the order of ten to fifteen per cent, which explains part of the price dispersion at that stage. Its performance level must therefore be stated in any comparison.
Deciding without weakening
Four principles from practice.
Distinguish the durable from the replaceable. A floor finish is changed in a week in fifteen years' time. Insulation or joinery is not. Decisions should bear first on what is easily replaced.
Decide by complete item, not by room. Two tile ranges in one dwelling often cost more than one, because of breaks and waste.
Decide early. A change of range after ordering incurs costs that cancel the saving.
Price the difference, not the range. The useful question is not whether a material is expensive but what the difference costs across the quantity actually laid.
What this means for an estimate
Three rules.
Always ask for the reference level of finish behind a quoted benchmark, or the comparison is empty.
Check whether the kitchen is included. It is the most frequent and heaviest exclusion.
Price finishes on real quantities, because a modest unit gap becomes significant once multiplied by area.
This article reflects professional practice and observed prices at the date of checking and serves as orientation. It does not constitute legal advice and does not replace assessment of the individual case.