The essentials in 30 seconds
- A per-square-meter estimate is only for framing; only a trade-by-trade estimate with quantities is binding.
- Construction prices move constantly: a price list that hasn't been updated in 6 months is already wrong.
- Two distinct margins: 5–10% technical contingency in the estimate, 15–20% reserve on the client's side.
- Context (access, older building, occupied site) can push a trade package up by 15–30%.
- An estimate only exists once it's presented: clear versions, correct VAT, readable options.
Why cost estimation is where projects are won or lost
In our conversations with interior designers, the quote comes up again and again as the profession's number-one pain point — even before project tracking. The reason is simple: a bad estimate costs you twice. Too high, and you lose the project. Too low, and the end of the job turns into a running negotiation over change orders — at the expense of the client relationship and your margin.
The good news: estimating is a skill of method more than intuition. It can be structured.
The 6-step method
- Thorough site survey and assessment. Actual surfaces (not the ones in the listing), the condition of what's already there (electrical, plumbing, substrates), access constraints (floor level, elevator, parking). Anything you don't survey, you'll discover on site — the hard way.
- Breakdown into trade packages. Demolition, structural work, plumbing, electrical, insulation, partitions/plasterwork, joinery, floor and wall coverings, painting, finishes. This granularity is what lets you compare contractors' bids and manage options.
- Quantities for each trade. The take-offs: square meters to paint (walls + ceilings, not floor area), linear meters of baseboards, number of electrical points… A wrong quantity makes even the best unit price useless.
- Applying reference prices. This is where the freshness of your data makes the difference — see the ranges below. Adjust each price to the specifics of the job rather than applying a national average.
- Explicit margins and contingencies. Build 5–10% technical contingency into the estimate, and recommend in writing that your client set aside an overall reserve of 15–20%. Making uncertainty visible protects the relationship — hiding it destroys it.
- Formatting the quote. Numbered versions, the right VAT rate on each line (10% for improvement work, 20% in certain cases, 5.5% for energy-efficiency work), options kept separate from the base scope. Great substance never rescues an unreadable format — we covered this point in our guide to quoting software for interior designers.
2026 reference prices (Paris region)
Indicative ranges observed in mid-2026 across the Paris-region market. Every job is specific — these figures are a starting point, not a selling price. (In Nodal, the connected pricing library gives you these references updated every month, line by line.)
| Trade package | Unit | Range (Paris region, 07/2026) |
|---|---|---|
| Wall and ceiling painting (prep + 2 coats) | m² treated | €25–45 |
| Plasterboard partition (supply, install, taping) | m² | €45–75 |
| Engineered wood flooring (supply + install) | m² | €60–120 |
| Electrical — full renovation | m² living area | €90–160 |
| Complete bathroom (plumbing, install, excl. high-end fixtures) | room | €4,000–8,500 |
| Kitchen (install + connections, excl. appliances) | unit | €3,500–9,000 |
To give your clients a rough overall figure before getting into the detail of each trade, our guide to renovating an apartment in Paris lays out the per-square-meter ranges by type of renovation.
Tooling up your estimates: the pricing library
The method above has a hidden cost: keeping prices current. Combing through supplier sites and cross-checking feedback from the field, project after project, takes hours every month — and it's the first thing interior designers drop when work picks up. The result: price lists that age, and estimates that drift.
That's exactly the problem a connected pricing library solves. In Nodal, every quote line draws on a real construction pricing database, updated every month — and every line stays editable, because your knowledge of the job has the final say. The quote is built from the library, VAT is calculated at the right rate, and client approval happens online, time-stamped. We described what that changes day to day in this article on coordination.