Give every bidder one version of the job
A preventivo is an offer; a computo metrico describes measured work, and a priced computo metrico estimativo connects quantities with rates and amounts. The title of the file does not establish its completeness. Ask for identifiable rows, units, quantities, product standards and the drawing revision on which the offer is based.
Start with your needs and a professional’s measured scope. If one contractor prices retained radiators and another includes their replacement, the difference is a design choice rather than a discount. Separate fixed decisions from optional alternatives so that bidders do not silently choose a cheaper specification for you.
Make the units and inclusions explicit
A useful row says what is supplied and installed, how it is measured and what it excludes. Ten square metres of partition are not ten running metres of wall. An electrical “point” needs a definition: cable route, box, mechanism, circuit work and making good may be priced elsewhere.
| Defined item | Quantity | Rate | Amount |
|---|---|---|---|
| Specified partition including agreed finish | 10 m² | 55 | 550 |
| Wall finish on an identified substrate | 35 m² | 18 | 630 |
| Defined electrical point package | 8 units | 65 | 520 |
| Extract total, not the whole renovation | — | — | 1 700 |
The quantities and rates above are invented. Agree how openings, returns, minimum charges and transport will be measured in your contract. The Lombardy 2026 measurement introduction separates measurement, inclusions/exclusions and technical descriptions for public estimates. That is a useful discipline for a private brief, not a rule that its rates or measurement conventions automatically govern your renovation.
Normalise the offers using confirmed additions
| Item | A | B | C |
|---|---|---|---|
| Original offer before IVA | 18 000 | 19 800 | 19 400 |
| Confirmed additions before IVA | 2 000 | 200 | 1 000 |
| Comparable contract before IVA | 20 000 | 20 000 | 20 400 |
| Assumed IVA 10% | 2 000 | 2 000 | 2 040 |
| Comparable gross amount | 22 000 | 22 000 | 22 440 |
A omitted €1,200 of waterproofing and €800 of protection and waste. B omitted €200 of defined checks and documentation. C omitted €1,000 of agreed carrying and disposal. Once corrected, A and B cost the same; C is €440 higher including the assumed IVA. If an omission remains unpriced, mark the offer incomplete rather than inventing a precise total.
Read the tax and technical boundary
The agency guide, IVA chapter distinguishes the contractor’s service, direct owner purchases and significant goods. Request the tax bases and rates as well as the gross amount. A 10% line on an offer does not prove that the same rate applies to every purchase, professional invoice or additional order.
Ask who designs and documents the installation changes. DM 37/2008 article 5 provides for a system design, with responsibility depending on the installation and relevant conditions. “Electrical work included” should be reconciled with the actual circuits, required checks, documents and connections to existing parts. A paperwork omission may also reveal an undefined technical scope.
Compare the conditions that change your exposure
- Identify the legal contractor, the actual work packages and proposed subcontracting.
- Check start and finish assumptions, access, working hours and product lead times.
- Ask which quantities are fixed, remeasured or merely provisional.
- Record the quote validity, deposit, progress-payment evidence and final-account process.
- List every exclusion and owner-supplied product with responsibility for delivery and fitting.
A 20% deposit on the comparable €22,000 contract is €4,400, leaving €17,600 of that contract unpaid. This is an invented agreed payment term, not an Italian statutory deposit. Compare when the money leaves your account and what has been delivered at that point. A cheaper total with a heavily front-loaded schedule can require a different cash decision.
If the contractor refers to the regional public-works price book, ask for the edition, item code, inclusions and any adjustment to your site. A quoted code is not proof that a whole private package is complete, fairly measured or cheaper than a competing offer.
Accept one version and control later changes
Civil Code article 1659 addresses contractor changes and written evidence of authorisation. Put the agreed scope, price basis, tax, programme and change mechanism into the contract. For a globally priced job, also make any extra compensation explicit; an approved drawing change and an agreed extra price are separate questions.
- Return clarification questions to all relevant bidders.
- Obtain corrected offers rather than relying on your own margin notes.
- Record the selected baseline with the accepted drawing and specification.
- For each later change, identify the old allowance or omitted work, the net increase and its IVA.
- Keep the approved change and updated forecast alongside the original contract.
Reno Pro can keep work, materials, notes and recorded payments organised. The comparison itself should remain traceable to the contractor’s documents. Choose a complete, understandable offer whose price and delivery conditions fit the project, rather than selecting a number whose missing scope becomes visible only on site.
Sources, date and scope
- Regione Lombardia — Criteri di misurazione e specifiche tecniche 1/2026 — premessa
- Regione Lombardia — Prezzario regionale dei lavori pubblici — edizione 2026
- Agenzia delle Entrate — Ristrutturazioni edilizie: le agevolazioni fiscali, febbraio 2026 — copia PDF
- Normattiva — Codice civile, art. 1659
- Gazzetta Ufficiale — DM 37/2008, art. 5 — progettazione degli impianti
Checked on 19 October 2026. Examples concern a flat in Milan unless stated otherwise; check the actual work against the rules of your comune and region. Teaching figures are invented to explain the accounting, not market averages or an offer. Appropriate professionals establish tax eligibility, technical suitability and required filings. Where used, the February 2026 Agenzia delle Entrate guide is linked as a copy of the agency-authored document.