The essentials in 30 seconds
- A cost plan (DPGF) is an estimate: it is never called a "quote". Works quotes are issued by the companies, in the client's name.
- You always consult at least two contractors, with a strictly identical template: same trade packages, same line items, same quantities, prices left blank.
- The comparison happens item by item: lowest bidder, gaps against the estimate, items left unpriced. Nothing can be compared if the templates differ.
- The bid analysis report formalises your reasoned recommendation; the final decision always belongs to the client, the project owner.
- Before freezing, have the client approve the retained bid: a time-stamped agreement in principle, not a signature. The same goes for every piece of additional works.
A cost plan is not a quote, and this distinction protects you
Let's start with the point of law too many tools and templates ignore: a quote, signed then countersigned, is a contract. If you hand your client a document titled "works quote" with your estimates inside, and they sign it, you have just committed yourself to prices that are not yours.
An interior designer is not a general contractor: they cannot collect the cost of the works and redistribute it to the companies. In practice, this shapes the entire document chain of the project:
- Your own quote covers nothing but your fees. Design, site monitoring, the tendering assignment: it is the only document your client signs with you. We covered how to build it in our guide to interior designer fees.
- Works quotes are issued by each company, in the client's name. The client signs them directly with the companies and therefore pays, at a minimum, two invoices: yours and that of each company retained.
- Your estimate of the works lives in a third document: the cost plan, also called the DPGF, an itemised, priced breakdown of the works (décomposition du prix global et forfaitaire). It is an estimate, drawn up for guidance, and it is not a quote.
This separation is not a quirk of vocabulary: it defines who commits to what. The day a line item slips on site, the difference between "the client signed my quote" and "the client approved my estimate, then signed the company's quote" changes everything.
The three lives of the DPGF
The DPGF is the most profitable document in your toolbox, because the same file serves three times over the course of the project:
| Phase | What the DPGF becomes | What's at stake |
|---|---|---|
| Design | A decision-making tool | Price the scenarios, frame the budget with the client before drawing too far |
| Tender | The template sent to the contractors | Identical line items for everyone, prices left blank: the bids you receive become comparable |
| Works | The tracking document | The frozen cost plan serves as the reference works budget; changes are added to it as additional works |
Most studios stop at the first life: an estimating spreadsheet, rebuilt for every project. The complete method uses all three, and the last two are where the time and the legal safety are won. For the upstream part (building the estimate, setting the right price ranges), see our guide to estimating renovation works.
Step 1: one identical template, at least two contractors
The golden rule of tendering fits in one sentence, heard from every seasoned professional: you always send the request to at least two different companies, systematically. Even when your trusted tradesperson seems the obvious choice. The client has the right to a choice, the comparison gives you the market's real prices, and your recommendation gains credibility because it rests on competing bids.
The condition that makes everything else possible: every company receives exactly the same template. Same trade packages, same line items, same quantities, same descriptions of the works, and prices left blank. If company A prices "bathroom renovation" as one global lump sum while company B details twelve lines, you are no longer comparing bids: you are comparing interpretations.
In practice, the template goes out as an Excel file, each line carrying its quantity and unit, so the company only has to fill in its unit prices. A serious contractor may add an item you had overlooked: that is valuable information, not an anomaly. Plan to follow up too, politely and in writing: a tender without dated follow-ups drags on forever, and you lose track of who received what, and when.
Step 2: collect the returns without re-typing
The classic trap of an improvised tender: the returns arrive as PDFs, modified Excel files and email bodies, and you spend an evening copying prices back into your spreadsheet. Every copy is a chance for error, on amounts that commit the rest of the project.
The clean method: keep the structure of the template and re-import the returns into the same framework, item by item. For each bid, note its date of receipt, its validity period and its conditions (deposit, lead times, any reservations). These details seem secondary on day one; they become decisive six weeks later, when the client finally makes up their mind and one bid has expired.
Step 3: compare item by item, and award by trade package
The useful comparison is not made on the grand total, it is made line by line. For each item: who is the lowest bidder, what is the gap against your estimate, who left it unpriced. An attractive total can hide a forgotten item; a high total can be explained by a better-quality offer on the package that matters.
And above all, nothing forces you to entrust everything to a single company. Fine-grained awarding happens by trade package: company A on the tiling, company B on the kitchen, and the estimate kept on the packages where no bid convinces. It is often the best economic compromise, provided you have anticipated the coordination it implies on site, a subject we cover in our guide to site supervision.
Step 4: the bid analysis report, your reasoned recommendation
In structured procurement, this phase has a name: bid analysis, the heart of the ACT phase (assistance with works contracts, in the French framework). For an interior design studio, the deliverable doesn't need to be a fifty-page dossier, but it must exist: a document that presents the comparison by trade package, the summary per company, your analysis notes and your reasoned recommendation, including the company or companies you propose, points of caution and reservations.
This report changes the nature of the conversation with your client. You no longer say "I think we should go with this one", you hand over a documented expert opinion. And it draws the legal line exactly where it belongs: choosing the companies is the decision of the client, the project owner; your report is the designer's reasoned opinion. You advise, they decide.
Step 5: the time-stamped client approval, then the freeze
This is the step almost every studio skips, and it is the one that protects them best. Before freezing the cost plan into the reference works budget, formally propose the retained bid to the client and obtain their approval, dated. Not a signature: an approval. The client does not sign a cost plan; their contractual documents remain the companies' quotes. But their time-stamped agreement in principle, on the retained bid as on the awarding choices, plays the role of a lightweight notice to proceed: the day one person's memory diverges from another's, the date settles it.
Once the approval is in, the cost plan freezes: it becomes the reference works budget of the site, untouchable. Any later change, and there will be some, goes through additional works: lines added to the tracking document, each subject to the same discipline of dated client approval, as you go rather than in one block at the end of the site. No more surprise catch-up invoices poisoning handovers.
So, what about Nodal?
Nodal equips exactly this method, without betraying its legal framework. The cost plan (DPGF) permanently carries the mention "an estimate, not a quote". The contractor template exports to Excel with prices left blank and is sent from the tool, with every company traced: version sent, time-stamped follow-ups, returns entered or imported with no re-typing. The comparison screen lines the bids up item by item, flags the lowest bidder and the gaps against the estimate, allows awarding by trade package, and generates the bid analysis report as a PDF, with your notes per package and your reasoned recommendation.
When it's time to freeze, Nodal suggests proposing the retained bid to the client: they approve it from their portal, a time-stamped approval, with the explicit mention that this is not a signature and that the companies' quotes remain their contractual documents. After the freeze, additional works follow the same dated approval circuit, line by line. Everything starts from the same pricing library that built the estimate, and fits into the project's 11-step pipeline.