Engagement letters with Claude: make a limited scope explicit

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An architect gets a call from a private individual who has just bought a sloping plot: before going any further, they simply want to know whether a single-storey house is feasible there, without a full topographic survey or an as-built record. One visit and a two-page note will be enough. The commission is short, almost trivial compared with a full construction project; the architect is tempted to treat it as such and send a simple summary email after the visit, with no other document.

That temptation is understandable, but it exposes the architect to a real risk: under French law, every professional engagement of an architect must be the subject of a prior written contract, whatever the length or scale of the commission. For a limited intervention, that contract is called an engagement letter (lettre de mission) — and despite its short format, it is a fully-fledged contract, just as binding as a full project-management (maîtrise d'œuvre) contract.

This article details what the professional regulations actually require, what an engagement letter must fix even for a one-hour intervention, how it differs from a full maîtrise d'œuvre contract, and the method for preparing one without turning a focused answer into a promise to resolve the entire project.

Summary

1. An engagement letter is a fully-fledged contract, not a lighter formality
2. What an engagement letter must fix, even for a short intervention
3. Engagement letter or full maîtrise d'œuvre contract: what changes
4. Preparing an engagement letter step by step
5. When an engagement letter is not enough
6. What we observe among independent architects
7. Training to secure engagement letters
8. Frequently asked questions

An engagement letter is a fully-fledged contract, not a lighter formality

Article 11 of the French architects' code of ethics (decree no. 80-217 of 20 March 1980, as amended) is unambiguous: every professional engagement of an architect must be the subject of a prior written agreement with the client, defining the nature and extent of the missions or interventions, as well as the terms of remuneration. This text carves out no exception for short commissions, one-off consultations or feasibility studies: a one-hour visit followed by a two-page note falls within its scope exactly like a full maîtrise d'œuvre contract covering design and site supervision.

What the architect risks without a written contract

The Ordre des architectes states this explicitly: without a contract established with the client, recovering amounts owed becomes more difficult in the event of a dispute, since courts can significantly reduce the fees claimed for lack of written proof of what was agreed. For an engagement letter covering a limited amount, this risk can look disproportionate against the time it would take to draft two pages — it is exactly the opposite: a limited amount makes a dispute that could have been avoided by a signed document even more damaging, since the cost of contentious recovery quickly exceeds the original stake.

An engagement letter produces the same effects as a long contract

Once signed, an engagement letter has the force of law between the parties within the meaning of Article 1103 of the Civil Code: neither the client nor the architect can unilaterally change its content, however short the text. A short format therefore does not mean a lighter commitment — it only means a reduced scope, which in turn demands particular rigor in drafting, since there are no lengthy general clauses left to cover unforeseen situations. A verbal agreement, however clear at the time, never replaces this document: it leaves no enforceable trace if the parties later remember things differently.

What an engagement letter must fix, even for a short intervention

A reliable engagement letter answers four questions before any other consideration: what exactly the architect will do, with which deliverables, based on what data supplied by the client, and for what fee.

Scope and deliverables, stated without ambiguity

The scope must specify the number of visits, the nature of the deliverable — feasibility note, sketch, written opinion — and above all what is not included: a full topographic survey, a soil study, the filing of an administrative application. The word "feasibility" used alone, without this precision, leads the client to think an authorization has already been secured, when a feasibility note never amounts to an administrative authorization.

Fictional example: a client asks for an opinion on the feasibility of a single-storey house on a sloping plot, for a single visit followed by a two-page note. The engagement letter must name this deliverable precisely and explicitly exclude the full topographic survey and the filing of a prior-declaration application — two services a hurried client might assume are included under the word "feasibility".

Fees: freely negotiated, never an imposed rate

Architects' fees are freely negotiated between the parties in France; there is no statutory scale or standard percentage applicable to an engagement letter, contrary to what some generic templates suggest. The letter must reflect the amount actually agreed with the client — a flat fee, an hourly rate or another arrangement — never an automatic split copied from a sample without verification. Payment terms — a deposit, payment on delivery of the note — must likewise match the real commercial agreement, not a default period copied from a template.

Engagement letter or full maîtrise d'œuvre contract: what changes

The difference between the two is therefore not the legal force of the document — identical in both cases — but its scope. An engagement letter that, in practice, gradually comes to cover design and then the filing of an administrative application has stopped being an engagement letter: it calls for a full maîtrise d'œuvre contract, or at minimum an amendment that formally widens its object and fee.

Preparing an engagement letter step by step

Step 1: Identify the precise object of the commission. A focused question — "does this plot allow a single-storey house" — must stay worded that way, without drifting into a promise to resolve the entire project.

Step 2: List the deliverables and the exclusions. Every included service must have a described counterpart; every service usually associated with a design commission but not included here — a full survey, filing an application, a soil study — must be explicitly named as excluded.

Step 3: Specify the data the client must supply. A feasibility note based on information not verified by the architect must say so, so the scope of the opinion given stays clear if a later dispute arises over a fact the client did not communicate.

Step 4: Reflect the fee actually agreed. The amount, its calculation method and the payment terms must match the original commercial agreement, never a default value from a generic template.

Step 5: Have the letter signed and dated before any intervention. Signature must happen before the service begins, not after a first visit already carried out on the sole basis of a verbal agreement — it is this order of operations that gives the document its full evidential value.

When an engagement letter is not enough

A well-drafted engagement letter does not cover every situation. A project that expands along the way — the initial feasibility leading to a request for a full design commission — is not handled by editing the initial letter's text as exchanges continue: it calls for either a new maîtrise d'œuvre contract or an amendment that formalizes the expansion, with its consequences on fees and timing. A client who later disputes the scope of what was verbally agreed before signature is likewise not settled by retroactively rewriting the letter: exchanges that predate signature must be kept separately, as evidence of context, without being folded into the final document as if they had always been part of the signed agreement. An engagement letter prepared with AI assistance remains, in every case, a draft: it must be reviewed and its scope confirmed by the architect before sending, and by a legal professional as soon as the commission touches unusual contractual issues.

What we observe among independent architects

In our exchanges with independent architects about their one-off interventions, reluctance to draw up an engagement letter almost never comes from disagreement over the principle: an architect knows a written contract protects better than an email exchange. What slows things down is the time that feels disproportionate for a commission of a few hours — rewording a scope each time, retrieving the template used for the last similar consultation, or hesitating over how to word the exclusions. That is a formatting bottleneck, not a doubt about the document's necessity — and it is exactly what a well-structured letter template removes, without ever excusing the architect from checking that the scope truly matches what was agreed with this particular client.

Training to secure engagement letters

Setting up an engagement-letter template once is not enough if its scope is copied without adaptation into every new request. For an architect practising as a self-employed professional (NAF code 7111Z in France), the FIFPL fund covers part of the cost of Qualiopi-certified training under 2026 criteria set at €300 per day and €900 per year, with e-learning capped at 50% of the daily rate. This funding must be arranged before training starts, not after.

Frequently asked questions

Does an engagement letter have the same legal value as a full maîtrise d'œuvre contract?

Yes: both documents fall under the same Article 11 of the architects' code of ethics and, once signed, produce the same binding effects within the meaning of Article 1103 of the Civil Code. Only the scope differs, generally wider and phased for a full maîtrise d'œuvre contract, more focused for an engagement letter. Neither format is therefore "less binding" than the other simply because it is shorter.

Can a service be invoiced without a signed engagement letter?

That is possible in practice, but strongly discouraged: in the event of a dispute over the amount or scope of the service, the absence of a written contract weakens the architect's position before a court, which may reduce the fees claimed for lack of written proof of the original agreement. Good practice remains to have the letter signed before any intervention, even for a single visit of a few hours. An architect who has already carried out a service without a signed letter should regularize the situation as soon as possible with a document dated the day of the regularization, never backdated to the date of the intervention already performed.

Does a simple advisory visit really need an engagement letter?

Yes, as soon as that visit constitutes a professional engagement of the architect within the meaning of Article 11 of the code of ethics, which in practice covers any paid service, however brief. A purely informal, free visit, with no technical opinion engaging the architect's liability, falls outside that scope, but this distinction should be assessed cautiously rather than assumed in the architect's favor. When in doubt about a visit's nature, the safest approach remains preparing a short engagement letter rather than assuming it counts as a non-binding, informal exchange.

Do engagement-letter fees follow a standard percentage?

No: architects' fees are freely negotiated between the parties, and no text imposes a percentage or reference scale for an engagement letter. A template that automatically applies a rate or a standard split must be corrected with the amount actually agreed, otherwise the letter does not reflect the real commercial agreement and loses some of its evidential value. That amount must come from the commercial exchange that preceded the letter — a proposal, an email, a phone call confirmed in writing — never from a value automatically carried over from an earlier, unrelated commission.

Can an engagement letter evolve into a full maîtrise d'œuvre contract?

Yes, this is a common situation when initial feasibility leads to a decision to build: the engagement letter is not rewritten retroactively, it is replaced by a new contract or completed by an amendment that formally widens its object, fees and timing. Our method for preparing an amendment details how to trace this kind of change without introducing a contradiction with the original document. In the interval between the initial letter and that new document, no expanded service should be carried out on the strength of a verbal agreement alone, for the same reasons that require signature before any initial intervention.

A reliable engagement letter rests on three elements that do not change with the length of the intervention: a scope stated without ambiguity, a fee matching the real agreement rather than a default template, and a signature obtained before the service begins. Once that foundation is in place, it is exactly what the engagement-letter generator applies automatically, never turning a focused answer into a promise to resolve the entire project.

To go further on a project that grows in scope, our method for preparing a maîtrise d'œuvre contract details the structure of a full contract, phase by phase.

Training 100% fundable via OPCO/FIFPL. Qualiopi-certified programme. To structure your engagement letters and contractual documents with AI as part of our AI for architectural management training, contact Educasium and specify your status (employee, self-employed, business owner) and your goal.