Ask any managing partner who has been through an office redesign what surprised them most. The answer is almost always the same: the cost. Not that the project was expensive (that was expected) but that the final invoice bore little resemblance to the number agreed at the start. Budget overruns on commercial interior design projects are not rare exceptions. When the brief is incomplete, the scope undefined, or the wrong questions asked too late, they are the rule.
The good news is that overruns are largely preventable. Understanding why they happen is the first step to stopping them before they start.
Why Budgets Overrun
The most common cause is not contractor dishonesty or unforeseen structural conditions, it is scope creep that begins before the project starts. A client approves a concept. The concept evolves. Finishes are upgraded, an extra meeting room is added, the reception desk becomes custom, the lighting specification is revised. Each individual decision feels minor. Cumulatively, they can add 20–35% to the original budget.
The second most common cause is an incomplete brief. When a designer or contractor is asked to quote without a detailed specification, they quote optimistically for the version of the project that works, not the version that accounts for structural surprises, long-lead materials, or phased delivery around live business operations. Dutch fit-out specialists consistently recommend reserving 10–15% of total project cost as contingency from the outset. In practice, many clients treat this as optional. It is not optional. It is standard capital project management applied to furniture and finishes rather than machinery.
The third cause is the most avoidable: the absence of a formal change control process. Without a written procedure for approving changes who can authorise them, how they are costed, when they are communicated small decisions accumulate invisibly until the final account reveals a number nobody recognises.
The Specification Problem
A proper interior design brief is a commercial document. It should define the scope of works; what is included, and explicitly what is not. It should specify the finish standard: materials, supplier tiers, quality level. It should contain a phasing plan that sequences works to minimise disruption to business operations. And it should establish a change control process before a single contractor is engaged.
What it should not be is a rendered impression with a ballpark figure attached. An indicative budget and a fixed-price tender are not the same thing. The gap between them is where overruns live. The distinction should be clear to every client before any financial commitment is made and any designer who does not explain this distinction clearly is not yet acting in your financial interest.
Cushman & Wakefield's 2025 Dutch Office Fit-Out Cost Guide confirms that the range for commercial interior projects in the Netherlands spans from €150 to over €800 per m², depending on specification. That is a fivefold range. A brief that does not precisely define which end of that range you are targeting is not a brief, it is an open invitation to cost escalation.
What a Well-Structured Project Looks Like
A well-structured interior design project follows a clear, phase-gated sequence. Concept design comes first, before any contractor is engaged and before any budget is committed beyond the design fee. This is where the brief is written, spatial options are explored, and the cost envelope is stress-tested against the client's actual budget and operational constraints. Only once the concept is approved and the specification is complete does the project move to detailed design, contractor tender, and execution.
At Xquizit Concepts, we separate the design phase from the execution phase deliberately. Our clients make financial commitments based on a detailed and specified brief , not on a rendered image and an optimistic estimate. This approach also means our clients can hold contractors to account, because there is a document that defines precisely what was agreed and what was not.
Three Things to Do Before You Sign Anything
Before committing to any interior design project, take three practical steps.
Demand a detailed specification before approving a budget. If your designer cannot provide one, your budget is not a budget. It is a best guess with no accountability attached to it. A professional specification lists materials, suppliers, scope of structural work, and what happens if something changes.
Establish a formal change control process at project kick-off. Every change to scope, finish, or timeline should be documented, costed, and approved in writing before it is implemented. A simple one-page sign-off process, agreed before work begins, prevents the majority of end-of-project disputes.
Separate your contingency from your working budget. Reserve 10–15% of total project cost in a contingency that is not available to spend unless genuinely needed. Do not allow it to be absorbed into the base scope. If it remains unspent at project completion, it is a success, not a planning failure.
An office redesign is a significant investment. It does not have to be a financial surprise. The difference between a project that lands on budget and one that does not is almost always decided in the first two weeks, before the first contractor walks through the door.