Stages of an interior design project: from measurement to construction

How many stages an interior design project has, and how long it takes

An interior design project is not ‘brief → layout → visualisation → drawings’, as it is sometimes presented. In practice it is seven sequential steps: initial meeting and contract → technical brief → layout → visualisation → technical documentation → furnishing schedule → handover for construction and design supervision. Each step ends with a result that the client sees and approves before the next one begins.

For an average property of around 100 m² with prompt approvals, the path from the first meeting to the handover of technical documentation takes about 2.5 months. The rest of the article covers what happens at each stage, what its result is, and how long it actually takes.

The initial meeting and contract

Before design work begins, the studio and the client agree the task and its terms: the contract, the timeline, the scope of work. This is not a formality: the contract determines exactly what is included in the interior design project and what isn't (more on these boundaries below, in the section on technical documentation), and it protects both sides from misunderstandings at later stages.

The technical brief: from the questionnaire to the A3 document set

The first substantive stage is gathering information and drawing up the technical brief. It consists of several sequential steps:

• the first meeting with the client and a questionnaire covering lifestyle, habits, family composition and expectations for the space;
• an on-site visit to the property;
• measurements and a measured survey drawing;
• photographic documentation of the current condition;
• an assessment of the building services: what already exists and what will need relocating or reinforcing;
• functional zoning: which zones are needed and how they relate to one another;
• style, concept and the selection of references.

The result of this stage is a bound A3 document set that the client signs. This is not a draft, but a fixed brief: from this point on, the studio designs exactly what is described in it, and any deviation is discussed and recorded separately. The technical brief takes about two weeks on average.

The concept design: layout and visualisation

The concept design is the stage where the decisions captured in text and zoning turn into space and image. It, too, consists of several steps:

1. Layout — the arrangement of walls, furniture and the ways the space will be used.
2. Geometric design — monochrome 3D sketches that show the shape of the space without colour or materials: this makes it easier to assess proportion and geometry without being distracted by decor.
3. Selection of materials and fittings, and the brief for the visualisation.
4. 3D visualisation and lighting design — the final colour renders with fully developed lighting, on which the client approves the look of the interior.

It is at this stage that decisions are made that are difficult and costly to change later: layout, form, light. For a property of around 100 m², the concept design takes 20 working days or more; elaborate styles with many bespoke elements take longer.

Technical documentation

Once the visualisation is approved, the studio prepares the technical documentation: a full set of drawings, diagrams and schedules coordinated with the building services, including floor plans, ceiling plans, socket and switch layouts, wall elevations and drawings of complex construction details. This document is not for the client but for the building team, who carry out the renovation from it.

This is also where the boundary of the interior design project runs: it does not include the construction and installation work itself, the cost of materials and furniture, or obtaining official approval for a reconfiguration. This is a deliberate division: the interior design project is responsible for the design and its documentation, and is not a substitute for the construction or the purchasing. For a property of around 100 m², technical documentation takes about 20 working days to prepare.

The schedule and procurement

The schedule is a table listing every item in the project, with prices and links to specific product codes: from tiles to hardware. It doesn't appear as a single file at the end. Compiling it starts back at the design-brief stage and continues alongside the design work, finishing about a week after the technical documentation is handed over.

Like design supervision, furnishing and procurement is a separate service, not a default part of the interior design project: the studio flags this at the outset, so the client has no false expectations about the scope of work.

How much time each stage takes

A benchmark for a property of around 100 m² at a typical pace of approvals:

• Survey and measurements — 1 site visit (a repeat visit for complex or larger properties)
• Technical brief — ≈ 2 weeks
• Concept design (layout + visualisation) — 20 working days or more
• Technical documentation — ≈ 20 working days
• Procurement schedule — finalised a week after the technical documentation is handed over
• Total to the handover of technical documentation — ≈ 2.5 months

These are average figures, not a guarantee. The actual timeline depends on the size of the property, the complexity of the style and, most of all, the speed at which the client makes decisions and approves materials. Every delay in the client's response pushes the whole schedule back, because the stages run sequentially: technical documentation isn't started until the concept design is approved.

What happens after the project: construction and design supervision

The approved technical documentation is handed over for construction. The interior design project is formally complete at this point, but the studio doesn't part ways with the property: checking that what gets built matches the approved drawings, materials and details is the job of design supervision. This is a separate service with its own contract and regular site visits, not an automatic continuation of the project.

How this sequence protects against rework

The main reason the stages run in this exact order and can't be compressed is that the cost of a mistake grows with every next step. Changing the furniture layout on a sketch is an hour's work. Changing it after the technical documentation has gone to the building team, let alone after the utilities have been installed, is already rework, with real money and a slipped schedule attached.

That's why the process has a built-in protocol: after each approval, whether of the technical brief, the concept design or the technical documentation, the decision is recorded and logged in correspondence with the client. This isn't bureaucracy for its own sake, but a way of not revisiting decisions that have already been made. The same logic continues on site: design supervision checks that the property matches the project precisely because a deviation spotted at the rough-installation stage costs incomparably less than one discovered in the finishes.

If you want to get to grips with the interior design project as a whole, from the set of documents it includes to how it differs from space planning and architectural design, see the overview in the article ‘Interior design project: the complete breakdown’. To commission an interior design project or discuss your property, visit the service page for ‘Interior Design Project’, and design supervision on site is covered by the service ‘Design Supervision’.