Interior Designer vs Architect vs Decorator: Which One Do You Need?

Starting a new commercial fit-out, restaurant, boutique or major home renovation? You're probably wondering whether you need to hire an interior designer, an architect or an interior decorator. The three roles overlap, but each has a distinct scope of responsibility — and in Quebec, the Architects Act draws a clear legal line between them.

This guide explains those differences in plain English so you can pick the right professional from day one and avoid paying for credentials your project doesn't actually need.

In Quebec, the professional activities reserved to architects are defined by Chapter A-21 of the Architects Act, Section 16. The text reads:

In the course of practicing architecture, the professional activities reserved to architects are as follows:

1. Prepare, amend, sign, and seal a plan, specification, terms of reference, certificate of completion, expert report, or supervision report relating to the construction, enlargement, or alteration of a building;

2. Supervise work relating to the construction, enlargement, or alteration of a building, including for the purpose of producing a certificate of compliance required under an Act;

3. In the course of carrying out a professional activity referred to in paragraph 1 or 2, give an opinion and sign and seal a written opinion.

For the purposes of this law, the interior design of a building or part of a building is considered equivalent to the construction, expansion, or modification of a building, as the case may be, if it results in a change of use or affects its structural integrity, firewalls or fire separations, exits and their access points, or the building envelope.

In practice, an architect is required when a project involves new construction, structural alterations, change of use, or work that affects firewalls, fire separations, exits or the building envelope of a building — except in the cases specifically exempted by Section 16.1 of the same Act.

When is an interior designer authorized to lead the project?

Under Section 16.1 of the Architects Act, an architect is not required for the following types of buildings — meaning an interior designer is authorized to prepare the plans and lead the project:

• A detached single-family dwelling with no more than one basement level, not exceeding two storeys, and a total gross floor area of less than 600 m².
• A semi-detached or row single-family dwelling with no more than one basement level, not exceeding two storeys, and a total gross floor area of less than 300 m².
• A multi-family dwelling of no more than four units, with no more than one basement level, not exceeding two storeys, and a total gross floor area of less than 300 m².
• A commercial, business or industrial establishment — or a combination of these — with no more than one basement level, not exceeding two storeys, and a total gross floor area of less than 300 m².
• An agricultural building, of no more than one storey, with a total gross floor area of less than 750 m² (new construction) or less than 1,050 m² (expansion or modification), as well as silos, manure storage and animal feed platforms.

Beyond these cases, an architect is legally required, and an interior designer typically works under or alongside the architect on the interior portions of the project. In all cases, an architect is required as soon as the work alters the building's structural integrity, firewalls, fire separations, exits or building envelope, or causes a change of use.

Source: Loi sur les architectes / Architects Act (chapter A-21), Sections 16 and 16.1 — consolidated text current as of February 2026. See the official text on LégisQuébec. For projects close to these thresholds, mixed-use buildings, or any doubt about applicability, consult the Ordre des architectes du Québec or a qualified architect before starting work.

Although the words sound similar, an interior designer and an interior decorator do quite different jobs.

What an interior designer does

The interior designer invests in the fixed elements of a space — bathrooms, kitchens, staircases, partitions, built-in storage, lighting plans. The designer modulates proportions, specifies finishing materials and uses light and color to create a coherent visual balance. The work covers aesthetics, functionality, safety, environmental and social criteria — and produces the drawings needed to obtain construction or renovation permits when required.

What an interior decorator does

The interior decorator focuses on movable elements and surface finishing: furniture, drapery, color palettes, wall coverings, art and accessories. Decorators typically come in once the space is built or renovated, to dress and style it.

A simple decision tree:

• If you are building a new structure from the ground up, or modifying load-bearing walls — start with an architect.
• If you are fitting out a commercial space (restaurant, café, boutique, office) under 300 m² and two storeys, or renovating a residence within the limits set by Section 16.1 — an interior designer can take you from concept through preliminary plans to execution drawings, while coordinating with the architect's official plans following the permit application submitted to the relevant municipality.
• If your space is already finished and you only need furnishings, color and styling — a decorator is the right fit.

An interior designer is by definition both creative and rigorous. The aesthetic aspects are taken care of as much as the functional, safety, environmental and social criteria — a choice toward expertise, creativity and passion, the qualities necessary for successful residential and commercial interior design.

Want to discuss your project with our team? Contact moodesign at 514-567-2383