The practical distinction
If the work stops at surfaces, joinery, lighting and furniture, it is interior design. If it touches structure, openings, floor levels, staircases or the building envelope, it is architectural work — and it carries consequences for structure, services and often for permits.
The distinction matters commercially. A designer without architectural training may plan a beautiful room that cannot be built without a structural change nobody priced.
When you need architectural input
- Removing or moving walls that may be structural
- Enlarging, adding or relocating windows and doors
- Changing floor levels, adding a mezzanine or moving a staircase
- Converting or repurposing a building
- Extending, or altering the envelope and façade
- Working on a protected or heritage structure
Why one studio for both is usually better
When architecture and interiors sit with one team, the plan is resolved once. Ceiling heights, structure, service routes and joinery are coordinated as a single set of decisions, so the interior is not a negotiation with the building.
It also removes the gap where responsibility usually disappears. There is no argument about whether a problem belongs to the architect or the interior designer.
A worked example
At Torre del Gallo in Tuscany, the brief looked like an interiors job: two apartments inside an existing stone tower. In practice it was architectural — the apartments had to interlock vertically within a protected masonry shell, which meant rethinking circulation and levels before a single finish was chosen.
