When should you bring in an interior designer?
Before you appoint a contractor — and, where the idea depends on technical feasibility, before you buy. Every later entry point costs more and leaves fewer options open.
Krizbai András · Last verified: August 2026
Before purchase: feasibility. The plan you picture is not always buildable. The position of load-bearing walls, risers and shafts, the fall available for drainage and whether an opening can be formed in a given wall all decide whether the kitchen can move to the other side. This is a few hours of review, and it prevents the most expensive misunderstanding of all: buying a property that cannot become the thing you bought it for.
After purchase, before demolition: full design. This is the normal entry point. The space is untouched, every decision is open, and the survey is accurate.
Before appointing a contractor: comparable quotes. Without documentation, three contractors price three different scopes, and the cheapest usually contains the least. A priceable bill of quantities is not a designer's luxury — it is the instrument that makes three quotes about the same thing. Money saved on design comes back out during construction.
During demolition: rescue, not design. Projects arrive here too, and help is possible — but at that point the existing condition sets the limits rather than the best solution. Service routes are fixed, floor build-ups are fixed, and part of the budget is spent.
For a hotel or office project the answer moves earlier still. There the interior designer is present during concept and permit stages, because room count, room plan and the proportion of public areas determine whether the building can be operated — and those are fixed by the architectural design.
Why bespoke joinery sets the date
Bespoke joinery has a lead time of 8–10 weeks, and it only starts from finalised, dimensioned production drawings. If the joinery is drawn after demolition, the contractor waits on site while the workshop is still cutting — the single most common delay in an apartment renovation. Entering early does not lengthen the design; it shortens the build, because the two overlap.
The mechanical and electrical drawings run on the same calendar. Light points, switch positions, underfloor heating circuits and ventilation routes all follow from the joinery drawings and the wall elevations. Without them the electrician estimates — and the socket ends up behind the cabinet.
Where this point sits internationally
In the RIBA Plan of Work 2020 it is Stage 0 (Strategic Definition) and Stage 1 (Preparation and Briefing) where feasibility and the brief are settled. That is where the designer belongs — not at Stage 4 (Technical Design). Appoint at Stage 4 and you inherit a closed set of decisions, and design the consequences of them.
For leased property and retail units the answer sits before the lease is signed. The landlord’s handover standard (shell & core or warm shell), the available electrical capacity, the ventilation provision and the reinstatement obligation are all in the lease — and all of them move the cost of the fit-out. After signature none of it is negotiable.
If you already hold a contractor’s quote, the situation is not lost. Reviewing the quote and scheduling what is missing from it usually returns more than it costs. But from here the design no longer chooses freely; it fits a price that already exists.
On timing, avoid these: appointing a contractor before there are drawings; surveying after demolition; and buying a property without checking the structural precondition of the plan.
Entering early is the cheapest decision in the project. How long a renovation takes → · How to choose an interior designer →