Interior Design Fees: Per Square Metre, Percentage or Fixed, and What Each Model Costs You
Three fee models dominate interior design contracts: a rate per square metre of interior area, a percentage of delivered project value, and a fixed lump sum. The three produce different totals on the same project, and more importantly they align the designer’s income with different outcomes. Choosing between them matters more than negotiating the number inside any one of them.
How each model calculates the number
Each model derives its fee from a different base: floor area, spend, or scope. Understanding the base explains why two proposals for the same apartment can differ by a factor of two without either being unreasonable.
| Model | Fee base | Behaviour if the client upgrades specification | Behaviour if the project shrinks |
|---|---|---|---|
| Rate per square metre | Interior floor area | Fee stays fixed | Fee stays fixed unless area changes |
| Percentage of project value | Delivered construction and furnishing spend | Fee rises with the upgrade | Fee falls with the reduction |
| Fixed lump sum | Defined scope and deliverables | Fee stays fixed until scope changes | Fee stays fixed, client loses the saving |
The alignment question follows directly from the table. A percentage fee pays the designer more when the client spends more, which is efficient when a client wants an advocate for quality and problematic when a client wants restraint. A per-square-metre fee is neutral on spending and therefore neutral on the temptation to specify upward.
Worked arithmetic on a single project
Comparing models requires converting each to a number against identical assumptions. Take a 300 square metre apartment with a delivered interior spend of USD 600,000, covering construction works, joinery, finishes and furniture.
| Model | Rate applied | Fee | Fee as share of delivered spend |
|---|---|---|---|
| Per square metre, entry tier | USD 70 per sq m | USD 21,000 | 3.5 percent |
| Per square metre, mid tier | USD 100 per sq m | USD 30,000 | 5.0 percent |
| Per square metre, full-service tier | USD 125 per sq m | USD 37,500 | 6.3 percent |
| Percentage of project value | 10 percent | USD 60,000 | 10.0 percent |
| Fixed lump sum | Agreed scope | USD 45,000 | 7.5 percent |
The arithmetic above uses illustrative rates to show the mechanics rather than to state market pricing. What the comparison demonstrates is that a per-square-metre rate becomes proportionally cheaper as specification rises, while a percentage fee scales with it. On a 300 square metre apartment finished simply, the two models converge. On the same apartment finished expensively, they diverge sharply.
What should be included before any rate is compared
A fee number means nothing without the deliverable list attached to it. Two proposals quoting the same rate can differ by half the work, and the difference usually sits in documentation depth rather than in the visible design.
- Measured survey. A physical dimensional survey of the actual space, not a redraw of the developer plan.
- Layout and furniture plan. Space planning with furniture positioned to scale and circulation checked.
- Photorealistic visualisation. A stated number of views at a stated resolution, with a defined number of revision rounds.
- Working drawing package. Setting-out plans, elevations, ceiling and lighting plans, and joinery details at 1:20 and 1:5.
- Specification schedule. Every finish, fitting and fixture coded, with a named product or a defined performance standard.
- Author supervision. A stated number of site visits during construction, with written reports.
Item four is where proposals differ most. A design package without joinery details at 1:5 pushes those decisions onto the workshop, which means the designer’s intent gets interpreted by a fabricator. The resulting work is sometimes excellent and is never predictable.
A visualisation shows what the client will get if everything goes correctly. A working drawing package is what makes it go correctly.
Why tiered per-square-metre pricing exists
Studios using a per-square-metre model commonly publish two or three tiers, and the tiers differ by depth of involvement rather than by design quality. A base tier delivers documentation and hands over. A full-service tier carries procurement, supplier coordination, delivery scheduling and installation supervision.
- Documentation tier
- Concept, layout, visualisation and drawings. The client procures and builds independently. Suits owners with a trusted contractor already engaged.
- Documentation with supervision
- Adds periodic site visits and written instructions during construction. Suits owners who want intent protected without handing over procurement.
- Full service
- Adds procurement, furniture specification, order management, delivery coordination and installation. Suits owners who are not resident during the works.
Non-resident owners generally find the full-service tier cheaper in practice despite the higher headline rate, because managing procurement remotely across time zones consumes either the owner’s time or a project manager’s fee. Studios offering luxury interior design in Dubai under a single contract absorb that coordination rather than charging it separately.
The clauses that decide whether a fee holds
A fee quoted at signature only holds if the contract defines what triggers an additional charge. Four definitions do most of the work, and their absence is the most common reason a final invoice exceeds a proposal.
- Revision rounds. A stated number of revisions per stage, with a rate for further rounds. Open-ended revision guarantees a variation claim.
- Scope change threshold. A definition of what counts as a change, typically an area change beyond a stated percentage or a change of layout after sign-off.
- Site visit allowance. A number of visits included, with a rate beyond it, since programme delays multiply visits.
- Procurement handling. Whether supplier margins are disclosed, and whether the studio takes a handling fee, a margin, or both.
Procurement disclosure deserves particular attention. A studio that buys furniture at trade price and resells at retail earns from the purchase in addition to the design fee, which is a legitimate model provided the client knows about it. The same arrangement undisclosed is a source of dispute.
How international practice frames the same problem
Work-stage frameworks used internationally split a project into defined phases so that fees and deliverables attach to specific moments rather than to a single undivided scope. The RIBA Plan of Work is the most widely referenced example, and its logic transfers to interior projects even where the exact stage numbering is not used contractually.
Stage-based fee release protects both parties. The client pays for completed stages rather than against a calendar, and the studio is not exposed to a project that stalls after significant work. Professional bodies including the Royal Institute of British Architects publish guidance on staged appointment structures that clients can read before negotiating.
Furniture procurement sits outside the design fee
Furniture cost is not a design fee and should be compared separately. A studio that specifies furniture without supplying it charges only for specification. A studio that supplies furniture earns on the supply, and the total cost to the client depends on both numbers together rather than on either alone.
Clients comparing options should ask for the furniture schedule with quantities and models, then price the same schedule independently. Where a showroom holds Italian furniture in stock, the comparison should include delivery date alongside price, because a piece available in three weeks and a piece available in eighteen weeks are not equivalent goods at the same price.
Choosing between the models
Per-square-metre pricing suits clients who want cost certainty at signature and intend to control specification themselves. Percentage pricing suits clients who want the designer motivated to pursue quality and who accept that the fee will grow with the project. Fixed lump sums suit tightly defined scopes that will not change, which in practice means smaller projects or single rooms.
One test cuts through the comparison. Ask each studio to quote its model against a written scope with the six deliverables listed above, then compare the totals rather than the rates. Proposals that resist being converted into a total for a defined scope are telling you something useful about how the project will be run.
