A percentage of construction cost or a fixed fee for a defined scope: how each basis behaves when the project grows, shrinks or slows down.
Design fees are quoted either as a percentage of construction cost or as a lump sum for a stated scope, and the choice changes what happens when the project changes. A percentage grows with the building; a lump sum holds until the scope moves. Neither is more honest than the other, but each creates a different incentive, and the incentive matters more than the headline number.
A percentage of construction cost at a glance
The fee is expressed as a share of the eventual construction value, usually with interim payments based on the current estimate and a reconciliation later. It scales automatically with the project, which suits schemes whose size is not yet settled. Its weakness is the incentive: a design that costs more to build also earns more fee, and an owner has to rely on professionalism rather than on structure.
A fixed lump sum for a defined scope at a glance
The fee is a stated amount for a stated list of deliverables, with additional services priced separately. It gives budget certainty and makes proposals comparable, provided the scope is written tightly. Its weakness is that everything outside the definition becomes an extra, so a loose scope produces a stream of additional fee requests that erode the certainty you paid for.
Budget certainty for the owner
A percentage of construction cost: Low until construction cost is known, since the fee moves with the estimate.
A fixed lump sum for a defined scope: High for the defined scope, and only as good as the definition.
Incentive created
A percentage of construction cost: Fee rises with construction cost, which is an unhelpful alignment on cost control.
A fixed lump sum for a defined scope: Fee is fixed, so the incentive is to complete the scope efficiently rather than expansively.
Behaviour when the project grows
A percentage of construction cost: Adjusts automatically, which avoids renegotiation but can surprise you.
A fixed lump sum for a defined scope: Requires a variation to the appointment, which is visible and can be challenged.
Behaviour when the project shrinks or stalls
A percentage of construction cost: Fee falls with the estimate, though work already done is usually payable.
A fixed lump sum for a defined scope: Fee stays, and a long stall usually triggers a claim for prolongation.
Comparability between proposals
A percentage of construction cost: Poor, because percentages apply to different assumed construction values.
A fixed lump sum for a defined scope: Good, provided every bidder prices an identical deliverables list.
Administration effort
A percentage of construction cost: Ongoing reconciliation against the current construction estimate.
A fixed lump sum for a defined scope: Simple until an additional service is claimed, then a scope argument.
Where it fails
A percentage of construction cost: A gold-plated design that nobody has an interest in questioning.
A fixed lump sum for a defined scope: A thin scope definition, producing extras for work you assumed was included.
When a percentage of construction cost wins
- An early appointment where the scheme size is not yet settled.
- A project likely to change substantially between concept and tender.
- A market convention your consultants will price more competitively under.
- An owner who wants the fee to fall automatically if the project shrinks.
- A framework relationship across several projects of varying size.
When a fixed lump sum for a defined scope wins
- A defined building on a known plot with a settled brief.
- An owner who needs a fixed soft cost line for a funding case.
- A competitive selection where proposals must be compared like for like.
- A project with a firm cost ceiling that the design must respect.
- A repeat building type where the work content is predictable.
How to decide
Use a lump sum wherever the scope can be defined, which is almost always once you have a plot, an envelope study and a brief, and write the deliverables list before asking for prices. Reserve the percentage basis for genuinely open-ended early work, and convert it to a lump sum as soon as the scheme is settled. Whichever you choose, tie payment to deliverables rather than to elapsed time, and price additional services in advance so that an extra has a known rate.
Compare proposals by building a table of deliverables and marking which are included, excluded or priced as extras in each. Then convert any percentage quotation into an amount using the same assumed construction cost for every bidder. The differences that emerge are almost always scope differences rather than value differences, and the exercise usually identifies one or two deliverables that nobody included.
Domira designs, builds and manages projects across Saudi Arabia for owners who are based abroad: land appraisal, feasibility, design, construction, handover and asset management under one accountable contract. Send us the plot or the brief and Domira will put the numbers in front of you before you commit.
Frequently Asked Questions
Is it better to pay design fees as a percentage or a fixed amount?
A fixed amount for a defined scope gives you budget certainty and comparable proposals, and it avoids paying more because the building became more expensive. A percentage suits genuinely open-ended early work. In practice, define the scope as soon as you can and convert to a lump sum, with additional services priced in advance at agreed rates.
What counts as an additional service on a design appointment?
Anything outside the stated deliverables: extra design options, a change of brief, redesign after an approval comment caused by a change you requested, additional site visits, or work caused by a delay outside the consultant control. The appointment should define the boundary and state the rate, otherwise each item becomes a negotiation while you need the work done.
Should design fees be paid monthly or by stage?
By stage, against delivery of the package for that stage, with the final instalment of each stage released when you have received and reviewed the deliverable. Monthly payment against time rewards elapsed effort rather than progress. If a project is long, combine the two: monthly invoicing within a stage, capped at the stage value until the deliverable arrives.
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