The three models compared
| Table fee | Hourly fee | Lump sum | |
|---|---|---|---|
| Reference quantity | chargeable costs | actual time spent | agreed scope of services |
| Risk borne by | client, if costs rise | client | designer |
| Suits | clearly defined building tasks | open tasks, advice, existing buildings | defined tasks with known effort |
| Evidence burden | cost calculation | time recording | scope demarcation |
| Point of dispute | zone and chargeable costs | reasonableness of hours | extent of services owed |
The third row is notable. The table fee shifts a risk onto the client that is frequently overlooked: as chargeable costs rise, so does the fee basis. A lump sum shifts the effort risk onto the designer.
When an hourly fee makes sense
It suits every situation where effort cannot be determined in advance. Four are typical.
| Situation | Why the effort is open |
|---|---|
| Advisory work without a defined output | feasibility assessments, site appraisals, support in negotiations |
| Work in existing buildings with an unknown starting condition | until the condition survey is complete |
| Additional services arising during the project | a framework agreement with hourly rates is more workable than negotiating mid-project |
| Work arising from changes | their extent is open at the time of commissioning |
Four points need regulating: rates by qualification level, how time is recorded and evidenced, a cap where appropriate, and the treatment of travel and waiting time. The last is the most often forgotten and the most often disputed.
A cap is the commonest compromise. It is permissible but should be worded with care as a cost ceiling: agreed as binding, it becomes an agreement as to a characteristic of the work, with the corresponding consequences.
When a lump sum makes sense
It suits situations where the scope can be described precisely and the effort is known from experience. Both conditions must hold together.
Its advantage is predictability for both sides. Its risk sits wholly with the designer, and that risk grows with three factors: imprecision in the scope description, length of the project, and number of parties involved.
Three provisions reduce it, and all three belong in the same contract. None of them can be imposed afterwards.
| Provision | What it achieves |
|---|---|
| Scope demarcation | what is not described is not covered by the lump sum; the HOAI service profiles are the appropriate reference even without invoicing by table |
| A change clause | where scope changes, the lump sum must be adjusted; without a provision the dispute arises later and the burden of proof sits with the designer |
| The assumptions | project duration, number of coordination meetings and assumed extent of specialist coordination; where they diverge, that is the anchor for an adjustment |
What applies unchanged
Two formal requirements apply irrespective of the model chosen. They are overlooked more often with hourly rates and lump sums than with table fees, because no ordinance text sits alongside.
| Requirement | Consequence of disregarding it |
|---|---|
| Text form for the agreement on the level | the base fee rate applies to basic services, regardless of the model intended |
| The duty to inform consumers, in text form before the binding contractual declaration | a fee above the base fee rate is capped at it |
The second point is the commonest trap in lump sum agreements with private clients. The consequence is precise: a fee above the base rate is capped at that rate. A lump sum below it is unaffected.
Both mechanisms are covered in the article on fee agreements. It also explains why the first consequence cannot be rebutted.
The service profiles remain decisive
One point is regularly underestimated with lump sums. Even where the table is not used for invoicing, the scope owed is frequently determined through the work phases.
The reason is practical. The service profiles are the only normed catalogue of what a design phase comprises. Agreeing a lump sum for phases 1 to 8 thereby describes what is owed without listing it item by item.
A recommendation follows to refer to the work phases even under free remuneration, and to name any departures expressly. The article on additional services covers the boundary.
Mixed models are the norm
In practice a single model is rarely used alone. A combination assigning the appropriate model to each part of the project is common and usually sensible.
| Part of the project | Suitable model |
|---|---|
| Basic services of the commissioned phases | table fee or lump sum |
| Condition survey before contract | lump sum or hourly fee |
| Additional services of open extent | hourly rates under a framework agreement |
| Work arising from changes | hourly rates or a separate lump sum |
| Aftercare in phase 9 | separate lump sum per inspection |
The last row is a practical answer to a structural problem: aftercare is weighted at two per cent and extends over years. A separate agreement per inspection resolves that more cleanly than dropping the phase.
What matters is delimiting the models clearly in the contract. A lump sum for basic services with hourly rates for everything else works only where what counts as a basic service is described. The service profiles in the annexes are the appropriate reference.
Ancillary expenses
Regardless of the model, ancillary expenses are not covered by the fee. Travel, reproduction and similar costs must be separately agreed, failing which they are reimbursed on individual evidence.
A lump sum for them is customary and permissible. It belongs in the same agreement as the fee, because a later provision may founder on the remuneration arrangement already made.
Related articles
This article reflects the position of the rules and case law at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.