The conditions
The reduction applies where a commission covers several essentially identical buildings, engineering structures, transport works or structural frames that are to be designed and built in temporal or spatial connection and under the same building conditions. Several objects built to a standard design or as series construction are equally covered.
Three elements must be examined, and all three are frequently construed too generously. The middle one is the only one that is alternative rather than cumulative.
| Element | What it requires | Common misreading |
|---|---|---|
| Essentially identical | more than similar; differences in layout, construction or specification rule it out | belonging to the same building type is enough |
| Temporal or spatial connection | either one suffices | both would have to be present |
| The same building conditions | conditions of execution, particularly ground and servicing | identical buildings are enough, whatever the ground |
The staging
The reduction affects the percentages of work phases 1 to 6 and is staged. The staging rises with the number of repetitions and reaches almost full removal from the eighth object.
| Repetition | Reduction of the percentages of phases 1 to 6 |
|---|---|
| First to fourth | 50 per cent |
| Fifth to seventh | 60 per cent |
| From the eighth | 90 per cent |
The first object is invoiced unreduced; the staging begins with the second. The count follows the objects rather than the commissions.
Phases 7 to 9 are unaffected, which makes sense: tendering, site supervision and aftercare arise in full for every object, however often the design is repeated.
| Phases | Effect of the reduction | Weighting in the building service profile |
|---|---|---|
| 1 to 6 | reduced under the staging | 62 % |
| 7 to 9 | unaffected | 38 %, of which site supervision alone is 32 % |
The greater part of the fee per object is therefore preserved. The reduction hits the design, not the supervision of the works.
A worked example
On a commission for four essentially identical residential buildings, the structure per object under the buildings service profile is set out below. It also shows how limited the effect of the reduction on the total fee remains.
| Phases 1 to 6 | Phases 7 to 9 | Total | |
|---|---|---|---|
| Unreduced | 62 % | 38 % | 100 % |
| Object 1 | 62 % | 38 % | 100 % |
| Objects 2 to 4 | 31 % | 38 % | 69 % |
The 50 per cent reduction acts on 62 percentage points, reducing the fee per repeated object by 31 percentage points, that is by not quite a third. The repeat building therefore carries a good two thirds of the full fee. The repeat object therefore carries a good two thirds of the full fee.
Chargeable costs are determined separately per object, unless a joint calculation is exceptionally agreed. Combining them would move the fee table into a different band and change the result.
Application to follow-on commissions
One point frequently overlooked and economically substantial: the reduction may apply even where the objects are not the subject of a single commission. The rule therefore reaches beyond the boundaries of a single commission.
Where a commission covers basic services that were already the subject of another commission between the same parties for an identical building, engineering structure or structural frame, the staging applies even where the basic services are not performed in temporal or spatial connection. The temporal and spatial connection then falls away as a precondition.
In practice: a practice designing an identical building for the same client years later may fall under the reduction, although it is a separate commission. The passage of time offers no protection.
For contract drafting it follows that with repeat clients, whether earlier commissions are relevant should be examined and the assessment recorded in the contract. Otherwise the dispute arises at final account stage.
Why the reduction is substantively right
Designers occasionally experience the provision as an imposition. Substantively it reflects a real effect, and its limits are carefully drawn.
The design effort of phases 1 to 6 arises largely once: the design, the detailing, the bills of quantities and the quantity take-off already largely exist for a second identical object. The effort of phases 7 to 9, by contrast, arises afresh per object, because each must be procured, supervised and handed over.
The reduction reflects precisely that division, and it does so accurately. A practice designing four identical buildings performs the design work once and site supervision four times.
What matters economically is that the reduction holds only for genuinely identical objects. Where adaptations are required, effort arises that a blanket application of the staging would leave unpaid. That is why examining the three criteria before contract is worthwhile.
Where the boundary is difficult
Three situations regularly lead to argument. What they share is that the objects are neither clearly identical nor clearly different.
| Situation | Assessment |
|---|---|
| Standard designs with adaptations | sit between the categories; the greater the adaptation effort, the less tenable the assumption of essentially identical objects |
| Mirroring and variants | a mirrored layout is essentially identical, a layout with altered circulation generally is not |
| Differing ground conditions | bear on the same building conditions and may preclude application, even for identical buildings |
In all three cases a contractual provision recording the parties' assessment is advisable. It does not eliminate the dispute but moves it to a point when both sides are still willing to negotiate.
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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.