Variations and additional works

They are treated differently and must not be confused. A variation replaces work, an additional work adds to it.

Kind	Content
A variation the client wants	a change of solution on the client's initiative
Additional work arising from the design	necessary work that was not in the design
An unforeseen circumstance	emerging during the works: ground conditions, the state of the existing building

The third is the most frequent in reconstruction and the hardest to plan for. Responsibility for the three is allocated differently, and the contract must deal with them separately: whoever does not distinguish them beforehand argues about them afterwards.

Three situations, and only in the first does the client hold a strong position. Position depends on when the terms were agreed.

Situation	How the price is formed
The variation concerns work already in the budget	the agreed unit price
The variation is similar to existing work	the unit price can be adapted and justified
The variation is entirely new work	the price has to be negotiated

A unit price was agreed at a time when competition still existed. In the third situation the price is negotiated without competition, which is always the weaker position. The practical conclusion: the more detailed the original budget, the more variations fall into the first category.

Four things, and the fourth is the most sensitive in practice. How a variation is initiated and who approves it. How work for which a unit price exists is priced. How work with no unit price is priced, for instance by an agreed percentage margin. And whether, and up to what amount, work may begin before written approval.

Situations arise on site where waiting costs more than the work itself, and then the work is done and argued about afterwards. A small monetary threshold up to which work may continue resolves most of those situations.

Five fields should appear on every variation, and the fourth is the most underrated. It concerns the effect on the programme.

Field	Note
Which budget line or position it relates to	ties the variation to the structure
What changes and why	the justification
Effect on cost	with the calculation
Effect on the programme	the one most often forgotten
Approval and date	the formalities

A variation that lengthens the construction period also increases site costs, as covered by the article on a common classification. Leaving the time effect out of account means the same variation returns as a second invoice.

Three reasons, and the second matters most to the contractor. It concerns the timing of payment.

A clear procedure reduces disputes, which are a cost to both parties. Written approval protects the contractor against non-payment. And pricing based on unit prices is faster than negotiating each time.

The second is worth raising when the variation procedure is discussed, since it changes the tone of the conversation: an oral agreement protects either party only for as long as no one disputes it. The contractor's interest here matches the client's.

There are three kinds of variation, those the client wants, those arising from the design and those arising from unforeseen circumstances, and responsibility for them is allocated differently, so the contract must distinguish them. Pricing has three situations, and only the one where the work is already in the budget gives the client a strong position, since the unit price was agreed while competition lasted. A variation must be tied to a budget line and its time effect accounted for, since a longer construction period also increases site costs.

Four rules: distinguish the three kinds of variation in the contract itself. Tie every variation to a budget line rather than to a separate document. Always account for the time effect, not only the cost. Agree a small threshold up to which work may continue before written approval.