Adprobatio operis

We have been referring to adprobatio operis. In fact, in modern German law it is the key moment in most contracts for work.^[2020] Upon successful completion of adprobatio operis, the contractor's remuner­ation becomes due, any claims of the locator, based on defects in the work that were known to him, are excluded, with regard to all other defects the short prescription periods begin to run and, as we have seen, the price risk usually passes to the customer.

The discussion of adprobatio operis in Roman law seems to have been confined to building contracts.^[2022] In our sources we find two different forms of adprobatio.^[2023] Sometimes it is referred to as an act of the conductor: he has to demonstrate that the building has been constructed skilfully and according to the specifications of the contract:

. ut bonitas [locatori] a conductore adprobaretur."^{[2024] [2025] No declaration of approval is required. In other places, however, it is exactly this approval on the part of the locator that is emphasized; Paulus provides a detailed discussion:}

"Si in lege locationis comprehensum sit, ut arbitratu domini opus adprobetur, perinde habetur, ac si viri boni arbitrium comprehensum fuisset, idemque servatur, si alterius cuiuslibet arbitrium comprehensum sit: nara fides bona exigit, ut arbitrium tale praestetur, quale viro bono convenit...."^nl)

Whether he examines the structure himself or designates a knowledge­able third party to do so, probatio is incumbent upon the customer. The standard set for his approval is that of the arbitrium viri boni.

Where the construction work was let "per aversionem"^[2027] (i.e. as a whole and for a lump-sum price), probatio operis of the completed work was necessary to relieve the builder finally of whatever price risk he still had to carry. It also terminated his responsibility for defects in the work.^[2028] Problems could arise in cases where the work was let "in pedes mensurasve":^[2029] by units of measure, or where the price was quantified in singulos dies. The latter example is discussed by lavolenus.^{[2030] [2031] The payment plan fixed in the contract could have some bearing on the question of adprobatio operis. Especially where the progress of the work was determined by the orders and instructions of the locator, the day-by-day equivalent of probatio could be regarded as sufficient:}

"[S]i ita opus locasti, ut bonitas eius tibi a conductore adprobaretur, tametsi convenit, ut in singulas operas certa pecunia daretur, praestari tamen tibi a conductore debet, si id opus vitiosum factum est.... nisi si ideo in operas singulas merces constituta erit, ut arbitrio domini opus efficerctur: turn enim nihil conductor praestare domino de bonitatc opens videtur."¹²⁵

6.