[IDEM libro trigesimo nono digestorum. ] §12.6.33.prSi in area tua aedificassem et tu aedes possideres, condictio locum non habebit, quia nullum negotium inter nos contraheretur: nam is, qui non debitam pecuniam soluerit, hoc ipso aliquid negotii gerit: cum autem aedificium in area sua ab alio positum dominus occupat, nullum negotium contrahit.
[THE SAME, Book 39.] If I have built on your ground, and you possess the building, an action for recovery (condictio) will have no place, because no transaction was contracted between us; for he who pays money which is not due, by this very act conducts some transaction; but when an owner takes possession of a building erected on his own ground by another, he contracts no transaction.
sed et si is, qui in aliena area aedificasset, ipse possessionem tradidisset, condictionem non habebit, quia nihil accipientis faceret, sed suam rem dominus habere incipiat.
But even if he who had built on another's ground has himself delivered possession, he will not have an action for recovery, because he would make nothing the property of the recipient, but the owner merely begins to have his own property.
et ideo constat, si quis, cum existimaret se heredem esse, insulam hereditariam fulsisset, nullo alio modo quam per retentionem impensas seruare posse.
And therefore it is well established that if anyone, thinking himself to be the heir, has shored up a block of apartments belonging to the inheritance, he can recover his expenses in no other way than by retention.