Is it obligatory to pay the increase in the cost of finishing a building, given that the actual cost significantly exceeded the expected cost due to a lack of oversight of labor and expenses, even though the contract stipulates paying the cost plus fees?

The aforementioned contract can be specified in several ways, including determining the price based on the actual cost price and a percentage profit margin. In this case, accurate and detailed financial data must be provided. If the cost in the contract is based on the actual cost, then the questioner must pay the actual cost in addition to the fees, because what the uncle stated about the cost was merely an estimate, and he is not obligated to guarantee an increase in cost unless there was an agreement to that effect.

If the cost increases due to workers' negligence or supervisory shortcomings, the uncle is obligated to guarantee the increase. As for handing over the project to a partner, there is no harm in it if the employer did not stipulate that the contractor must perform the work himself.

If the contract was an agency, and you authorized the agent to appoint his partner or knew about it and approved it, then the uncle is not liable for anything. However, if you were unaware of this, the preponderant opinion is that he is not permitted to do so, and he must guarantee the increased cost, because an agent guarantees the damage resulting from his violation.