Is it valid for two owners to contract with one contractor, stipulating a fixed total share from their combined property regardless of individual ownership amounts?

Primary text

If two owners stipulate a fixed total share from their collective property to one contractor, the contract is valid even if the exact individual contribution of each owner is unknown. This uncertainty is permissible because it does not involve a significant legal risk (*gharar*) or demonstrable harm (*darar*), similar to selling a single house owned by two people for a lump sum without specifying each owner's share; the compensation for the total subject matter is known.