In the Code of Hammurabi, rule number 229 and 230 say if a builder has built a house for a man, and has not made his work sound, and the house he built has fallen and caused the death of its owner, that builder shall be put to death, and if it is the owner's son that is killed, the builder's son shall be put to death. What if the builder didn't have a son? Or any children at all for that matter?
The Hammurabi Code dates from 1754BC and is the preserved legal code of Baylonian law. It provides for various punishments according to the circumstances of the case.
There are several translations of the code and the sections you cite; Code 229 and 230 appear to be comparable to other translations. The question you pose is simple, yet can lead to complicated answers. The simple answer is no one can be absolutely sure what the next course of action would be for the builder in your scenario.
There are basically two scenarios to complete the legal requirements of an eye for an eye, which is how the code is structured. Children are subservient to their parents and can be seized by the government for execution if the code calls for it. Under this law, the builder may have to give up a daughter as punishment rather than a son.
If the builder has no son, or if the judges demand it, they could also charge the builder under Code 14: "If a man has stolen a child, he shall be put to death." It would be possible to argue the builder stole the inhabitant's child upon building a poor house and therefore should be put to death. Likewise, the judges may also direct him to be put to death if a daughter is not suitable payment for the deed.
I suspect, given the structure of the Code, the builder would face losing someone of value to them, which would most closely mirror the loss of the inhabitant. This might be a daughter, wife, grandchild or other significant party. I think as a last resort the builder would be put to death.