The point at which you will stop hiring workers will depend on the marginal product of labor, which is the additional output that is produced by adding one more worker. In the short run, the marginal product of labor will initially increase as more workers are added, but it will eventually reach a point of diminishing returns, where the marginal product begins to decline. This occurs because at some point, the additional workers will not have enough resources (such as tools and materials) to work with, and the production process will become less efficient.
In the long run, all inputs are variable, so the marginal product of labor will continue to decline as more workers are added. Eventually, the marginal cost of hiring additional workers will exceed the marginal benefit, and it will no longer be profitable to hire more workers.
In the context of a construction business, you would likely stop hiring workers when the marginal product of labor begins to decline, or when the marginal cost of hiring additional workers exceeds the marginal benefit. This decision would be based on your analysis of the costs and benefits of hiring more workers, and your assessment of the efficiency and productivity of your construction process