A garage conversion that looked like the easy job until the sewer lateral moved

Take a garage conversion, 380 square feet, the kind of project that looks like the easy one on the list because the slab, walls, and roof are already there. A plumber cuts two test holes to find the sewer lateral for the bathroom tie-in. It is not where the county's card says it is. A third hole comes up empty too. At some point the whole lateral had been rerouted around the far side of the house, likely when the original clay line failed, and nothing was ever updated on record. So instead of a nine foot tie-in, the run becomes 40 feet under the driveway, and the driveway is the only access for a truck to the back of the lot. That means saw cutting, digging, laying pipe, and running over plywood for five weeks. That one surprise runs about $6,800 in a case like this. The unit ends up rented to a tenant who works nights and stays low-maintenance, which is its own kind of win. But a contingency budgeted for framing surprises can get spent entirely before framing even starts, which is the real lesson: underground utilities deserve their own line item, separate from structural contingency, especially on a lot with any history of prior repairs.