Compare the installation packages
Compare a prefab system's product schedule and fitting requirements with a custom assembly's design, substrate, waterproofing and fabrication work. Normalize the footprint and features first. A custom quote with niches and a bench is not a direct price comparison to a basic manufactured stall.
Normalize the proposals
Use the same dimensions, fixtures and enclosure features for both options, then isolate the work that differs. Mark demolition, substrate preparation, connections and finish restoration as included or excluded. Ask each contractor to identify the condition that would change the recommended assembly. This exposes a real scope difference instead of treating two product labels as a complete comparison. Where either option requires specialist fabrication, identify who measures and approves those components before ordering.
Can a prefab product reduce all site preparation?
No. The floor, walls and connections must still meet the product requirements. A standard unit may limit fabrication, but it does not establish that the existing room is ready to receive it.
The owner should confirm the proposed service scope and provider availability independently. This guidance does not identify an approved contractor, establish coverage for a specific property or guarantee acceptance of the project.