Can you get through the upper and lower floors of high-rise commercial housing by yourself? Can you build a staircase?

You can get through, but it's more troublesome. You need to abide by the owners' convention and communicate with the property management office. After they agree, let the formal decoration company with business license design with reference to the structure and architectural drawings of the building, and then bring the design drawings, engineering details and your real estate license of the formal decoration company with business license and construction qualification certificate to the Urban Construction Planning Bureau for approval and construction application.