How to offset a polysurface overall by a certain distance?

Here is an exterior wall shape, which is a combined multi-curved surface.

Now I’m using Rhino’s offset surface tool, but I can’t generate an operation that offsets a certain distance outward.

Using the Surface Offset command produces incorrect results.

How can such a surface be offset outward and be directly created as a solid body?

9-导出门窗模型.rar (6.2 MB)

If you stretch the surfaces one by one, there will be gaps between the stretched entities.