Mosinee, WI Fence Regulations: Retaining Walls (2026)

The City of Mosinee's exterior property requirements, Sec. 42-1380 of the Code of Ordinances (Ord. No. 97-10, adopted September 8, 1997), address retaining walls only at subsection (h), and only where a wall abuts public property. That subsection requires such walls to be structurally sound and bars constructing or maintaining them in a manner that causes a repeated flow of mud, gravel or debris onto a public sidewalk, street or alley. The code does not set a maximum height, does not require an engineering stamp, and does not create a building-permit track specific to retaining walls; the standard is a maintenance and nuisance one, not a design-review one.

The related erosion provision in subsection (f) works the other direction: whenever soil erosion spills over onto a sidewalk, street or alley from any cause, the property owner must correct the condition by building a suitable retaining wall, grading, sodding or planting ground cover, so a wall can become the required fix for an erosion problem even where none previously existed. Because both subsections sit inside the general exterior-maintenance article rather than the land use chapter's dimensional standards, a private retaining wall that does not abut public property and is not causing erosion runoff falls outside this section altogether.