An unpermitted ADU can make it difficult to sell or refinance your property. If an unpermitted unit is discovered and is under construction, the county will issue a stop work order. If the building is complete, it will need an as-built permit, which has extra fees and requires substantial physical work on the building to assess the condition and details.
For unpermitted ADUs built before January 1, 2018, state law says a permit to legalize cannot be denied even if there is a violation of ADU laws or building standards, unless it is a “health and safety concern” or if the building is deemed “substandard” by state Health and Safety Code.