My township refernces the county for building code, which then references 2009 michigan residential building code. That code says the following regarding permitting:
" 105.2. Work exempt from permit. Exemptions from permit requirements of the code shall not
be deemed to grant authorization for any work to be done in any manner in violation of the
provisions of the code or any other laws or ordinances of this jurisdiction. Permits shall not be
required for any of the following:
(i)One-story detached accessory structures used as tool and storage sheds, playhouses and
similar uses, provided the floor area does not exceed 120 square feet (11.15m2)."
So going the size i want, it sounds like I will need to explore building permit stuff :-/
Be sure to check zoning ordinances as well.