Residential Alterations/Additions Permit

How Do I Apply? 

Please visit the Building Construction Permit section of our Citizenserve Citizen Access Portal to apply online.

When is a Residential Alterations/Additions Permit Required?

A residential alterations/additions permit is required whenever changes or additions to a residence are made, including deck installations, additions, carport conversions, electrical panel upgrades, water heater installations, HVAC installations, or changes in plumbing.

Types of Residential Alterations/Additions Permits

What Will I Need to Submit?

  • For decks, room additions, finished basements, and remodeling projects building plans (pdf format preferred) showing footing/foundation detail, framing member sizes, header sizes, door and window location and sizes, truss or rafter design, flooring detail, and any electrical or plumbing. Also include floor plan, wall cut detail, elevations, and any applicable stair details.
    • When electric is included, an electrical permit is required regardless of the size of the structure. The minimum service to be installed is: 1 (one) GFI receptacle, 1 (one) light with wall switch, and every man door requires an interior switch and exterior light. 
  • For decks and room additions, a detailed plot plan (PDF) showing the location of your home and proposed building or structure on the lot. Show distances to property lines and keep in mind that structures may not be located over easements or septic systems.
  • For electrical upgrades, mechanical upgrades, plumbing upgrades, and water heaters, a building permit is generally the only submittal required.

Fees & Plan Review

Building Permit Fees (PDF)

The plan review process typically takes about 10 working days. However, water heater, electrical, mechanical, and plumbing upgrade permits can be done same-day.

When the permit is ready, you will be notified via email that the permit is ready for pick up as well as the final amount of the permit fee.

Building permit fees are based on cost of construction. At the time of application, you will provide us with your estimated cost of construction and our plan reviewers will calculate an estimated cost of construction per ICC Building Safety Journal. The higher of these two estimates will be multiplied by 0.73%; this amount, or the minimum permit amount, whichever is higher, is the building permit fee that will be charged. There may be other fees associated with your permit, such as floodplain permit fees, land disturbance fees, and other fees as applicable.


At least one inspection will be required. When the permit is issued, the necessary inspections required will be listed on your permit card. At the inspector's discretion, some inspections may not be applicable to the particular permit in question. The inspector will note those inspections are "N/A" at a later date.

Inspections must be called into the office by 3 p.m. the business day prior to your requested inspection date. To schedule your inspection, call 636-949-7345. If it is necessary to cancel or change your inspection, please do so as soon as possible. Also, please remember to post your permit so that it is visible from the street.


Please contact the St. Charles County Building and Code Enforcement Division at 636-949-7345 or