Lot Level Impervious Limit Overages Policy for Homeowner Additions

The following policies have been established by the Johnston County Stormwater Manager to address built upon area (BUA) or impervious surface overages on single-family residential lots:

1. Built-upon area policies for existing development:
• If the BUA limit or maximum impervious area is NOT on the recorded plat, then the County will not require homeowners to comply with a limit when they apply for building permit. It is up to the homeowner to verify any restrictive covenants or HOA requirements.
• If the BUA limit or maximum impervious area IS recorded on the plat and a building permit is required, then homeowners must comply with that limit when applying for a building permit.
2. If the homeowner addition DOES NOT require a building permit:
• Homeowners Associations and homeowners should self-regulate any additions of impervious surfaces that do not require building permits. Where a HOA elects to regulate, the Homeowner's Guidance Manual can be used as a reference. Johnston County does not review additions that do not require a building permit.
3. If the homeowner addition DOES require a building permit:
• Option 1: Borrow built upon area from a bank of unused BUA in the development. The homeowner must coordinate with the developer/engineer or the homeowner’s association (HOA) to use some of the "banked" BUA. The homeowner is required to show proof of BUA availability and the final BUA on the lot and in the BUA bank after obtaining the BUA. The homeowner records the new plat with the updated BUA. 
• Rain garden – Must be sized per County tool. The placement must consider and comply with setbacks from property lines, septic lines, well, structures. Record a new plat with new BUA and lot level stormwater measure shown in a stormwater drainage easement. Contact Environmental Health for septic and well setbacks.
• Rain barrel – Must be sized per County tool. Rain barrels must be located in a stormwater drainage easement. Record a new plat with new BUA and rain barrel(s) shown in stormwater drainage easement(s).
• Option 2: Design and install a lot level stormwater measure. Refer to the Homeowner's Stormwater Guidance Manual for design and installation guidance for rain gardens and rain barrels. As-built certifications will be required.
• Option 3: Infiltration device or other engineered device that meets the State/County requirements – Must be sized by an engineer and located in drainage easement, adhering to setbacks from septic lines, from wells, from property lines, and from structures. Record a new plat with new BUA and infiltration device shown in stormwater drainage easement. Contact Environmental Health for septic and well setbacks.

Questions regarding these policies should be directed to the Stormwater Manager at 919-209-8333