Lot Level Impervious Limit Overages Policy for Homebuilders/New Home Construction

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:

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 homebuilders/new home construction to comply with a limit when they apply for building permit. It is up to the builder/owner 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 homebuilders/new home construction must comply with that limit when applying for a building permit.

If the homebuilder or new construction will exceed the BUA or impervious area limit:

• Option 1: Borrow built upon area from another lot. Homebuilder must document where BUA is coming from and record the BUA limit for the borrowed lot and current lot on a new plat. It is the homebuilder's responsibility to coordinate with developer/engineer, not the County's responsibility.
• Option 2: Borrow from BUA bank in the development. Homebuilder coordinates with developer/engineer to use some of the "banked" BUA. The homebuilder is required to show proof of BUA availability and the final BUA on the lot and in the BUA bank after obtaining the BUA. A new plat shall be recorded with the updated BUA limit.
• Option 3: Roof drain infiltration system. If a homebuilder wants to install a roof drain infiltration system, the system must be designed by an engineer, and all setbacks must be followed. Record a new plat with new BUA and infiltration device shown in stormwater drainage easement. Contact Environmental Health for septic and well setbacks.
• Option 4: Stormwater control measure (SCM). If the homebuilder wants to install a different SCM contained in the NCDEQ Stormwater Manual Minimum Design Criteria, the SCM must be designed by an engineer and all setbacks must be followed. Record a new plat with new BUA and stormwater measure shown in stormwater drainage easement. Contact Environmental Health for septic and well setbacks.
• Option 5: If a large number of lots are involved, the entire subdivision could be redesigned with a regional stormwater facility. An engineered plan revision would need to be submitted and approved.

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