The 15 percent line
Brentwood’s grading rules are in Chapter 56 of the city code, rewritten by Ordinance 2024-09, and the city’s engineering department reviews and approves land disturbance plans. One detail decides many residential jobs. Building a single-family house or its driveway is exempt from the grading permit only when the lot’s grades are under 15 percent.
On a steeper lot, the plan goes to engineering, so walls, benches and erosion control are worked out on paper before any machine moves.
The other exemptions, and where they end
For a homeowner, the two exemptions that matter are the slope and the size of an addition. Count the roof and any new paving together when you measure an addition against the 800-square-foot line.
- An addition that adds less than 800 square feet of impervious surface is exempt.
- Every exemption ends once disturbance reaches one acre, or when the lot is part of a larger plan of development.
- Sites over five acres post security with the city.
- No more than 50 acres may be under active soil disturbance at one time.
Ground that drains to the Little Harpeth
The one-acre line matches Tennessee’s construction stormwater permit, which also starts at an acre, so a larger Brentwood job answers to the city and the state at once.
The Little Harpeth River runs through the city, including the 27-acre Deerwood Arboretum. Crockett Park covers more than 170 acres, and Concord Park 40 acres at Concord Road and Knox Valley Drive. A regrade that sends more water downhill ends up in that river system, so on sloped lots we treat drainage and silt control as part of the grade itself.
Brentwood incorporated in 1969 and grew from 35.4 to 40.8 square miles with a 2001 annexation; 37,060 people lived here in 2010. The Maryland Farms office complex stands on what was an American Saddle Horse farm, which is the whole arc of site preparation in one address.