Two cases came before the Oak Hill Planning Commission in the same month a few years back. One was a driveway and pool addition on Granny White Trace. The other was a stormwater mitigation plan on Cherrywood Drive. Neither project involved a new house, a subdivision, or anything that would normally draw a public hearing. Both still required Planning Commission review, because both sat on land that triggered two separate ordinances at once: the city's steep-slope regulations and its Radnor Lake Natural Area Impact Zone.
That pairing is the detail worth understanding before you fall for a lot in either city. Oak Hill and Forest Hills are not neighborhoods inside Metro Nashville. They are their own incorporated municipalities, each running its own zoning code, its own building department, and its own Planning Commission, separate from Metro. And the features that make a lot in either city desirable, a wooded hillside, a ridge line facing Radnor Lake State Natural Area, proximity to Percy Warner Park, are frequently the same features that pull a routine project into a longer, more expensive review process.
Two Cities, Not One Neighborhood
Oak Hill spans roughly eight square miles in southern Davidson County, bordered by 12 South and Green Hills to the north, Brentwood to the south, Crieve Hall to the east, and Forest Hills to the west. Zoning there permits only single-family dwellings, along with churches and schools that require a conditional use permit and a minimum of 6.42 acres. There is no commercial use anywhere in the city. The Tennessee Governor's Residence, a Georgian-style mansion built in 1931 at 882 Curtiswood Lane South, has sat inside Oak Hill's boundaries since 1949, which gives some sense of how long this has been a strictly residential enclave.
Forest Hills, just west of Oak Hill along Hillsboro Pike, runs its own parallel system. Its building and zoning department reviews every application, and if plans do not comply with city ordinances, the homeowner has to seek a variance from that city's own Board of Zoning Appeals, not Metro's.
Neither city is large. Both maintain full planning infrastructure anyway, because both were built around the idea that residential character, not density, is the thing worth protecting. That protection is administered locally, which means a project that would clear a standard Metro review can still stall in either city if it touches the wrong slope or the wrong tree line.
The Ordinance That Follows the View
Oak Hill's steep-slope rule is specific: any area of 1,000 or more square feet with a grade of 15 percent or greater cannot receive a building permit until a site plan meets the city's steep-slope requirements and clears Planning Commission review. That plan has to show the exact size, shape, and drainage of the lot, and no construction that cuts the toe of a slope is allowed unless a licensed geotechnical engineer has signed off on a stabilization plan.
Separately, any property that backs up to Radnor Lake State Natural Area falls under the Radnor Lake Natural Area Impact Zone. The Planning Commission's job there is to keep visual and watershed impact to a minimum, which in practice means ridge lines and cleared areas have to stay as unobtrusive as possible when viewed from inside the natural area itself. A new residence, an addition, or a subdivision in this zone needs Planning Commission approval before anything moves forward.
The two ordinances are written separately, but the city's own guidance notes they frequently apply to the same parcel. A lot with a hillside view of Radnor Lake is, almost by definition, a lot with slope. That is why the Granny White Trace and Cherrywood Drive cases both carried the same double designation, Zone C, Steep Slope, RLNAIZ, on the same public agenda.
| Trigger | What gets reviewed | Who reviews it |
|---|---|---|
| Steep slope (1,000+ sq ft at 15%+ grade) | Site plan, drainage, slope stabilization | Oak Hill Planning Commission |
| Radnor Lake Impact Zone (property backs to the natural area) | Ridge line visibility, watershed impact | Oak Hill Planning Commission |
| Both together | Combined review, one filing | Oak Hill Planning Commission, single combined fee |
What a Hillside Lot Actually Costs to Build On
The dollar figures are public. A combined steep-slope and Radnor Lake review carries a $2,000 fee that covers up to two reviews, with additional reviews billed at $500 each. A straightforward variance or administrative appeal runs $250. A conditional use permit without added impervious surface is $1,000, but one that adds impervious surface, a pool deck, an expanded driveway, jumps to $4,000. None of these numbers include the architect's or engineer's time to prepare the site plan those reviews require.
Oak Hill also grants variances only on hardship grounds, things like existing slope, easements, or mature trees that predate the current owner, not on convenience. If a buyer's renovation plan simply doesn't fit the lot as drawn, wanting more square footage is not, on its own, a reason the Board of Zoning Appeals will accept.
Even after approval, Oak Hill inspects in stages, pre-development, foundation, framing, and insulation, with mechanical, electrical, and plumbing inspections required before structural sign-off, and no occupancy without a final certificate. None of this is unusual for residential construction generally. What is unusual is how much of it gets triggered by a lot's natural terrain rather than by its size or its owner's plans.
Forest Hills Asks Before You Draw
Forest Hills folds a version of the same caution directly into its permit application. Before a building permit is issued, the applicant has to submit a geotechnical study, a formal site investigation covering soil properties, risk assessment, and specific recommendations for construction methods that avoid erosion or slope degradation. That study has to meet the professional standard of care used by engineers across Middle Tennessee. It is due at the application stage, before design work is finalized, not after.
Forest Hills also zones by acreage in a way tied to specific roads rather than to a uniform citywide minimum. Its Estates A district requires three acres and applies along Hillsboro Pike, chosen specifically to preserve a more rural setback along that corridor. Its Estates 1A district requires six acres and covers the area adjoining Percy Warner Park along Chickering and Page Roads, protecting what the city's own ordinance calls a countryside, park-like character. Open space subdivisions in Forest Hills have to set aside at least 30 percent of total acreage as permanently preserved open space, unaltered by clearing or grading.
Buying three or six acres in Forest Hills is not simply a matter of finding a larger lot. It means the parcel sits inside a district the city has deliberately shaped around a nearby landmark, Hillsboro Pike or Percy Warner Park, and that shaping carries forward into anything built there next.
The Feature and the Friction Are the Same Thing
Put the two cities side by side and a pattern holds. The lots buyers want most in Oak Hill and Forest Hills, ridge views toward Radnor Lake, wooded acreage backing to Percy Warner Park, frontage along a protected corridor like Hillsboro Pike, are the same lots carrying the heaviest review requirements. That is not a coincidence. Both cities wrote their ordinances specifically to protect the qualities that make these parcels desirable in the first place. The view is the reason the lot costs what it costs. The view is also the reason the pool addition needs a hearing.
For a buyer evaluating a specific property, that means the standard questions, price per acre, days on market, comparable sales, are only half the picture. The other half is whether the parcel sits inside a steep-slope area, whether it backs to Radnor Lake, whether it falls inside a Forest Hills district tied to a road or a park boundary. Those answers change the timeline and the budget for anything built there next, regardless of what the listing photos show.
A short list worth working through before writing an offer on a hillside or wooded lot in either city:
- Ask whether the parcel falls inside Oak Hill's Radnor Lake Impact Zone or has any area of 15 percent grade or greater.
- Request any existing survey, geotechnical report, or prior Planning Commission filings tied to the property.
- In Forest Hills, confirm which zoning district applies and whether it carries an acreage minimum tied to a specific road or park boundary.
- Budget review fees and professional site studies as a separate line item from construction costs, not folded into a general contingency.
A Few Questions Worth Answering Directly
Does this apply if I'm not changing the exterior? Oak Hill's certificate process is built around exterior and site work. Interior renovations that do not touch the building's footprint or the surrounding grade generally sit outside steep-slope and Radnor Lake review, though it is worth confirming with the Building and Zoning Office before assuming an interior project is exempt.
What if my lot already has an existing nonconforming structure? Both cities allow certain modifications to nonconforming structures, but only if the change meets the currently adopted code otherwise. A pool or addition on a lot that already exceeds its maximum lot coverage, for instance, still has to fit within that coverage limit even if the existing structure predates the rule.
Does buying, rather than building, trigger any of this? Not directly. These ordinances attach to construction activity, not to a sale itself. But permit history follows the parcel, and a buyer who skips reviewing it can inherit unresolved conditions, an unpermitted addition or an incomplete stormwater plan, without realizing it until they try to build something themselves.
Oak Hill and Forest Hills reward patience more than almost any other estate market in Middle Tennessee. The lots that draw buyers here were shaped by decades of deliberate, narrow zoning, and the review process protecting them is just as deliberate. Working through that process with someone who has already read the ordinance, not just the listing, is the difference between a smooth close and a stalled one.
If you are evaluating a specific lot in Oak Hill or Forest Hills, or preparing one for sale, Heather Hamel can help you understand what a parcel's zoning history means before you commit to a plan. Begin a private consultation to start that conversation.
