If you're underwriting a teardown or a major addition anywhere between Whilden Street and Ben Sawyer Boulevard right now, you've probably heard the headline number: 5,500 square feet. That's the new maximum home size Mount Pleasant Town Council adopted for Old Mount Pleasant on February 10, 2026, and it's the figure that's been repeated in every conversation about the neighborhood's building rules since.
It's also, for most lots in this overlay, not the number that actually stops you. A second rule buried in the same ordinance almost always binds first, and if you're pricing a deal off the 5,500-square-foot ceiling alone, you're underwriting the wrong constraint.
The Number Everyone's Repeating
Before February, there were no building-area restrictions at all for homes in Old Mount Pleasant, or in the handful of legacy neighborhoods that share its overlay district: The Groves, Cooper Estates, Shemwood, and Bayview Acres. A buyer could pick up a 1960s ranch on a small lot, tear it down, and build up to whatever the market would bear. That's exactly what had been happening. Council members had spent months hearing from residents about newer homes going up significantly taller and larger than the small, closely-set houses around them, and by the time the ordinance reached a final vote, the town had settled on two hard numbers: no home over 5,500 square feet, and no home covering more than half the lot.
Both numbers apply. Whichever one is smaller wins.
The Number That Actually Stops You First
Here's the arithmetic the ordinance itself sets up, and it's worth doing before you write an offer.
Fifty percent of the lot equals 5,500 square feet only on a lot of exactly 11,000 square feet, a little over a quarter acre. Below that lot size, the building-area-ratio limit is the tighter number. Above it, the flat 5,500-square-foot cap takes over.
| Lot size | 50% BAR limit | Flat cap | Binding constraint |
|---|---|---|---|
| 6,000 sq ft | 3,000 sq ft | 5,500 sq ft | BAR limit |
| 8,500 sq ft | 4,250 sq ft | 5,500 sq ft | BAR limit |
| 11,000 sq ft | 5,500 sq ft | 5,500 sq ft | Break-even |
| 14,000 sq ft | 7,000 sq ft | 5,500 sq ft | Flat cap |
Old Mount Pleasant is described in town planning discussion as an enclave of homes situated close together on small parcels, a mix of modest single-story ranches and newer, larger rebuilds on the same size lots. That description matters here. On a great many of those parcels, especially anything under a quarter acre, the lot-coverage rule is what actually caps your build, not the round number everyone quotes. A 6,000-square-foot lot doesn't get you anywhere near 5,500 square feet of house. It gets you 3,000, and that's before you've accounted for setbacks.
If you're comparing this deal to a rebuild you did somewhere else in Mount Pleasant where no such limit exists, or to a pre-February project in this same neighborhood, your old math on achievable square footage no longer applies here.
What the Council Actually Eased Up On
The ordinance isn't a story of pure restriction, and treating it that way will cost you on the accessory dwelling side.
Two provisions from the original draft got stripped out before final passage. Council removed a proposed 40 percent footprint cap on ADUs. It also dropped a rule that would have required any accessory structure to be no taller than the primary house on the lot. Both of those would have meaningfully limited what you could build as a secondary structure, a carriage house, an in-law suite, a garage apartment, and neither survived the final vote.
What replaced them is a setback rule tied to height rather than size. A standard accessory structure needs a six-foot setback from the property line. Once that structure hits 18 feet or taller, the setback jumps to 10 feet. Councilman Daniel Brownstein, describing the pressure that drove the whole ordinance, pointed to what he called simply scale issues in the neighborhood.
"I feel like I'm in a fishbowl. I have no privacy in my backyard."
That's how Planning Director Michele Reed characterized the complaint she'd heard repeatedly from residents in the run-up to the vote, and it's a useful lens for the ADU rules specifically. The town wasn't trying to shrink accessory buildings. It was trying to keep tall ones far enough from the fence line that a neighbor's yard doesn't become someone else's second-story window view. If your project includes a detached ADU under 18 feet, you have more flexibility on footprint than the earlier draft would have allowed. Push past 18 feet and the setback math changes.
Where the Line Actually Falls
This ordinance does not apply townwide, and that distinction matters if you're comparing sites.
The overlay covers Old Mount Pleasant and the specific legacy neighborhoods named in the ordinance, an area that runs from Whilden Street to Ben Sawyer Boulevard and sits between Johnnie Dodds Boulevard and Coleman Boulevard. Council considered extending these same restrictions across all of Mount Pleasant and chose not to, at least for now. Public input on the rule had come almost entirely from residents inside this specific footprint, and the town left the door open to revisit a townwide version later without committing to one yet.
Worth separating this from the neighboring Old Village Historic District, which has run its own building-area-ratio review through the town's Board of Architectural Review for years, independent of this February ordinance. The two areas sit next to each other and get talked about together constantly, but they're governed by different, longer-standing frameworks. A comp from Old Village's BAR process won't tell you what's allowed in Old Mount Pleasant, and vice versa.
What Changed, in Order
For anyone trying to track the difference between the January proposal and what actually passed:
- The original draft would have applied the new size and setback rules townwide. Council narrowed the final version to Old Mount Pleasant and the named overlay neighborhoods only.
- A proposed 40 percent footprint cap on ADUs was removed before final passage.
- A requirement that accessory structures be no taller than the primary home was also removed.
- In their place, council adopted a height-triggered setback: six feet standard, 10 feet once an accessory structure reaches 18 feet or taller.
- The 5,500-square-foot maximum home size and the 50 percent building-area-ratio limit were both adopted as written, with no cap on whichever number binds tighter on a given lot.
The ordinance passed unanimously on February 10 and took effect immediately, so there's no phase-in period to plan around. If you're closing on a lot in this footprint now, these rules already govern whatever gets built there.
What This Means If You're Underwriting a Project Here
Run the lot-size math before you run the comps. If the parcel is under 11,000 square feet, the number that governs your build isn't 5,500, it's half the lot. That changes your per-square-foot cost basis, your exit price ceiling, and whether the deal still works at the price you're paying for the dirt.
If your plan includes a detached ADU, decide early whether you need it over 18 feet. That single design choice determines which setback rule you're building to, and it's cheaper to solve on paper than after a foundation is poured.
And if you're comparing this site to something in the adjacent Old Village Historic District, treat them as two separate rulebooks. They sit a few blocks apart and get lumped together in casual conversation, but the entitlement path for each one runs through a different process with different history behind it.
This is the kind of detail that's easy to miss if you're working from a listing sheet and a set of assumptions from your last project somewhere else in Mount Pleasant. It's also exactly the kind of local entitlement question PRL Consulting Group works through with investors and builders before they're locked into a purchase contract, not after.
A note on how this is written: nothing here is legal or zoning advice, and ordinance language and enforcement details can shift. Before you finalize a purchase or design based on any figure in this piece, confirm current requirements directly with the Town of Mount Pleasant's Planning, Land Use, and Neighborhoods department.
A few questions that come up on almost every deal in this overlay:
Does the 5,500-square-foot cap include garages and porches? The ordinance sets building-area-ratio and total home size limits at the town level, and how specific structures like attached garages or covered porches count toward that total is a detail worth confirming with Planning staff before you finalize a design, since it directly affects how much of your 50 percent lot allowance is left for living space.
Can I still build an ADU without triggering the 10-foot setback? Yes, as long as the structure stays under 18 feet. The six-foot standard setback applies below that height, with no footprint cap remaining after council removed the proposed 40 percent limit.
Does this ordinance apply to the rest of Mount Pleasant? Not currently. Council limited the February ordinance to Old Mount Pleasant and its named overlay neighborhoods, though members have left open the possibility of extending similar rules townwide in the future.
If you're pricing land in Old Mount Pleasant, comparing it against Old Village, or trying to figure out what a specific parcel actually allows under both rules at once, that's a conversation worth having before you're under contract. Reach out to PRL Consulting Group to talk through the entitlement math on your next Old Mount Pleasant project.
