Most buyers comparing Flanders to Hampton Bays or Riverhead look at one number: the median. In July 2026 that number in the 11901 zip code sits somewhere between $649K median list price and a $662,500 median sale price, up 44% year-over-year, depending on whose feed you trust. Both readings are correct in their own way, and neither tells you what actually matters. What matters is a wastewater project a mile away, across the traffic circle in Riverside, that is finally moving after more than a decade of stalls. If you are shopping Flanders this year, that project is the hidden variable in almost every offer you write.
What changed between fall 2025 and spring 2026
For years the story of Riverside was a plan on a shelf. In 2015 the town approved a redevelopment blueprint calling for up to 2,300 housing units around the traffic circle. Nothing followed, in large part because the soil could not carry the septic load. Two facts changed that.
First, in the fall of 2025, the sewer district received a major boost when it got $19 million in funds through the federal Infrastructure Investment and Jobs Act. Second, by the April 29, 2026 community meeting at the Flanders Community Center, Southampton Town's consultants said design was underway on a $44 million sewer district and they anticipate the system coming online in late 2029 or early 2030.
The plan itself was also rewritten. The original 2015 vision of up to 2,300 units has been scaled down because the town cannot build its initial sewage treatment plant as originally proposed; the plant has been downgraded to 290,000 gallons per day, and the new plan, presented by Paul Knight of Historical Concepts, calls for an estimated 532 housing units.
Layered on top: a proposal from Georgica Green Ventures for up to 40 below-market rental apartments near the Riverside traffic circle, primarily one-bedroom units around 700 square feet, with rents from a bit over $1,400 to about $3,000 per month, contingent on the same sewer buildout.
If you are used to Long Island revitalization plans that never break ground, the meaningful shift is not the drawings. It is that investment here stagnated for years, in part due to the inability to install more septic systems in an area with a high water table adjacent to the river, and the constraint is now being solved with real money on a real schedule.
Why a sewer on the north side of Route 24 changes what you buy on the south side
Flanders sits directly across Route 24 from the Riverside traffic circle. Its lots are governed by the same hydrology that stalled Riverside for a decade. That means two practical things for a buyer here.
The first is regulatory. All lands south of Route 24 sit in Suffolk County Health Department's Groundwater Management Zone 3, which triggers minimum 40,000-square-foot lot requirements for many uses. If you are looking at an older Flanders home on a smaller nonconforming lot, the septic constraints that shape what you can add, expand, or subdivide are not going away when the Riverside plant turns on. The sewer district serves Riverside, not Flanders. That distinction is invisible on a listing page and central to any renovation math.
The second is locational. The 532 new units coming online across the circle are not competing supply for a typical Flanders single-family buyer. The Georgica Green project alone is largely one-bedroom rentals around 700 square feet, with two studios and a dozen two-bedroom units. What they are is anchor demand for the small commercial spine along Route 24, which today is thin. The broader plan carves out nearly 1,000 new residential units and 72,000 square feet of commercial space along Riverleigh Avenue and Old Quogue Road south of Flanders Road. Whether you welcome that or not is a personal call. Underwriting a purchase without pricing it in is a mistake.
Reading the 2026 numbers without getting fooled
Buyers pulling comps for Flanders right now will find two market stories that seem to contradict each other.
| Source window | Reading |
|---|---|
| Homes.com, current | $662,500 median sale price, up 44% year-over-year, 20 days on market |
| Movoto, July 2026 | $649K median list price in 11901, down 7% from June 2026, with a median of 48 days on the market |
Both can be true at the same time. Sale prices reflect what already closed, weighted by whatever mix of waterfront and interior homes traded in the last few months. List prices reflect what is sitting on the market right now, which after a spring cycle skews toward homes that have not yet found their buyer. When those two lines diverge this sharply in a small hamlet, the story is not "the market jumped 44%." The story is that a handful of higher-end sales dragged the closed number, and the current inventory is negotiating harder than headline year-over-year change suggests.
For context on what a Flanders dollar actually reaches: recent listings in the hamlet include a renovated two-bedroom ranch in a waterfront community fully redone in 2024 and a waterfront home at the end of a peninsula on Peconic Bay at roughly 2,100 square feet with three bedrooms and 3.5 baths. The waterfront pockets off Long Neck and Pine Neck price on a completely different curve than the interior lots along Flanders Boulevard.
The parts of Flanders that do not need a revitalization plan
While the Riverside timeline plays out, daily life in Flanders runs on a set of local anchors that have been stable for years. Underwriting a purchase here means knowing what those are, because they are the reason resale holds even if the sewer project slips a year.
- Sears Bellows County Park: an extensive trail system, freshwater pond fishing, 70 tent and trailer campsites, and 693 acres sitting in the Central Pine Barrens, with the Suffolk County Parks page as the practical reference for permits and seasons.
- The Big Duck at Big Duck Ranch, 1012 Flanders Road, a National Register landmark stewarded by Friends of The Big Duck, the Southampton-Town-appointed steward of Big Duck Ranch, which maintains the Long Island Duck Farming Exhibit in the Victorian Barn.
- A short list of restaurants that residents actually use: The Watershed Kitchen and Bar, Jerry and the Mermaid, Barrow Food House, Farm Country Kitchen, and Digger's Ales N' Eats in nearby Riverhead, which serves Riverside, Pine Valley, Parkview Community, Riverhead, Southampton, Northampton, Flanders, Calverton, Northville, and Aquebogue.
- Civic infrastructure: the David W. Crohan Community Center on Route 24 and the Flanders, Riverside and Northampton Community Association, which has funded projects including a Peconic River Pedestrian Bridge design through a NYS Department of State grant and hamlet beautification through a Suffolk County legislative grant. The town's own Flanders/Riverside/Northampton page is the cleanest source for civic notices.
These are the pieces of Flanders a buyer inherits on day one. The 532 units across the circle are the pieces a buyer inherits on year four or five.
Three timing questions worth asking before you write an offer
- Is the lot you are buying in Groundwater Management Zone 3? If any future plan involves an accessory unit, a pool with a cabana, or expanding bedroom count, the septic math starts here. This is a title-and-planning conversation, not a lender one.
- Where does the parcel sit relative to Flanders Road frontage? Homes on or immediately off Route 24 will feel the traffic and commercial texture of the revitalization first. Interior blocks toward Long Neck and Pine Neck are insulated from the streetscape changes but not from the tax base effects.
- What is your hold period? If you plan to sell inside three years, you are selling into an in-progress construction cycle across the circle. If you plan to hold past 2030, you are selling into a hamlet with a functioning sewer district and a redeveloped neighbor. Those are different resale stories.
FAQ
Will Flanders get sewers next? Not under the current $44 million project. The Riverside Wastewater Recovery System is designed for Riverside parcels. Councilperson Martel described hook-up as mandatory, much like the Suffolk water subsidy, but that mandate applies to the Riverside service area, not to Flanders lots south of Route 24.
Is the 2029 to 2030 turn-on date realistic? It is a target from the town's consultants at an April 2026 meeting, not a guaranteed date. Design was reported at 60% complete at that meeting. Slippage is common in wastewater projects and worth pricing in.
What is the Peconic River Pedestrian Bridge? A design-phase project by the Flanders, Riverside and Northampton Community Association funded through a NYS Department of State grant, intended to give Flanders and Riverside residents a walkable link across the river to downtown Riverhead. It is not built, but it is in the queue.
If you are weighing a Flanders offer this summer, or trying to price a Flanders home for a fall list, the timing questions above are worth working through with someone who tracks the Riverside revitalization week by week. Reach out to Sophia Walker REALTOR® for a free home valuation or a straightforward conversation about what a specific Flanders address is likely to trade for in this market, in English or Spanish.
