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Single Family ResidenceResidential
$3,424,812$1,149 / ft²
TopHap EstimateOur estimate of what this home would sell for today, based on nearby sales, the home's size and features, and local price trends. It is a starting point, not an appraisal.· confidence 94How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Jul 14, 2026
Last sold for $1,855,000 on Jun 18, 2018

21 KNOLL ST

RIVERSIDE, CT 06878
4
Beds
3.5
Baths
2,980 ft²
Living AreaTotal finished area of the structures, from county records. Some counties include shared space like hallways or a building gym, so it may not match a listing.
0.26 ac
Lot SizeThe size of the land the home sits on, from county records.
1930
Year BuiltThe year the home was originally built, according to county records.
2
StoriesHow many floors the home has above ground.
10
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.
1
ParkingThe number of parking spaces on the property, including the garage.

Valuation

$3.4M
$3.2M low$3.6M high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$1,855,000 · Jun 18, 2018
Est. Owner EquityRoughly how much of the home's value the owner would keep after paying off known loans. It is our estimate minus the loans still owed.$3,424,812
Est. Lendable EquityThe part of the owner's equity a lender would typically let them borrow against — about 80% of their equity.$2,739,850

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$18,520 (2025)
Assessed ValueThe value the county assigns to this home to calculate property tax. It is often lower than what the home would sell for.$1,498,490 (2025)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$929,810
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$568,680
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$1,498,490
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$1,048,943

Climate Risk

Overall riskThe average of the five hazard scores below, on a 0 to 100 scale. Higher means greater projected risk over the coming decades.44
1
FloodProjected flooding risk from rivers, heavy rain, and storm surge, scored 0 to 100. Higher is riskier.
17
WildfireProjected wildfire risk, scored 0 to 100, based on how much land burns in a typical year. Higher is riskier.
64
HeatProjected heat risk, scored 0 to 100, based on how many extremely hot days a year are expected. Higher is riskier.
95
StormProjected risk from heavy rainstorms, scored 0 to 100, based on how often extreme rainfall is expected. Higher is riskier.
43
DroughtProjected water shortage risk, scored 0 to 100. Higher means more strain on the local water supply.
FEMA Flood ZoneFEMA's flood zone for this address. Zones starting with A or V are high risk, and lenders usually require flood insurance there.minimal

Scores 0–100; higher = greater projected risk.

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
StyleThe architectural style of the home, such as ranch or colonial.Colonial
CountyWESTERN CONNECTICUT
Effective Year BuiltAn adjusted build year that accounts for condition and major remodels. A big renovation can make a home count as newer than it is.1970
Lot (acres)The size of the land the home sits on, from county records.0.26
ConstructionThe main material the home's frame and walls are built from.Frame (Unspecified)
RoofThe main material covering the roof, such as asphalt shingle or tile.Asphalt
HeatingThe type of heating system in the home.Hot Water
CoolingThe type of cooling or air conditioning in the home.Yes
FireplaceWhether the home has a fireplace, and what kind.Yes
GarageWhether the property has a garage, and details like whether it is attached to the home.Garage, Attached
PoolWhether the property has a pool, and what kind, such as in-ground.No
FeaturesExtra features found in county records. Records are not complete everywhere, so a missing feature does not always mean the home lacks it.Deck

Transaction History(11)

Sales and refinances filed with the county for this home. Not every transfer is a normal sale, so check the type before comparing prices.

Assigned SchoolsThe public schools this address is zoned for. Boundaries change, so confirm with the district before you count on it.

E
Riverside SchoolA+
Elementary · Grades KG–5 · 0.2 mi
M
Eastern Middle SchoolA+
Middle · Grades 6–8 · 0.4 mi
H
Greenwich High SchoolA+
High · Grades 9–12 · 1.9 mi

District: Greenwich School District

Neighborhood · ZIP 06878These are comparison scores, not percentages. 100 equals the national average, so 150 means about 50% above average.

CrimeLocal crime compared with the rest of the country, where 100 is average. It reflects things like population density, income, and how crime gets reported.75
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.114
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.97

Index scale: 100 = US average (tick). Lower is better.

Homes occupiedThe share of homes here that someone lives in. The rest sit empty, including vacation and for-sale homes.95%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.38%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.4.5%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.0.9%
PopulationHow many people live in this area.10,020
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.2,709 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$233,152
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$352,822
Average tempThe average temperature here across a full year.52°F
Annual precipHow much rain and melted snow falls here in a typical year.50 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.58%

Ownership

OccupancyWhether the owner appears to live here or somewhere else. It is inferred from the mailing address on record.Owner occupied
Company ownedWhether the owner is a company or trust rather than a person.Yes

Data by ATTOM. Valuations are automated estimates, not appraisals. Photos from Google Street View and may not depict the current property state.

How this home compares

21 Knoll St measured against every home in its neighborhood, its ZIP code and its county, using county assessor records refreshed nightly. A home can stand out in one of those areas and look ordinary in another, because each one holds a different mix of homes.

  • Worth more than 94% of homes in Western Connecticut County
  • Costs more per square foot than 98% of homes in Western Connecticut County
  • Bigger than 77% of homes in Western Connecticut County
  • Has a smaller lot than 74% of homes in Western Connecticut County
  • Older than 86% of homes in Western Connecticut County

What homes are worth in Riverside 06878

Each bar is how many homes fall in that price range. The marker is this home.

This home
$975K$7.7M

This home is worth more than 65% of homes in Riverside 06878.

How it measures up in Riverside 06878

The dot is this home. The mark in the middle is the typical home in Riverside 06878.

Estimated value$3,424,812
CheaperTypical $2,651,720Pricier

Pricier than 65% of homes nearby

Price per ft²$1149
CheaperTypical $943Pricier

Pricier than 77% of homes nearby

Living area2,980 ft²
SmallerTypical 2,806 ft²Bigger

Bigger than 54% of homes nearby

Lot size0.26 ac
SmallerTypical 0.3 acBigger

Bigger than 33% of homes nearby

Year built1930
OlderTypical 1957Newer

Newer than 15% of homes nearby

How 21 Knoll St ranks against every home in each area.
MeasureThis homeRiverside 06878Western Connecticut County
Estimated valuepricier than$3,424,81265% of homes94% of homes
Price per ft²pricier than$114977% of homes98% of homes
Living areabigger than2,980 ft²54% of homes77% of homes
Lot sizebigger than0.26 ac33% of homes26% of homes
Year builtnewer than193015% of homes14% of homes

About 21 Knoll St

How much is 21 Knoll St, Riverside, CT worth?

The TopHap Estimate for 21 Knoll St, Riverside, CT is $3,424,812 as of Jul 14, 2026. The likely range is $3,220,366 to $3,629,258. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Knoll St, Riverside, CT last sell?

21 Knoll St, Riverside, CT last sold on Jun 18, 2018 for $1,855,000, according to the county's recorded deed. TopHap holds 8 recorded sales for this parcel.

How big is 21 Knoll St, Riverside, CT?

21 Knoll St, Riverside, CT has 4 bedrooms, 3.5 bathrooms, 2,980 square feet of living space and a 0.26-acre lot.

When was 21 Knoll St, Riverside, CT built?

21 Knoll St, Riverside, CT was built in 1930, making it 96 years old. It is a colonial home. The building has 2 stories.

What schools serve 21 Knoll St, Riverside, CT?

21 Knoll St, Riverside, CT is assigned to Riverside School (elementary), rated A+; Eastern Middle School (middle), rated A+; Greenwich High School (high), rated A+. All sit in Greenwich School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Knoll St, Riverside, CT compare to other homes in Riverside 06878?

Among the 2,615 homes in Riverside 06878, it is worth more than 65% of them ($3,424,812 against a typical $2,651,720), its price per square foot is higher than 77% of them ($1149 against a typical $943), it is bigger than 54% of them (2,980 ft² against a typical 2,806 ft²), its lot is bigger than 33% of them (0.26 ac against a typical 0.3 ac) and it is newer than 15% of them (1930 against a typical 1957). Measured against all of Western Connecticut County, it is worth more than 94% of homes there. These shares are recounted nightly from the full county assessor record for each area, not from active listings.

What are the property taxes on 21 Knoll St, Riverside, CT?

The 2025 property tax bill for 21 Knoll St, Riverside, CT was $18,520. The county assessed it at $1,498,490.

More homes on Knoll St

Closest homes

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Assigned schools

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