listed Aug 4, 2026 SingleFamilyResidence
$18,500,000
4-Bedroom Home in MASHTA ISLAND

631 N Mashta Drive, Key Biscayne, FL 33149

SingleFamilyResidence in MASHTA ISLAND, Key Biscayne · No CDD on record
MASHTA ISLAND · Key Biscayne, FL 33149 · Miami-Dade County
Listing data checked against the MLS November 3, 2026 at 11:00 PM ET · rechecked hourly
4Bedrooms
5Bathrooms
2,255Sq Ft
1958Year Built
$8204Per Sq Ft
No CDD on record4 bedrooms
How to read this page: MLS listing facts carry their source; everything else is labelled as a public record, a calculation, an estimate, or something to verify. Where local data is too thin to support a number, the page says so instead of guessing.
Highlights

631 N Mashta Drive in Mashta Island, Key Biscayne is listed at $18,500,000 (2,255 sq ft, about $8,204 per sq ft). It has been listed Aug 4, 2026. Listing facts: built in 1958. Figures are from the MLS record and county data; deemed reliable but not guaranteed.

  • No CDD assessment on record
  • Built 1958 · 68 yrs
  • 2,255 sq ft of living area
  • listed Aug 4, 2026
Listing description

About this home

BRING ALL OFFERS! Exceptional waterfront opportunity in prestigious Key Biscayne. Set on a 15,000 sq.

ft. lot with 100 feet of water frontage, this residence offers open-water views, direct Biscayne Bay access, and no fixed bridges to the ocean. Currently undergoing a complete renovation, it will feature modern finishes, impact windows and doors, new systems, spacious living areas, a chef's kitchen, and luxurious bathrooms.

Enjoy a private dock, deep-water access, pool, breathtaking sunsets, and an unmatched boating lifestyle in one of South Florida's most desirable communities One of the most compelling waterfront opportunities currently available in all of Key Biscayne. Perfectly positioned on the exclusive and highly coveted Mashta Island, this exceptional property offers approximately 100 feet of prime waterfront, deep-water dockage, direct Biscayne Bay access, and no fixed bridges to the Atlantic Ocean, creating an unparalleled opportunity for boating enthusiasts and yacht owners. Mashta Island has long been recognized as one of South Florida's most prestigious residential enclaves, offering exceptional privacy, quiet tree-lined streets, oversized waterfront estates, and immediate access to the open waters of Biscayne Bay while remaining only minutes from Brickell, Downtown Miami, Coconut Grove, Coral Gables, Miami Beach, and Miami International Airport.

Very few neighborhoods offer this combination of island living, security, boating lifestyle, and proximity to the city's financial and cultural centers. The residence is currently on renovation designed to transform the property into a contemporary waterfront estate while preserving the exceptional value of its location and oversized waterfront parcel. This is substantially more than a cosmetic renovation.

The project includes major improvements throughout the residence, including redesigned living spaces, upgraded electrical and plumbing systems, new HVAC equipment, impact-resistant windows and doors, premium flooring, modern architectural lighting, designer finishes, and a completely reimagined interior intended to meet today's luxury lifestyle expectations. Upon completion, the home is anticipated to offer spacious entertaining areas, beautifully appointed bedroom suites, bathrooms, an impressive chef's kitchen featuring custom cabinetry, premium appliances, elegant countertops, and thoughtfully designed indoor-outdoor living spaces that maximize the spectacular waterfront setting. The property's exceptional orientation provides beautiful water views and unforgettable sunsets while creating an ideal environment for entertaining, family gatherings, and year-round outdoor living.

The expansive backyard offers generous space surrounding the swimming pool together with multiple areas for outdoor dining, lounging, and enjoying the waterfront lifestyle that has made Key Biscayne one of the most desirable residential communities in South Florida. For boating enthusiasts, few properties can offer the combination of oversized waterfront, private dockage, deep-water access, and unrestricted navigation to Biscayne Bay and the Atlantic Ocean without fixed bridges. Whether accommodating a large sport yacht, cruising yacht, center console, or multiple vessels, the waterfront configuration provides flexibility rarely available in today's market.

Key Biscayne continues to be recognized as one of South Florida's most exclusive island communities, celebrated for its pristine beaches, excellent schools, private clubs, marinas, tennis facilities, parks, bicycle paths, restaurants, and relaxed coastal lifestyle. Residents enjoy the unique advantage of living within a peaceful island environment while remaining only a short drive from Miami's world-class shopping, fine dining, cultural institutions, private airports, international business centers, and professional sports venues. The supply of premium waterfront homes on Mashta Island remains extremely limited due to the neighborhood's esta…

All 49 photos

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Description provided by Coldwell Banker and reproduced from the MLS; not independently verified.

Listing courtesy of Coldwell Banker · Listing agent: Javier Gustavo Quiroz · 561-395-2233Provided via the MIAMI Association of REALTORS / Southeast Florida MLS (SEFMLS) Internet Data Exchange · Listing information provided by the Southeast Florida MLS (SEFMLS) / MIAMI Association of REALTORS. Information deemed reliable but not guaranteed by the MLS to be accurate. · Listing information provided by the Southeast Florida MLS (SEFMLS) / MIAMI Association of REALTORS(R). Information is deemed reliable but not guaranteed by the MLS to be accurate. · deemed reliable but not guaranteedIDX information is provided exclusively for consumers' personal, non-commercial use and may not be used for any purpose other than to identify prospective properties consumers may be interested in purchasing. Data is deemed reliable but is not guaranteed by the MLS to be accurate.
The Messtimate™

The Messtimate

Insufficient local evidence for an automated estimate. The Messtimate is a deliberately simple range — living area × recent closed-sale $/sq ft from comparable homes nearby — and it only renders when at least 3 defensible sales exist within about 10 miles in Miami-Dade County in the last 18 months. None qualify for this home, so no dollar range is shown. It is not an appraisal or a valuation.

Want a property-specific value review? A licensed Momentum Realty agent can prepare a free comparative market analysis using the home, the lot, its condition, and the live market.

Methodology: the range would be 2,255 sq ft × the interquartile $/sq ft of comparable closed sales (same property type, living area within 30%, closed within 18 months, nearest verified subdivision, 3-mile, then 10-mile same-county stage). Estimate for general information only; never an appraisal, valuation, or offer. Updated November 1, 2026.

How it stacks up

Comparable recent sales

No closed sales of a similar home within about 10 miles in Miami-Dade County in the last 18 months are in our MLS data set, so this page shows no comparable-sales median or automated estimate for MASHTA ISLAND. A licensed Momentum Realty agent can prepare a property-specific comparative market analysis on request.

Property facts & sources

Every fact, sourced

Listing data, public records, our calculations, and what to verify — each fact shown once. Estimates and calculations shown are for general information only, are not appraisals or advice, and should be independently verified.

Listing facts MLS

List price$18,500,000
Bed / bath4 / 5
Living area2,255 sq ft
Year built1958
Property typeSingleFamilyResidence
MLS #B26058354
Listing statuslisted Aug 4, 2026

Public records & third-party data

FEMA flood zoneNot verified — check msc.fema.gov
CountyMiami-Dade
Area listings2 active · 0 under contract
Estimated first-year tax~$194,250/yr
CDD assessmentNone on record
HOANot reported

Calculated estimates

Price per sq ft$8204
Estimated monthly payment$127,085
Insurance (illustrative)$84k–$174k/yr

Buyer should verify Buyer verify

Exact HOA dues, fees, and restrictionsRoof age and conditionHVAC age and conditionA property-specific insurance quoteSurvey and lot boundariesPermit historyFlood-insurance requirementsSchool zoning (confirm with the district)Property taxes after sale (homestead reset)CDD / community assessmentsSquare footage and room dimensions
Financing

Estimated monthly payment

$127,085/mo
  • Principal & interest $100,862/mo 79%
  • Taxes $16,188/mo 13%
  • Insurance $10,036/mo 8%

$127,085/mo at 20% down, 30-yr @ 7.24% · edit any field to update.

Editable estimate — not a loan offer. Estimates only; see data & estimate notes.

What it really costs to own 631 N Mashta Drive

The parts of the monthly number a mortgage calculator leaves out, from this listing's MLS record, the county tax roll, Citizens and FEMA. Property facts only.

Property taxThe current owner's bill is $112,485/yr per the MLS listing record (TaxAnnualAmount, 2026-11-01). Florida reassesses at sale, so a buyer's first bill is usually higher than the seller's; the county millage here is not verified, so no reset figure is printed.
Home and flood insuranceThe average Citizens Property Insurance premium in Miami-Dade County is $1,891/yr (56,357 policies, Citizens detail by county, April 2026); private-market quotes differ by roof age, wind mitigation and distance to the coast. The page's modeled range for this home is $84,500–$174,500/yr; neither is a quote.
Roof and ageBuilt in 1958. An original roof would be about 68 years old; under Florida's 2022 reform (SB 2-D) carriers may require an inspection past 15 years, so budget for a roof report and ask for the roof permit date.
Estimated ownership costs

Estimated costs & disclosures

Estimated ownership costs for general information. Confirm each with the county, your lender, and an insurer. See data & estimate notes.

Property tax (first-year est.)
~$194,250/yr

Estimate: a typical Miami-Dade effective rate applied to the list price before any exemptions. Florida bills change with reassessment, homestead and other exemptions, and local taxing districts — this is not your expected bill. Confirm with the county property appraiser.

CDD assessment
None on record

No CDD assessment appears in our records for this community. CDD assessments show on the county tax bill — confirm with the tax collector.

Insurance (illustrative range)
$84k–$174k/yr

An illustrative modeled range, not based on carrier underwriting and not a quote. Florida premiums vary significantly by roof age, wind-mitigation features, claims history, and carrier — a real quote can land well outside this range. Flood zone not verified for this address — check msc.fema.gov and confirm coverage. Get a quote from a licensed insurer before relying on any figure.

HOA
Not reported

Not stated in the listing. Confirm with the listing agent or the county record; $0 is used in the payment estimate.

Environmental data

Flood zone & elevation

Sourced environmental data for the parcel. Confirm with FEMA and your insurer.

FEMA flood zone
Not verified

Not yet verified for this address. Look up the parcel at msc.fema.gov before relying on any flood assumption.

Ground elevation
Not on record

Approximate parcel elevation from USGS; confirm exact elevation with a survey.

Windstorm / insurance
Obtain a quote

Miami-Dade County is on the Florida coast; wind coverage is a major part of the premium. Premiums and coverage vary by home (roof age, wind mitigation, claims history); obtain a quote from a licensed insurer.

County hazard risk ratings (FEMA National Risk Index, county level)
Hazard risk

Natural hazard risk

FEMA National Risk Index for Miami-Dade County, FL: overall Very High. Ratings compare this county with every county in the United States for expected annual loss from each hazard.

HurricaneVery High
Coastal floodingVery High
Inland floodingVery High
Heat waveRelatively High
WildfireRelatively Moderate
TornadoRelatively High
LightningVery High
Strong windRelatively Moderate
DroughtRelatively Moderate
HailRelatively High
Cold waveVery High

Source: FEMA National Risk Index (county level, hazard risk ratings only). Ratings describe the county, not this parcel; the flood zone shown above is parcel-specific. Verify insurance requirements with your lender and agent.

Internet & broadband — how to check availability for this address
Connectivity

Internet & broadband

Fiber
Check availability

Address-level fiber service is not confirmed for this home. Check the FCC National Broadband Map (broadbandmap.fcc.gov) or the provider for this address.

Cable
Check availability

Cable broadband is common in Florida and Georgia towns but not confirmed for this address; verify with the provider.

Fixed wireless / satellite
Check availability

5G home internet and satellite service depend on the exact location; check coverage for this address.

Momentum Research · MASHTA ISLAND

Pricing & the MASHTA ISLAND market

How this home is priced against recent nearby sales, and where MASHTA ISLAND has been over 25 years. Momentum Research analysis of MIAMI MLS records; closed sales, deemed reliable but not guaranteed. Estimates only; see data notes.

Median $/sq ft by year

Community sold $/sq ft, 2013–2025. This home lists at $8204/sq ft.

$396$1691$29872013: $167320132014: $64620142025: $27362025

Median sale price by year

12-month median closed price, 2013–2025.

$2.3M$7.9M$13.5M2013: $6.7M20132014: $3.4M20142025: $12.4M2025
Property timeline

This home’s history

  • 1958BuiltPer public record
  • About Aug 2026Listed (per MLS)Approximate list date from the MLS cumulative days-on-market count (listed about Aug 4, 2026)
  • Aug 4, 2026First seen on movewithmomentum.comObserved at $18,500,000
  • NowActiveCurrently for sale

Build year is from public record. The MLS list date is approximate (today minus the cumulative days on market the MLS reports, which can span relistings). Other milestones reflect movewithmomentum.com’s own observations since we began tracking this listing and are not the MLS listing history; dates and prices are deemed reliable but not guaranteed.

Transparency

Price & listing history

Listed for $18,500,000Coldwell Banker · listed Aug 4, 2026
Public records

Building permits

Permit history not yet linkedConfirm permit history with the county building department.

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Listed by Coldwell Banker · MLS # B26058354

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Keep looking

Similar homes for sale near MASHTA ISLAND

Active listings nearby at a comparable size and price. Listings held by brokerages other than Momentum Realty are marked with the listing broker. Deemed reliable but not guaranteed.

Recently off market in MASHTA ISLAND

Just listed: new homes for sale in this area in the last 48 hours · updated hourly · RSS · This area market today: new listings, price cuts, pendings

In the area

Recent Mashta Island news

Recent local developments near this home, compiled from news and public sources. Provided for general information; verify details with the original source.

Oct 2026 · Parks Amenities

Coral Gables extends Art Cinema lease and moves toward Aragon Avenue expansion

The commission extended the cinema operators' lease by five years, to September 2035, and directed staff to pursue West Construction at about $1.24M for the expansion. The project converts a storefront at 240 Aragon Ave. into a 92-seat theater with a lobby and cafe. The city had earlier provided $450,000.

Why it matters: The expansion adds a cultural and cafe destination to the Miracle Mile and Aragon Avenue area downtown. The project is about 11 miles north of Mashta Island, elsewhere in Miami-Dade County.

Miami Today

Oct 2026 · Development

Homestead lands aerospace tenants building on spaceport designation

AST SpaceMobile has expanded satellite manufacturing into Homestead, and Global Engine Stands signed a 10-year lease for 35,000 SF at the Park of Commerce. The park has about 500,000 SF of available industrial space and nearly 500,000 SF more recently approved. The mayor said other prospects have discussed bringing several hundred jobs.

Why it matters: Aerospace and aviation tenants add industrial employment options in South Dade and put more of the Park of Commerce's space into use. The project is about 13 miles southwest of Mashta Island, elsewhere in Miami-Dade County.

Miami Today

Oct 2026 · Retail Dining

Shops at Sunset Place nears demolition for mixed-use redevelopment

The plan calls for 1,513 residences in seven towers of 12 to 33 stories, a 287-room hotel, a 1,300-seat theater, 202,462 square feet of retail and 65,892 square feet of office. Demolition is now targeted for early 2027 and a first phase around 2029. Plans estimate about $149 million in infrastructure improvements.

Why it matters: Replaces a largely vacant mall with housing, hotel and street-level retail near Dadeland and the South Dade Metrorail line. The project is about 8 miles north of Mashta Island, elsewhere in Miami-Dade County.

Miami Today

Sep 2026 · Development

University of Miami agreement with Coral Gables would add a hospital of up to 100 beds

A development agreement would allow construction of a hospital with up to 100 beds on the university's Coral Gables campus, offering inpatient, outpatient and emergency care. The agreement would also reshape the campus, which includes the Gables Village residential complex of 1,458 beds slated for mid-2029. Cost, size and timeline for the hospital were not stated.

Why it matters: A campus hospital would add inpatient and emergency care capacity and healthcare employment in the Coral Gables area. The site is about 9 miles north of Mashta Island.

Miami Today

Go deeper

More on MASHTA ISLAND

Go deeper on MASHTA ISLAND

See schools, amenities, builders, HOA/CDD detail, and every active & sold home in the community — the single biggest advantage of buying here over a portal.

Assigned schools

Assigned schools

Schools currently assigned to this address in Miami-Dade County, provided as neutral factual data. Assignments can change — confirm current zoning with the school district. This is not a statement about the home's suitability for any person or family.

School zoningThis address is in the Miami-Dade County School District. Specific elementary, middle, and high-school assignments vary by street and can change. Confirm current zoning with the district before relying on it.
Nearby & guides

City, county & community guides

Where this home sits, with links to the matching guides. General reference only.

Before you decide

Buyer research checklist

Items worth confirming for 631 N Mashta Drive, chosen from what the record shows. This is general guidance, not advice about this specific property.

  • Built in 1958 (68 years): ask for the roof and HVAC replacement dates — insurers commonly ask for roof age on homes this old, and it changes the premium.
  • Confirm whether a mandatory HOA applies to this parcel and what it charges.
  • Look up the parcel on FEMA's Flood Map Service Center and confirm with your insurer whether flood insurance is required.
  • Get a homeowners insurance quote for this specific address in Miami-Dade County; a wind-mitigation inspection and, on older homes, a four-point inspection can change the premium.
  • Listed living area is 2,255 sq ft: verify it against the property appraiser's record and measure before relying on it.
  • Order a survey to confirm lot boundaries and easements.
  • Review permit history with the county.
  • Property taxes: the estimate on this page (about $194,250/yr) assumes reassessment at the list price; the seller's current bill is not a guide Exemptions and portability change the actual bill — confirm with the county property appraiser.
  • Confirm school zoning directly with the district.
Provenance

Data sources & freshness

Listing recordMIAMI / SEFMLS, checked against the MLS hourly (last: November 3, 2026)
Comparable salesFewer than 3 defensible closed sales within about 10 miles in Miami-Dade County — no medians or automated estimate shown
Flood zone & elevationNot verified for this address — look it up at msc.fema.gov
Taxes & monthly costTypical county effective rate applied to the list price; an estimate, not a bill
Insurance figureModeled estimate; obtain a real quote before offering
Schools2025-26 district assignments; verify with the district

Momentum Research lines are our own analysis of MIAMI / SEFMLS records; MLS data is deemed reliable but not guaranteed. Estimates are informational, not appraisals or advice. Methodology: how Momentum scores are computed.

Answered before you ask

Frequently asked questions

How big is 631 N Mashta Drive and when was it built?

Per the listing record, 631 N Mashta Drive was built in 1958 and has 2,255 sq ft of living area, 4 bedrooms and 5 bathrooms. Living area and lot size come from the MLS record and should be verified against the county property appraiser.

What community is 631 N Mashta Drive in?

631 N Mashta Drive is in Mashta Island in Key Biscayne, Miami-Dade County. Too few comparable closed sales exist nearby for this page to show local sales statistics; a licensed agent can prepare a comparative market analysis.

Why might property taxes on 631 N Mashta Drive differ from the current owner's?

The estimate on this page (about $194,250 per year) assumes reassessment at the list price less the homestead exemption. Florida reassesses a home after it sells; for a homesteaded seller the Save Our Homes cap on their assessment does not transfer, and a buyer's own exemptions and portability are applied separately, so the two bills usually differ. Any tax figure shown here is an estimate, not the actual bill — confirm with the county property appraiser and tax collector.

Is 631 N Mashta Drive in a flood zone?

A flood designation has not been verified for this address. Look up the parcel on FEMA's Flood Map Service Center (msc.fema.gov) and confirm with your insurer.

Can I rely on the figures on this page?

No. Estimated taxes, insurance, payments, and any market or comparable-sales summary are opinions and estimates for general information only and should not be relied upon. Verify all information independently before making any decision.

Ready when you are

See 631 N Mashta Drive in person

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Equal Housing Opportunity. Content on this page is compiled from public records, MLS data, and automated sources and may contain errors or be out of date. It is general information only, not a representation about any specific property, community, builder, or association. Verify information independently before relying on it. Momentum Realty supports the Fair Housing Act and does not discriminate on the basis of race, color, religion, sex, handicap, familial status, national origin, sexual orientation, or gender identity. Information about schools, distances, and amenities is provided as neutral factual data to help you research the property and is not a statement about who should or should not live here or the suitability of the home or neighborhood for any person or group. School data may change — confirm current assignments with the school district.

Found an error? If you are the owner, listing agent, or a party to this property and believe any information is inaccurate, email jon@movewithmomentum.com and we will review and correct or remove it promptly.

MLS / IDX. The data relating to real estate for sale on this web site comes in part from the Internet Data Exchange (IDX) program of the MIAMI Association of REALTORS / Southeast Florida MLS (SEFMLS) Internet Data Exchange. Real estate listings held by brokerage firms other than Momentum Realty are marked with the listing broker's name and include the name of the listing agent. Data provided is deemed reliable but is not guaranteed by the MLS to be accurate. The information being provided is for consumers' personal, non-commercial use and may not be used for any purpose other than to identify prospective properties consumers may be interested in purchasing. Source: MIAMI Association of REALTORS / Southeast Florida MLS (SEFMLS). Listing information provided by the Southeast Florida MLS (SEFMLS) / MIAMI Association of REALTORS(R). Information is deemed reliable but not guaranteed by the MLS to be accurate. All rights reserved.

Listing data is deemed reliable but is not guaranteed and is subject to change or withdrawal without notice. Square footage and lot size are approximate. Florida real estate brokerage services provided by EAB RE Investments LLC dba Momentum Realty. Georgia real estate brokerage services provided by Momentum Realty LLC. Site designed by Move With Momentum LLC, © 2026.

Estimates, methodology & disclaimers

Opinion & estimate — do not rely on this page. Any figure on this page that is not a verbatim fact from the listing or a public record — including estimated property taxes, insurance, CDD/HOA amounts, mortgage payments, comparable-sales summaries, and market statistics — is an opinion and estimate provided for general informational purposes only. These figures may be inaccurate or out of date, are not appraisals, valuations, or financial, legal, tax, or investment advice, and should not be relied upon. Do not make any purchase, offer, financing, or other decision based on this page. Independently verify everything — price, square footage, lot size, year built, taxes, CDD/HOA, flood status, school assignments, permits, and community rules — with the listing broker, the county, your lender, a licensed inspector, an insurer, and your own advisors before acting.

Estimate methodology. Tax estimates apply county millage to the list price (less the homestead exemption where the parcel is matched to the certified roll) and will differ from the actual assessed bill. Cost and market figures are derived from available data and simple calculations, not a professional appraisal. We make no representation that any estimate reflects fair market value.

Automated content. Some summaries, distances, and estimates on this page are generated automatically from public and proprietary data sources and may contain errors or omissions. We strive for accuracy but cannot guarantee the completeness or accuracy of any information. Verify anything important independently.

No warranty; measurements & photos. No guarantee, warranty, or representation of any kind is made regarding the completeness or accuracy of any information, descriptions, or measurements on this page — including square-footage measurements and property condition — all of which should be independently verified through appropriate means, including in-person inspection and public records. Photographs may be virtually staged or digitally enhanced and may not reflect actual property conditions. Momentum Realty and its agents expressly disclaim any liability in connection with the information provided.