Diamond House (170 East 77 Street)

1. BUILDING OVERVIEW (ANALYST FRAMING)

Diamond House is a Postwar Resale Condo (Built 1940) located in the Upper East Side market. Standing 10 floors tall with 76 units, it functions as a prewar-style condo conversion offering full-service amenities.

Based on transaction history and the current NYXRCSA benchmark of 331.14 (Oct 2025), the building is classified as Yield-Oriented (Secondary: Distressed/Correction).

This classification is justified by a severe structural decoupling from broader market appreciation. While the NYXRCSA index reached an all-time high of 331.14 in late 2025, Diamond House has exhibited nominal capital destruction over 15-year holding periods. The definitive signal is Unit 5D, which sold in Sep 2007 (Sponsor era) for $1.72M and resold in Jan 2022 for $1.69M—a realized nominal loss despite a 14-year hold. Furthermore, large format units like Unit 10A have suffered massive volatility, crashing from $4.35M (2015) to $2.91M (2021), forcing a 33% reset. The building explicitly "Underperforms Upper East Side by 18.4%" according to source data. Value is derived from rental velocity in smaller units rather than equity compounding.

2. UNIT MIX & COMPOSITION

Based on actual inventory counts from 77 recorded sales, the inventory is diverse but bifurcated in performance:

• 1BR: ~25% of activity (19 sales). Med PPSF $1,100.

• 2BR: ~31% of activity (24 sales). Med PPSF $1,277. Dominant Liquid Inventory.

• 4BR+: ~16% of activity (12 sales). Med PPSF $1,411.

• Other: 3BRs and Studio/Combos make up the balance.

Influence on Behavior: The unit mix creates two distinct liquidity profiles. The 1BR/2BR units maintain healthy velocity (Median DOM 70–81 days). However, the large 4BR units face extreme friction, with a Median DOM of 271 days. This indicates that while the building works as a commodity housing asset, it struggles to support "trophy" family-sized valuations (Driver 4).

3. LINE (STACK) PERFORMANCE — RESALE ONLY

Note: Pursuant to the Sponsor Normalization Rule, approximately 20 sales from 2007–2009 marked "No Listing" (e.g., Units 2B, 7A/8A, 9C, 10D, 4F, 10A) are treated as Sponsor Baseline and excluded from resale liquidity metrics.

A. Liquidity

• Fastest: Unit 8B sold in 6 days (Rent 2025) / Unit 6G sold in 19 days (2021).

• Slowest: Unit 10A took 545 days (2021). Unit 2B took 412 days (2013). Unit 3C (Rental) took 264 days (2023).

• Median Resale DOM: The building-wide median is 81 days. However, the spread is massive: 1BRs clear in ~81 days, while 4BRs linger for 271 days.

B. Price Strength

• Ceiling (Peak): Pricing power peaked in 2014–2015. Unit PHF sold for $1,716 PPSF in 2014. Unit 10A sold for $1,707 PPSF in 2015.

• Baseline (Current): The 2023–2025 baseline has reset significantly lower.

  • Unit 6G (2BR): $1,310 PPSF (2025).

  • Unit 9C (4BR): $1,340 PPSF (2023).

  • Unit 10A (4BR): $1,142 PPSF (2021).

• Regression: Current trades are clearing ~20–25% below the building's 2015 nominal PPSF peaks.

C. Appreciation

• Negative Trend: Unit 5D lost value between 2007 ($1.72M) and 2022 ($1.69M).

• Crash: Unit 10A lost -$1.44M (-33%) between 2015 and 2021.

• Stagnation: Unit 6G sold for $1.644M in 2021 and $1.680M in 2025, a negligible gain of 2.2% over 4 years.

4. BUILDING-WIDE PPSF TREND (NORMALIZED)

The building is in a Structural Regression phase.

• Sponsor Baseline (2007): Sales cleared $1,270–$1,430 PPSF (Units 5D, 6A, 4B).

• Cycle Peak (2014–2015): Sales surged to $1,500–$1,700 PPSF (Units 6A, PHF, 10A).

• Correction (2021–2022): Prices compressed to $1,100–$1,250 PPSF (Units 10A, 5D, 10E).

• Current Reality (2023–2025): Recent sales cleared at $1,310–$1,340 PPSF.

• Trend: Bearish. Despite the NYXRCSA index rising to 331.14 (All-Time High), Diamond House is trading at 2007 nominal levels. It has effectively erased 18 years of market appreciation for long-term holders.

5. RENT CAPTURE ANALYSIS

Effective Annual Rent Calculation: (Achieved Rent × (365 − Rental DOM) ÷ 365).

A. Rent Capture

• Unit 8B (2025):

  • Rent: $7,750 ($83 PPSF).

  • DOM: 6 days.

  • Effective Rent: ~$7,622/mo.

  • Status: Elite Capture/Efficient.

• Unit 3C (2023):

  • Ask: $25,000 $\to$ Rented: $17,500 ($84 PPSF).

  • DOM: 264 days.

  • Effective Rent: ~$4,842/mo.

  • Status: Catastrophic Failure. The unit required a 30% discount and sat vacant for nearly 9 months, destroying 72% of the first year's revenue.

B. Rent Appreciation

• Growth Segment: Unit 8B rented for $5,800 in 2020, $7,000 in 2023, and $7,750 in 2025. This represents +33.6% total growth over 5 years.

• Stagnation: Unit 5A (4BR) rented for $16,995 in Jan 2024 and $16,950 in Apr 2025. 0% Growth.

6. B³ SCORING SYSTEM (0–100)

• Liquidity Score: 45/100 (Bifurcated. Small units clear fast [6 days], but large units [10A, 3C] suffer extreme friction [271-545 days]. Weighted down by 4BR illiquidity).

• Rent Capture Score: 60/100 (High nominal PPSF [$80+], and strong growth in 2BRs. Penalized heavily for large unit failures [Unit 3C vacancy]).

• Appreciation Score: 20/100 (Confirmed nominal losses on Unit 10A [-33%] and Unit 5D [-1.7% over 15 years]. Zero Beta vs NYXRCSA).

• Composite Score: 41.75/100.

7. TRANSACTION EXAMPLES

Resale Depreciation (Capital Destruction):

• Unit 10A (4BR / 2,547 sqft):

  • Sold Jun 2015: $4,350,000 ($1,707 PPSF).

  • Sold Feb 2021: $2,910,000 ($1,142 PPSF).

  • Result: -33.1% Nominal Loss ($1.44M) over 5.6 years. Driver: 1 (Market Regime) & 4 (Unit Size Imbalance).

Resale Depreciation (Long Term Hold):

• Unit 5D (2BR / 1,357 sqft):

  • Sold Sep 2007 (Sponsor): $1,725,933 ($1,271 PPSF).

  • Sold Jan 2022: $1,695,000 ($1,249 PPSF).

  • Result: -1.8% Nominal Loss over 14.3 years. Driver: 1 & 5 (Sponsor Normalization).

Resale Stagnation (Dead Money):

• Unit 6G (2BR / 1,282 sqft):

  • Sold Jul 2021: $1,644,000 ($1,282 PPSF).

  • Sold Aug 2025: $1,680,000 ($1,310 PPSF).

  • Result: +2.2% Nominal Gain over 4.1 years. Driver: 1.

Rent Growth (Efficient):

• Unit 8B (2BR Rental):

  • Apr 2020 Rent: $5,800.

  • Apr 2025 Rent: $7,750.

• Result:+33.6% Total Growth over 5 years. Driver: 1.

8. RISKS & RED FLAGS

• Wealth Trap: Buying large units at 2014–2015 prices ($1,700 PPSF) resulted in massive losses by 2021 (Unit 10A lost 33%).

• Liquidity Trap (Large Units): 4-Bedroom units have a median DOM of 271 days. Unit 10A took 545 days to sell.

• Sponsor Premium Trap: Units bought in 2007 (5D) are selling for less today, proving the sponsor pricing was never recovered.

9. EXECUTIVE SUMMARY

Diamond House (170 East 77 Street) is a Yield-Oriented condo that behaves as a "Tale of Two Cities." While efficient 2-bedroom units generate strong rental growth (+33% on Unit 8B) and liquidity, the building functions as a wealth trap for large-format inventory. Despite the NYXRCSA index hitting an all-time high of 331.14 in 2025, 4-bedroom resale values in this building have collapsed, with Unit 10A realizing a 33% nominal loss ($1.4M) from its 2015 peak. Long-term holders have also suffered; Unit 5D sold for less in 2022 than it did in 2007. Investors should view 2BR units as functional yield plays (entry <$1,300 PPSF), but avoid large combinations where liquidity freezes (270+ days DOM) and capital destruction is proven.

B³ SCORECARD

• Liquidity Score: 45

• Rent Capture Score: 60

• Appreciation Score: 20

• Composite Score: 41.75

• Category: Yield-Oriented (Distressed/Correction)

• Unit Mix: 31% 2BR / 25% 1BR / 16% 4BR+ [Transaction Weighted]

• Sponsor Normalization: Sales from 2007–2009 marked "No Listing" or DOM $\le$ 30 reclassified as Sponsor/Conversion Baseline (approx. 20 transactions).