Data Source & Sample Composition
All 412 studies in this dataset were generated using the Cost Seg Smart engine (version 2.2.0, calibrated 2026-03-14). The engine applies real industry-standard 2026 construction cost data, MACRS classification rules per Rev. Proc. 87-56, and the methodology described in the IRS Cost Segregation Audit Techniques Guide (Pub 5653).
Property characteristics — square footage, year built, purchase price, location, structural features — are drawn from real US metropolitan property profiles representative of typical investor purchases at each property type. The 260 total comprises the original 107 golden_batch fixtures, 20 condo and multifamily 5+ fixtures added 2026-04-27, plus 133 additional fixtures added 2026-04-28 to bring every property type to n=20.
Engine Pipeline (Cost Seg Smart v2.2.0)
The engine produces each study via a deterministic pipeline:
- Land valuation: User override → County assessor (with reliability gate) → Statistical (metro → state → national) prior. Land is excluded from the depreciable basis.
- Component library: Base $/SF costs from industry-standard 2026 construction cost data, segmented by residential (27.5-year long-term) or commercial (39-year long-term) construction.
- Multiplier stack: Geographic cost factor × quality multiplier × property-type adjustment × construction era profile × STR intensity (FF&E uplift if applicable) × PPI time index × indirect cost (25%).
- Caps: 15-year residential cap (18%), office 5-year cap (28%, flag-gated). Caps prevent unrealistic over-acceleration on edge cases.
- Reconciliation: S = adjusted_basis ÷ total_unadjusted_RCN. S < 1.0 means the property's market basis is below modeled replacement cost; S > 1.0 means premium-market property exceeds RCN.
- Premium land floor: For statistical-only land valuation with rf_raw ≥ 2.0 (typical urban condo or premium STR), the engine enforces minimum land allocations: STR 50%, SFR 40%, MF 35%.
- QC gate: 16 automated quality-control checks classify each study PASS / REVIEW / FAIL, with a compound-OK downgrade rule for single soft flags.
Year-1 Federal Tax Savings Computation
Year-1 federal tax savings = (5-year basis + 7-year basis + 15-year basis) × bonus_depreciation × federal_marginal_rate.
Locked assumptions used throughout this report:
- Bonus depreciation: 100% — per the One Big Beautiful Bill Act, signed July 2025, which permanently restored 100% bonus for property placed in service after 2024.
- Federal marginal rate: 37% — top US individual bracket. Most relevant for high-income real estate investors who commission cost seg studies.
- State income tax: excluded — varies 0–13% by state. Including would obscure cross-state comparability.
- $500K normalization — for cross-property comparison, year-1 savings are scaled to a $500K purchase price. This isolates the property-type effect from the price effect.
Quality Control
Each study runs through 16 automated checks before inclusion. Checks fall into five reason-family categories: hard_invariant, market_regime, calibration_outlier, input_quality, and narrative_safety. Studies flagged FAIL are excluded entirely. Studies flagged REVIEW are included with the qc_status field preserved. PASS studies represent the cleanest data; the dataset's QC pass rate is 97% overall (with 100% pass in 7 of 13 property types).
Reconciliation Factor (S) and rf_raw
S is the engine's reconciliation factor: S = adjusted_basis ÷ total_unadjusted_RCN. By construction, S × total_unadjusted = depreciable_basis exactly.
rf_raw is a diagnostic ratio similar to S but inclusive of cost variance. Interpretation: rf_raw 0.4–0.7 typical US property pricing; 0.7–1.2 moderate market premium; 1.2–2.0 significant premium (urban condos); > 2.0 extreme premium triggers the engine's premium land floor.
Limitations
- Single engine version. Different engineering methodologies may yield reclassification splits within ±2–4 percentage points for the same property.
- Sample size. Each property type has n=20 in this v1.2 release. Per-type IQRs are reported in the main report alongside medians so readers can see real dispersion. Future releases will expand sample sizes further.
- Geographic coverage. National but uneven; metro-level breakdowns are not published in this release.
- Audit risk discussed qualitatively. No individual study in this dataset has been subjected to actual IRS audit.
- Year-1 savings assume 100% bonus depreciation. Property placed in service in 2023 (80%) or 2024 (60%) yields proportionally lower year-1 deductions.
License
Released under Creative Commons Attribution 4.0 International (CC-BY 4.0). Use, share, and adapt for any purpose, including commercial, with attribution.
Annual Refresh
The Benchmarks Report will be refreshed annually each Q1, with construction cost basis updated to the latest industry-standard construction cost data release. v1: April 30, 2026. v2 planned: Q1 2027.
Contact
Citation requests, methodology challenges, or data inquiries: research@costsegsmart.com.