10.4 Functional and External Obsolescence

Completing Accrued Depreciation: FO and EO

Physical deterioration (Section 10.3) is only one slice of accrued depreciation. A building can be freshly painted and still lose value because the layout is obsolete or because a factory opened next door. ECO Area V separates those ideas carefully:

Teach carefully: Some informal outlines mix “locational” under functional headings. On the AQB National Exam logic used in this guide, functional = on-site utility/design problems; external = off-site problems. Locational and economic are the usual external sub-types (neighborhood nuisance vs market/industry downturn). If a stem says “poor floor plan,” think functional. If it says “odor from the plant across the street,” think external.

Functional Obsolescence (ECO V.d)

Functional obsolescence (FO) is a loss in value due to a flaw in the structure, materials, or design that reduces the improvement’s utility relative to market standards as of the effective date.

Two forms: deficiency and superadequacy

Both are functional because the problem is in the improvement’s utility package, not in brick crumbling (physical) and not in the city changing zoning two miles away (external)—unless the stem clearly frames otherwise.

Curable vs incurable functional obsolescence

Same economic idea as physical curability:

• Curable FO: Cost to cure ≤ value added by curing (market-rational to fix).
• Incurable FO: Not economically rational to cure as of the effective date (layout would require structural gutting that costs more than it returns, etc.).

Note on superadequacy cure: You rarely “cure” a superadequacy by spending more. Cure might mean removing an offending feature if removal is cheap and market-preferred—or simply accepting incurable FO equal to cost not recovered in value.

Measuring Functional Obsolescence — Worked Examples

Worked Example 1 — Curable functional deficiency (cost to cure)

Subject: Three-bedroom home, one bath. Market standard for the tier: two baths.
Cost to add a second full bath: $15,000
Market value added by second bath (pairs): $20,000

$15,000 ≤ $20,000 → curable functional obsolescence.
FO depreciation amount (simplified) = cost to cure = $15,000
(Some advanced treatments also consider related costs; exam stems usually want cost to cure when they give this pattern.)

If cost to add the bath were $25,000 and value added only $20,000, the deficiency would be incurable as a cost-to-cure project; measure FO by capitalized loss or market extraction instead of calling $25,000 “curable.”

Worked Example 2 — Incurable functional deficiency (capitalized rent loss)

Subject: Small retail bay with awkward column layout reducing efficiency.
Rent loss vs functional competitors: $3,000 per year
Market cap rate: 8%
Incurable FO ≈ $3,000 ÷ 0.08 = $37,500

Use this when the defect cannot be cured rationally but shows up in income.

Worked Example 3 — Superadequacy (excess cost)

Reproduction cost includes a specialty mezzanine costing $60,000.
Market contribution of mezzanine (pairs / broker evidence): $10,000.
If still using reproduction cost new that includes $60,000:

Functional obsolescence (superadequacy) ≈ $60,000 − $10,000 = $50,000
(Simplified excess-cost method.)

If you had used replacement cost that never included the mezzanine, you would not take this same $50,000 line—consistency with Section 10.2.

Worked Example 4 — Curable FO vs physical deferred maintenance

External Obsolescence (ECO V.e)

External obsolescence (EO)—also called economic obsolescence in many texts—is a loss in value from negative influences outside the property. The owner cannot cure them by remodeling alone.

Locational vs economic (external subtypes)

Both are external because the loss agent is off-site (or market-wide), not a missing bathroom inside the house.

Always incurable from the owner’s perspective

Key exam doctrine:

External obsolescence is incurable to the individual property owner as of the effective date—the owner cannot order the city to move the freeway or reopen the factory by writing a contractor check on the subject alone.

(Governments or markets may change later; that does not make EO “curable physical” today.)

Measuring External Obsolescence — Worked Examples

Worked Example 5 — Paired sales (locational EO)

Two similar houses:

Indicated locational loss ≈ $30,000. If Sale B matches the subject’s exposure, external obsolescence indication ≈ $30,000 (after confirming other elements are equal).

Worked Example 6 — Capitalized income loss (economic/locational EO)

Subject apartment rent loss due to nearby industrial odor: $200 per unit per month × 10 units = $2,000/month = $24,000/year.
Cap rate: 6%
EO ≈ $24,000 ÷ 0.06 = $400,000

Worked Example 7 — Allocating EO between land and building

External forces often hit land as well as improvements. Cost approach depreciation is applied to improvements; land value from Area III should already reflect adverse location if site value is market-based from similarly affected sites.

Trap: Taking full paired-sale EO off the building and using already-discounted land comps double-counts.
Good practice: If land comps are from the same adverse location, land is already correct; apply only the improvement-related portion of EO to the building—or use extraction carefully. Exam stems that give a single EO number and a clear instruction (“depreciation of improvements”) want that number applied in the cost approach depreciation section without inventing a second land hit.

Full Breakdown Mini-Case (All Three Causes)

Subject: 25-year-old house. Site value (already reflecting a mildly inferior street): $95,000.
Replacement cost new: $350,000.

Depreciated improvements: $350,000 − $112,000 = $238,000
Cost-approach indication: $95,000 + $238,000 = $333,000

Labeling Drill (High-Yield)

Relationship to Reproduction vs Replacement

• Reproduction cost tends to increase measured FO (you cost obsolete and superadequate features, then deduct).
• Replacement cost tends to reduce some FO by never costing obsolete features—but may still need FO for deficiencies relative even to a modern standard, or for subject-specific quirks not captured in the replacement model.
• External obsolescence exists regardless of reproduction vs replacement; off-site forces are not cured by changing the cost basis.

Common Exam Traps

• Calling highway noise functional obsolescence.
• Calling a bad floor plan external obsolescence.
• Treating external obsolescence as curable because “the city might rezone someday.”
• Double-counting superadequacy in reproduction cost and again as a positive “feature” in sales comparison without analysis.
• Using cost to cure for incurable FO when cost to cure exceeds value added.
• Forgetting that EO may already be in land value if comps share the same external influence.
• Swapping ECO letters: remember V.d functional, V.e external for this guide’s blueprint mapping.

Formula Card — Depreciation Causes

1. Physical curable ≈ cost to cure (when cost ≤ value added)
2. Physical incurable ≈ age-life on short- and long-lived components
3. Functional curable ≈ cost to cure (deficiency) when economically justified
4. Functional incurable ≈ capitalized rent loss, paired data, or excess cost (superadequacy)
5. External ≈ paired data or capitalized loss; incurable to owner; watch land allocation
6. Cost approach = Land + (Cost new − sum of all depreciation)

Bridge to Chapter 11

You can now name and classify every major depreciation cause under ECO V.c–e and run basic quantification. Chapter 11 (depreciation methods and cost-approach reconciliation) drills age-life, modified age-life, breakdown procedure, and market extraction of depreciation, then reconciles the cost approach indication. Keep physical vs functional vs external labels clean—method chapters assume you already know what you are measuring, not only how to ratio it.

Master FO and EO and you stop leaving Area V points on the table whenever a stem describes a perfect structure in a bad location—or a flawed design on a perfect lot.