Cost Approach: Replacement Cost New and Depreciation

The Cost Approach in Residential Valuation

The cost approach estimates value by answering a simple question: what would it cost a typical buyer to reproduce or replace the improvements on the site, minus any loss in value those improvements have suffered, plus the land value? Appraisers and property managers use this approach most often for new construction, special-use properties, and as a cross-check against the sales comparison and income approaches.

The formula is straightforward:

Value = Land Value + Replacement Cost New – Total Depreciation

Understanding each piece of that formula is the goal of this lesson.

Replacement Cost New vs. Reproduction Cost New

Reproduction cost new is the cost to build an exact duplicate of the existing structure using the same materials and design—even if those materials are now obsolete or inefficient.

Replacement cost new (RCN) is the cost to build a structure of equal utility using current materials, standards, and design. Most residential appraisals use replacement cost new because it avoids embedding obsolete features into the cost estimate.

For the IREM CPM and the state salesperson license exam, you will encounter both terms. Know that RCN is the more common choice in modern practice.

Using a Published Cost Service

Published cost services—such as the Marshall & Swift/Boeckh residential cost manual, or similar school-licensed digital tools—organize construction costs by building type, quality class, occupancy, and region. The general steps are:

1. Identify the building class and type. Classify the structure by construction quality (economy, average, good, excellent) and structural type (wood frame, masonry, etc.).

2. Look up the base cost per square foot. The manual provides a base unit cost for a standard size and shape of that building type.

3. Apply size and shape adjustments. Very small or irregularly shaped buildings cost more per square foot to build; the manual provides adjustment factors.

4. Apply the local cost multiplier. Construction costs vary by city and region. Multiply the adjusted base cost by the published local multiplier to reflect your market area.

5. Apply the current-cost (time) multiplier. Cost manuals are updated periodically; if using an older edition, a time multiplier adjusts for construction cost inflation.

6. Add site improvements. Driveways, walks, fencing, landscaping, and utility connections are priced separately and added to the dwelling cost.

7. Add entrepreneurial profit. A developer expects a return above hard and soft costs. This is typically estimated as a percentage of total costs and must be included when the market evidence supports it.

The result is the replacement cost new of the total improvement.

Types of Depreciation

Depreciation in appraisal means any loss in value from any cause—it is not the same as the tax or accounting concept of depreciation. There are three categories:

Physical Deterioration

Loss caused by wear, age, and the elements.

• Curable physical deterioration: Items that a typical buyer would expect a seller to fix because the cost to cure is equal to or less than the value added. Examples: worn carpet, peeling paint, minor roof repairs.
• Incurable physical deterioration: Items too costly to fix relative to the value added, or items that simply cannot be cured. Examples: structural settling of the foundation, deteriorated framing.

Functional Obsolescence

Loss caused by a deficiency or superadequacy in the design or layout of the structure itself.

• Curable functional obsolescence: Adding a missing feature the market demands (e.g., a second bathroom in a four-bedroom house) where the cost to cure does not exceed the value gained.
• Incurable functional obsolescence: A design flaw that cannot be fixed cost-effectively, such as an outdated floor plan with poor room flow.

External (Economic) Obsolescence

Loss caused by factors outside the property—always considered incurable because the owner cannot control them. Examples: a nearby industrial facility that generates noise or odor, a decline in neighborhood property values, or an adverse zoning change.

Estimating Depreciation: Two Methods

Age-life method (straight-line): Divides the effective age of the improvement by its total economic life to get a depreciation percentage, then applies that percentage to RCN.

> Depreciation % = Effective Age ÷ Total Economic Life

Effective age reflects the actual condition of the property, which may differ from its chronological age. A well-maintained 20-year-old house may have an effective age of only 10 years.

Breakdown method: Estimates each category of depreciation separately and sums them. This is more precise when significant functional or external obsolescence exists alongside physical deterioration.

When the two methods yield different answers, the breakdown method is generally more reliable because it accounts for each depreciation cause individually. The age-life method can understate or overstate depreciation when one category dominates.

Accuracy and Professional Responsibility

Cost estimates that are significantly wrong can mislead buyers, lenders, and insurers. Always use the most current edition of the cost manual available and document the edition and multipliers you applied. If you are unsure of a building quality class, err toward the more conservative (lower) class and note your reasoning. Licensing law in most states requires that appraisal-related work be completed honestly and without misrepresentation—knowingly inflating or deflating a cost estimate can result in license suspension or revocation.