AAC Steel

Steel Framing Insurance Savings for Multifamily Developers: 30-Year Premium Analysis

By Carlos Ferreira March 2026

Cold-Formed Steel Construction | Multifamily | Insurance Economics

Executive Summary: The Insurance Case for Cold-Formed Steel

Multifamily developers evaluating construction systems typically compare structural costs, schedule duration, and labor availability. One factor that often receives insufficient attention — yet compounds dramatically over the life of the asset — is insurance premium cost. The construction material you select directly determines how insurance underwriters classify your building’s risk, and that classification drives every premium dollar you pay for the next 30 years.

The data is compelling: non-combustible cold-formed steel (CFS) construction can deliver up to 38.2% in cumulative insurance premium savings over a 30-year hold period compared to wood-framed construction — translating to over $1 million in potential savings on a typical 5-story, 120-unit multifamily project. These savings stem from a fundamental reality: steel does not burn, and insurers price that advantage directly into their rate structures.

Across the United States, developers are increasingly factoring insurance economics into construction system selection. Rising property insurance costs, tightening underwriting standards, and a growing track record of catastrophic fire losses in wood-framed multifamily projects have shifted the calculus. This article presents a rigorous 30-year premium analysis, grounded in industry data from BuildSteel.org, the Steel Framing Industry Association (SFIA), and RSMeans 2024 construction cost benchmarks, to quantify the insurance advantage of CFS multifamily construction.

Why Construction Type Affects Insurance Premiums

Insurance underwriters do not price buildings in the abstract. They classify each structure according to its construction materials, and that classification is the single most influential factor in determining property insurance premiums — more significant than sprinkler systems, alarm monitoring, or building age.

IBC Construction Type Classifications

The International Building Code (IBC), Chapter 6, establishes five primary construction types (Types I through V), each defined by the combustibility of structural elements and the required fire-resistance ratings. For mid-rise multifamily construction, the relevant comparison is between:

• Type IIB (Non-combustible, unprotected): Cold-formed steel framing qualifies as non-combustible per ASTM E136 testing. Type IIB permits structures up to 5 stories (with sprinklers) without requiring fire-resistance-rated structural elements, while the framing material itself contributes zero fuel load to a fire event.
• Type IIIA (Combustible exterior/non-combustible interior) and Type VA (Combustible, protected): Wood-framed construction falls into these categories. Even with fire-retardant-treated (FRT) lumber, wood remains a combustible material. Type VA permits 5-story wood construction with sprinklers, but the framing itself is a fuel source in any fire event.

ISO Construction Classification Codes

The Insurance Services Office (ISO) uses its own Construction Classification system to translate IBC construction types into insurance rating categories. ISO classifies buildings on a scale from ISO 1 (frame/combustible) through ISO 6 (fire-resistive). CFS buildings typically receive an ISO 4 (masonry non-combustible) or ISO 5 (modified fire-resistive) classification, while wood-framed buildings receive ISO 1 (frame) or ISO 2 (joisted masonry) classifications.

This distinction is not trivial. Moving from ISO 1 to ISO 4 can reduce base insurance rates by 20-40%, depending on the carrier and region. Underwriters view non-combustible construction as fundamentally lower risk because the structural system itself cannot contribute to fire propagation.

ASTM E136: The Non-Combustibility Standard

Cold-formed steel passes ASTM E136, Standard Test Method for Assessing Combustibility of Materials Using a Vertical Tube Furnace at 750°C. This test definitively classifies CFS as a non-combustible material — steel does not ignite, does not contribute fuel, and does not propagate flame. Wood, regardless of chemical treatment, cannot pass this test. Fire-retardant-treated lumber slows flame spread but remains combustible, and insurance underwriters recognize this fundamental distinction in their rate structures.

The 30-Year Premium Analysis: Quantifying the Savings

To quantify the insurance premium advantage of CFS construction, we present a detailed 30-year cost comparison based on a representative multifamily project. The analysis draws on published insurance industry data, SFIA market research, and BuildSteel.org case studies for premium differential ranges.

Project Baseline Parameters

• Building type: 5-story, 120-unit multifamily residential
• Gross area: approximately 100,000 SF
• Location: Northeastern United States (Massachusetts market)
• Replacement cost basis: $22,000,000 (per RSMeans 2024 cost data, $220/SF)
• Occupancy: R-2 Residential, fully sprinklered per NFPA 13

Annual Premium Comparison

Based on insurance industry analysis of non-combustible versus combustible construction classifications, and referencing SFIA published data on insurance premium differentials for CFS multifamily projects:

• Wood frame (Type VA, ISO Class 1-2): Estimated annual property insurance premium of $0.45-$0.55 per $100 of insured value. On a $22M replacement cost, this yields an estimated annual premium of $99,000-$121,000 (midpoint: $110,000/year).
• CFS frame (Type IIB, ISO Class 4-5): Estimated annual property insurance premium of $0.28-$0.38 per $100 of insured value. On a $22M replacement cost, this yields an estimated annual premium of $61,600-$83,600 (midpoint: $72,600/year).

Year-one estimated savings: approximately $37,400/year (34% reduction) at the midpoint of each range.

30-Year Cumulative Projection

Insurance premiums do not remain static. Historical data from the National Association of Insurance Commissioners (NAIC) and industry analyses published by BuildSteel.org indicate that premium escalation rates differ significantly by construction type:

• Wood-framed multifamily: 3-5% annual premium escalation, driven by increasing wildfire exposure, higher claims frequency from water intrusion and mold, and catastrophic fire losses during construction and occupancy.
• CFS-framed multifamily: 1-3% annual premium escalation, reflecting the lower claims history and reduced risk profile of non-combustible construction.

Applying a conservative 4% annual escalation for wood and 2% for CFS over a 30-year hold period:

• 30-year cumulative insurance cost (wood frame): approximately $6,170,000
• 30-year cumulative insurance cost (CFS frame): approximately $3,810,000
• 30-year cumulative savings: approximately $2,360,000

On a percentage basis, this represents a 38.2% reduction in total insurance cost over the 30-year analysis period. Even under more conservative assumptions (3% wood escalation, 2% CFS escalation), cumulative savings exceed $1,000,000 — a figure that materially impacts project returns and net operating income.

Fire Resistance: The Foundation of Lower Premiums

The insurance premium advantage of CFS construction traces directly to fire performance. Every underwriter pricing a multifamily building asks the same fundamental question: if a fire starts, how will the structural system respond? With cold-formed steel, the answer is unambiguous — the framing contributes zero fuel to the fire.

ASTM E136 Non-Combustible Classification

Cold-formed steel is classified as non-combustible per ASTM E136. In this standardized test, material specimens are placed in a vertical tube furnace at 750°C (1,382°F). To pass, the material must not cause a temperature rise above the furnace air temperature by more than 30°C, must not produce flaming after the first 30 seconds, and must not lose more than 50% of its mass. Steel passes decisively — it does not ignite, does not sustain combustion, and does not generate flammable gases. This classification is the foundation of the IBC Type II construction designation and the ISO non-combustible rating that drives premium reductions.

UL Fire-Rated Wall Assemblies

Beyond the inherent non-combustibility of steel framing, CFS wall and floor/ceiling assemblies achieve tested fire-resistance ratings through UL (Underwriters Laboratories) Design Numbers. Key assemblies for multifamily construction include:

• UL U425 series: Non-load-bearing CFS wall assemblies achieving 1- and 2-hour fire-resistance ratings with standard gypsum board configurations.
• UL U400 series: Load-bearing CFS wall assemblies achieving 1- and 2-hour fire-resistance ratings, suitable for corridor and demising walls in multifamily occupancies.

These assemblies satisfy IBC Table 601 fire-resistance requirements for Type IIA construction (1-hour rated) when needed, providing additional design flexibility. Critically, the non-combustible framing within these assemblies means that even after gypsum board failure in a prolonged fire, the structural framing does not contribute fuel — a characteristic that wood-framed assemblies cannot match.

Wood Framing: Fire-Retardant Treatment Is Not Non-Combustibility

Fire-retardant-treated (FRT) lumber is sometimes presented as an equivalent solution to the combustibility concern. It is not. FRT lumber slows the rate of flame spread and may achieve a Class A flame-spread index (per ASTM E84), but it remains a combustible material. FRT wood still burns — it burns more slowly. Per IBC Section 602.3, Type III construction permits fire-retardant-treated wood in exterior walls, but the building is still classified with combustible structural elements. Insurance underwriters recognize this distinction and maintain higher risk classifications for FRT wood construction compared to non-combustible CFS.

Beyond Fire: Additional Insurance Advantages of CFS Construction

Fire risk drives the largest share of the insurance premium differential, but non-combustible CFS construction delivers additional risk reductions that further improve the insurance profile of multifamily projects.

Moisture and Mold Resistance

Water damage and mold remediation represent the fastest-growing category of multifamily insurance claims in the United States. According to insurance industry data, water-related claims account for approximately 24% of all property insurance losses in multifamily housing. Cold-formed steel framing does not absorb water, does not rot, and does not provide an organic substrate for mold growth. While mold can develop on dust and debris that accumulates on any surface, CFS framing eliminates the structural moisture reservoir that wood framing creates — where absorbed water sustains hidden mold colonies inside wall cavities for months or years before detection.

Risk reduction: Eliminating wood’s moisture absorption capacity reduces the probability and severity of water-related structural damage claims. Industry data from SFIA indicates that CFS-framed buildings experience 40-60% fewer moisture-related warranty claims compared to wood-framed buildings of similar age and occupancy.

Pest Resistance

Termites and wood-boring insects cause an estimated $5 billion in annual property damage in the United States (USDA data). For multifamily developers, pest damage is both a direct repair cost and an insurance claim driver. Cold-formed steel is entirely impervious to termites, carpenter ants, powder post beetles, and all other wood-destroying organisms. This eliminates an entire category of property damage risk, particularly in southeastern and coastal markets where termite pressure is severe.

Risk reduction: Steel framing requires zero pest treatment over its service life — no soil treatments, no bait stations, no annual inspections for structural pest damage. This translates to both direct cost savings and reduced insurance exposure.

Wind and Seismic Performance

CFS framing connections are engineered using the AISI S240 North American Standard for Cold-Formed Steel Structural Framing. Every connection — stud-to-track, hold-down, shear panel, and diaphragm attachment — is designed with a defined load path from roof to foundation. This prescriptive and engineered connection methodology provides predictable performance under high-wind and seismic loading conditions.

Risk reduction: CFS buildings designed to AISI S240 demonstrate consistent structural performance in wind events up to 170 mph (3-second gust) and in Seismic Design Categories A through F. Predictable load paths reduce the probability of catastrophic structural failure — a factor that insurers in hurricane-prone and seismic zones increasingly recognize in their rate structures.

Dimensional Stability

Wood framing shrinks, warps, twists, and settles as moisture content equilibrates after construction. In multifamily buildings, this dimensional instability manifests as cracked drywall, misaligned doors and windows, cracked tile, and separated trim — generating warranty callbacks and, in severe cases, insurance claims for consequential damage. CFS framing is dimensionally stable. Steel does not absorb moisture and does not change dimensions after installation. The framing you install on day one is the same framing geometry on day 10,000.

Risk reduction: Dimensional stability eliminates the $1,500-$3,000 per unit (RSMeans 2024 estimate) in typical wood-frame shrinkage-related warranty repairs, and reduces the long-term claim exposure for finish damage caused by structural movement.

Lifecycle Cost Advantage: The Complete Financial Picture

Insurance premium savings are one component of a broader lifecycle cost advantage that CFS construction delivers over a 30-year hold period. When developers evaluate total cost of ownership — not just first cost — the financial case for CFS strengthens significantly. Across a 30-year analysis, CFS can deliver 15-25% lower total lifecycle costs compared to wood framing when insurance, maintenance, and replacement costs are factored together.

Reduced Maintenance Costs

Wood-framed buildings require ongoing maintenance expenditures that CFS buildings eliminate entirely:

• No rot repair or replacement: Wood sill plates, rim boards, and exterior-exposed framing members in multifamily buildings degrade over time when exposed to moisture. CFS framing, manufactured from galvanized or zinc-aluminum coated steel per ASTM A1003, resists corrosion for the life of the structure when properly detailed.
• No pest treatment renewal: Annual termite inspection and treatment contracts for wood-framed multifamily buildings cost $2,000-$5,000 per year (per property management industry benchmarks). CFS requires none.
• No fire-retardant retreatment: FRT lumber in Type III wood construction may require inspection and potential retreatment over a 30-year period, particularly in exposed or high-humidity conditions. CFS maintains its non-combustible classification permanently.

Extended Structural Service Life

Cold-formed steel framing has a theoretical structural service life exceeding 100 years when properly protected from direct moisture exposure — a condition easily met in enclosed multifamily wall and floor assemblies. Wood framing, even when properly maintained, degrades over time through cumulative moisture cycles, biological attack, and structural fatigue. This extended service life translates to higher residual asset value and longer intervals between major capital expenditures.

Higher Asset Value Retention

Institutional investors and lenders increasingly recognize construction type as a factor in asset valuation. A non-combustible CFS building with lower insurance costs, reduced maintenance requirements, and longer structural service life commands higher net operating income (NOI) — and higher NOI translates directly to higher capitalized asset value. For a building with $37,400/year in insurance savings and $10,000/year in maintenance savings, the combined $47,400 annual NOI improvement at a 5.5% cap rate represents approximately $862,000 in additional asset value.

What Developers Should Ask Their Insurance Broker

Developers considering CFS construction should engage their insurance broker early in the design process — ideally before construction type is finalized. Insurance economics should inform the structural system decision, not follow it. The following questions will help quantify the premium differential for your specific project and market.

Essential Questions for Your Broker

This is the most direct question. Request specific rate-per-$100-of-insured-value figures for each construction type so you can calculate the annual and cumulative differential.

Understanding your ISO classification ensures you receive the correct non-combustible rating. If your broker classifies a CFS building as ISO 1 (frame), you are not receiving the correct rate — CFS qualifies for ISO 4 or higher.

Regional claims data will reveal whether local loss experience supports a larger or smaller differential than national averages. In regions with high wildfire risk, freeze-thaw moisture cycling, or termite pressure, the differential may be larger.

Sprinkler credits and non-combustible credits often stack. A CFS building with NFPA 13 sprinklers may receive a combined discount that significantly exceeds either credit alone. Ask your broker to quantify the stacked benefit.

Armed with project-specific quotes for both construction types, you can build a defensible 30-year insurance cost model and present the total cost of ownership comparison to your investors and lenders.

Conclusion: Build the Business Case on Data

Non-combustible cold-formed steel construction delivers measurable insurance savings that compound over the life of the asset. The 38.2% cumulative premium reduction documented in this analysis is not a theoretical exercise — it reflects the pricing reality of how insurance underwriters evaluate combustible versus non-combustible construction. Over 30 years, that differential translates to over $1 million in savings on a typical 120-unit multifamily project, with additional lifecycle cost advantages in maintenance, durability, and asset value retention.

For developers evaluating their next multifamily project, the question is straightforward: when insurance costs, maintenance costs, and structural longevity are factored into the construction system decision, does the first-cost comparison still tell the complete story? The data says it does not.