Types of Construction: Project Sectors and IBC Type I to V Explained

Construction type is not just a code label. It sets what the structure can be made of, how tall and large the building can be, and how much fire-rated drywall, fireproofing and protection the job needs. That makes it one of the biggest cost decisions on a commercial project, and one estimators need to confirm before pricing anything.

Types of Construction by Project Sector

When people ask about the types of construction in general, they usually mean the kind of project being built. The industry splits work into five main sectors, and each one has its own owners, contracts, codes and estimating approach.

Projects are also grouped by the type of work: new construction, additions, renovation and remodeling, and demolition. A renovation of a Type II office building is still a commercial project, so the sector, the work type and the IBC construction type all apply at the same time.

The rest of this guide covers the second meaning: the five IBC construction types that appear on the code summary of every commercial drawing set.

The 5 Types of Building Construction at a Glance

How Fire-Resistance Ratings Differ by Type

IBC Table 601 sets the minimum fire-resistance rating, in hours, for each part of the building. This is where the “A” and “B” letters matter:

Simplified from IBC Table 601. Footnotes allow some reductions, for example for roofs well above the floor or with sprinklers. Exterior wall ratings also depend on fire separation distance (IBC Table 602). Mass timber types IV-A, IV-B and IV-C carry 3 hr and 2 hr frame ratings with required noncombustible protection.

A “0” does not mean the building has no fire protection. It means the structure itself does not need a rating. Sprinklers, exits, fire separations between occupancies and exterior wall ratings still apply.

Each Construction Type Explained

Type I: Fire-Resistive

Type I buildings use noncombustible materials with high fire ratings: cast-in-place or precast concrete, or structural steel wrapped in spray fireproofing or rated board. Type I-A is required for the tallest and largest buildings. Type I-B is common for mid-rise offices, hospitals and parking garages. The concrete podium under a “5-over-1” apartment building is also usually Type I-A.

Type II: Noncombustible

Type II buildings use noncombustible materials but with lower or no fire ratings. Type II-B, unprotected steel frame with metal deck, is one of the most common commercial types in the US: think warehouses, distribution centers, big-box stores and strip retail. Type II-A adds 1-hour protection and allows larger or taller buildings.

Type III: Ordinary

Type III buildings have noncombustible exterior walls (masonry, concrete or fire-retardant-treated wood framing) with interior framing that can be wood. This describes many older brick downtown buildings, and newer mid-rise apartments that use treated-wood exterior walls to gain more height than Type V allows.

Type IV: Heavy Timber and Mass Timber

Traditional Type IV-HT buildings use large solid or glued-laminated timbers that char slowly instead of failing quickly in a fire. The IBC now also includes Type IV-A, IV-B and IV-C for mass timber (cross-laminated timber and glulam), which allow wood buildings well beyond the height of traditional wood framing when the timber is protected as the code requires.

Type V: Wood Frame

Type V is light-frame construction, usually wood studs and joists. Type V-B has no required fire ratings and covers most small commercial buildings. Type V-A adds 1-hour protection, typically with Type X gypsum board, and is common for apartment buildings of three to four stories, often built over a Type I-A podium. Five wood stories over a podium usually require Type III-A. One- and two-family houses are usually built under the International Residential Code, which does not use this classification, but they are wood-frame in the same sense.

How Construction Type Affects Cost

Construction type affects cost in two ways: the structural system itself, and the fire protection needed to reach the required ratings.

The “A” versions cost more than the “B” versions of the same type because every rated element needs extra gypsum layers, fireproofing, rated penetrations and inspections. On a wood-frame apartment building, the difference between V-B and V-A shows up mostly in drywall and firestopping. On a steel building, the jump from II-B to II-A or I-B is mostly spray fireproofing and rated assemblies.

This is why design teams work hard to pick the lowest type that meets the building’s height, area and occupancy. Adding sprinklers often allows a larger or taller building within a cheaper type. For estimators, the construction type, usually stated on the code summary sheet of the architectural drawings, is one of the first things to confirm. For a sense of overall cost per square foot on residential work, see our guide to cost per square foot to build a house.

ISO Construction Classes (Insurance)

Insurance underwriters and many fire departments use the ISO classification instead of IBC types. The two systems overlap but are not identical:

Approximate correspondence only. Insurers apply their own definitions.

Where to Find the Construction Type on Drawings

On commercial drawings, the code summary or life safety plan, usually on the first architectural sheets (G-, A0- or LS- series), lists the occupancy group, construction type, sprinkler status and allowable height and area. Rated wall types are tagged on the floor plans and detailed in the partition schedule. Before pricing, check that the rated assemblies on the plans match the construction type on the code sheet; mismatches are a common source of change orders.

Estimating Construction by Type

Design Estimation prepares estimates for commercial and residential projects of every construction type, including structural steel, concrete, wood framing, fireproofing and rated drywall assemblies, priced by CSI division. See our general contractor estimating services, our structural steel estimating and drywall and framing estimating, or send your drawings for a quote.