This edition of Code Counts examines several major applications of code that are helping drive Type III and V mid-rise development. We’ll look at the three major configurations behind a new generation of wood multi-story mixed-use and multi-residential projects: tuck-under, wrap-around, and podium. Then we’ll identify code provisions that help developers and owners safely increase mid-rise occupant density.

You may have already inspected one or more of these mid-rise building types in recent years. If not, there’s a fair probability you will soon. A brief look at each:

Developers of apartments, senior living centers, student housing, hotels, and condominiums are highly skilled at using what’s allowed by building code to maximize real estate opportunity.

Today there is ample evidence of their practical building approach with a surge of Type III and V wood building construction. The development attraction is the cost and density light-frame wood construction offers developers and owners.

Perhaps more interesting to you, as a code professional, are the ways housing and hospitality professionals work with wood and within code to increase density without compromising the life safety imperative that’s at the heart of your work.

This edition of Code Counts examines several major applications of code that are helping drive Type III and V mid-rise development. We’ll look at the three major configurations behind a new generation of wood multi-story mixed-use and multi-residential projects: tuck-under, wrap-around, and podium. Then we’ll identify code provisions that help developers and owners safely increase mid-rise occupant density.

You may have already inspected one or more of these mid-rise building types in recent years. If not, there’s a fair probability you will soon. A brief look at each:

Tuck-Under

Tuck-under units are typically three stories with a private parking garage at ground level. This construction configuration offers the lowest density. However, wood tuck-under structures are economical to build and ideally suited in areas where density may not be a priority, such as a rural area. In some urban areas that are looking to mitigate car parking, the tuck-under is gaining traction in a walk-up configuration (replacing parking with additional ground floor units)

Wrap-Around

The wrap-around style is characterized by a central multi-story concrete parking structure surrounded by multiple stories of wood-frame housing. The advantage: Occupants have easy access to parking as well as security and aesthetic appeal. In a typical format, a five-story wrap-around will accommodate 60 to 80 units per acre, a density suited for large urban or suburban areas. Wrap-around is usually more expensive to build than tuck-under.

Podium

Sometimes called pedestal or platform construction, a podium is characterized by 4 to 5 stories of light wood framing typically over a one- or two-story podium of concrete or steel-frame construction separated by a 3-hour fire-resistance rated horizontal assembly. In effect, a hybrid of two buildings styles in one. The lower podium unit may include retail and/or above or below-grade parking. This construction approach allows increased density and is especially suited for smaller in-fill urban lots.

Code-Compliant Strategies to Increase Mid-Rise Building Density

With today’s housing shortages in many communities, density has become a rallying cry for developers as well as many civic leaders. There are several opportunities within the 2018 IBC (first printing: August 2017) to increase density per acre with wood. Here’s a look at code-compliant ways to increase mid-rise building height, floor size, and livable space:

Height

2018 IBC, Chapter 9 Fire Protection and Life Safety Systems, addresses fire protection requirements and cites new Group R occupancies must be equipped with an automatic sprinkler system designed and installed in accordance with NFPA 13 or NFPA 13R requirements. Height limits for Group R-1 and R-2 occupancies (hotels and multifamily apartment buildings) equipped throughout with an NFPA 13 sprinkler system range from 60 feet and three stories in Type VB construction to 85 feet and five stories in Type IIIA construction, per Tables 504.3 and 504.4. Group R-1 and R-2 buildings equipped with NFPA 13R sprinkler systems are limited to 60 feet and four stories in all construction types except Type VB (which is limited to three stories).

Floor Size

A compliant NFPA 13 sprinkler system also permits the developer to increase the allowable floor area for multi-story buildings by up to two times the tabulated area according to 2018 IBC Table 506.2. For example, say the base tabular floor area for a Type V-A building with a Group R-1 or R-2 occupancy is 12,000 SF per story. The addition of a code-compliant NFPA 13 sprinkler system allows the developer to boost the total square footage by an additional 24,000 SF up to 36,000 SF per story. For a Type III-A building, the total square footage can expand up to 72,000 square feet per story, per 2018 IBC Table 506.2 for a multi-story building protected with an NFPA 13 sprinkler system. Additional area increases may also be applicable depending on open frontage in accordance with Section 506.3.

Livable Space

For Type III and V wood-frame buildings, an additional level can be added with a mezzanine. 2018 IBC Section 505.2.1 states “… a mezzanine or mezzanines within a room shall be not greater than one-third [emphasis added] of the floor area of that room or space in which they are located. The enclosed portion of a room shall not be included in a determination of the floor area of the room in which the mezzanine is located. In determining the allowable mezzanine area, the area of the mezzanine shall not be included in the floor area of the room.”

2018 IBC notes an important mezzanine exception for dwelling units located in buildings equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1 (NFPA 13) or 903.3.1.2 (NFPA 13R). That exception allows a mezzanine size of up to one-half of the floor area of the room depending on specific limits for openness.

Summary

As you work with developers, building owners, architects, general contractors, and others in the building trades on mid-rise projects, keep wood-frame buildings and these aspects of the code in mind.

Learn more about three common design configurations for wood-frame multi-story projects: tuck-under, wrap around and podium in our 4 part series. Each article gives you practical ideas and tips on how to maximize the value of your next multi-story project by using wood and one or more of these building types.

  1. Multi-story DensityHow Wood Can Increase the Density of your Next Multi-Story Project
  2. What’s Allowed?: How to Maximize Building Heights and Sizes in your Next Multi-Story Project
  3. Podium Design:  How a Podium Design Can Maximize Value on your Next Multi-Story Project
  4. Case Studies: How Four Multi-Story Projects Boosted their Value Using Wood

 

Disclosure statement: The views and opinions expressed in this article are those of the Think Wood and do not necessarily reflect those of the International Code Council, or Hanley Wood.