2018 IBC Increases Structural Design, Elevator Costs for Multifamily Buildings

Filed in Codes and Standards, Multifamily by on May 4, 2018 2 Comments

multifamily constructionA new Home Innovation Research Labs report on the Estimated Costs of the 2018 ICC Code Changes for Multifamily Buildings shows minimum cost impacts for typical multifamily buildings ranging from $2,500 for a small 2-story multifamily project to $25,000 for a larger 5-story project.

The higher costs are primarily due to significant changes involving elevators and wind load design.

Using a similar methodology to its studies for the International Residential Code, Home Innovation looked at four multifamily buildings ranging from a 2-story, 24-unit building to a 5-story, 167-unit building. Two of the four buildings included public spaces such as community or fitness rooms, leasing offices or retail spaces. The study also looked at a typical 4-story townhouse.

The 2018 International Building Code (IBC) requires all elevators, including service elevators and elevators not accessible to the public, to have a two-way text- and video-based communication system for the hearing- and speech-impaired. It was difficult to quantify the cost, as no consensus standard for such a system exists, but an estimated cost per elevator is between $2,500 and $5,000.

As anticipated, new roof uplift pressures in the 2016 edition of the ASCE 7 Minimum Design Loads for Buildings and Other Structures standard, incorporated by reference in the 2018 IBC, significantly increased costs for roof sheathing and some roof cladding systems.

Cost increases of $2,400 to $4,300 per building were estimated for buildings with wood hip- or gable-roof assemblies. Buildings with low-slope, mechanically attached, single-ply roof membranes or similar systems could see cost increases of $8,400 to $16,700 per building.

Fire code officials’ ability to require a fire watch during construction was strengthened and expanded to include periods where temporary heating is used. For larger projects, the cost to provide a 24/7 fire watch can exceed $233,000.

On the positive side, the requirement to seal button- and snap-lock mechanical ducts located in conditioned space was removed from the 2018 International Mechanical Code, saving $1,800 to $11,200 for the reference multifamily buildings.

An IBC change allowing the private garage for a building’s tenants to be treated as enclosed public parking structures could save at least $10,700 by allowing builders to avoid fire barriers for every one thousand square feet of garage area. This fixes an unintended consequence of language added to the 2015 IBC to clarify what constitutes a private garage.

More information on significant changes in the 2018 IBC and NAHB’s recommended amendments can be found in the 2018 Code Adoption Toolkit.


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  1. Phillip Kinard says:

    Yay!! As a retired builder and real estate SFH rentals I am thrilled with additional codes. Keep adding to the cost of construction and it keeps demand high for my rental homes with fewer and fewer first time home builders in the market able to afford to buy. INSANE. WE FINALLY GOT THE CODE TO WHERE THE HOUSE IS SO TIGHT WE HAVE TO BRING IN OUTSIDE AIR. Brilliant.

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