Building Code Model and Commentary

Model Code

The International Codes developed by the International Code Council (ICC) establish standard building safety and engineering regulations and help protect critical infrastructure, which is the lifeline of a community during and after a major hazard event. Jurisdictions have the option of adopting local amendments to the International Codes that are tailored to address risks associated with hazard areas. While it is not required, adopting more stringent standards to mitigate hazards leads to safer, stronger, and more resilient communities.

The types and associated levels of risk can vary widely among communities. Amendments to the local building code depend largely on area-specific conditions and/or mitigation objectives that the community has defined relative to one or more hazards. This model has been prepared from a planner’s perspective and presents several examples where tailored building code standards, specifically related to hazard mitigation, can be implemented into local building codes. Local building officials and other hazard mitigation staff are the administrators of building codes and should take the lead role in tailoring language for your jurisdiction and selecting appropriate methodologies.

Land development and zoning codes address mostly site conditions and exterior building treatment, but rarely address what happens within the building itself before, during, or following construction. Building code standards are most effective when paired with other hazard mitigation strategies that are identified in this guide, specifically: Community Wildfire Protection Plan; Hazard Mitigation Plan; Resilience Planning; Conservation Easement; Stream Buffers and Setbacks; Stormwater Ordinance; Site-Specific Hazard Assessment; Subdivision and Site Design Standards; and Wildland-Urban Interface Code.

Text in beige shading provides model language while commentary is located in the column at the right. The model language used in this document is based on existing building codes from communities around the state and nation. The language is illustrative only; consult local building officials and legal counsel to tailor language for your jurisdiction.

Organization of this Model

Following some introductory material on applicability and submittal requirements, the remainder of this model is organized by hazard. Some hazards include more building-code related information than others, whereas others are either not included at all or are better addressed through site development standards.

Cost-Benefit Considerations

In 2019, the National Institute of Building Sciences released a report, Natural Hazard Mitigation Saves, that is intended to inform future code changes to make communities more resilient, help jurisdictions make decisions on what codes to adopt and enforce, and assist policymakers in developing effective federal programs that support pre-disaster mitigation. The report also includes research that helps quantify the benefits of exceeding the baseline standards found in the 2015 International Building Code (IBC) and 2015 International Residential Code (IRC). The report suggests that implementing measures in new construction to exceed select provisions in the 2015 IRC and 2015 IBC and implementation of the IWUIC saves society approximately $4 for every $1 spent on mitigation. The benefit-cost ratio increased further to $6 for every $1 spent on mitigation provided by federal mitigation grants through the Federal Emergency Management Association (FEMA), the U.S. Economic Development Administration (EDA), and the U.S. Department of Housing and Urban Development (HUD). 

Commentary

New Construction Versus Existing Structures

Applying standards to new construction is a conventional approach to ensuring life safety is protected. However, retrofitting existing structures to today’s modern standards is less straightforward. Older structures can be at a higher risk of sustaining damage during a natural hazard event if they are not upgraded through renovation and repair projects over time. The International Existing Building Code (IEBC) establishes standards for when existing buildings are required to be made compliant with seismic design provisions, flood design requirements, and other International Codes as a result of alterations, repairs, additions, changes of occupancy, and relocations (IEBC 2015 Chapter 1, Section 101; Chapter 3, Section 301; and Chapter 4).

Applicability Thresholds

To ensure that a community’s building stock (both old and new) is resilient, local governments should identify thresholds for when new and existing projects are required to comply with the adopted building code standards. Such thresholds are often included in the applicability section of the building code.

Note: This language can be added to Section 104 of Chapter 1 of the IBC:

Application Submittal Requirements

It is critical that staff reviewing a building permit request is provided with the necessary information to help them identify the level of risk associated with that project. Depending on the nature of the request, it is common for communities to require that all building permit applications (depending on the request) be accompanied by a site plan. In cases where improvements are proposed in highly sensitive areas, a Site-Specific Hazard Assessment may be required by the building official. The jurisdiction’s building code can establish what type of information is required to be on the site plan.

Note: This language can be added to Section 107 in Chapter 1 of the IBC:

Flood

The best way to mitigate risks associated with flooding is to avoid constructing in areas that are at risk for flooding. The Stream Buffers and Setbacks section and Stormwater Ordinance section of this guide provides guidance for preventing development near flood risk areas and management of on-site stormwater.

Many communities have adopted floodplain regulations as part of their land development codes that are separate from the community’s building codes. Colorado has minimum requirements for floodplain regulations that are established by the Colorado Water Conservation Board. Some Colorado standards for certain floodplain management activities exceed those required by the National Flood Insurance Program (NFIP). In those cases, the stricter of the State standards take precedence.

Addressing existing structures located in flood-prone areas is particularly challenging. Existing structures can use flood mitigation techniques (aside from avoidance of floodplain areas) including:

• Dry flood-proofing (making the building watertight to prevent water entry);
• Wet flood-proofing (making uninhabited or non-critical parts of the building resistant to water damage);
• Relocation of the building; and
• Incorporating floodwalls into site design to keep water away from the building.

In addition to the techniques above, a relatively simple approach to preventing water damage to structures is requiring gutters and downspouts on all buildings to direct water away from the foundation to prevent damage from trapped moisture. For this reason, Boulder County has adopted amendments to the IBC requiring all buildings (with exception to a few) to provide gutters or downspouts.

Note: This language can be added as a new Section 1805 in Chapter 18 of the IBC:

Drought

Drought originates from a lack of precipitation over an extended period of time, resulting in a water shortage. The demand that people place on a water supply can exacerbate the impacts of drought. Local government can establish policies and implement strategies to manage and protect water resources so that impacts are minimized during times of drought. Some communities have adopted amendments to the International Plumbing Code (IPC) and the IRC to reduce flow rates through water fixtures to conserve limited water resources. In addition to adopting local building code amendments, upgrading water supply and delivery systems to eliminate breaks and leaks will help conserve water. The model code language below provides additional guidance on how drought impacts can be minimized.

Note: This language, which was taken from the City of Westminster Building Code, can replace the figures in Table P2903.2 found in Section P2903 in Chapter 29 of the IRC:

Note: This language, which was taken from the City of Westminster Building Code, can be added to Section 601 in Chapter 6 of the IPC:

Note: This language, which was taken from the City of Denver Building Code, can be added to Section 401 in Chapter 4 of the IPC:

Note: This language, which was taken from the City of Westminster Building Code, can replace the figures in Table 604.4 found in Section 604 in Chapter 6 of the IPC:

Wildfire

As residential developments expand into wildland areas, people and property are increasingly at risk from wildland fire. Several preventative measures can be taken to minimize the spread of fire on the site as well as to make the building more fire-resistant. In addition to adopting local building code amendments to protect structures, the Wildland-Urban Interface Code and the Community Wildfire Protection Plan sections of this guide provide guidance for how wildfire hazards can be minimized through other measures.

Note: This language, which was taken from the Boulder County Building Code, can be added to Section 723 in Chapter 7 of the IBC:

Note: This language, which was taken from the Larimer County Building Code and the Boulder County Building Code, can be added as a new Section 327 in Chapter 3 of the IRC:

Some communities address wildfire concerns through a separate set of code standards specific to the Wildland-Urban Interface by adopting a standalone WUI Code – which is available as part of the International Code family but can also be integrated into the community’s land development code for site development issues aside from structural requirements. For more information, see the WUI Code section of this guide.

Extreme Heat

Extreme heat is a weather condition that results in temperatures that are much warmer than average for a particular time and place. According to the Centers for Disease Control and Prevention, extreme heat causes more deaths than any other weather-related hazard. More than 65,000 Americans visit emergency rooms each summer for acute heat illness. To respond to the growing challenges related extreme heat, some communities are implementing strategies to minimize the impacts of extreme heat through building design.

Power outages are commonly associated with extreme heat events because of increased demand on electric grids to run air conditioning systems.  When demand threatens to exceed the grid’s capacity to supply electricity, utility providers take precautions to reduce strain on the system. Designing building infrastructure to withstand extreme heat events will help alleviate stress on utility infrastructure and avoid electric service interruption.

One cost effective approach is the use of cool surfaces on building roofs. Cool surfaces are measured by how much light they reflect (solar reflectance or “SR”) and how efficiently they radiate heat (thermal emittance or “TE”). A cool roofing surface is both highly reflective and highly emissive to reduce the amount of light that is converted into heat and to maximize the amount of heat that is radiated away. High solar reflectance is the most important property of a cool surface. Increasing the reflectance of buildings through white surfaces or other reflective colored surfaces can reduce the temperature of buildings, thereby reducing the demand for cooling the building through mechanical systems. White roofs are typically 30 to 65 degrees Fahrenheit cooler than dark roofs in afternoon sunshine.

The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) developed procedures for calculating building heating and cooling loads (commonly referred to as design-day values) that are referenced by the International Energy Conservation Code (IECC). Design-day describes a period of time with maximum conditions that an HVAC system is designed to accommodate and maintain a desired indoor temperature and humidity. In an extreme heat event, the outside temperature may exceed the design-day value, thereby rending the mechanical systems undersized.

Improperly sized cooling equipment may place additional stress on mechanical, electrical, and plumbing systems, resulting in increased stress and demand on public utility infrastructure.

To prepare for extreme heat events, mechanical equipment can be evaluated using elevated design-day criteria. Supplemental systems can also be added to fill the gap of the de-rating due to temperature. Another approach is ensuring there are redundant systems in place that are de-rated for their design intent at operating temperatures.

Note: This language, which was taken from the City of Philadelphia Building Code, can be added to Section 1504 in Chapter 15 of the IBC and Section R905 in Chapter 9 of the IRC:

Landslide, Mud/Debris Flow, Rockfall

Designing buildings and structures for the direct effects of a landslide, debris flow, or rockfall is not typically cost-effective. However, many improvements can be made to a site to reduce the structural risk to debris flow and/or rockfall. The most effective ways to prevent damages from a gravity-driven movement of earth is to:

• Select non-hillside or stable slope sites for development; (avoidance)
• Construct channels, drainage systems, retention structures, and deflection walls;
• Plant groundcover to stabilize soils;
• Reinforce soils using geo-synthetic materials; and
• Avoid cut and fill building sites.

Most of these can be addressed by land development codes and engineering standards, rather than building codes. The Landslide, Mud/Debris Flow, and Rockfall section of this guide provides guidance for how land movement related hazards can be avoided.

Soil Hazards

As with landslide and other gravitational hazards, mitigating soil hazards can best be achieved through careful site selection, including geotechnical study of the site. In subsidence-prone areas, foundations must be appropriately constructed, and utility lines and connections must be stress-resistant. When retrofitting structures to be more subsidence-resistant, engineering best management practices such as shear walls, geo-fabrics, and earth reinforcement techniques such as dynamic compaction can be used to increase resistance to subsidence damage and to stabilize collapsible soils.

Note: This language, which was taken from Weld County’s adopted building code, can be added as a new Section 1805 in Chapter 18 of the IBC:

Wind Hazards

The key strategy for protecting a building from wind damage is to maintain the structural integrity of the building envelope,

including roofs and windows. Bracing roof trusses and gables and using hurricane straps to strengthen the connection between the roof and walls and walls and foundation will help the structure withstand lateral and uplift forces. Chapter 16, Section 1609 of the IBC and Chapter 3, Section 301 of the IRC establishes general standards based on regional climactic data for the appropriate design of buildings and structures to withstand wind loads.

Winds blowing over mountain ranges or through gorges or river valleys in some regions can develop speeds that are substantially higher than the values indicated on the map. The basic design windspeed map provided in the IBC (Figure 1609.3(1)) and IRC (Figure R301.2(4)A) identifies the Front Range Area as a “special wind region” requiring further examination for unusual wind conditions.

In 2006 the Structural Engineers Association of Colorado (SEAC) prepared a Colorado Front Range Gust Map that several communities have adopted to supplement the basic wind design criteria found in the IBC and IRC. This map is intended provide local communities with area-specific windspeed data to inform the design of buildings and structures in the Front Range area. It is important to note, when selecting basic wind speeds in regions with a diversity of terrain, use of regional climatic data and consultation with a wind engineer or meteorologist is advised.

Larimer and Boulder counties have adopted area-specific windspeed maps depicting wind exposure categories for anticipated wind events.  

Note: This language, (similar to those found in Boulder and Larimer Counties), can be used to amend Section 1609.3 in Chapter 16 of the IBC or Section R301.2.1 in Chapter 3 of the IRC:

Severe Winter Storm

Chapter 16, Section 1608 of the IBC and Chapter 3, Section 301 of the IRC establishes general standards based on regional climactic data for the appropriate design of buildings and structures to withstand snow loads.

Due to extreme variations for local snowfall amounts throughout most of the mountainous regions of Colorado, The IBC (Figure 1608.2) and IRC (Figure 301.2(4)B) require that site-specific case studies be established to calculate ground snow loads.

In 2016 the Structural Engineers Association of Colorado (SEAC) prepared a Colorado Design Snow Loads study that several communities have adopted to replace the basic snow load design criteria found in the IBC and IRC. This study provides detailed statistical analysis that aims to achieve uniform resistance against snow loads throughout the entire state of Colorado.

Note: This language can replace Section 1608.2 in Chapter 16 of the IBC:

Power outages are also associated with severe winter storms. Heat sources and other critical building infrastructure may be compromised during these events. Elevating building insulation standards helps to prevent heat loss during extreme cold, but in order to maintain comfortable temperatures for extended periods of time, primary or supplemental heating systems need to be operational in some capacity. In 2014, FEMA released a report (FEMA P-1019) outlining best practices for improving reliability of emergency power systems during severe natural hazard events. While the report primarily focuses on critical facilities (hospitals, rescue stations, emergency shelters, communications facilities, etc.), these concepts and principles could be modified to apply to other facilities and buildings. 

Earthquake

There are several ways in which building codes can improve a building’s resistance to seismic events. The primary focus of earthquake design is ensuring that people can safely exit a building following an earthquake. While implementing additional design measures may allow buildings to better withstand the effects of an earthquake, they are not always intended to ensure full functionality of a building following an event.

Implementing earthquake resilient construction practices can be accomplished through a variety of structural engineering measures or structural components (e.g., shear walls, braced frames, moment resisting frames, diaphragms, base isolation, energy dissipating devices such as visco-elastic dampers, elastomeric dampers, and hysteretic-loop dampers, and bracing of nonstructural components). More simple building techniques can also be used including avoiding soft stories (a multi-story building in which one or more floors have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability) and bolting the sill plate of houses to the foundation.

The IBC establishes “seismic design categories” based on the spectral accelerations as mapped by the USGS and the site soils classification as determined by a geotechnical engineer. The seismic design category increases in seismic resistance as a function of a letter, seismic design category “A” is the least seismic resistant while category “F” is the highest. The most common mitigation technique used by communities to address seismic events is to require the minimum seismic design category for all types of buildings to exceed that required by the IBC. Benefits and costs of designing to exceed International Code requirements for earthquake depend on several factors including added cost of construction, building economic design life, building replacement cost, and other variables.

Note: This language can be added to Section 1613 in Chapter 16 of the IBC: