Arpit Jain 18 min March 22, 2026

Navigating North Dakota's Structural Code: A Guide to Snow Loads, Frost Depths, and Wind Design

Core Structural Design Requirements in North Dakota

Designing structures in North Dakota demands careful attention to the state's severe climate. The North Dakota State Building Code, which adopts the 2021 International Building Code (IBC) and International Residential Code (IRC) with specific state amendments, establishes the minimum requirements for safety and durability. Key design parameters are primarily defined in the state amendments, particularly Appendix N.

Here are the critical takeaways for structural and foundation design:

• Governing Code: The North Dakota State Building Code (found in North Dakota Century Code Title 54, Chapter 21.3) is the primary governing document. It adopts the 2021 IBC and IRC and includes crucial state-specific amendments.
• Snow Loads: Ground snow loads (Pg) are specified by county in Appendix N of the state building code. These values are mandatory and range from 40 psf to 70 psf. For example, Cass County (Fargo) has a Pg of 40 psf, while Williams County (Williston) has a Pg of 50 psf. These values are the starting point for calculating roof snow loads per ASCE 7-16.
• Frost Depth: The minimum required depth for the bottom of footings is also mandated by county in Appendix N. The frost depth for the entire state is set at a minimum of 60 inches (5 feet). This is a critical requirement to prevent foundation damage from frost heave.
• Wind Speeds: North Dakota follows the wind speed maps and design procedures outlined in ASCE 7-16, as referenced by the 2021 IBC. The state does not publish its own separate wind speed map. Basic design wind speeds (V) vary by location and risk category but are generally found in the ASCE 7-16 figures (e.g., Figure 26.5-1B for Risk Category II buildings).
• Special Inspections: North Dakota adopts IBC Chapter 17 on Special Inspections without significant state amendments. Therefore, the requirements for inspections of structural steel welding, high-strength bolting, concrete, and other critical systems follow the IBC model code directly.

Jurisdiction (County)	Ground Snow Load (Pg)	Minimum Frost Depth
Bismarck (Burleigh)	50 psf	60 inches
Fargo (Cass)	40 psf	60 inches
Grand Forks (Grand Forks)	50 psf	60 inches
Williston (Williams)	50 psf	60 inches
Data from North Dakota State Building Code Appendix N.

Why This Topic Matters for North Dakota Projects

North Dakota's climate is characterized by heavy snowfall, deep ground freeze, and high winds, making structural design a high-stakes discipline. Failing to correctly apply the state's specific load and foundation requirements can lead to catastrophic failures, including roof collapse, foundation heave, and structural damage from wind forces.

For architects, engineers, and contractors, understanding these requirements is fundamental to the project lifecycle:

• Early Design: Correctly establishing snow, wind, and seismic loads during the schematic design phase is crucial for sizing structural members and foundations, which directly impacts project cost and feasibility.
• Permitting & Plan Review: Building departments across North Dakota will verify that design loads and foundation depths comply with the state building code and any local amendments. Incorrect values on construction documents are a common reason for plan review rejection.
• Construction & Inspection: Field inspectors will verify that footing depths meet the 60-inch minimum and that any special inspections required by IBC Chapter 17 are being performed and documented correctly.

The core relationship is that the North Dakota State Building Code provides the prescriptive environmental loads (snow load, frost depth) and references nationally recognized standards like ASCE 7 for the methodology to apply those loads (wind design, calculating roof snow loads) and material-specific standards for construction.

What are the design ground snow load (Pg) and frost depth requirements for foundation design in key North Dakota jurisdictions, including Bismarck (Burleigh County), Fargo (Cass County), and Williston? Are there specific local amendments that supersede the state-level requirements?

The design ground snow loads (Pg) and minimum frost depths are explicitly defined in the North Dakota State Building Code amendments. These state-level requirements are uniform and must be followed by all jurisdictions, though a local jurisdiction could theoretically adopt a more stringent requirement.

The primary source for these values is Appendix N of the North Dakota State Building Code. This appendix provides a table listing the ground snow load and footing depth for each of the state's 53 counties.

Deeper Explanation

1. Ground Snow Loads (Pg): The ground snow load is the basis for calculating the actual snow load on a roof. The calculation methodology is found in IBC §1608 and ASCE 7-16, Chapter 7. Key values from Appendix N include:

• Bismarck (Burleigh County): Pg = 50 psf
• Fargo (Cass County): Pg = 40 psf
• Williston (Williams County): Pg = 50 psf

An engineer uses this Pg value along with factors for exposure (Ce), thermal conditions (Ct), and building importance (Is) to determine the flat roof snow load (Pf). Additional calculations are required for sloped roofs and to account for snow drifts, which can create significantly higher localized loads.

2. Frost Depth Requirements: To prevent structural damage from frost heave, IBC §1809.5 and IRC §R403.1.4 require footings to be placed below the frost line. The North Dakota State Building Code amends this with a specific, non-negotiable value.

• Statewide Requirement: Appendix N mandates a minimum footing depth of 60 inches (5 feet) below undisturbed ground for the entire state, including Bismarck, Fargo, and Williston.
• Practical Application: This means the bottom of all exterior footings and footings for unheated spaces (like attached garages) must be at least 60 inches below the final grade. This applies to continuous wall footings, isolated column pads, and deck footings.
• Exceptions: Frost-protected shallow foundations designed in accordance with ASCE 32 are a permitted exception to the prescriptive 60-inch depth requirement, but they require a specific engineering design.

3. Local Amendments: While North Dakota operates under a state-mandated code, major cities have the authority to manage their own building departments and enforcement. However, they generally do not amend the state-mandated structural design loads.

• Fargo: The City of Fargo adopts the North Dakota State Building Code and does not publish amendments that alter the 40 psf ground snow load or 60-inch frost depth.
• Bismarck: The City of Bismarck also enforces the state code, adhering to the 50 psf ground snow load and 60-inch frost depth for Burleigh County.
• Williston: Similarly, Williston follows the state requirements.

Design professionals should always confirm with the local building department at the start of a project, but the values in Appendix N are the established standard of care across the state.

As a structural engineer, where can I find the official North Dakota wind speed map and how do state or local amendments affect the application of ASCE 7 for wind load calculations on low-rise commercial structures, particularly concerning roof uplift requirements?

The official source for wind speed data for North Dakota is not a state-specific map but rather the wind speed maps provided in the American Society of Civil Engineers' standard, ASCE 7-16, "Minimum Design Loads and Associated Criteria for Buildings and Other Structures." The 2021 IBC, adopted by North Dakota, directly references ASCE 7-16 for these requirements.

North Dakota does not have state amendments that modify the ASCE 7 wind maps or the fundamental design procedures. Therefore, engineers must use the maps and methodologies within ASCE 7-16 directly.

Deeper Explanation

1. Locating Wind Speed Data: For any project in North Dakota, a structural engineer will refer to the following figures in ASCE 7-16 (referenced in IBC §1609):

• Figure 26.5-1A, B, C, D: For Risk Category I, II, III, and IV buildings, respectively.
• Most low-rise commercial structures fall under Risk Category II, requiring the use of Figure 26.5-1B.
• By locating a project site on this map, you can determine the "basic" design wind speed (V). For most of North Dakota, this value is approximately 100-115 mph for a Risk Category II building. Online tools like the ATC Hazards by Location website can provide site-specific values based on latitude and longitude.

2. Application of ASCE 7 for Roof Uplift: Once the basic wind speed is determined, the engineer must follow the procedures in ASCE 7-16, Chapters 26 through 31, to calculate the design wind pressures. For roof uplift on low-rise commercial structures, the "Directional Procedure for Buildings of All Heights" (Chapter 27) or the "Envelope Procedure for Low-Rise Buildings" (Chapter 28) is typically used.

Key factors in this calculation include:

• Wind Directionality Factor (Kd): Typically 0.85.
• Exposure Category (B, C, or D): This is critical and must be determined based on the surrounding terrain roughness. Fargo, with its urban and suburban areas, would often be Exposure B, while a building in the open, flat terrain of western North Dakota would likely be Exposure C.
• Topographic Factor (Kzt): Generally 1.0 for the flat topography of North Dakota, unless the structure is on an isolated hill or escarpment.
• Ground Elevation Factor (Ke): Accounts for air density and is generally close to 1.0.
• External Pressure Coefficients (GCp): These coefficients are found in ASCE 7 figures and vary dramatically across the roof surface. The highest uplift pressures occur at roof corners, edges, and ridges.

The final calculated uplift pressures are used to design the roof structure (decking, purlins, trusses) and, critically, the fastening specifications for the roof deck and roofing membrane to the structure.

Are there any North Dakota state amendments that modify the typical IBC requirements for Special Inspections on structural steel welding or high-strength bolting?

No, the North Dakota State Building Code does not contain amendments that modify the standard requirements for Special Inspections as outlined in Chapter 17 of the 2021 International Building Code (IBC).

Designers, contractors, and inspectors in North Dakota must follow the IBC Chapter 17 requirements for structural steel, high-strength bolting, and other materials and systems exactly as written in the model code.

Deeper Explanation

IBC Chapter 17 is a foundational part of ensuring that the constructed work complies with the approved construction documents and engineering design. The owner is responsible for engaging a qualified special inspection agency, and the design professional of record is responsible for preparing the statement of special inspections.

For structural steel, the key requirements are found in IBC §1705.2:

• Structural Steel Welding (IBC §1705.2.1): Special inspection is required for structural-steel elements in seismic force-resisting systems and for specific welds as mandated by the registered design professional. Inspections typically involve continuous observation of welding operations and non-destructive testing (NDT) such as ultrasonic or magnetic particle testing on complete-joint-penetration (CJP) groove welds.
• High-Strength Bolting (IBC §1705.2.2): Special inspection is required for the installation of high-strength bolts in accordance with AISC 360. This includes verifying the faying surfaces, bolt type, and observing the bolting method (e.g., turn-of-nut, calibrated wrench, or direct tension indicator). For snug-tightened joints, inspection is not required, but for pretensioned and slip-critical joints, it is mandatory.

Since North Dakota adopts Chapter 17 without amendment, the full scope of these requirements applies to all commercial projects in the state where structural steel is used. The building official has the final authority to enforce these provisions and can require the submission of special inspection reports as a condition for issuing a Certificate of Occupancy.

What are the snow load requirements for my roof in Grand Forks, North Dakota?

The starting point for determining your roof snow load in Grand Forks is the ground snow load (Pg), which is 50 pounds per square foot (psf).

This value is mandated by the North Dakota State Building Code, Appendix N, for Grand Forks County. This ground snow load must then be converted into a roof snow load by a qualified design professional using the formulas and factors provided in ASCE 7-16.

Deeper Explanation

The 50 psf ground snow load is not the final load applied to the roof design. The actual roof snow load (Pf for flat roofs or Ps for sloped roofs) depends on several site- and building-specific factors, as defined in ASCE 7-16, Chapter 7:

1. Importance Factor (Is): This factor accounts for the building's use. For a typical commercial building or home (Risk Category II), Is = 1.0. For an essential facility like a hospital or fire station (Risk Category IV), Is = 1.2, increasing the design load by 20%.
2. Exposure Factor (Ce): This considers how exposed the roof is to wind, which can blow snow off the roof. It ranges from 0.7 for fully exposed roofs in open terrain to 1.2 for sheltered roofs.
3. Thermal Factor (Ct): This accounts for heat loss through the roof, which can melt snow. For a heated structure, Ct is typically 1.0. For an unheated structure or "cold roof," it can be as high as 1.2.
4. Slope Factor (Cs): For sloped roofs, this factor reduces the load as the pitch increases, since snow tends to slide off steeper roofs.

Example Calculation (Simplified): For a standard heated commercial building in a moderately exposed location in Grand Forks:

• Pf = 0.7 * Ce * Ct * Is * Pg
• Pf = 0.7 * 1.0 (typical exposure) * 1.0 (heated) * 1.0 (standard building) * 50 psf
• Pf ≈ 35 psf

This 35 psf would be the balanced snow load on the flat roof. An engineer must also calculate and design for unbalanced loads, drifts, sliding snow, and rain-on-snow surcharges as required by ASCE 7.

What's the required frost line depth for foundations in North Dakota?

The required minimum frost line depth for all foundations in North Dakota is 60 inches (5 feet).

This requirement is mandated statewide by the North Dakota State Building Code in Appendix N and is based on historical temperature and soil data to protect buildings from the damaging effects of frost heave.

Deeper Explanation

This 60-inch minimum depth is a prescriptive requirement found in both the commercial and residential codes as adopted by the state.

• Commercial Buildings (IBC): IBC §1809.5 requires footings to be protected from frost. The North Dakota amendment provides the specific depth of 60 inches, making it enforceable across the state.
• Residential Buildings (IRC): IRC §R403.1.4.1 contains the same requirement for residential structures. It states that the footing "shall be placed not less than 12 inches (305 mm) below the undisturbed ground surface. The frost line depth shall be in accordance with the jurisdiction’s building code." In North Dakota, that jurisdiction's code specifies 60 inches.

This depth applies to all exterior footings and any footings in unheated interior spaces, such as an unconditioned crawl space or an attached garage. The measurement is taken from the final exterior grade to the bottom of the footing.

How deep do my footings need to be for a deck in Bismarck?

Your deck footings in Bismarck must be at least 60 inches (5 feet) deep.

This depth is required to place the bottom of the footing below the mandated frost line for Burleigh County, as specified in the North Dakota State Building Code. Placing footings at this depth prevents the deck from lifting and shifting during winter freeze-thaw cycles.

Deeper Explanation

Even though a deck is an accessory structure, its footings are subject to the same frost protection requirements as a house foundation under the International Residential Code (IRC).

• Code Reference: IRC §R403.1.4 requires footings to be protected from frost. The North Dakota State Building Code Appendix N sets this depth at 60 inches for Burleigh County, where Bismarck is located.
• Why It's Critical: In cold climates, moisture in the soil freezes and expands, exerting immense upward pressure—a phenomenon known as frost heave. If a deck footing is too shallow (e.g., only 24 or 36 inches deep), the frozen soil can lift the post, causing the deck to become unlevel, pull away from the house, and become unsafe.
• Application: This requirement applies to any deck that is attached to the house or is of a size and height that requires a building permit. For small, free-standing decks or platforms that sit directly on grade (often called "floating decks"), footing requirements may be waived by the local building official, but this should be confirmed with the City of Bismarck Building Inspections Division. For any standard deck construction, expect to dig footing holes to the 5-foot minimum depth.

Additional Considerations for North Dakota Projects

Jurisdictional Variations and Code Enforcement

North Dakota is a "home rule" state with a mandatory statewide building code. This means:

1. Statewide Minimum: The North Dakota State Building Code (NDCC 54-21.3) establishes the absolute minimum standard for all construction. No city or county can adopt a code that is less stringent.
2. Local Enforcement: Cities with a population over 2,500 are required to have a building official and enforce the state code. Smaller cities and counties may opt in.
3. Local Amendments: While local jurisdictions rarely amend the core structural loads from Appendix N, they may have specific administrative ordinances, permit fee schedules, zoning requirements, or stricter interpretations. Always contact the local building department (e.g., Fargo, Bismarck, Minot) at the project's outset.

Coordination for a Cold Climate Design

Successful design in North Dakota requires tight coordination between disciplines to address the harsh climate:

• Structural & Architectural: The 60-inch frost depth for foundations must be coordinated with the architectural design for slab-on-grade details, foundation wall insulation placement (required by the energy code), and finished floor elevations.
• Structural & Geotechnical: While the code sets a minimum frost depth, a geotechnical report may recommend an even deeper foundation due to poor or expansive soils, which are common in some parts of the state. The geotechnical engineer's recommendation will govern if it is more stringent than the code minimum.
• Structural & MEP: The depth of underground utilities (water, sewer) must be coordinated with the foundation design. Plumbing and mechanical codes require these lines to be buried below the frost line to prevent freezing, and their entry points through the foundation wall must be detailed to prevent air and water leakage.

Common Mistakes and Misinterpretations

• Ignoring Snow Drifts: Designing a roof only for the balanced snow load is a major error. ASCE 7 requires extensive analysis of drift loads (leeward drifts, windward drifts, sliding snow) on lower roofs, against parapets, and around rooftop equipment. These drift loads can easily be two to three times the balanced snow load.
• Misidentifying Wind Exposure: Incorrectly assigning Exposure Category B (suburban) to a building in a wide-open rural area (which should be Exposure C) can lead to a significant underestimation of wind loads and roof uplift pressures.
• Forgetting Unheated Spaces: The 60-inch frost depth applies to foundations of unheated spaces like attached garages. Using a shallow, thickened-edge slab for a garage is not compliant unless it's specifically designed as a frost-protected shallow foundation per ASCE 32.
• Deck Ledger Board Attachment: Simply bolting a deck ledger to the house's siding is incorrect and dangerous. The IRC provides prescriptive details (see IRC §R507.9.1.1) for a weather-resistant, properly flashed, and structurally sound connection to the band joist of the primary structure.

North Dakota Structural Design FAQ

1. Does North Dakota have a statewide building code? Yes. North Dakota has a mandatory statewide building code based on the 2021 International Building Code (IBC) and International Residential Code (IRC), with state-specific amendments.

2. What is the current building code in North Dakota? As of early 2024, North Dakota uses the 2021 suite of I-Codes, which became effective on January 1, 2023. This includes the 2021 IBC, IRC, IMC, IFC, etc.

3. How do I calculate roof snow load from the ground snow load? You must use the formulas in Chapter 7 of ASCE 7-16. The basic formula for a flat roof is Pf = 0.7 * Ce * Ct * Is * Pg, but this must be adjusted for roof slope, and additional calculations for drifts and unbalanced loads are required. This should be done by a qualified engineer.

4. Are unheated garages required to have footings below the frost line? Yes. The foundations supporting an unheated attached or detached garage must have their footings placed at or below the 60-inch minimum frost depth to prevent heave.

5. What is the seismic design category for North Dakota? North Dakota has very low seismic activity. Most of the state falls into Seismic Design Category (SDC) A, with some areas potentially in SDC B. The specific category must be determined on a site-specific basis per ASCE 7.

6. Where can I find the official North Dakota State Building Code? The code is established in the North Dakota Century Code (NDCC), Title 54, Chapter 21.3. The North Dakota Department of Commerce, Division of Community Services, oversees the code and provides information on its website.

7. Can I use a monolithic slab (frost-protected shallow foundation) in North Dakota? Yes, but it is not a simple thickened-edge slab. It must be specifically engineered as a Frost-Protected Shallow Foundation (FPSF) in accordance with ASCE 32, which involves specific placement and sizing of vertical and horizontal rigid insulation.

8. Are there special requirements for preventing ice dams? Yes, the 2021 IRC and International Energy Conservation Code (IECC) have provisions to mitigate ice damming. This includes requirements for proper attic ventilation and minimum roof/ceiling insulation levels (R-60 in Zone 7), which helps keep the roof surface cold. In some cases, an ice barrier membrane is required at the eaves.

9. Do I need a structural engineer for my project in North Dakota? An engineer is generally required for all buildings other than single-family homes designed per the prescriptive methods of the IRC. All commercial projects, complex residential designs, and any project using non-prescriptive materials or methods will require sealed engineering documents.

10. What wind exposure category should I use for a project in Fargo? The exposure category depends on the surrounding terrain. In densely developed urban or suburban parts of Fargo, Exposure B would be appropriate. For a building on the edge of the city near open fields, Exposure C would be more accurate and result in higher design wind loads. The determination must be made according to the definitions in ASCE 7.