The Short Answer
Structural calculations are the engineering analysis that proves a structure can safely carry the loads required by code. They document the loads acting on the building, combine those loads according to code-defined load combinations, and check each structural member and connection against its capacity. Building departments require calculations to verify that a design is not just drawn but demonstrably safe. Our licensed engineers perform these calculations and stamp them, accepting responsibility for the results.
Defining the Loads
Every calculation package starts by identifying the loads the structure must resist. These are drawn from the governing building code and the project location.
- Dead loads — the permanent weight of the structure and finishes.
- Live loads — occupancy loads such as people, furniture, and storage, set by use type.
- Wind loads — based on the site's design wind speed and exposure.
- Seismic loads — based on the site's seismic parameters and soil class.
- Snow loads — where applicable, based on ground snow at the location.
Load Combinations
Loads rarely act alone, and codes require engineers to evaluate specific combinations — for example, dead plus live, or dead plus seismic. Each combination represents a plausible worst-case scenario the structure must survive. The engineer analyzes the structure under every governing combination to find the maximum demand on each element.
Member and Connection Checks
With demands established, the engineer checks each member — beams, columns, footings, walls — against its capacity for bending, shear, axial force, and deflection. Connections are checked separately, because a connection is often the weakest link in a load path. A member passes when its capacity exceeds the demand with the code-required margin of safety.
Lateral System Analysis
Resisting wind and seismic forces requires a dedicated lateral system — shear walls, braced frames, or moment frames. The calculations trace lateral loads from the roof and floors down through the lateral elements and into the foundation, verifying each part of that path.
Why AHJs Require Calculations
Drawings show what is intended to be built, but they do not by themselves prove the design works. Calculations are the evidence. The authority having jurisdiction reviews them to confirm the design meets the adopted code before issuing a permit. Well-organized calculations that clearly reference the drawings also speed up plan review and reduce correction cycles.
When It Applies
Calculations are required whenever a project's structural elements must be shown to meet code — new construction, additions, wall openings with new beams, equipment anchorage, rooftop equipment support, and retrofits. Even modest projects that touch the load path typically require at least member-level calculations. If you are unsure, the local building department or our team can confirm what your scope requires.
Frequently Asked Questions
Are calculations the same as drawings?
No. Drawings communicate the design; calculations prove it carries code loads. Most permit submittals require both.
Can I reuse calculations from a similar project?
No. Loads depend on the specific location, geometry, and use, so each project needs its own analysis performed by a licensed engineer.
Who signs the calculations?
A licensed professional engineer performs, reviews, and stamps the calculations and accepts responsibility for the design.