Self-storage facilities have structural requirements that differ from most other commercial building types. Long clear spans, heavy storage occupancy live loads, multi-story configurations, and fire separation requirements all create specific engineering demands. Our self-storage structural engineering work covers new construction and additions for developers and contractors across all 50 states. Here is what goes into a complete self-storage structural package.
What Makes Self-Storage Structurally Unique
The defining structural feature of a single-story self-storage building is the long clear span between exterior walls. Unit rows run the length of the building with no interior load-bearing walls, which means the roof structure must span 30 to 60 feet or more depending on the building width. This clear span requirement drives the roof structural system selection and influences the foundation design.
Unlike office or retail buildings, self-storage units have no interior partitions that provide lateral bracing or load distribution. All lateral loads from wind and seismic forces must be transferred to the exterior walls and then to the foundation through a diaphragm-to-shear-wall load path. The structural engineer must design this load path explicitly because there are no interior elements to assist in the lateral force transfer.
Storage occupancy also carries a significantly higher live load requirement than office or retail occupancy. IBC Table 1607.1 requires 125 pounds per square foot for storage areas versus 50 pounds per square foot for office space. This difference has a direct impact on the design of floor framing in multi-story facilities and must be accounted for in the structural system. Our structural engineering team designs to the correct occupancy live load in every state we work in.
Foundation Requirements for Large Footprints
Self-storage buildings typically cover large ground areas, which introduces foundation challenges related to soil variability across the site. A geotechnical investigation with borings at multiple locations is important to characterize soil conditions across the full footprint rather than assuming uniform conditions from a single boring location.
Slab-on-grade design for self-storage must account for the heavy storage live loads and for forklift or cart traffic in drive aisles. The slab thickness, reinforcement, joint spacing, and subgrade preparation must all be designed for these demands. Drive-aisle slabs in exterior-access facilities take significant repeated loading from moving vehicles and require more robust design than interior unit slabs.
Multi-Story Self-Storage Engineering
Multi-story self-storage has grown significantly in urban and suburban markets where land cost makes single-story facilities impractical. The structural demands of multi-story self-storage are substantially greater than single-story. Upper floor framing must carry the storage live load of 125 psf plus the dead load of the floor assembly, spanning between column lines or load-bearing walls. Our new building engineering team handles multi-story self-storage up to mid-rise heights.
The stair and elevator core in a multi-story facility provides both the vertical circulation and significant lateral resistance. The concrete or masonry core walls act as a primary shear wall element and must be sized to carry the lateral loads from the full building height. The connection between the floor diaphragm and the core walls is a critical detail that must be explicitly designed.
Fire Separation and Life Safety from a Structural Standpoint
Self-storage facilities classified as Group S-1 occupancy under IBC require fire barriers between units when the building area or height exceeds certain thresholds. These fire barriers must be supported by structural elements that can maintain their integrity for the required fire rating period. The structural engineer and the architect must coordinate to ensure that fire-rated walls are structurally supported and that penetrations for any systems are properly protected.
In multi-story facilities, floor assemblies must meet fire resistance rating requirements that affect the structural assembly selection. A concrete topping slab over metal deck typically achieves the required fire rating while also serving as the structural floor diaphragm, but the thickness and configuration must be designed to meet both structural and fire requirements simultaneously.
What a Complete Self-Storage Permit Set Includes
A complete structural permit set for a self-storage facility includes a foundation plan with footing locations and sizes, a slab design sheet with thickness, reinforcement, and joint details, a roof framing plan showing the structural system and member sizes, lateral analysis and shear wall or braced frame design, structural details for connections and special conditions, and the design criteria summary on the cover sheet. Learn more about our services at rightangleeng.com/engineering.
Frequently Asked Questions
Does every self-storage facility require a PE stamp on the structural drawings?
Yes, in virtually every jurisdiction. Commercial buildings require permit drawings prepared and stamped by a licensed professional engineer. The specific requirements vary by state, but any self-storage project of commercial scale requires PE-stamped structural drawings as part of the permit package.
Can pre-engineered metal buildings be used for self-storage?
Yes, and they are commonly used for single-story self-storage. Pre-engineered metal building manufacturers provide the steel superstructure package, but the local PE must design the foundation and anchorage based on the manufacturer’s anchor bolt plan and column reaction loads. The manufacturer’s structural engineering covers only the metal frame itself.
What is the typical timeline from engineering to permit submittal?
For a single-story self-storage facility with good site information and a geotechnical report, structural engineering typically takes two to four weeks. Multi-story facilities with more complex structural systems take longer. Permit review times vary widely by jurisdiction from a few weeks to several months.
Start Your Self-Storage Engineering Project
We provide PE-stamped structural engineering for self-storage facilities in all 50 states. Submit your project at rightangleeng.com/get-started.
References
International Building Code. (2021). Table 1607.1: Minimum Uniformly Distributed Live Loads. International Code Council.
National Fire Protection Association. (2021). NFPA 13: Standard for the Installation of Sprinkler Systems.
American Concrete Institute. (2019). ACI 360R: Guide to Design and Construction of Slabs on Ground.