Pre-Engineered Metal Building Foundations in California: What Changed Under the 2025 Building Code

A pre-engineered metal building is a steel building whose frames, purlins, girts and panels are designed and fabricated by the manufacturer for one specific order. They are common for shops, barns, equipment sheds and warehouses.

The steel is only half of the permit. The building still needs a foundation designed for your site, soil and county code. Here is how the work splits, what the 2025 code changed, and the order of steps that avoids redesign.

Who designs the foundation for a pre-engineered metal building?

Usually not the manufacturer. The Metal Building Manufacturers Association (MBMA) Common Industry Practices (2024 Edition) state that the manufacturer is not responsible for the design, materials or workmanship of the foundation. Its job is to report the loads the building puts on the foundation and show where the anchor bolts go.

The owner's engineer of record, typically a California-licensed civil or structural engineer, designs the footings, slab, anchor bolt embedment and thrust details. San Diego County's steel building guidance describes a typical split: the manufacturer's framing plans and calculations are stamped by a California-licensed engineer, and another California-licensed engineer prepares the foundation plan and calculations if the manufacturer does not.

That is common practice, not a fixed rule. Business and Professions Code Section 6737 exempts licensed architects practicing architecture from engineering registration.

Who designs what on a metal building

Illustrative diagram — not to scale

1. 1Steel frame: the manufacturer designs it and reports the loads the building puts on the foundation.
2. 2Anchor bolts: the manufacturer shows where they go; the engineer of record designs their embedment.
3. 3Foundation: the owner's engineer of record, typically a California-licensed civil or structural engineer, designs the footings, slab and thrust details.

The building department plan-checks both, and some counties add steps: San Diego County requires a signed certification from a California-licensed engineer or architect before final approval. The foundation package is the core of our metal building foundation design service.

What do I need from the manufacturer before foundation design can start?

• Anchor bolt plan. MBMA says it shows only the location, diameter and projection of each anchor bolt (also called an anchor rod). Embedment depth is the foundation engineer's call.
• Column reactions. These are the forces each column base puts on the foundation, downward, sideways and uplift, under dead, live, snow, wind and seismic loads. The footings are sized for them.

Check the design criteria on the order, too. MBMA puts the job of specifying the code, design loads and factors such as risk category and wind exposure on the buyer's side, and the manufacturer assumes no loads the order documents do not state.

Risk category is a I–IV rating of how critical the building's occupancy is; most shops and storage buildings are I or II. Wind exposure is a letter rating of how open the terrain around the site is.

How does a metal building foundation resist column thrust?

Most pre-engineered buildings use gable rigid frames, which push sideways on their foundations. Newman explains that under gravity loads the two columns of a frame push outward in opposite directions. Under wind or seismic loads, they usually push the same way.

• Hairpins. U-shaped reinforcing bars at each column extend into the floor slab, so the slab reinforcement ties the frame together. A later saw cut or trench, or a construction joint where slab reinforcing stops, can defeat them.
• Tie rods or grade beams. A steel rod or a reinforced concrete beam runs across the building between opposite columns. Newman places concrete grade beams at the more reliable end of that range.
• Larger footings. Footings can resist the thrust on their own, through their weight and the soil's resistance. Piers or piles are used where weak soil sits over firmer material.

Uplift matters too. Newman notes that single-story metal buildings weigh roughly 2 to 5 pounds per square foot, so strong wind can lift the frame, and footing size is often set by the weight needed to hold it down. The right approach depends on the reactions, soil, slab use and budget.

Do I need a soils report for a metal building in California?

Often, yes. Section 1803 of the 2025 California Building Code requires a geotechnical investigation, though the building official may waive it where satisfactory data from adjacent areas shows one is not needed.

Seismic Design Category (SDC) is a code rating from A to F based on expected ground shaking, soil, and the building's use. For SDC C through F, Section 1803.5.11 requires the investigation to evaluate slope instability, liquefaction, settlement and surface displacement from faulting or lateral spreading. Santa Cruz County, for example, says most of the county will be SDC D or E.

Counties publish their own triggers. Butte County requires a soils report at permit submittal for non-residential structures other than Group U (utility) or Group S (storage) buildings used solely for agriculture or minor storage. It also requires one for any structure:

• On highly expansive soil
• On or near slopes steeper than 1 vertical to 3 horizontal
• On slabs or shallow footings over more than 12 inches of fill
• On deep foundations

So an agricultural barn can be exempt from the use-based trigger and still need a report because of its site. Without a report, Butte County foundations use a presumptive bearing pressure of 1,500 pounds per square foot.

Why does site class matter more under ASCE 7-22?

Site class describes how stiff the top 30 meters (about 100 feet) of ground is, from hard rock to soft soil. Softer ground generally shakes a building harder.

ASCE 7-22 adds intermediate site classes, such as CD and DE, and uses multi-period response spectra. The U.S. Geological Survey found that the older two-period spectrum could substantially understate shaking for moderately long-period structures, such as taller buildings, on soft soil where large earthquakes dominate the hazard. For a low-rise metal building, the more practical change is the new default site class.

A measured site class replaces that conservative default and can move the design either way.

What changed for structural design in the 2025 California Building Code?

The California Building Standards Commission published the 2025 California Building Standards Code (Title 24) on July 1, 2025, effective January 1, 2026. Notices from the City of Lathrop and Riverside County apply it to permit applications submitted on or after that date. Each jurisdiction sets its own rules for earlier applications.

The 2025 California Building Code, based on the 2024 International Building Code, references ASCE 7-22 for structural loads statewide, and county criteria sheets such as Butte County's list it. For a California metal building, the changes that matter most are:

• Seismic. New intermediate site classes and multi-period spectra, described above.
• Snow. ASCE says ground snow loads were revised to reflect newer data and reliability-targeted values. Butte County points designers to the ASCE Hazard Tool for ground snow loads.
• Tornado. ASCE 7-22 added a tornado chapter, but the National Institute of Standards and Technology (NIST) explains it applies only to Risk Category III and IV buildings in the tornado-prone region, roughly the lower 48 states east of the Continental Divide. California is west of that line.

You may have heard about a code freeze. Assembly Bill 130, signed June 30, 2025, limits new state and local building standards affecting residential units from October 1, 2025 through June 1, 2031. It did not stop the 2025 code from taking effect, and Lathrop's notice states that non-residential projects are not affected.

Do I need engineered plans and a permit for a metal building in California?

In almost every case, yes. The model code (CBC Section 105.2) exempts one-story detached accessory structures, such as tool and storage sheds, up to 120 square feet. Cities and counties adopt, and sometimes amend, that rule locally.

San Diego County's list is a good example of a full submittal:

• Stamped framing plans and calculations
• The foundation plan and calculations
• A plot plan
• A stormwater best management practices (BMP) plan

A pad that needs significant earthwork may also need grading plans and a grading permit.

What is the right order of steps for a metal building project?

1. Survey the site. A topographic survey maps the grades, drainage and features the site plan depends on. MBMA's Common Industry Practices also expect the owner to furnish a current site survey, certified by a licensed land surveyor, that shows property lines and easements, and to have the property lines staked on the job site. That is boundary surveying work.
2. Check soils early, so the site class goes into the building order instead of turning up later.
3. Lay out the site. A site layout and plot plan fixes the footprint, setbacks, access and drainage.
4. Order the building and give the manufacturer your county's design criteria sheet.
5. Get the final reactions and anchor bolt plan.
6. Design the foundation, plus any grading and drainage plans.
7. Submit for the permit and answer plan check comments.
8. Stake the building and anchor bolts. Construction staking sets building lines and bolt locations from the approved plans.

Where a contract follows the AISC Code of Standard Practice (ANSI/AISC 303-22), horizontal tolerance is as tight as 1/4 inch for 3/4- and 7/8-inch rods. Section 7.5 of that standard also has the owner's construction representative, usually the general contractor, survey the as-built anchor rod locations and confirm they are within tolerance. MBMA makes the erector responsible for confirming bolt locations before setting steel, so check them before the steel arrives.

What this means for your project

• Do not form or pour until you have the final anchor bolt plan and reactions.
• Budget for two engineering packages. Unless your quote says otherwise, the building price does not include foundation design.
• Ask about soils early. Planning for a report at the start beats adding one after plan check.
• Match the order to the 2025 code. If you will apply in 2026 or later, the manufacturer's criteria should cite the 2025 California Building Code and ASCE 7-22.
• Protect the thrust system. If the design uses hairpins, get an engineer's review before anyone cuts the slab.

Requirements vary by county and city, and your building department has the final say. If you have a metal building on order or are comparing quotes, contact us about your metal building foundation with the site address and the manufacturer's drawings.