IBC Chapter 17 requires special inspections and structural observations for specific construction materials and methods. Special inspections are inspections of selected materials, equipment, installation, fabrication, erection, or placement of components and connections that require the expertise of an approved special inspection agency. The requirements are not optional: IBC Section 1704.2 requires that the building permit applicant submit a Statement of Special Inspections (SSI) before the permit is issued.
Despite being a permit prerequisite, the special inspection documentation is one of the most frequently incomplete items on construction drawing submittals. Plan reviewers check for the SSI early in the review because missing or incomplete special inspection requirements generate correction notices that must be resolved before the permit can be issued. These are the errors that come up most often.
Missing Statement of Special Inspections
No SSI included in the drawing set
IBC Section 1704.2.3 requires the submittal of a Statement of Special Inspections as part of the permit application. The SSI must identify each type of special inspection required by the project, the inspection frequency (continuous or periodic), the applicable code sections, and the name of the special inspection agency that will perform the inspections. Many jurisdictions provide a standard SSI form; others accept a project-specific document prepared by the engineer of record.
The most common error is simply not including the SSI in the drawing set. The structural engineer may intend to submit it separately, but plan reviewers expect to see it with the construction documents so they can verify that the required inspections match the structural design. A permit application without an SSI will be returned as incomplete in most jurisdictions before the technical review even begins.
Structural steel special inspections
Not specifying the correct inspection level
IBC Section 1705.2 and Table 1705.2 list the special inspection requirements for structural steel construction. The required inspections depend on the type of connection (bolted, welded, or both), the structural demand (seismic force-resisting system vs. gravity-only), and the Seismic Design Category. In Seismic Design Categories D, E, and F, AISC 341 (Seismic Provisions for Structural Steel Buildings) adds additional inspection requirements beyond the base IBC requirements.
| Inspection item | Frequency | Common error |
|---|---|---|
| High-strength bolt installation (pretensioned) | Periodic | Not requiring inspection for slip-critical connections |
| Structural welding (CJP groove welds) | Continuous | Specifying periodic instead of continuous for CJP welds |
| Structural welding (fillet welds, PJP) | Periodic | Omitting fillet weld inspection from SSI entirely |
| Nondestructive testing of welds | Per AISC 360/341 | Not specifying NDT scope, method, or percentage |
| Steel frame joint details (SDC D-F) | Periodic | Missing AISC 341 seismic connection inspections |
The distinction between continuous and periodic inspection is significant. Continuous inspection means the special inspector must be present during the entire installation or fabrication process. Periodic inspection means the special inspector performs inspections at defined intervals or stages. Complete joint penetration (CJP) groove welds require continuous inspection per IBC Table 1705.2.1. Specifying periodic inspection for CJP welds is a code violation that plan reviewers will catch immediately.
Missing NDT requirements
Nondestructive testing (NDT) of structural welds is required by AISC 360 Chapter N and, for seismic applications, AISC 341. The structural drawings or project specifications must identify the NDT method (ultrasonic, radiographic, magnetic particle, or penetrant), the percentage of welds to be tested, and the acceptance criteria. For CJP groove welds in tension, AISC 360 Section N5.5 requires ultrasonic or radiographic testing.
The most frequent error is structural drawings that require CJP groove welds but do not specify any NDT requirements. The plan reviewer will issue a comment requiring the engineer to add NDT requirements to either the structural general notes or the SSI. Another common error is specifying NDT for shop welds but not for field welds, or vice versa.
Concrete special inspections
Incomplete concrete inspection requirements
IBC Section 1705.3 and Table 1705.3 list the special inspection requirements for concrete construction. These include inspection of reinforcing steel placement, concrete batching and delivery, concrete placement, post-tensioning tendon stressing, and concrete strength testing. The specific inspections required depend on the structural application and the Seismic Design Category.
Plan reviewers consistently flag two concrete inspection errors. The first is omitting reinforcing steel placement inspection from the SSI. IBC Table 1705.3 requires periodic inspection of reinforcing steel, including bar size, spacing, cover, splice lengths, and support. This is not just a field quality control item: it is a code-required special inspection that must be documented in the SSI.
The second frequent error is not specifying concrete strength testing frequency. ACI 318 Section 26.12 requires a minimum of one strength test (a set of cylinders) for each 150 cubic yards of concrete or each day of placement, whichever produces more tests. The SSI must reference this testing frequency. Drawings that note "concrete testing per ACI 318" without specifying the frequency or the number of test specimens per set (typically two for the standard 28-day break) will be flagged.
Masonry special inspections
Misapplying Level 1 vs. Level 2 inspection
IBC Section 1705.4 references TMS 402/602 for masonry special inspection requirements. TMS 602 Section 1.6 defines two levels of quality assurance: Level 1 (basic) and Level 2 (comprehensive). The required level depends on the structural function of the masonry and the Seismic Design Category. Load- bearing masonry shear walls in Seismic Design Category C or higher require Level 2 quality assurance, which includes continuous inspection during grouting and more frequent prism testing.
The common error is specifying Level 1 quality assurance for masonry shear walls in Seismic Design Category C or above. Level 1 permits periodic inspection during grouting; Level 2 requires continuous inspection. For a reinforced masonry shear wall, the difference means a special inspector must be present for every grout pour rather than checking in periodically. Plan reviewers check the Seismic Design Category on the structural general notes against the masonry QA level in the SSI.
Soils and foundation special inspections
Not requiring geotechnical inspection for driven piles or drilled shafts
IBC Section 1705.6 through 1705.9 require special inspections for soil conditions, fill placement, driven piles, drilled shafts, and helical piles. The specific requirements vary by foundation type, but the common thread is that the SSI must identify the geotechnical inspections that will verify the assumptions in the geotechnical report.
The most common error is an SSI that covers only the structural materials (steel, concrete, masonry) but omits the geotechnical special inspections. A project with driven piles requires continuous inspection during pile driving to verify that each pile achieves the required capacity (IBC Section 1705.7). A project with compacted structural fill requires periodic testing to verify that the fill meets the required density (IBC Section 1705.6). Plan reviewers cross-reference the foundation plan with the SSI to verify that every foundation type on the drawings has corresponding special inspection requirements.
| Foundation type | Required inspection | Reference |
|---|---|---|
| Driven piles | Continuous during driving; load tests if required | IBC 1705.7 |
| Drilled shafts | Continuous during drilling and concrete placement | IBC 1705.8 |
| Helical piles | Continuous during installation; torque monitoring | IBC 1705.9 |
| Compacted fill | Periodic density testing at specified lifts | IBC 1705.6 |
| Shallow foundations on controlled fill | Verification of bearing capacity and fill depth | IBC 1705.6 |
Seismic Design Category triggers
Not including seismic-specific inspection requirements
IBC Section 1705.13 adds special inspection requirements for seismic force-resisting systems in Seismic Design Categories C through F. These go beyond the base material inspections in Sections 1705.2 through 1705.12 and include verification of designated seismic systems, architectural components attached to the structure, mechanical and electrical equipment anchorage, and storage rack installations.
The error that plan reviewers flag most often is an SSI that covers the structural material inspections but omits Section 1705.13 entirely. In Seismic Design Category D, for example, the anchorage of mechanical equipment weighing more than 400 pounds requires special inspection to verify it matches the seismic bracing design. Suspended ceiling systems, access floors, and masonry veneer each have their own seismic special inspection requirements. An SSI that addresses only the primary structure but ignores the nonstructural component inspections will generate plan review comments across both structural and architectural disciplines.
Catching special inspection errors before submittal
Special inspection requirements touch every structural material on the project and extend into geotechnical, architectural, and mechanical disciplines for seismic applications. The most efficient way to verify completeness is to cross-reference the structural drawings (foundation type, steel connections, concrete members, masonry walls) against the SSI item by item, checking that every material and connection type on the drawings has a corresponding inspection requirement in the SSI. Reviewing the structural, geotechnical, and architectural drawings against IBC Chapter 17, AISC 360/341, ACI 318, and TMS 402/602 in a single pass catches the gaps that are hardest to find when each discipline reviews in isolation.