Special Inspections Pitfalls - Part 2

The original Speaking in Code “Special Inspection Pitfalls” article was published in January 2025. Due to the large number of pitfall scenarios discovered during the research for the original article and the popularity of the article, we have developed PITFALLS (Part 2). Click here to read Part 1.

A pitfall is defined as a particular activity or situation where things go wrong or may cause problems. Project special inspections certainly have a fair share of potential pitfalls during building construction phases with all the disciplines involved in the construction schedule. For whatever reason, there are times when certain code-required special inspections are not accomplished on a project or performed properly.

There are numerous other reasons why code-required special inspections are not provided on project work. One of the primary reasons that special inspections are overlooked is the sheer volume of special inspections and the numerous sources of code-acceptance criteria. There are hundreds of model codes and standards that specify code-required special inspections and thousands of pages to review to determine what specific special inspections are required involving specific disciplines and various structural elements of a building. There are also dozens of different special inspections required on nonstructural elements of buildings and structures.

Read on to learn more about common special inspections pitfalls!

GEOTECHNICAL ENGINEERING AND SOILS SPECIAL INSPECTIONS

PITFALL 1: The geotechnical engineer of record for a project in southwest Virginia works out of an office in Indiana. The approved geotechnical report for the project is inadequate for its earthwork and foundation phases. It doesn’t address the numerous unsuitable soils on site, karst features, and near-surface rock pinnacles. Project earthwork phase estimates reflect double or triple preliminary earthwork construction costs.

RESPONSE: The person or firm that selected the geotechnical engineering firm to provide the subsurface investigation and foundation recommendations did not consider the importance of experience and local knowledge of subsurface conditions during the selection process. The International Building Code (IBC), in Chapter 18, Section 1803.1, is clear in their thinking that soils mechanics and foundation engineering are diverse, complicated, and not an exact science. The practice of geotechnical engineering and the development of project foundation designs require local knowledge and judgment based on local experience. The lack of this local knowledge could result in unwanted and costly surprises during construction phases.

PITFALL 2: With earthwork construction phases going full bore, the soils special inspector was performing soil density tests using a nuclear density gauge, and his test results were “all over the lot” with numerous failing test results. The project construction manager complained that he had never seen the soils special inspector do any standardization tests at the project site, and that the special inspector had been unable to furnish any paperwork proving that he had performed any standardization testing or standard count procedures at the project site.

RESPONSE: The approved geotechnical report for the project required that density tests be performed in accordance with ASTM D6938, “Standard Test Methods for In-Place Density and Water Content of Soil by Nuclear Methods.” The soils special inspector must verify that all recommendations of the geotechnical report are followed during construction phases according to IBC Chapter 17, Section 1705.6. ASTM D6938 requires that nuclear gage standardization tests be done at the start of each day’s use and a record of the test data be retained. Standardization tests are even more critical before performing density tests in trenches and excavations. They ensure accurate measurements by compensating for gauge performance variations due to environmental factors or instrument drift.

CONCRETE SPECIAL INSPECTIONS

PITFALL 1: A large high-rise construction project (six stories) had four different approved concrete mixes used on the project concrete construction over time. There were at least a few instances where the wrong concrete mixture had been placed on project elements, and the error was not discovered until after the concrete was placed. In one case, an exposure class FO (no air) was placed instead of the required exposure class F1 (air entrained) with a higher compressive strength requirement than the FO class. In another case, the mistake was reversed with an exposure class F1 placed rather than the required exposure class FO. Whose fault is this?

RESPONSE: There’s a lot of blame to go around on this one. The contractor and the concrete special inspector should certainly have been checking the concrete truck delivery tickets to verify that the concrete in the ready-mix truck was the correct concrete mixture required for the particular project concrete elements being placed at the time. This process is required of the special inspector according to IBC Chapter 17, Table 1705.3, “Required Special Inspections and Tests of Concrete Construction.” Inspection Task #5 of Table 1705.3 requires that the special inspector verify (by review of the concrete delivery ticket) that the concrete mixture in the ready-mix truck is not only one of the project’s approved concrete mixtures but that the concrete mix is appropriate for the specific type of concrete work being placed with the particular load of concrete.

PITFALL 2: Attempting to determine the appropriate actual concrete temperature versus the proper ambient air temperature for project concrete placement is confusing and complicated. Sometimes, the specifications do not do a particularly good job of advising us of the correct concrete temperature and/or air temperature for specific project concrete placement applications. How can we be sure that the correct temperatures are applied in the field according to the code?

RESPONSE: It is a good question, and keeping up with the correct concrete placement temperature under all possible environmental conditions and specific project element size and thickness can be overwhelming. The short answer is to (at least) keep a copy of Section 4 of ACI 301, “Specifications for Structural Concrete,” at your fingertips. Section 4 of ACI 301 is only about five pages long and will probably answer 75% of your code-required concrete temperature questions. Most of your concrete temperature questions usually involve cold-weather concrete placements where the concrete code temperature requirement will increase as the size of the concrete element being placed decreases in thickness. ACI 301, Section 4.2.2.5(a), displays the entire range of code-required concrete temperatures. More cold-weather information can be found in ACI 306R, “Cold Weather Concreting,” and additional hot-weather details can be found in ACI 305.1, “Specification for Hot Weather Concreting.” Do not forget the existence of Table 5.1, “Recommended Concrete Temperatures,” in ACI 306R, which lists many temperature data related to protecting the recently placed concrete under a wide range of air temperatures versus various sizes of project concrete elements.

MASONRY SPECIAL INSPECTIONS

PITFALL 1: The project is a new large high school with a lot of exposed unpainted masonry on the exterior and interior. The masonry portion of the project is about 25% complete, and it utilizes mostly colored masonry mortar. The existing mortar joints are about four or five different colors (rather than the preferred one). The varying colors of the mortar joints distract from the overall beauty of the masonry walls, PLUS there have been many failures in project mortar compressive strength tests during construction phases. Many compressive strength test results indicate compressive strengths of less than 1,000 psi.

RESPONSE: The reasons for the varying mortar colors and the low compressive strength of the mortar could be the same. First, the approved mortar mixture should comply with ASTM C270, “Standard Specification for Mortar.” In-place masonry mortars that exhibit many different colors (and strengths) can often be attributed to the fact that mortar proportions at the job site were not carefully controlled. The materials in a mortar mix are proportioned by volume, and when the masonry sand takes on more moisture from rain, it bulks. When wet sand bulks, the person making the mortar gets less sand in the volumetric measure used to produce it. Statistics show that a 5% increase in sand moisture can increase the sand volume by 20% to 40% due to bulking. The masonry sand must be covered every night so that tomorrow’s mix proportions will be the same as the day before. Mix proportion redundancy is the name of the game when it comes to consistent mortar colors and compressive strengths. Article 1.7B of the masonry code (TMS 402/602) states, “protect cementitious materials for mortar and grout from precipitation and groundwater” and “the performance of masonry materials can be reduced by contamination from dirt, water, and other materials during delivery or at the project site.” ASTM C270, ASTM C780, and ASTM C1586 all speak to the importance of covering and protecting the masonry sand from weather elements. Doing so keeps the masonry sand proportions of the mortar mix from being compromised by high sand-water contents, which can reduce the actual amount of masonry sand per batch.

PITFALL 2: TMS 402/602, “Building Code Requirements and Specifications for Masonry Structures,” comprises 344 pages of narrative. The first 254 pages are identified as the building code requirements for masonry structures, while the last 90 pages are the specifications for masonry structures. Is it correct to assume that TMS 402 (254 pages) is the actual masonry building code and offers mandatory code- required compliance criteria AND that TMS 602 (90 pages) merely contains specifications for which compliance criteria are non-mandatory?

RESPONSE: No. To assume that TMS 602, “Specification for Masonry Structures,” is less important than TMS 402 (Masonry Code) and is non-mandatory insofar as masonry special inspections is wrong. Most masonry special inspections acceptance and compliance criteria are in TMS 602 (specifications), written in mandatory language. The quality, inspection, testing, and placement of materials used in masonry construction are covered in TMS 602 and other reference standards adopted by TMS 602. In fact, Section 1.4 of TMS 402 (Masonry Code) adopts TMS 602, which makes TMS 602 code by reference.

PITFALL 3: A special inspections question often asked about the masonry discipline is whether or not project special inspections include field monitoring of masonry walls to observe the masonry wall during construction phases for levelness and plumbness.

RESPONSE: The answer to this question is yes. TMS 602, Table 4, “Minimum Special Inspection Requirements,” inspection task 3 (c), sets forth code compliance criteria regarding the size and location of structural members. It refers specifically to TMS 602, Article 3.3F, which lists the site tolerances for numerous items, including variation from plumb, true to line, and the levelness of the top surface of load- bearing masonry walls. Because masonry is usually used as an exposed material, it is subjected to tighter dimensional tolerances than those for structural frames. The tolerances given in Article 3.3F are based on structural performance – not aesthetics.

SPRAYED FIRE-RESISTANT MATERIALS (SFRM)

PITFALL 1: Bond strength in the context of sprayed fire-resistant material (SFRM) refers to the adhesive force or strength with which the SFRM material adheres to the underlying structural member (like a steel beam). Strong bond strength is critical because if the SFRM detaches from the steel beam, it loses its ability to protect the steel from high temperatures during a fire. The IBC sets minimum bond strength requirements for SFRM, which can vary depending on the building’s height, with high-rise buildings needing significantly higher bond strengths. The primary pitfall question is how do you know when the lower bond strength requirement ends and the higher bond strength begins? This can be difficult to determine by the code verbiage presented in IBC Chapter 17.

RESPONSE: IBC Chapter 4, Section 403, has to be perused to realize and appreciate the minimum bond strength requirements from low-rise to high-rise buildings. The minimum SFRM bond strength for low-rise buildings is 150 psf, and low-rise buildings are any buildings less than 74 feet in height as measured from the lowest access level for fire department vehicles. See the (modified) IBC Table 403.2.3 for high-rise buildings below.

It is important to note that if you have an eight-story building with a height of 88 feet, the code-required bond strength is 430 psf, applicable throughout the building. In other words, the SFRM on each building floor is required to have a minimum bond strength of 430 psf. Lower bond strengths are not allowed on the lower floors.

SUMMARY REMARKS

There are dozens of special inspections pitfalls that can come into play on almost every construction project nationwide. That is because no single architect or structural engineer can be aware of all of the code-required special inspections of each project discipline—geotechnical, soils, concrete, reinforcing steel, masonry, structural steel, sprayed fire-resistant materials (SFRM), cold-formed steel, wood, seismic force-resisting elements, etc. Similarly, no project special inspector, building official, or contractor can know all potential project special inspections required by the hundreds of building codes and standards. However, when the entire project team works together in total unison toward detecting code discrepancies and construction resolutions, the integrity of the construction and code compliance is more assured.

But wait! We have a lot more to say!

For a complete picture of the Code and how it relates to Special Inspections, F&R would love to provide a virtual AIA-accredited Lunch & Learn presentation to the professionals at your firm.

Alan S. Tuck, Director of Code Compliance & Training | T 540.344.7939 | M 540.798.4440 | [email protected]