Material substitutions are nothing new in construction. They can be legitimate responses to site constraints, lead times, and budget pressure. But in recent years, I have observed a growing trend: these substitutions are occurring more frequently and often carry greater risk. Global supply chain disruptions, material shortages, and tariffs have all played a role, forcing project teams to substitute alternative products midstream. What is often missing is the thorough engineering review required to assess whether those changes are technically appropriate.
As a structural forensic engineer, I have investigated a growing number of failures stemming from these seemingly "small" changes. Sometimes the materials themselves are not defective, but they behave differently from the originally specified product in subtle yet critical ways. When those differences are not adequately understood, building performance suffers, liability gets murky, and construction defect claims emerge.
This article explores the technical risks of mid-project substitutions and how they often become the centerpiece of legal disputes.
The Cost of
Convenience: When Small Changes Lead to Big Problems
Substitutions can be made on a
project for a variety of reasons. A supplier may recommend a different product,
a contractor may propose a value-engineered change, or a material may simply be
unavailable. These decisions are sometimes made informally – approved via
email, embedded in an RFI, or passed through a shop drawing – without fully
appreciating the performance implications.
The following examples are drawn from real-world cases I’ve been involved in, though modified slightly to preserve confidentiality. Each of these cases involved a material substitution that, on paper, seemed reasonable. None involved clearly defective materials. The issues emerged from a variety of circumstances, including mismatches in performance, overlooked fabrication behavior, environmental incompatibility, or other context-specific concerns.
- Galvanic Corrosion from Dissimilar Metals. In a coastal building, stainless steel anchors were substituted in place of hot-dip galvanized ones for curtainwall supports. At first glance, stainless steel seemed like a reasonable alternative – it’s typically more durable and corrosion-resistant. However, in practice, the combination of stainless steel fasteners and aluminum framing in direct contact without proper isolation triggered galvanic corrosion. Within several years, rust staining and material deterioration became visible at the façade. When damage appeared, the parties disputed who had responsibility to assess compatibility: the delegated designer, the engineer of record, or the contractor. Ultimately, the substitution had been made without sufficient evaluation of the galvanic corrosion risk in a coastal environment.
- High-Strength Rebar—But at What Cost? In a large foundation system, high-strength rebar was proposed to be utilized in place of conventional rebar to reduce congestion and expedite installation. Fewer pieces and simplified layouts made the change attractive. However, the rebar’s material properties introduced new risks. High-strength steel can be more susceptible to cracking, such as due to hydrogen embrittlement, especially when combined with certain fabrication and coating processes. In this case, cracking was observed at bends following galvanizing, potentially resulting from a combination of contributing factors, including embrittlement risk, lower ductility, complex geometry and fabrication sequence. While the material met design strength requirements for service conditions, the performance implications during fabrication were not fully evaluated when the substitution was made.
- Incompatible Joint Sealant Causing Water Damage. At a high-end retail complex, the specified construction joint sealant for plaza-level waterproofing became unavailable due to material shortage. The contractor proposed a substitute that had been used successfully in prior projects. Within months of project completion, water intrusion was reported. Forensics revealed that the sealant had debonded at several locations, allowing moisture to bypass the waterproofing system. The substitute product, though suitable for narrower joints, lacked the elongation properties needed for the wider joints and high thermal movement expected at the site. While the product itself was not defective, it was incompatible with the specific geometry and performance demands of the design.
- Hollow Structural Section Substitution and Excessive Deflection. In another matter, ASTM A500 Grade C rectangular tubes were replaced with imported metric hollow sections due to tariff-related procurement constraints. The substitutes were close in size and strength but varied slightly in wall thickness and stiffness. After construction, the building experienced excessive lateral drift exceeding design expectations under service loads. A forensic review revealed that the lower flexural stiffness of the substituted members, especially at critical moment connections, contributed to the observed deflection. This case underscores that even small deviations in geometry or material properties, especially in systems governed by serviceability rather than ultimate strength, can have real-world consequences.
In each of these case studies, a thorough evaluation of the technical implications of the substitutions was missing or incomplete. This is what makes substitution-related claims so complex. Failure is not always obvious, and responsibility often falls between scopes. Delegated design plays a role, but so does the engineer of record. Contractors may initiate changes, but design professionals must evaluate them, and sometimes, under time pressure and with limited information.
The Role of the
Forensic Engineering Expert
- Tracing the Change: Reviewing project records to identify when the substitution was introduced, under what documentation (e.g., RFI, submittal, shop drawing), and who approved it.
- Comparative Technical Analysis: Examining differences between the specified and substituted materials, including:
- Strength, stiffness, and ductility
- Behavior under fabrication (bending, welding, galvanizing)
- Compatibility with adjacent materials (e.g., galvanic interactions)
- Durability and expected service performance
- Testing and Validation: Conducting lab tests to confirm material properties or diagnose failure modes.
- Causation and Standard of Care: Determining whether the substitution could reasonably have been foreseen to cause the observed issue, and whether the parties met their professional obligations.
Implications for
Legal Strategy
- Was there proper documentation of the change?
- Was design review delegated, and were protocols followed?
- Did the team comply with relevant standards (ASTM, ACI, AISC)?
- Was an equivalency analysis performed and documented?
In many disputes, the answers to these questions form the foundation of both claims and defenses.
Conclusion: A Call
for Caution
In today’s fast-moving construction environment, material substitutions are inevitable. But even small changes can trigger major technical and legal consequences when not properly vetted. A multidisciplinary approach – one that includes design, procurement, construction, and engineering oversight – is often required. From a structural forensic perspective, the lesson is clear: materials cannot be evaluated by nameplate or strength rating alone. Context matters. Geometry, fabrication sequence, environmental exposure, and system interaction all affect performance. Without full understanding, substitutions that seem minor may introduce significant risk.
Disclaimer: The views and opinions expressed in this article are those of the author and do not necessarily reflect the opinions, position, or policy of Berkeley Research Group, LLC or its other employees and affiliates.
Author: Dr. Thanh Do, PhD, PE, is a Director in BRG’s Global Construction practice. He specializes in root cause investigations of structural failures, standard of care evaluations, construction and design defect analysis, Design-Build delivery, and early dispute resolution. As a structural engineer, forensic investigator, and technical storyteller, Dr. Do helps clients turn complex engineering issues into clear, persuasive narratives in construction disputes.