How to handle contractor substitution requests? | Architecture 2

Over the years as a practicing architect, I have learned to be very careful when considering (and accepting) substitution requests from the contractor. What might initially seem like a fairly straightforward aspect of the construction phase of a project, can turn out to be a big headache if not navigated with care.

First, there is the consideration of whether a contractor's substitution request is even permitted. In a publicly bid project, normally all requests for substitution are to be submitted prior to the closing of the bid period. This is to ensure that all bidders competing on the project have the same advantage of knowing what substitutes will be allowed. Further, substitution requests are not normally permitted after award of the competitively bid project. However, there are circumstances that develop post-bid-award that can alter this system, allowing the consideration of post-bid substitution requests. An example of this might be if a specified product is no longer available when it was available during the bid phase. In such cases, giving the proposed substitution request consideration for approval is appropriate.

After determining if a request for substitution is allowed, the next challenge is in the review. In theory, a valid substitution would be something "equal to or better than" the originally specified product. But is that all there is to it? The answer is a bit more complicated. Architects (and the entire design team) take a lot of care to design buildings, systems, and components to work together. While one single element of a composite system may be proposed for substitution, what is the impact of the change on the remainder of the entire system, and the overall design itself?

In my experience, while there are many substitutions that can be a one-for-one exchange without any impacts on the performance or design of the entire composite system, a proposed substitution often comes with many caveats that can cause issues for the architect. As an example, take the case of a contractor proposing the substitution of one manufacture's 50-ton roof-top package HVAC unit with another manufacture's 50-ton unit. Let's say that the proposal looks attractive because it will save $5,000 over the originally specified unit cost. On the surface, the specifications and anticipated performance (heating/cooling/ventilation) might be similar or within design tolerances. But what if the proposed substitution has different structural and acoustic requirements? What happens if the steel framing to support the unit is significantly different with the substitution unit and the steel is already framed and in place? In this case, an engineer might have some re-design to do. Further, the modifications to the steel framing alone might cost well above the proposed savings ($5,000) as proposed.

Substitutions can be complicated and may require significant re-design and/or changes to work already in place. As such, it is important to conduct a high-level evaluation and expose all potential downstream impacts of a proposed substitution early before moving forward with detailed review. In performing this high-level evaluation first, you may be able to quickly save everyone time, money, and complications in the process.