Every building starts with design intent. The owner has expectations for function, quality, performance, appearance, cost, and schedule. The architect and engineers respond with solutions expressing the design intent to satisfy those expectations. Eventually those solutions become drawings and specifications that tell the contractor what to build.
So where, exactly, is the design intent documented? That seemingly simple question can be difficult to answer.
Look at a typical exterior wall. The architectural drawings show the configuration and appearance. Structural drawings show the supporting construction. Mechanical documents may establish energy performance requirements. The specifications describe air barriers, insulation, masonry, metal panels, sealants, flashings, and perhaps a dozen other products needed to construct the wall.
Each document contains part of the answer. Where can someone find the answer describing the exterior wall as a complete system and explaining what the system is intended to accomplish - and why?
Often there is no single answer.
Drawings and specifications are excellent at documenting the designed solution. That is exactly what construction documents are intended to do. The difficulty is assuming that the designed solution and the design intent are the same thing.
Suppose the project requires a high-performance exterior wall. During design, the team establishes requirements for thermal performance, air leakage, water resistance, durability, appearance, and perhaps maintainability. The team evaluates several assemblies and eventually selects one solution.
Months later the contractor proposes a substitution or value engineering alternative. The proposed wall is different, but is it equivalent? Equivalent to what?
If the only available information is the selected products shown on the drawings and in the specifications, the team can compare one product with another. That comparison may completely miss the reason the products were originally selected.
The performance and design requirements existed during design. The decisions existed during design. The intent existed during design. What may be missing is a durable record connecting them.
That is the Design Intent Gap.
When schematic design begins, we hear that there is not enough information to prepare specifications. That is true if by “specifications” we mean detailed construction specifications organized around selected materials and products.
It does not mean the design team knows nothing.
The team may know that the building needs a rain screen exterior wall. It may know the required thermal performance. It may know that the owner wants masonry at public entrances and a lighter-weight cladding elsewhere. It may know the expected service life, fire resistance, acoustic performance, and appearance.
Those are significant design decisions. Why wait to document them?
For years I have advocated a simple approach: Say what you know, when you know it. Be sure to include the WHY that provides the context and relative importance.
As additional decisions are made, add them. When a decision changes, change the record. When a material is finally selected, identify it. Documentation can progress with the design instead of waiting for the design to progress far enough to fit the documentation.
The problem is not that architects and engineers fail to consider design intent. They do it every day. The problem is that our normal project documents do not give design intent an obvious home.
Some information ends up in meeting minutes. Some is found in the owner’s project requirements. Some appears in drawing notes. Some is buried in specifications. Some survives in emails and PDF markups. Much of it remains with the people who made the decisions.
This works surprisingly well while those people remain engaged and remember the history. It works less well when the team changes, when the project pauses, when a substitution occurs, or when someone needs to understand a decision months or years later.
The construction industry spends enormous effort creating a permanent record of what to build. We devote little attention to preserving why the solution became what it is.
Perhaps design intent deserves to become a recognized project deliverable — something to guide and measure compliance.
Choose one important system on a current project: the exterior wall, roof, structural floor, HVAC system, or another major element.
Ask the architect, engineer, estimator, contractor, and owner to independently describe the design intent for that system. Will the answers match?
If they do, ask the next question: Where is that common understanding documented so someone joining the project tomorrow, next month, next year, can find it?
If there is no obvious answer, you have found the gap.
Closing the Design Intent Gap does not require another drawing or another hundred-page document. It begins by recognizing that design intent is valuable project information and deciding that the information is worth capturing.
The next question is how.