Design and Virtual Construction: Why LOD400 Matters

Today’s fast-paced world of design and construction is fractured. Risk aversion, shortened construction timeframes, and more complex projects are creating a gap of information between what was designed and what should be built, costing time and money.

At Walter P Moore, our solution is to solve design virtually, by producing a Building Information Model (BIM) at Level of Development 400 (LOD400). By broadening design to anticipate construction issues and delivering a fabrication-ready model, engineers can create more certainty in cost, schedule, and design intent.

Nearly 50 years ago, Boyd Paulson created a simple yet powerful rubric for understanding the relationship between the influence of decision-making for project outcomes versus the committed project costs. The following holds true for every project every time: over the course of the project schedule, the influence to change outcomes steadily decreases, and the committed project costs go up.

By supplementing Boyd’s analysis, at any point in time, the final cost of the project is an uncertain/unknown. It is estimated, but it will not be known exactly until the project is complete. It is this uncertainty that is the breeding ground for risk, unmet cost and schedule expectations, and loss of trust between project partners.

One way to combat this problem is to improve the shape of the influence curve. If engineers can maintain a higher level of influence over project outcomes and hold off on the committed project costs, it is one way to ensure the final cost and schedule better aligns with initial estimates. This article will discuss a method to improve the shape of the influence curve.

Over the past 10 years, a number of AEC industry stakeholders have contributed to the development of a common language for BIMs used with increasing frequency and reliance in the industry. The BIM Forum publishes annually a Level of Development (LOD) Specification that provides guidance on the expectations of the BIM for the project. This is performed by applying a numeric value to specific components within the BIM based on the specific criteria those elements satisfy. In general, the higher LOD numeric value, the further along that element is on the spectrum from concept to fabrication ready.

This common language helps reduce barriers to understanding the nature of the BIM, and therefore increases confidence and the right level of reliance by those who need the information in the BIM to construct the building.

In this article, any references to LOD400 are a reference to the definition provided by the BIM Forum (2021 version quoted): “The Model Element is graphically represented within the Model as a specific system, object, or assembly in terms of size, shape, location, quantity, and orientation with detailing, fabrication, assembly, and installation information. Non-graphic information may also be attached to the Model Element.”

Here also is the common language interpretation, also from the LOD Specification: “An LOD400 element is modeled at sufficient detail and accuracy for fabrication of the represented component. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modeled information such as notes or dimension callouts.”

It is clear the definition LOD400 represents elements that are fabrication ready. All information sufficient to fabricate the element is contained in the modeled element. This exceeds the LOD of a BIM element universally accepted by the design industry as acceptable for permit-level documents. The modeled elements are not merely sufficient for bidding, procurement, or mill order. The modeled elements are ready to be fabricated.