Everything to Know About Level of Development (LOD) in BIM
Level of development (LOD) is a set of specifications that gives professionals in the AEC industry the power to document, articulate and specify the content of BIM effectively and clearly. Serving as an industry standard, LOD defines the development stages of different systems in BIM. By using LOD specifications, architects, engineers and other professionals can clearly communicate with each other without confusions for faster execution.
What is Level of Development (LOD)?
Level of Development (LOD) specification allows professionals in the industry to clearly articulate how an element’s geometry and associated information has evolved throughout the entire process. It signifies the degree to which different members of the team can rely on information associated with an element.
The LOD specification helps designers define the inherent characteristics of the elements in a model at different stages of development. The clarity in illustration gives depth to a model, signifying how much and at which level someone should rely on a model’s element.
Using LOD, designers and engineers can clearly communicate with other professionals who will be using the model further about the usability and limitations of a model. LOD specifications were designed to standardize the use of the LOD framework and use it as an efficient and collaborative communication tool.
The Origin of LOD
LOD was first introduced by the American Institute of Architects in 2008 when it defined five different levels of development to define the detailing levels in a BIM model. But the concept of LOD is present much before that.
The first instance of LOD usage can be traced to a construction analysis software company, Vicosoftware, which made use of LOD-like system to associate digital models with the cost of a project. The company made all the parameters and details associated with a digital model accessible for everyone at various stages of the design process.
Fundamental Definitions Associated with LOD
In the current context, there are six different levels of development that are defined by the American Institute of Architects (AIA).
According to AIA, LOD outlines the design requirements at each stage. At LOD 100, which is the pre-design stage, the model consists of 2D symbols and the masses to signify an element’s existence. At LOD 200, the elements are partially defined by outlining its approximate quantity, size, shape, and location. By LOD 300, the elements are defined with exact dimensions and their relative positions bolstering precision. LOD 350 describes the information about an element precisely and outlines an element’s relation and connection with other components. The LOD 400 level outlines the basic information about the construction of various elements. By LOD 500, the model begins representing the real-life functions of elements in a real building. Here are all the levels of development with their definition in detail.
A basic level model is developed to represent crude information related to a concept such as an area, volume, location, height, and orientation of elements.
The stage defines a general model with approximate values for each of the element. Information such as quantities, size, shape, orientation, and location along with other non-geometric information is associated with each of the model’s element.
The detailed design level outlines accurate models and drawings with specific assemblies, accurate quantities, precise size, shape, and location. The stage helps create a model in detail with all the information about different elements defined with accuracy.
The stage defines how different elements interact with other elements and systems with the help of graphics and documented definitions.
At this stage, all the elements are defined as specific assemblies with detailed and complete information about assembly, detailing and fabrication. Also, details regarding quantity, size, shape, orientation, location and non-geometric information are also attached to the model.
The as-built stage enables modeling all the elements as constructed assemblies- i.e. how they will appear in real life. This stage can define information about maintenance and operation and different kinds of actual and accurate information are attached to the elements.
Capability of BIM Model according to LOD level
The Approved Use Guide by Real Estate department of the U.S. General Services Administration (GSA) provides the guide to understand what the BIM model should be capable of at different development stage. i.e. LOD 200 BIM can be used to create estimated cost based on the measurement of a generic element.
|Model Content||LOD 100||LOD 200||LOD 300||LOD 400||LOD 500|
|3D Model Based Coordination||Site level coordination||Major large object coordination||General object level coordination||Design certainty coordination||N/A|
|4D Scheduling||Total project construction duration. Phasing of major elements||Time-scaled, ordered appearance of major activities||Time-scaled, ordered appearance of detailed assemblies||Fabrication and assembly detail including construction means and methods (cranes, man-lifts, shoring, etc.)||N/A|
|Cost Estimation||Conceptual cost allowance Example $/sf of floor area, $/hospital bed, $/parking stall, etc. assumptions on future content||Estimated cost based on measurement of the generic element (i.e. generic interior wall)||Estimated cost based on measurement of specific assembly (i.e. specific wall type)||Committed purchase price of specific assembly at buyout||Record cost|
|Program Compliance||Gross departmental areas||Specific room requirements||FF&E, casework, utility connections|
|Sustainable Materials||LEED strategies||Approximate quantities of materials by LEED categories||Precise quantities of materials with percentages of recycled and/or locally purchased materials||Specific manufacturer selections||Purchase documentation|
|Analysis/Simulation||Strategy and performance criteria based on volumes and areas||Conceptual design based on geometry and assumed system types||Approximate simulation based on specific building assemblies and engineered systems||Precise simulation based on the specific manufacturer and detailed system components||Commissioning and recording of measured performance|
Source: Approved Use Metrix by U.S. General Services Administration- Real Estate Services
Advantages of Level of Development (LOD) in Design
Level of development is an extremely important element of the entire BIM process. Without LOD, it can become hard for everyone to work on the same page, creating inconsistencies that can hamper a project’s prospects. With the help of LOD specifications, communication and collaboration can become easier and faster, making room for efficient deployment of resources at all levels of design and construction. Here are some of the benefits of the level of development specifications in the design process:
• Better collaboration and communication between different teams
With the help of standardized specification and detailed information about all the elements, designers can provide guidelines and data for people working downstream to ensure zero lapses in execution and maintenance. LOD makes it easier to define a standard for contractors who must take care of BIM execution. At the same time, design managers can explain the requirements at various levels of the design process to the teams in a better way.
• Articulated Scope associated with a BIM deliverable
With the help of LOD, BIM models become more accurate. At the same time, all the teams including the owners can precisely specify the level of detail they want from a BIM model and get clarity on the scope of the final BIM deliverable.
The Benefit of Clarity Due to LOD for an AEC Project
In an era where everything is handled digitally and all critical projects make use of 3D model, it becomes hard for designers to make other teams understand the project expectations. Most often, handling a BIM model comes with a unique challenge- different people perceive different definitions of completion.
LOD creates a standardized definition of what completion means and eliminates chances of discrepancies associated with project completion. Using LOD, teams working under different disciplines can communicate with each other in a better way with greater clarity. LOD enhances clarity in design by making use of advanced techniques and technology.
Here is a walk-through of LOD stages of an ongoing hotel project – a three-story new construction on a two-acre land, 56,000 square foot, 95 rooms.
Conceptual Information Model (Client Requirements, Conceptual Design)
System/Component Oriented Modeling (Basic Design)
System/Component Oriented Modeling (Detailed Design)
Element Oriented Modeling (Construction Documents, Fabrication & Assembly)
Element Oriented Modeling (As-built, Facility Management)
Exterior Visualization and Walk-through
Overcoming the LOD Lexicon
If used without standardization, 3D BIM models can cause massive blunders owing to the difference in precision and accuracy definitions between two teams. LOD is structured to minimize errors with the help of a numerical lexicon which the designers and the end-users of a BIM model share for common understanding.
LOD is just like a key to a lock which can open the right gate for project completion. In other words, it’s a way to accurately execute various elements in a model. With LOD, design, and execution teams can come at the same page and see that a model’s elements with clarity and understand when an element reaches desired level of maturity that can be called as completion.
Winding up the topic, we would like to throw some light on the fact that without a proper LOD specification in place, a BIM model can turn out to be less significant for the entire execution team. With proper Level of Development specifications, the accuracy, precision and value of the entire BIM process as well as 3D models can be enhanced phenomenally for the entire lifecycle of a project. Interested in learning more about BIM? Get in touch with our experts, today.