Architecture : Design BIM LOD 400 Successes, Limitations, and Lessons Learned

By Anthony Offak and Benjamin Crosby for Autodesk University

As Building Information Modeling (BIM) and virtual design and construction (VDC) pull us to new levels of collaboration, we might find ourselves afraid of that next BIM level. At Volvo’s new plant that was recently completed in South Carolina, the general contractor, architects/engineers (A/E), and subcontractors formed design-build relationships that we’ll present as a case study. We’ll discuss examples of BIM Level of Development (LOD) 400 implemented to prevent errors and save cost and time, such as the A/E’s mechanical engineer using LOD 400 for major elements of the design model to help the mechanical subcontractor.

We’ll discuss how this was accomplished from contract, coordination, permit, and delivery standpoints. We’ll show what elements were taken to LOD 400 by the A/E, and what was taken to 350-400 by the trade contractors. We’ll share lessons learned and limitations one has to keep in mind. Now that we’ve had this success, how do we learn from it, and how can you move forward and let LOD 400 take your project to the next level?

Case Study: New Volvo Plant in South Carolina

In 2015 Volvo decided on building a new Greenfield vehicle manufacturing plant that would start operations in early 2017. The plant’s campus is composed of various buildings. Most buildings were design-build awarded at the end of 2015 to Yates Construction, who acted as the general contractor. Immediately the project began in the design phase. Yates had assembled the design-build team, and for this case study we will be focusing on the relationship of Albert Kahn Associates (Kahn) as the architect and engineer and Jesco Construction as the mechanical trade contractor.

The buildings involved for the case study are the Administration Building, the Body Shop, the Assembly Shop, the Utility Plant, the Conveyor Bridges (tunnels) and the trestles that connected all of them. In all, these buildings involved for the case study totaled over 1.4 million square feet and over $400 million in construction cost. Since the majority of buildings had to be operational in early 2017, most construction packages had to be issued before June of 2016.

Scope of work for Volvo project.

Project Workflow Influences from Design to Installation
With such a tight window to design and build, the team worked together to evaluate and propose ways to speed up delivery of the construction drawing packages. The team had to contend with Volvo’s BIM requirements which mandated delivering a model with LOD 350 and 400 elements at the end of project and met their specific BIM Execution Plan. These requirements caused the entire team, including Volvo, to apply some strategies of an Integrated Project Delivery approach to a Design-Build Team approach along with a Design Assist approach. The owner would work with Yates and Kahn to give quick decisions to design questions to keep schedule on track. Yates then had Kahn work the trade contractors to make parts of the Design Model as a Fabrication Model.

Project LOD for Volvo Compared to Other Project Workflows
When LOD 400 is required for the final model deliverable to the client you will usually have these workflows:

Typical Design-Bid-Build Projects

  • A/E produce LOD 100 to 300 up to when construction documents are issued.
  • LOD 350 to 400 would be created either by the subcontractor for Shop drawings and Fabrication Models during the Construction Phase and then incorporated into a Record Model that is given to the client.

Typical Design Assist Projects

  • A/E produce LOD 100 to 300 up to when construction documents are issued.
  • The Shop drawings and Fabrication Models can begin in the Schematic Phase and will have LOD 350 to 400 but will not be complete until the construction phase.
  • The Fabrication Model is then incorporated into the Design Model if elements were installed per the Fabrication Model. Items not installed per the model will be updated in the Design Model to create a Record Model that is then given to the client.

Typical Design-Build Projects

  • A/E will produce architecture and structural design models in LOD 100 to 300 up to when construction documents are issued.
  • The separate trade contractors for MEP will create and share Shop Drawing and Fabrication Models with LOD 350 to 400 from the Schematic Phase until the Construction Phase.
  • The Fabrication Model is then incorporated into the Design Model if elements were installed per the Fabrication Model. Items not installed per the model will be updated in the Design Model to create a Record Model that is then given to the client.

For Volvo, the team decided on combining the workflows to achieve installation sooner:

Design-Assist Build Combination

  • Albert Kahn Associates would produce architecture and structural design (foundations and substructure) models in LOD 100 to 300 up to when construction documents are issued. It would produce a MEP planning model used by Jesco Construction to share with subcontractors.
  • Kahn’s structural engineers would design and create models for the foundation, but for the superstructure they would design and engineer the trusses and members while the steel fabricator would create the actual model in LOD 350 to 400.
  • Kahn’s MEP engineers would follow this concept and design and engineer the MEP systems. The MEP fabricators would then create the actual model in LOD 350 to 400.
  • Jesco Construction engaged Kahn to create a Fabrication Model for some of the mechanical systems.
  • Items are to be installed per the Fabrication Model which will turn into the Record Model to give to Volvo. Items not installed per the model will be updated in the Record Model.
Graph of LOD during phases of Volvo.

A Quick Look at LOD 350, Why We Use It, and Why LOD 500 Is a Myth
LOD 350 was created by the BIMForum (an AIA AGC partnership). As LOD came into use, it became obvious that there was a distinct difference in why trade contractors were putting elements into models. Some elements were there just for coordination, while some trades were placing elements so they could actively prefabricate elements. There was a noticeable difference in the model content between these two approaches. So while the original LOD definitions had LOD 400 as shop/fabrication content, there was a need for LOD 350 content to equate to coordinated items.

Here is another way to look at LOD definitions:

100 = Sketch to get things aligned and early criteria met

200 = Design per requirements and criteria, but still needs coordination and fit — don’t dimension this

300 = Designed and engineered as to be built — full dimensions are available and should be followed per design requirements

350 = Design requirements coordinated with trades for installation — space allocation and fit based of design criteria

400 = Fabrication level content — meets design criteria, space allocation, and shows the parts and pieces for assembly

500 = Not really sure, some say as-built — but why are they not using the 350-400

BIMForum LOD examples.

Decision for A/E to Produce Mechanical Revit Design Model to LOD 400
As previously discussed, the design-build team was working to meet the tight schedule with Kahn and Jesco envisioning how they could decrease the time it took to be able to start fabrication and installation of mechanical systems and equipment. Kahn previously had experience on a smaller scale of LOD 400 so they knew they could do it. Kahn’s structural engineers had been working this coordinated method of engineer/fabrication for over five years, so mechanical engineers were able to take that experience regards to organization and coordination and apply it to the relationship with Jesco.

Kahn knew that like structural elements, if mechanical elements were modeled to LOD 400 and Jesco agreed to install the items per the model location, the team could prevent clashes, and save time and money on installation rework. Jesco agreed to this path and they put together a mini BIM execution plan that included which systems would be modeled and by whom.

Revit screen capture of systems being modeled.

Process for Mechanical Systems with LOD 400 for the Revit Design Model
Albert Kahn Associates agreed to model ductwork, mechanical equipment, and hot and chilled water systems with an LOD 400 in Revit. Jesco Construction agreed to model the hanger locations and share for coordination and clash detection.

The team then agreed on the process to institute the design:

1. The Kahn mechanical engineer after coordinating with Volvo would propose a system and/or equipment.

2. Volvo, Yates, and Jesco would then analyze the proposed design for meeting the Volvo’s requirements, the price, the lead time, and any other related analysis such as constructability.
a. If the proposed design was not accepted, Jesco or Kahn would propose an alternate with Volvo, Yates, and Jesco analyzing this new proposal.

b. If the proposed design was accepted, Kahn would create it in the Revit model.

3. Kahn knew the fastest way to have LOD 400 models would be to use those already created.
a. Kahn first contacted manufacturers to find out if they had any Revit families.

b. If not, Kahn would search on websites such as BIMobject and Revitcity to see if similar Revit families were available to modified to match requirements.

c. If still not found, then Kahn would model them to LOD 400 level. This was required only for about 5% of the models.

4. As the Revit model was being created, Kahn would share it with Jesco to find clashes. Hangers would be added in and checked for clashes in the Federated Model.

5. After all the elements of a system were modeled and found clash free, the Federated Model was then used by Jesco to purchase the equipment, or work with subcontractors to fabricate the system.

6. Jesco would then work with the installation subcontractor to install the systems and equipment based upon location in the latest coordinated Federated Model.

Workflow used on Volvo for design of mechanical systems.

Tools Used to Create the LOD 400 Mechanical Systems Modeled in Revit 
Kahn utilized a staff member whose daily sole task during the design phase was to find LOD 400 models or create/modify the required ones for the project. They often would look through manufacturer websites or contact them to get the appropriate LOD 400 family for the Revit model.

They also were tasked with keeping track of all the families being used. They had to keep them organized in a fashion that any of the mechanical engineers on the project could easily deduce where the family was located to insert into Revit, and where to look on the component list. They would also search for any manufacturer plugins to place the systems or components in Revit.

Example of LOD 400 families from Greenheck.
Example of LOD 400 family from BIMobject.com.

If there were no exact models they would look for a similar model and then modify it to reflect what was required for the design.

Example of family modified for LOD 400.

One engineered system was designed using Victaulic pipes. Kahn used Victaulic’s toolbar in Revit to place the components to create the system. Kahn utilized the free version of the toolbar but has determined in the future it would have been to use the fee based toolbar to use the additional tools

Examples of families placed from Victaulic Revit toolbar.
Navisworks image of Revit model with mechanical systems modeled.

A/E Cons for Mechanical Systems Modeled with LOD 400 in Revit
No system or process is perfect, otherwise everyone would be using it. The process of using LOD 400 components in the Design Model is no exception. The following are what Kahn saw as cons with LOD 400 families for the Revit design model:

1. Extra time and effort for the engineer when compared to LOD 300 in the Design Model.
a. LOD 400 models require effort to research families of what will actually be used.

b. May have to create/modify LOD 400 families if suitable ones cannot be found.

c. More families loaded into the Revit model will make the model open and operate slower. Depending on your machine this could be exasperated by lack of RAM or CPU power.

d. If LOD 400 families are not organized properly, engineers could waste time looking for what is needed. Workflow regarding organization needs to be kept clear.

e. Need additional coordination time with fabricators and installers. In LOD 300 projects, rarely any coordination with fabricators/installers other than shop drawings review occur, on LOD 400 it is vital to have them be a part of the team discussion.

2. Wasted effort related to the workflow.
a. When the client changes a portion of the building after the initial design, the whole research process may need to occur again. In LOD 300 you have more a generic model.

i. For LOD 300 the unit is unknown usually when construction documents are issued, so the roofing contractor will coordinate size and location of roof curbs once the unit is purchased.

ii. For LOD 400, the unit is known, so exact size and location of roof curbs are known, and might be already purchased and installed. If the AHU changes, these roof curbs may not work and have to spend extra money to correct the situation.

b. If items are not installed as the design model that was used for fabrication, then you will either create unforeseen clashes or not have the proper material required.

3. Additional engineering cost is required and a project budget needs to reflect this.

Pros for Mechanical Systems Modeled with LOD 400 in Revit
Although LOD 400 models will have more upfront time dedicated to the design model, the overall time it saves on the construction schedule greatly outweighs this extra effort. The following are what Kahn and Jesco found were the pros to using LOD 400 for the design model.

1. Knowing which manufacturers will be purchased as the design model is being created is a huge plus. It allows for accurate equipment to be modeled, actual locations, and for clashes and clearance requirements to be checked during the design phase instead of construction phase as often occurs on LOD 300 projects.

2. By having the exact equipment or system shown in the exact place desired and agreed upon by the team, then you can avoid extra pieces being fabricated and most in field modifications.

3. The design model can actually be used as the fabrication model, which in turn means it can become the Record Model with no changes, as long as items are installed as shown in the Design Model.

A/E Lessons Learned from Modeling Mechanical Systems to LOD 400 in Revit
While Kahn has modeled in LOD 400 on a small scale on previous projects and learned lessons from them, this design-build project reinforced some lessons and introduced new lessons. Others can learn from all of this if they need to do a similar task for a project.

1. Time and fees 
a. Kahn knew that LOD 400 would be an extra effort and time when you institute it in the design phase, but had figured more time for the A/E would be saved during the construction administration phase than what had occurred. In the end, an extra 15–20% more hours were required by the mechanical engineers versus a normal design-build project using LOD 300.

b. An A/E should request an additional fee to do this task. Scale of project and task would be dependent along with knowledge of whether the preferred design has LOD 400 families to use. In the short time this project has been constructed, some of the manufacturers that previously did not have Revit families before now have them available. This reduces creation time or modification time to get a family that has what would be required.

2. Saving time
a. Use manufacturers and third-party websites to get LOD 300 and 400 models, or use as a base to create the family you need for your own model.

b. Do your research to learn about the different software plugins or apps that could be used in Revit to create the systems. Make sure you test it out and if there are different levels, do a cost analysis to see which is the best to use. Remember it may cost an extra $100 but if it saves more than two hours for a task then it just paid for itself that first time.

3. Good execution plan
a. This project reinforced Kahn’s already logical workflow and file/folder structure to keep track of all the families to load or modify for the project.

b. Know that Revit models with families that have additional data will eventually start to slow down loading the local file of the central model and navigating around in it. Figure out how to limit this by putting families and systems onto work sets and maybe break out the central files even more or use view templates to limit the amount of data being processed in the background.

c. Have a set and agreed-upon process for when items change. There will always be changes and on fast track projects the project teams to agree on how to quickly integrate the changes. Any required changes that occur during installation should be modified in the model(s) as they occur to keep the coordinated Federated Model current to actual conditions.

d. Coordination between all parties involved must be followed to make sure the proper chain of command is known and followed. This way the fabricator could halt fabrication until a decision is made and the installer can hold an area that might be revised.

Process for Fabricating and Installing Mechanical Systems from Revit Design Model
As previously stated the tight schedule was a huge reason for the push for the Revit Design Model to be used for the Fabrication Model, but the process had to be done just right otherwise it would fail. Out of the 142 BIM models used on the project, 85 of them were related to MEP. To keep the schedule Yates Construction, Albert Kahn Associates, and Jesco Construction agreed that upon completion of a system being designed, they would have three weeks to finish any coordination prior to sending that system’s Design Model off to the subcontractors for fabrication. In this time frame, final coordination was occurring to give a clash free model. For example if duct hangers were involved, that model would be brought into Navisworks to create the coordinated Federated Model that could be used for clash detection and sequencing.

Navisworks rendering of Federated Model.

Also during these three weeks, preliminary shop drawings from the subcontractor would be looked over. This was possible due to the coordination and sharing of the Design Model with the fabricator while the systems were being designed and modeled. The fabricator was able to start their shop drawings with the parts they knew would not change or could change with minor impact to issuing the shop drawings. After the design model was determined to be clash free and the shop drawings approved, fabrication began.

Workflow for fabrication on Volvo project.

After fabrication and the material arrived at the site, it would be installed. The items were to be installed per the exact location of the Federated Model. There were unforeseen clashes, but Jesco and Yates were able to figure out the causes and the solutions. With a few exceptions, the systems and equipment was installed per the model thus allowing the Revit Model to become the Record Model which could then be turned over to Volvo.

Working to Install per Federated Model locations
Since the Design Model was used for the Fabrication Model, the processes involving the Federated Model had to be done just right otherwise it would fail. At first it worked, but then it began to fail. In the Administration Building some of early MEP systems were not being installed per the Federated model. Yates and Jesco worked together figure out what was causing the issue and came up with the solution.

Problems

  • Some subcontractors never used to this type of workflow and didn’t trust BIM.
  • New management wasn’t involved in BIM weekly calls and never communicated when they needed clash free areas.
  • Some subcontractors didn’t participate in BIM Coordination meetings, didn’t contact Jesco/Yates to see if current model was clash free and ready for fabrication, or didn’t share the model for a federated model to check for clashes.
  • Some subcontractors would start fabrication from not fully coordinated models.

Solutions

  • Identify areas being changed and re-coordinate with all trades affected.
  • Have daily meetings for coordination.
  • Ensure installation drawings were revised accordingly to the latest changes.
  • Field supervision for installation using the latest Federated Model.
Clashes that occurred when model not followed for installation.

Lessons Learned from Installing per Federated Model Locations
The entire Design Build Team was able to learn and figure out how to improve the process for the next project.

What Was Learned

  • Always have field/management member involved with BIM meeting and the process.
  • Have at least one monthly review with 4D in BIM meetings to understand when critical areas are about to be installed.
  • Even if it’s coordinated in the Federated Model, make sure it is installed per shop drawings obtained from the coordinated model.

What to Improve Next Time

  • Train key management members to understand the BIM process.
  • Encourage subcontractors to use model review tools on-site.
  • Weekly review the Federated Model with superintendents.
  • Incorporate outstanding problems from BIM weekly meeting into subcontractor meetings to keep everyone on same page.

Conclusion

BIM LOD 400 might not be right for all, but if done correctly it has the ability to reduce the schedule which in effect could reduce construction costs. One has to keep in mind, this will require additional effort during the design phase with constant coordination and sharing of CAD models. The team worked hard to gain a high level of collaboration and great coordination. We “reevaluated” and “adjusted” contractual barriers to deliver for our client on their fast-paced schedule. We know that we will do this again not because we are forced to, but because we want to. With what we learned we know We Can and We Will do it even better that next time, and we encourage you to try it too.

Anthony Offak, RA, LEED AP BD+C, wears many hats at Albert Kahn Associates, one of which is the office’s sole CAD/BIM manager. He helped start the company’s Workflow Improvement Team almost 15 years ago and has helped guide the company’s CAD standards and workflows since then. Whether it as a project architect, project manager, or BIM/CAD manager, he is always looking aiming for continuous improvement of workflows and project organization for the team. He enjoys researching and trying out new apps, plug-ins, and hardware that can make fellow co-workers be more productive and can help create less errors and omissions giving the client a better building.

Benjamin Crosby, CM-BIM, CM-Lean, CCM, LEED AP BD+C, is passionate about building and education. As a builder educator, he motivates people to understand virtual design and construction and how it will improve their projects and careers. He has a CM degree with Math and Physics minors, is a member of the BIMForum BxP Committee and LOD Core Group, AGC IT Forum Steering Committee, CMAA Professional Development Committee, and instructs the AGC BIM and Lean Programs.

Learn more with the full class at AU online: Design BIM LOD 400 — Case Study of Volvo: Successes, Limitations, and Lessons Learned.

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