A Review - BIMForum LOD Specification-2015

Currently, the 2015 BIM Forum LOD (Level Of Development) Specification (BFLodS) is in a draft format and available for public review and comment. This is the third edition of the document with the earlier releases in 2013 and 2014. It can be downloaded for free from the BIMForum website - https://bimforum.org/lod/.  I have previously referenced the BFLodS, but not specifically commented on it. We have to take our hats off to the participants in this Model Progression Specification initiative.  Their contribution to the industry will never be fully acknowledged. However, their effort does not appear to have been reciprocated by the construction industry in constructively contributing back.  In my research for this article, I’ve found very few quality comments or reviews on the document, and it is difficult to see evidence of the industry using this great resource (in the Australian and New-Zealand region). Detailed public debate and sharing of experiences are a necessary evil to produce robust documents, which instill confidence to its users. Level Of Development has proven to be a difficult subject. It is a means to an end, and it often appears challenging for the project team to obtain real value from the Level Of Development process.

NOTE: All reference in this article to the term "LOD" is referring to Level Of Development unless otherwise stated.

Update Note: 17/11/2015

See bottom of post for updated details on the final release of the LOD 2015 Specification released in November 2015:

Below comments are applicable to the 2015 BFLodS Draft version.

LOD, LODSpec, BIM, Model Progression Specification
Above image: part cover of 2015 BIMForum LOD Specification

BIMForum Background: The BIMForum operates as a unified group whose mission is: “to facilitate and accelerate the adoption of building information modeling (BIM) in the AEC industry.” 1 The group is closely connected with The Associated General Contractors (AGC) of America and collaborates with industry organisations such as: American Institute of Architects, National Institute for Building Sciences, National Institute of Standards and Technology, International Alliance for Interoperability, Collaboration Techniques Tools and Technologies (C3T) Task Force of AGC of America, the 3xPT Strategy Group, formed by the Construction Users Roundtable (CURT®)1. The group has established several sub-groups to address each relevant industry sector and topic.

Level Of Development Definitions: “The LOD definitions that are used in this [BIMForum LOD] Specification are identical to those published in the AIA’s updated Digital Practice Documents” 2 (AIA G202™–2013, Project Building Information Modeling Protocol Form). The main exception is the additions of LOD 350. “The working group identified the need for an LOD that would define model elements sufficiently developed to enable coordination between disciplines – e.g. clash detection/avoidance, layout, etc. The requirements for this level are higher than those for 300, but not as high as those for 400, thus it was designated LOD 350.” 2.
The definitions of AIA G202™ – LOD 100, LOD 200, LOD 300, & LOD 400 are thus used in the BFLodS under license. From reading the BFLodS, it comes across the authors had reservations on the current AIA LOD definition wording. The added glossary gives a watered down definition of “Specific”. They have also inserted the word “Actual” in the main body of the BFLodS for LOD 350 and LOD 400.

The expanded definitions use the following interpretations of these terms:
  •          Specific: 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 call-outs.
  •          Actual: The model element includes all the qualities of a specific element and is representative of the manufacturer’s model to be installed or the construction intent of an assembly.”2

The glossary definition of Specific is relating to the LOD300 definition.
LOD 300: “The Model Element is graphically represented within the Model as a specific system, object or assembly in terms of quantity, size, shape, location, and orientation. Non-graphic information may also be attached to the Model Element.”4

The BFLodS is inferring that LOD 300 is referring to a “designed element” (we would also call it “Design Intent” 11).
In the majority of Building Services equipment of LOD 300, BFLodS uses the wording “Modeled as design-specified”2.  I will further elaborate on this later in the post.
I personally believe the use of the word “Specific” in the AIA G202™–2013 is unfortunate.  Design Models or “Design Intent models” 6 are just that.  There is less than 20% of it, which we would say is “specific” or explicit.

Nominal definition general: “Of or relating to the presumed or approximate value, rather than the actual value.
According to design; normal.
Similarly referring to a value divided by any measure which acts to standardize it.
A measure compared with a standard reference value by division, to produce a ratio without unit or dimension.”5.0
Nominal dimension, n. size definition Construction: “The dimension used in naming something. Its actual size may be larger (full) or smaller (shy) by an allowed tolerance. Sawn timber usually measures less than its nominal dimension, and is further reduced, by another 3 or 4 mm, by plaining or otherwise working it to its dressed dimension. A 100 by 50 mm nominal-sized timber may actually be 87 by 42 mm. Pipes and tubes are named by their diameter, e.g. a 50 mm outside-diameter drain pipe, and this is usually very close to their actual size. “5.1

“Nominal” is commonly used within the design sector of the construction industry. Its use would still require a glossary defining it within the document to avoid ambiguity or miss use. This is standard for any legal document.
I would suggest the AIA and BIMForum collaboratively change the definitions to:

LOD 300: The Model Element is graphically represented within the Model as a “nominal” system, object or assembly in terms of quantity, size, shape, location, and orientation. Non-graphic information may also be attached to the Model Element.

LOD 350: The Model Element is graphically represented within the Model as an “actual” system, object, or assembly in terms of quantity, size, shape, orientation, and interfaces with other building systems. Non-graphic information may also be attached to the Model Element.

LOD 400: The Model Element is graphically represented within the Model as an “actual” 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.

LOD and project stages: As per the AIA G202™–2013 guide: “It should also be noted that there is no intended correspondence between an LOD and traditional design phases.”7  How is it possible for the AIA, to create a Level of Development definition, which has no correlation in any way to design phases? Bear in mind, the primary purpose of LOD is around certainty at milestones.  If a traditional tender (Lump Sum / Design Bid Build contract) is not a milestone we don’t want certainty around, what is the point? If we are unable to get 80% of a design intent model 6, i.e.: the 3D Geometry, which has generated traditional lump sum tender documents, to reach LOD 300, we have a problem.  The BFLodS is essential for identifying the 20% of the geometry which is the exception, and don’t meet LOD300, or is not modeled and identified as LOD 100. The BFLodS must be composed in a manner to make this simple approach reality.
I accept, it is more difficult to link earlier design stages, or early contractor involvement procurement approaches with LOD’s, as different project types will have slightly different resolution levels (at sketch design / design development) depending on the areas the designers believe is critical to the overall design outcome.

Any above changes are unfortunately outside the scope of the BIMForum LOD Specification group, as they are somewhat held to ransom by the AIA G202™–2013. Hopefully, the next the AIA G202™ review will be completed by 2018, and will address these issues.

Major References: The BFLodS specifically references the AIA G202™–20134 along with the accompanying Guide 7. It is however not clear if these documents create an integral aspect around the use and understanding of Level of Development, and thus always need to be released alongside with the BFLodS? The AIA G202™–2013 Guide 7 has 18 pages alone explaining the exact use of LODs. The BFLodS has 4 pages in the Introduction section. It would be preferable for the BFLodS to be a standalone document, where possible, and this may mean the introduction section needs expansion. What’s odd; when I look back at the BFLodS draft 2013 (April 19, 2013), it contained a detailed section “4.1 LOD Definitions Explained”. This section gives a comprehensive rundown on the general application of LODs with the example of a wall, and its development from LOD 100 to LOD 400. This section was removed from the BFLodS 2013 final version for some reason. I would be in favor of putting something similar to it back in again.

Primary purpose: In my opinion, the purpose of such a document is to provide a common language for all readers. Present a clear and concise, easy to use tool, which removes any LOD ambiguity between parties, and can be directly referenced in contracts and/or BIM execution plans. It should avoid overstepping its “Scope” (identified below) in requiring additional data for exchanges beyond what would be seen as reasonable.

BFLodS Scope: The document scope set out by the authors to meet the use of: definitions were developed to address model element geometry, with three of the most common uses in mind – quantity take-off, 3D coordination and 3D control and planning.”2 These definitions come from the “Building Information Modelling Execution Planning Guide – Version 2.0 2010 – Penn State”

The Pen State definitions are as follows:

“3D Coordination - A process in which Clash Detection software is used during the coordination process to determine field conflicts by comparing 3D models of building systems. The goal of clash detection is to eliminate the major system conflicts prior to installation.”3

I think everyone would agree, coordination is a minimum goal of a BIM process, and can be used by all design and construction parties.

“3D Control and Planning (Digital Layout) - A process that utilizes a model to layout the building assemblies and produce lift drawings. Lift drawings are 2D/3D component drawings used by foremen during on site construction.”3

I required some investigation to find out exactly what “Lift Drawings” are! It is a US-centric term. 3D Control and Planning is broken down to two items:

  •           Lift drawings are drawings/models generated by the Contractor using the design paper documentation provided. It is used to thoroughly check the integrity of the supplied design information, allowing the contractor to quickly request clarification or additional information. This approach is commonly used in the US for in-situ concrete work. On complex Australian projects, the architectural team will typically generate “concrete outline/set-out drawings”. Both the US and Australia still generate “Builders Work Drawings”12 which are somewhat similar to Lift Drawings.
  •           Digital Layout is the next generation of the above. The Contractor may now be receiving 2D or 3D CAD files. This CAD geometry is then used directly to automatically set-out (layout) elements using electronic optical (laser) instruments (robotic stations). I have previously talked about this subject in “Using the BIModel directly for set-out:”.
This use of the model is becoming more frequent. In Australia it is predominantly engaged by sub-contractors, utilizing their own models for layout. It should be noted, this use of the model may only occur for elements which have reached a minimum of LOD 350. The above article identifies how a design model goes through a shop drawing process, in order for it to reach LOD350.

“Quantity Take-off  - A process in which a BIM model can be used to generate an accurate quantity take-off and cost estimate early in the design process and provide cost effects of additions and modifications with potential to save time and money and avoid budget overruns. This process also allows designers to see the cost effects of their changes in a timely manner which can help curb excessive budget overruns due to project modifications.”3

I’m glad to see this as part of the LOD specification. The use of the model for quantities /costings should be utilized more. The extent of the non-geometric information to execute this: requires structured communication between the designer and estimator.
I am puzzled as to why the BFLodS working group does not appear to have a qualified Quantity Surveyor or Cost Estimator on it?  Costings are the most significant use of the model within the BFLodS scope. From looking at the Authors profiles, I see a few have estimating experience, but I’m not able to identify an individual representing the design cost management industry. Many of the data attribute required within the BFLodS (main document), “must” be costing related, as very little data outside; materiality, object type, object size and object system and name assignment are required for 3D coordination and digital layout?

(Quote: James Bedrick - BIMForum co-chair) It costs money to put information into a model, and you don’t want to be pushing information in there, if nobody is asking for it14. If the data is not used directly for quantity take off, Digital Layout or 3d Coordination, they should be removed as part of BFLodS data requirements.
In my opinion, some of the data attribute required in the BFLodS main document appear overkill. The purpose of LODs is about model element certainty around “model exchanges”. “The Level of Development (LOD) framework addresses several issues that arise when a BIM is used as a communication or collaboration tool, i.e., when someone other than the author extracts information from it”.

When we get beyond LOD 300, Sub-contractors will price off their own models. If other parties require this data, an explanation of the requirement needs to be given to the reader. As I will mention later in the post, I believe, consideration of these data attributes to become part of the Attachment 1 – Model Development Specification (MDS) Attributes Table is worth investigation. It will provide the project team with far greater flexibility in how they manage the attribute data. 

Authorized Use and Model Status: AIA G202™–2013 has a lot of detail on authorized use. The BFLodS has none, despite the fact it has added the additional LOD definition of LOD 350. Authorized Use, is very beneficial to LOD users and I believe readers should have a clear understanding of how LOD350 is different from LOD 300 and LOD 400.

Authorized Use not being included in the BFLodS, is a good example of how the document needs to be read in conjunction with the AIA G202™–2013 guide.

Imagery: The document contains a large number of detailed imagery. Most people in the construction sector are picture people, so this input is essential. The images are very good at clarifying the geometry requirements.

Document Structure: Each section of the document is clearly numbered, to enable cross-referencing between project specific documents. The Introduction Sections 1 to 5 however, does not contain the paragraph numbering rigor. If this document is used in a contractual context, it needs to allow specific cross-references on a paragraph, by paragraph level.

Sector Scope: The later versions of the BFLodS have continued to expand areas in the civil works space. However, it is still very “building” centric. The document lacks detail in the infrastructure space (e.g. Rail, Roads, Plant, Water, Bridges, Damps, and Tunnels). Unfortunately, the Uniformat II Classification is a building focused document. Thus, the use of the BIM Forum LOD specification outside of the buildings construction industry is questionable. The UK BIM Toolkit (https://toolkit.thenbs.com/) which houses their level of definition approach caters for both the building and infrastructure building sectors.

Wording: Some of the wording is not clear on how to achieve the required outcome and thus confusing. Some examples below:

e.g. 1
A1010.10 – Wall Foundations – LOD 300 –
6) Geotechnical bearing strata elevation is modeled from geotechnical report………..
Image notes 3) “Geotechnical regions are shown for context and not required to be modeled as part of this element at this LOD”2

Is this not a contradiction? I am unable to comprehend how a model element author graphically shows geotechnical strata’s without modeling them or by providing a 2D detail section, which is what the reference image “6 A1010.10-LOD-300 Wall Foundation” shows. The use of 2D imagery also contradicts the BFLodS notes 4.1, in regard to the use of 2D supplementation.

e.g. 2
D2010.40 – Domestic Water Piping – LOD 300 –
“approximate allowances for spacing and clearances required for all specified hangers, supports, vibration and seismic control that are to be utilized in the layout of all risers, mains, and branches”2

The side reference image “103 D2010.40-LOD-300 Domestic Water Piping” clearly shows no modeling of hangers and supports. There is no method identified on how a model element author will communicate the allowance of the hanger spacing’s and clearances.

e.g. 3
A2010 – Walls for Subgrade Enc – LOD 300 –
Element modeling to include:
…….. Material strength
Required non-graphic information associated with model elements includes:
Concrete strength, Reinforcing Strength…….”

How do you “model” Material strength, and why do you need to when the Model element Author is providing attributes for concrete and reinforcing strength?

There appears to be an opportunity for several terms within the document to be misinterpreted. A document like this must be 100% clear. Maybe it requires a glossary or a re-examination of the terms!

Required non-graphic information associated with model elements includes:
Expanding on the above item, what exactly does “Required non-graphic information associated with model elements includes:”2 mean and how is it intended to be used?
Jan Reinhardt (BIMForum LOD Specification – Co-chair) stated at a recent BIMForum event: “We want to have lean models that are elegant to work with, [and] have unique element identifiers. We are not making a representation as to what the technology is, and to where these attributes are stored. They [data attributes] can be stored off site; the model (can be) in a website or a relational database, that is associated with specific model elements, by virtue of a unique identifier.”14

I believe the BFLodS requires clarification on how non-graphic information can be attached to the model and can it include accompanying digital documentation. At the moment as a document user, I’m just not clear.

Attributes Table– Attachment 1: The 2015 document is now the first BIMForum LOD Specification to include an “Attachment 1” – Model Development Specification (MDS) Attributes Table (in a Microsoft Excel format). The contents of the main document have not changed.  It still includes references to non-geometric data (as per the 2013 & 2014 version). We thus end up with non-geometric data called up in the main document, and other, differently worded non-geometric data called up with attachment 1. Attachment 1 also includes; approval data, fabrication data, specification data, installation data, commissioning data etc.

Example of different wording for data across both documents:
“Main Document – A1010 – Standard Foundations – LOD 300 – Required non-graphic information associated with model elements includes:
·         Concrete strength
·         Reinforcing strength

Attachment 1 – A, B – Concrete – Attributes – LOD 300
·         Member Type
·         Concrete Compression Strength      
·         Reinforcing Steel Flexture     
·         Reinforcing Steel Shear” 2

So readers end up scratching their head. This use of different data language is common throughout the separate documents.
In the AIA E202™ - 2008 and AIA G202™–2013, they have never specified specific data. It has always said, Non-graphic information may also be attached to the Model Element.”With the use of the word “may” the general interpretation of LOD definitions has been around certainty of geometry. If data was required, the project team would create a separate data attribute table.
On the announcement of the release of the 2015 BFLodS to include a separate document for data attributes, I immediately assumed the main documents would have been substantially revised to cater for this. However, the main document is unchanged, and now it is more confusing.
When the UK BIM groups were looking at their Level of Definition, they gave a lot of consideration to separating out Level of Detail (geometry related) and Level of Information (non-graphic data attributes). In keeping within the AIA G202™–2013 framework; I believe the BIM Forum could come up with a simple approach, maybe similar to my suggested below method:

  1.         Level Of Development graphical (LODg)
  2.        Level of Development information (LODi)

LODg would be similar to the main document of the BIM Forum LOD Specification. It would contain all the fantastic images, and assist in defining:
            Quantities, size, shape, orientation and interfaces
(All the above items can be generated by any 3D CAD authoring application).

LODi is relating to any related attributed data or information. These would include, but not limited to:
Materiality, Element location (space within), connected system name, Installation data, start-up and commissioning data, compliance data etc.

The above approach is far simpler; it’s scalable and gives the project team greater flexibility. 
The former 2013 and 2014 BFLodS approaches, of having non-geometric data specified in the document has frustrated me, as “some” of the data attributes are not required for many of my projects. I thus have to create a separate section of the BIM Execution Plan excluding data called up in the BFLodS. Not exactly the most “Lean” approach!

Attribute Parameters: I’m guessing the scope of the Attribute table is not restricted to “quantity take-off, 3D coordination and 3D control and planning”2 as it contains warranty and installation information. The more you look at the quantity of data parameters in it the scarier it is. We have to question; why this data is required in the 3D model? The table reminds me a lot of the “VA / NATSPEC BIM Object Element Matrix”, which is a document that receives much criticism. I still have to find a project outside of the VA (US Veteran Affairs) scope which truly utilizes it. My views on adding large amounts of data directly in the 3D model are identified here: “Is the 3D Geometry, restricting BIM?”.
From Jan Reinhardt above comments; I believe the BIM Forum authors would agree with this approach; however being able to separate the geometry from the data is not explained within the BFLodS. A separate database platform (without the geometry), is far more accessible, traceable and quality controllable, and may include schedules and specifications. The schedules can still be linked to models via unique Type codes, and in turn, the schedules can directly reference the specification. The quantity of data in the BFLodS Attribute table is just not user-friendly. The final question in this area: How is the person receiving this model, actually going to use all this data and leverage it beyond what they already traditionally receive?

Equipment and proprietary products: LOD 300 is intended to identify equipment (manufacture’s model) as generic (i.e. manufactured product unspecified). The BFLodS clearly defines the “actual” equipment (e.g. D5040 – Lighting) is not specified until LOD 350. We see equipment at LOD 300 called up as:
“Modeled as design-specified size, shape, spacing, and location of equipment….” 2
with LOD 350 equipment identified as:
“Modeled as actual construction elements size, shape, spacing, and location…”2

BFLodS LOD examples provided (Section 4.1)
“100 cost/sf attached to floor slabs
200 light fixture, generic/approximate size/shape/location
300 Design specified 2x4 troffer, specific size/shape/location
350 Actual model, Lightolier DPA2G12LS232, specific size/shape/location
400 As 350, plus special mounting details, as in a decorative soffit”2

However, this approach has not been applied to equipment proprietary products:

e.g. 1   B2020.10 – Exterior Operating Windows – LOD 300
“Units are modeled based on specified location and nominal size. Outer geometry of window frame elements and glazing modeled to within 1/8” [3 mm] precision.”

e.g. 2   B2070.10 – Exterior Louvers – LOD 300
“Louver assembly modeled by type, indicative of area and location of intended louver/vent.
Includes accurate frame (boundary dimensions) and blades.”2

Other examples include proprietary railing systems, cladding systems, cold formed metal studs, door frames, windows, louvers, roof accessories, rainwater management etc.

The BFLodS authors did manage to pick it up in Slabs on grade of all places:

A4020 – Structural Slabs-on-Grade – LOD 300
“Element modeling to include:
All sloping surfaces included in model element with exception of elements affected by manufacturer selection which are not known at this LOD. Such conditions could include floor geometry differences where different specified manufacturers will not be known until the actual system is selected.”2

All LOD 300 proprietary products should be consistently defined. I would suggest consideration of changing the wording to: “Design-specified nominal size, shape, orientation etc.”.  It is not until the contractor determines the actual product, can we call size, shape and orientation as actual.

You may also have noted Windows are one of the only elements in the whole document to call up modeling precision (1/8” [3 mm]).  I’m not sure why they have that there, as mullion profile sizes can dramatically change between design intent 11 and the selection of the actual supplier’s product.

General Observations:

A10 Foundations – LOD200
Structural building grids for local project coordinate system are defined in model and coordinated with global civil coordinate system (State Plane Coordinate System, etc).”2
Shouldn’t all well put together BIM Execution Plan’s; clearly identify model coordinates and how and when they are engaged. Why is it within the LOD Specification?

A1010.10 – Wall Foundations (Shallow Foundations) – LOD200
Image: 5 A1010.10-LOD-200 Wall Foundation
“2) Site is generically modeled from geotechnical information in geotechnical report.”2
Should the site (ground surface) not come from the Land Surveyor’s model?  A geotechnical report will contain; subsurface exploration data, including subsurface soil profile, exploration logs, laboratory or in situ test results, and ground water information. What are they actually asking for? Wording requires clarification.

B1010.10 – Floor Structural Frame (Concrete) - LOD300
Required non-graphic information associated with model elements includes:
Penetrations for items such as MEP
Typical details
Is this referring to supplementary 2D drawings or how else is the information conveyed? Statements require clarification.

D1050.70 – Pneumatic Tube Systems – LOD 400
Supplementary components added to the model required for fabrication and field installation.”2
This statement is repeated across most building services manufactured equipment. What is an example of these supplementary components, which is not covered already by the component reaching LOD 350? Is it referring to project customized parts, which will become a new integral part of the manufactured component?

AIA G202TM 2013 Guide notes: § 2.5.1 – “Note that “fabrication,” as the term is used here, refers to projectspecific fabrication rather than manufacture of standard components. So, an LOD 400 store front Model Element would include the detail necessary to install it, but not to manufacture it. An LOD 400 custom metal railing Model Element would include detail necessary for manufacture.”7

I have to question the use of LOD 400 within the BFLodS for manufactured standard components. Shouldn’t LOD350 be adequate to cover all required geometry as it includes; “interfaces with other building systems”? This requires further clarification from the BFLodS.

I could go on and on with these types of comments but it will bore everyone. We should be able to agree, many of the statements within the BFLodS require further clarification.

The Elephant in the Room: Fundamentally when it comes to exchanging “Design” Building Information Models it is about “Communication”. Models are a tool and are just one tool of a set of design communication platforms including; Specifications, Schedules, Imagery, Physical Models, and drawings. Design Models are very effective at; providing the big picture, enabling coordination and collaboration, extracting item quantities and material volumes/areas. However “design models” are poor at providing large-scale detail and conveying specific design intent 11. Drawings excel in this area. Look at any large scale detail from a design consultant drawing set, and it will provide a higher level of detail in an area, in comparison to the same region of the 3D design model.

“2D Supplementary Drawings

In current practice models are often supplemented with 2D information such as detail drawings. This Specification does not address this supplementation, but rather deals only with what is actually modeled in 3D and any non-graphic information associated with the modeled elements.” 2

How is it, the BIM Forum can say we have a different set of rules around models in comparison to traditional construction documentation? All the other documents are integral, but a model can’t be! It’s like throwing the baby out with the bathwater.

LOD, BIM, Drawings, Integration

Above: The Elephant in the room – Traditional Documentation - Surely we can create an integrated Model and Documentation approach.

BIM may be a way of reducing traditional drawing documentation; however, in the foreseeable future, it will not eliminate it. I recently attended an industry forum where Amanda Comunale, Director of Construction Piping Services, Victaulic, USA (one of the most BIM mature plumbing sub-contractors); stated and value the fitters on Site still have with piping spool drawings. Paper, maybe in a digital (PDF) form, still contents considerable value.

The manufacturing and aerospace industries are 10 to 15 years ahead of the construction industry. Drawings are still a significant part of their processes. Boeing now calls drawing generated from 3D solid models: “Associated Information Documents”13.

The UK Level of Definition recognizes that some traditional documentation and models will go hand in hand. Their framework still does require some work, however; it is an integrated and lean approach which is it easier to relate to. 


Above: Extract from the NBS – BIMToolkit
Uniclass2015 - Ss_20_05_65_40 In-situ concrete augered piling system

AIA G202TM 2013 –Guide: “Project elements may be adequately designed or specified in data such as specifications or non-model drawings, schedules or other data. The Model Element table [LOD Table] is primarily intended to define and coordinate the progressive development of Model data over the Project Milestones. As such, it is a somewhat limited subset of all the Project data and this should be discussed with all the Project Participants. For example an estimator may rely on the LOD of the Model Elements but may also have to look outside the Model to complete the estimate.”7

The bottom line – the future use of model sharing framework must be an integrated approach, encompassing drawings, schedules, specifications and other associated documentation.

Document Support: The BFLodS has been put together for the construction community. For users to have confidence in a document like this, it must be adequately supported. This can be achieved via a contact email address or a questions forum. The BFLodS has no contact information on the document itself, and I’m unable to see any location on a message board or forum on the BIMForum website. Over the past few weeks I have tried to contact the BIMForum via their email: communications@bimforum.org but had no reply. I believe it is important such a document should have some form of visible support. An online forum approach allows the entire community to learn and share knowledge, and ultimately improve the ongoing developing document. It could be as simple and easy to moderate as a Linked-in group. You would think a group with the name “Forum” in their title, would be trying to generate as much discussion as possible!

Pain point’s summary:  Big items to resolve for the BFLodS:
  •          Definition revision: The AIA - LOD definitions somehow have to replace the word “specific”. In limbo of this, the BFLodS must ensure LOD 300 can be achieved by design intent 11 elements, especially in the allowance for non-specified proprietary products.
  •          Including Infrastructure: Expanding the scope of the BFLodS to include infrastructure components.
  •          Better Introductory Notes: Expanding the documents introductory notes, thus removing the reliance on the AIA G202TM 2013 guide, and clarifying areas above identified as unclear; and provide a numbered paragraph section approach.
  •          Clear separation of Geometry and Data: There needs to be a clearer distinction between geometric data and non-geometric data, with the geometric data scope clearly defined in one documents and non-geometric data in a separate tabular format data file.
  •          Model integration into Documentation: The AIA LOD approach must allow an integrated approach and other documentation including schedules and specifications.

NATSPEC and LOD: It needs to be taken into account; my comments are coming from an Australian opinion. I understand the US and Australian construction industries are slightly different, but I believe the items I mentioned above should be relevant to both communities. To date, the Australian industry has not tried to create its own Level of Development/Detail/Information framework, with NATSPEC (Australian national not-for-profit organization which generates the National Building Specification) creating a document “BIM and LOD”8. It recommends the use of the BFLodS for model graphic information and “NATSPEC BIM object element matrix” for Model non-graphic information.


Above: Image extract from BIM and LOD8

With the introductory of the BFLodS 2015, including Attachment 1 (Model Development Specification), I’m not sure where NATSPEC will now stand. When NATSPEC were generating the “BIM and LOD”8 document, they failed to see how much non-geometric information is called up in the BFLodS which would contradict the NATSPEC BIM object element matrix. Now with the release of the 2015 version, the “NATSPEC BIM object element matrix” will directly compete with the BIM Forum LOD Specification - Attachment 1” – Model Development Specification (MDS) Attributes Table.

Collaborate ANZ:  In my last LOD article I wrote (Developing LOD, mid: 2013), the Australian and New Zealand group – Collaborate ANZ were looking at LODs for the ANZ industry. 24 months later, they released their findings: - Collaborate ANZ - CWG-001 - Level of Development (LOD) – May 2015 9 (Free download). It’s a bit of a disappointment. To summarize the 3-page document; it says: “Refer to the NATSPEC document - BIM and LOD”

How I currently use LODs within the available options:
Currently. for LODs we have two approaches within the industry:
  1.      AIA G202TM 2013 4
  2.           UK Level of Definition – part of NBS Toolkit 10

I believe the UK approach, may well be better,
  •          Its scope includes infrastructure,
  •          It’s integral with other documentation deliverables,
  •          And is just one part of a much larger UK BIM framework.

I am not well versed in the UK Level of definition but the challenges I currently see are:
  •          It is new to the industry and few in the ANZ region have a solid understanding of it.
  •          I’m unclear how much of the other UK BIM framework I should include maintaining the systems integrity.
  •      The UK BIM Framework is around achieving a Level 2 BIM goal. Level 2 BIM is a UK government deliverable and has little to no meaning outside the UK. 

As a result, when I need to get into LODs, as part of a BIM Execution Plan (BEP), I’m currently using the BIM Forum LOD Specification 2014 version, with all the data requirements removed. I specify my Data Requirement separately within the Project BEP. I only include LODs in BEP if I believe there is value in it, or recently when I inherited a BEP which already outlined LOD deliverables.

In its current proposed format, I can’t see myself adopting the BFLodS 2015 version. Within how I work I find the 2014 document simpler.

Close: Again, I take my hat off to the BIM Forum LOD group. For a non-profit organization, they have achieved a document no one else has. The UK initiative is government funded, with the Level of Definition approach starting from a clean slate with a more mature BIM industry. Thus, the UK approach "should" be better.  I have to praise the BFLodS have continued each year to update the document and support the industry. It is so easy for me to criticize what is incorrect with it, in comparison to what they did well. It is also not possible to tell how much private constructive feedback the group received, to ensure they are on the right path. All I can say is; well-done guys. 

I also congratulate any readers who have read to this point. I encourage further debate and comment on the above. Can I suggest; to keep the industry informed, please comment below; or if you want to respond to another website, place a link below.

Update November 2015, following final 2015 release: 

As of October 30th 2015 the BIMForum has released the update 2015 LOD specification, and it is available for download from the BIMForum Website. We have noted the following amendments which have been suggested in the above text:

  • The introduction section is further expanded to assist in clarification in some areas.
  • The document has not added authorized uses; however it now better identifies LOD 350's proposed use: (Section 1.3.3-1) “clash detection/avoidance, layout, etc.”
  • Paragraphs are now numbered. This will assist readers in referencing specific paragraphs from other documentation (just as I’m doing so here).
  • The LOD Definitions now contain a “BIMForum interpretation” (Section 2.3). These extra sections of text are very useful in clarifying the intent behind each LOD.

New questionable wording added:
(Section 1.1.1-2) At completion of the Schematic Design phase, for example, the model will include many elements at LOD 200, but will also include many at LOD 100, as well as some at LOD 300, and possibly even LOD 400.”  Why has this statement been added to the specification? It has been taken from the AIA G202 Guide (Reference 7). It diminishes the credibility in the level of coordination, constructability, and documentation required for each building element, in ensuring its integration into the overall building system. Claiming to have model element certainty of LOD 300 or LOD 400 in a schematic design model (RIBA Stage 2) is a false and pointless statement. Even if the designer knows the exact product to be specified; its exact final location is still in question, and thus it does not meet the LOD 300 requirement (as stated in the LOD Specification): “can be measured directly from the model without referring to non-modeled information such as notes or dimension call-outs.” I suspect the original authors may have intended on saying Design Development phase. I would still be questioning the LOD 400 statement. The sentence requires some realistic, normal projects scenario wording.

(Section 2.3.1) “BIMForum Interpretation: LOD 100 elements are not geometric representations.” I’m puzzled as to why it states this? The AIA G202TM clearly states they can be geometric representations, and the LOD Specification clearly has graphic images showing geometric representations for LOD 100 elements?

1 – BIM Forum Website - https://bimforum.org
5.1 – Wiktonary – definitions - https://en.wiktionary.org
11 – The American Institute of Architects - On DesignIntent -  By Eric Lum, Ph.D., AIA, CDT, LEED® AP
14 - Youtube – LOD Specification Update - Fall 2014 - James Bedrick and Jan Reinhardt


  1. Hi Brian,
    Love your blog and great article on the BIM LOD spec. I've downloaded the draft so now I need to find the time to read it!

    Will see if I can add any comment once read the draft.

    Many thanks,
    Jinoh Son

  2. Most relevant and insightful. You read my mind, in part. Now about "in the manor"...

  3. Hi Brian
    Good points for discussion
    On Point of caution
    I read the UK BIM Framework associated papers and used it in Project deliveries
    I would strongly disagree with your suggestions of it being a better reference.
    A Discussion could end up being a long-winded discussion, the UK BIM team does a very good promotion Job but have an actual look at the Details before reiterating their promotional spin.
    I have never been a fan of the AIA documents as they are far too broad.
    The BIM Forum LOD Specifications are a great recourse but need adjustment to the Australian Context.
    Another good and reliable resource is the USACE M3 Document is a clear and concise document far superior to what others have produced.
    In the end, Australia needs to create its adjusted version of documents, but so far we had disjointed discussion clubs with little output except ANZR
    I take my head off to the ANZR team that has produced a workable framework used internationally.
    I think we have some of the brightest BIM heads in the world right here
    What we are missing are Focus and Results

  4. Great post, most valuable and insightful. I will certainly come back to this and use as a resource.

  5. As the developer of the Object Element Matrix and a member of the BFLOD Committee, you need to be aware that the Object Element Matrix was used a "point of departure" for BFLOD V.2.

    Dianne Davis dedavis@jmt.com

    As such, the BFLOD group was able to take the structure and goals of the Object Element Matrix and add additional industry content through the other committees on the team.

    Therefore, in my mind, the Object Element Matrix fulfilled its role of bringing attention to the structure of objects, information requirements, LOD, and BIM Use Cases, and has been superseded by the BFLOD.


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