As-Built: LOD 500 under the Microscope

Overview:
Introduction:  The construction and BIM (Building Information Modelling) sector is now mature enough to place judgment on the effectiveness of the AIA G202TM LOD 500 (Level of Development) framework! LOD 500 is commonly becoming the final client BIM deliverable, and thus can be seen as the client’s most important Level Of Development within the Model Element Progression Specification.

LOD 500, AIA G202 2013, As-Built, Model Progression Specification


Article Scope: We will look in detail at the main aspects of specifying an As-Built BIModel and how to achieve the best outcome. This article will focus on the graphical data aspect of LOD 500, i.e. the 3D geometry. We will examine:
  • Current challenges with the AIA G202TM 2013 LOD 500 framework.
  • Alternative As-Built industry frameworks for BIModel deliverables.
  • Technical challenges and frameworks with creating measured As-Built BIModels.
  • Proposal to replace the LOD 500 framework and provide As-Built Certainty.
  • Establish Authorized Uses for As-Built BIModels within the proposed framework.
  • Best practice approach to obtaining a quality As-Built BIModel outcome.



Managing the process of recording and augmenting non-graphical data (i.e. information) from design to construction/commissioning is a separate topic and outside the scope of this article. Information is sometimes addressed using a separate Level of Information (LOI) or, data object element matrix framework. COBie is also used in this area.

Copyright:  The works held within the article are the copyright of the BIMFix Blog, its author Brian Renehan and the other credited references. It may not be copied in part or in whole without the written permission of the author.

LOD Background: Level of Detail (LoD) was first defined by Vicosoftware in 2005 and further defined Level Of Development (LOD) by the American institute of Architects  through the document: – AIA E202TM 2008. It was a groundbreaking BIM document when first published, and setup one of the first accepted BIM frameworks in the industry. AIA G202TM 2013 (which supersedes E202TM 2008) describes Level of Development as a way to: “identify the specific minimum content requirements and associated Authorized Uses for each Model Element at five progressively detailed levels of completeness.”1

LOD 500: The AIA G202TM 2013 definition: “Model Element Content Requirements. The Model Element is a field verified representation in terms of size, shape, location, quantity, and orientation.“1 Put simply: The LOD 500 field verified representation may be viewed as an “as‐built” Model. 2 LOD 500 is one of the commonly used BIM Industry standards for As-Built BIModels.

As-Built: There are several definitions of what As-Built means. Even within the AIA official documentation, the definition widely varies (e.g.: AIA Best Practices - BP 10.10.04 16 vs.  AIA - The Architect's Handbook of Professional Practice 23 - : i.e.: Red Ink mark-ups vs. field measured).   There are also multiple similar terms thrown around the industry in regard to As-Built's. They include: As-constructed, record drawings, as-measured drawings, as-is drawings, as designed record drawings (B101TM-2007) etc.  For the purpose of this article; we will use the term “As-Built”. It is derived from the principle behind the AIA Best Practices - BP 10.10.04 16 “As-Built Drawings”. We will enhance it, allowing for currently available document management systems (DMS) technologies and BIM processes.

Proposed Scope of As-Built for the purpose of this article:

A process managed by the Main Contractor.  The construction documentation is continually updated through construction to reflect all corresponded amendments. Promptly following element installation, it is field verified by visually comparing it against the documentation with recognizable deviations recorded, and the documentation updated accordingly.


Challenges around LOD 500:

Below are some key areas which contribute to uncertainty around LOD 500:
  •   It is non-sequential with no clear Level of Detail association.
  • Field verified is not explained within the AIA G202TM framework.
  • No representation grades of certainty are identified within LOD 500.
  •  No clear authorized uses.
  • Misuse for existing conditions modeling.



Non-sequential: LOD 500 is not a sequential or cumulative approach.  According to the accompanying “Guide 2” to G202TM
“For obvious reasons, a LOD 500 element is the last stage of representation for that Model Element….Model Elements do not necessarily need to be brought up to LOD 400 before going to LOD 500…..A Model Element representing paint might never be developed beyond LOD 100, but the owner may want the color field verified in certain areas.” 2

Thus the problem:  A Model Author is going to supply a client with a BIModel. They identify specific model elements as LOD 500.  Other than knowing the elements are field verified, the client has no idea what they’re getting. Before it was field verified, it may have been LOD 100, 200, 300, 350 or 400. The client just won’t know.


  • Thus: The Client will not be able to predict the model elements Level of Detail (LoD) until they receive it (as this is outside the scope of the LOD 500 definition). Level of Detail (LoD) is described as: “how much detail is included in the model element.6
  • And; will not be able to determine its former Level of Development even when they receive the model elements.  


Field Verified Uncertainty:  From AIA G202TM 1; LOD 500 definition:  “The Model Element is a field verified representation.1   So; what exactly is “Field verified”?  Users would assume the accompanying documentation would clarify it! AIA G202TM 1 and the accompanying “Guide” 2 contain no explanation for Field Verification. As mentioned above, if we look at other AIA documents (Ref: 16 & 23) which define as-built drawings and the verification process, these contradicting definitions only add to the uncertainty. So no one can read the G202TM 1 framework and confidently say an As-built field verified model element is ……. This will ultimately result in clients getting the absolute minimum interpretation for field verified model elements.

No Grades of As-Built: AIA G202TM 1 only provides one defined as-built field verified condition. Clients, however, may require various grades of as-built representation certainty. The certainty a client requires for components critical to their facility logistics, will be different to a trivial component which may remain unchanged throughout the facility lifecycle. Thus, an As-Built framework must enable grades of representation certainty. This may be as simple as an As-Built grade of:
  • field verified by visual inspection, or
  • field verified by a measured survey



LOD 500 Authorized Uses:  AIA G202TM 1 identifies Authorized Use as: “the permitted uses of Digital Data authorized in the Digital Data and/or Building Information Modeling protocols established pursuant to the terms of this Exhibit.” AIA G202TM 1 provides no specific Authorized Uses for LOD 500It is as if the Authors of AIA G202TM 1 found it too challenging in clearly communicating how LOD 500 can be used. AIA E202TM 2008 3 contained only one authorized use: “General Usage. The Model may be utilized for maintaining, altering, and adding to the Project, but only to the extent consistent with any licenses granted in the Agreement or in a separate licensing agreement.”

This has been removed from AIA G202TM 2013 1. In all the other LODs, the AIA clearly identify several Authorized Uses for each. In the 2013 iteration, they cannot identify one for LOD 500! In the “Guide” the AIA mentions “Potential Uses”, but there is no clear and concise “Authorized Uses”. Do the document authors really know how LOD 500 elements can be used?

LOD 500 Authorized Use Challenge:  The authorized use of a model element which was formally LOD 400, and then field verified to LOD 500, may be used completely differently from a model element which was formally LOD 100, and then field verified to LOD 500. Thus, it’s very questionable if LOD 500 elements can be allocated an Authorized Use?  Later in this article, I will suggest an approach which removes this ambiguity, and enables Authorised Uses to be defined for As-Built model elements.

Why Authorized Use is Important! Authorized use is the sole area in the G202TM 1 form, which enables the Model Element Author to restrict the scope of use for a model element. No vendor can provide a product which has a limitless scope.  So, authorized uses are included to clarify purpose, and removes overly restrictive broad sweeping disclaimers, which in an ever evolving technology environment may not address new unforeseen scopes.

LOD 500 Existing Conditions Modelling:  Recent BIM projects in Australia have had deliverables which included existing conditions surveyed model, being defined as a LOD 500 model within the brief. This may be due to the term “field verified” not being clearly defined within AIA G202TM 1, or users not understanding the difference between an As-Built BIModel and an Existing Conditions BIModel.  AIA G202™ 1 does not mention modeling “Existing Conditions” or “Surveying Model”.  The recently updated draft BIMForum “Level of Development Specification 2015” only identifies “existing conditions” under Grading (G1070.10) for Existing Surfaces. To be true to the AIA Level of Development approach; it identifies a model elements development. Modeling an existing conditions model element does not involve element progression. Thus, client modeling brief’s; for existing conditions should “NEVER” refer to Level Of Development, including LOD 500; and only refer to Level of Detail (LoD).  There are standards for Level of Detail (e.g. CityGML, BLOM3D & NAVTEQ) which can deal with modeling of existing conditions.

LOD 500 Existing conditions alternative: From recent discussions with local Surveyors; they were using the BIM Forum LOD Specification, but substituting Level Of Development, with Level of Detail. They commonly use LOD 200 to specify the surveyed model element LoD (Level of Detail). LOD 200 is used, as the surveyor does not have certainty on the internal make-up of the elements (e.g. wall layers and core material).  As the BIMForum LOD specification6 has clear and concise images, and the document is now becoming commonplace in the industry; this appears to be a reasonable approach, and will require a thorough explanation with-in the BEP (BIM Execution Plan).

Scan-to-BIM: Existing conditions modeling may include a “Scan-to-BIM” (Scan2BIM) approach:
“Scan-to-BIM”; the process of using Laser Scan Point Clouds to generate 3D CAD Geometry, which in-turn may be developed into an Existing Conditions BIModel. Currently, this is not a fully automated process.


LOD 500 Framework Alternatives:

UK – Level 2 BIM – As-Constructed Model: PAS 1192-2:2013, identifies the requirements to reach BIM Level 2, and the transfer of the Project information Model (PIM) into an Asset Information Model (AIM). This includes Level of Model Detail which is identified in the “Employer Information Requirements”. For a LOD 500 equivalent, it specifies Level of Detail 6 (as-constructed) to occur at Building Handover and Close out. The exact requirements for Level of Detail 6 can come from the “NBS Definitions Library” which is part of The BIM Toolkit.

From PAS 1192-2 - “As-Constructed:” defines the defect and deviation to the designed model occurring during construction.  The “as-constructed” model and its appended documentation are continually updated through re-measurement as construction progresses. This allows for deviation to be reviewed with respect to the following packages and making knowledgeable assessment of impact and resolution.” 8

NOTE: PAS 1192-2 also has a separate definition for “As-Built” which removes the re-measurement aspect of the definition.  Other PAS 1192-2 As-Constructed requirements:
“9.4.8 Clash avoidance/checking shall continue during the construction process as the models are updated with as-constructed information and checked against the construction tolerances specified in the contract.”8

“In addition, appropriate surveys such as point cloud or LiDAR shall be provided to verify the completeness of the as-constructed model.” 8

UK As-Constructed Effectiveness: The UK framework for achieving an As-Constructed model is still very new. Of the existing As-Built BIModel frameworks mentioned within this article, it is the most comprehensive, and it contains several processes which will enable a quality outcome. One confusing area is in the As-Constructed definition itself: “updated through re-measurement as construction progresses.”  At no point in the framework does it define or reference the scope of “re-measurement”; how is it achieved, what is the Level of Accuracy (LOA), and how is it Quality Assured? 

From my As-Built best practice recommendations below, many of the steps can be identified from the UK approach.

US Army Corps of Engineers – Minimum Modeling Matrix (M3) Version: 1.3 (Sep-19-2014) 24  M3 LOD  (Level of Development) framework utilizes similar definitions to the AIA G202TM 2013 1. It uses LOD 100, 200 & 300, but, in addition, has a grade classification suffix attribute when specifying design model elements for construction documents:

A             3D + Facility Data
B             2D + Facility Data
C             2D Only (Drafting, linework, text, and or part of an assembly)

The framework does not include LOD 400 or LOD500.  For As-built information, it has a sequential approach.  The Level of Development specified for Design Model remains unchanged for the As-Built, however, the As-Built grade it progresses to is added as a suffix.  As-Built Grades:



+Original Grade (A, B, or C) adjusted for contract changes and field conditions.” or,
- “Not included in or tied to the model (however is still required in the deliverable)”

LOD Element Matrix, BIM, Model Progression Specification

Above image – Extract from US Army Corps of Engineers – Minimum Modelling Matrix (M3) – Scope-LOD-Grade 24

3M Effectiveness: This system has two benefits over an AIA G202TM - LOD500 specification:
  • It is a sequential approach, and thus in understanding the Design Model element Level Of Development, we understand what the As-Built Level of Detail will look like.
  • The As-Built BIModel will be “Lean” and not contain unwieldy geometry generated from LOD 350 and LOD 400 model elements. This makes it easier for the Facility Manager and other future model users to manage and use.


The 3M Grade explanations appear to lack clarity, and is an area we suggest requires improvement. The 3M framework has been developed by the Client with their end use in mind.  The premise behind the M3 framework has potential and will be a key aspect of the proposed below As-Built specification framework.


Measured As-Built Processes:

Laser Scanning:  One current approach to “Field verifying” is engaging a surveyor to laser scan and area and generate a point cloud. This laser scan is then compared to the geometry of the “As-planned” BIModel in an analysis exercise referred to as Scan-vs-BIM (Not to be confused with Scan-to-BIM).

Scan-vs-BIM: A process of taking an “As-planned BIModel”, and comparing it against a “Surveyed Point Cloud”; identifying missing components, component deviations, and from this analysis updating the “As-Planned BIModel” to become an “As-Built BIModel”. In an ideal world, this would be an automated process accurate within reportable deviations, and maintain the BIM Data before processing occurred. Unfortunately there is currently no commercial software solution available capable of achieving this. Thus to date; the comparison is carried out manually by visual inspections, in a hit and miss approach.

Scan-vs-BIM Challenges: There are multiple challenges with this technology solution:
  • BIM authoring applications are designed to model orthogonally – built components are often anything but. Elements are: off plumb, warped, deflect between spans, etc.
  • The future designers of as-constructed models will prefer the BIModel to be orthogonal and plumb. Off plumb BIModels could potentially reduce functionality within the BIM authoring applications (e.g. Structural analysis, Sustainability analysis, Systems connections, dimensioning and area take-off etc.).
  • The main current BIM authoring applications (Such as ArchiCAD, Revit & Tekla) are currently not capable of carrying out point cloud verses geometry deviation analysis.
  • Point cloud deviation analysis will require 3rd party middleware software to manually interpret and investigate the deviations. The geometry will then be manually updated in the separate BIM Authoring application.
  • When laser scanners do not have a direct line of sight, it results in survey data voids (shadows) and makes it difficult to interpret the deviation analysis results.
  • The point cloud will contain the highest Level of Detail, which will not be required in the BIModel.
  • The BIModel will contain a large amount of data imbedded in it, and so model elements cannot be deleted and re-drawn; they can only be modified.
Point Cloud Scan, BIM, Model
Above: Deviation analyzes comparing a point cloud to a BIModel.  Extract from Assessment of Quality of As-is Building Information Models Generated from Point Clouds Using Deviation Analysis – 2011. 11

The above limitations result in a time-consuming process, with no trackable Quality Control outcome.

Traditional Surveying Methods: Total Stations is an electronic theodolite integrated with an electronic distance meter to read slope and distances from the instrument to a particular point. This is the technology with is commonly used to generate traditional CAD surveys. The method is still very relevant and often essential. It is not uncommon to have a survey outcome, which has been generated by both Laser Scanners and Total Stations.  As Total Station surveys contain only specific survey points, it will mean the Level Of Accuracy (LOA) between the survey and the model can be lowered. This does not mean the surveying method or BIModel outcome is of a higher accuracy.

As-Built Measured Tolerance Deviations:  If we are to talk about tolerances for As-Builts, we would be trying to achieve values specified at the 92 percent confidence level of elements, within ± of 50mm. These were figures which come from a paper on a historic building (11th Century Fort)10 utilizing Scan to BIM, but without further research into modern buildings using Digital Layout from Building Information Models; we are unable to provide more relevant figures. Typically these figures should be given at the 95 percent confidence level of elements.  This technology is also rapidly developing, and it is possible in the near future, BIM applications may be better able to automatically compare and update the BIModel.

LOA – Level Of Accuracy:  Is a specified acceptable tolerance band deviation between the item being measured and the reported measurement. Typically given in millimeters in a +/- (plus or minus) format. E.g. Between +/- 5mm and +/- 10mm.

LOA, LOD, BIM, Level of Accuracy
Above extract from: RICS professional guidance, global measured surveys of land, buildings and utilities 3rd edition. Page 13 - Survey detail accuracy band table - December 2014.

This approach can be used for specifying the LOA between the physical building and the Survey measured output, or between the survey output and the processed As-Built BIModel. LOA should not be confused with construction tolerances; which are the agreed acceptable deviations between the construction documentation/BIModel and the As-Built Survey measured output.

USIBD Level of Accuracy (LOA) Specification – 2014:  Released last year, the US institute of Building Documentation produced an LOA framework. It can be downloaded from the USIBD Website. This framework provides a clear process in defining LOA deviations between the as-measured survey and As-Built BIModel.

Measured As-Builts Challenges:  Outdated data is an ongoing problem for measured As-Built model elements. It takes very little remedial work for aspects of a measured as-built to be incorrect, without a rigorous model maintenance regime in place. Building owners to date; have not carried the relevant indemnity insurance cover for BIModel data accuracy. When it comes to planned building alterations, the building owner will happily hand over the BIModel, with a disclaimer identifying they are not responsible or liable for any of the data. The client will advise; data must be rigorously checked via re-measurement prior to use. Thus, it is questionable for a building owner to ask for measured as-build model elements, without a predetermined authorized use.


Author’s Alternative approach to LOD 500:

Level of Development graphical As-Built: is a proposed cumulative grade specification to identify the specific minimum requirements for verification:
  • Visual As-Built (VAB) model elements, and
  • Measured As-Built (MAB) model elements.


These have been identified as the two model element As-built levels which will meet client requirements and are loosely in line with the AIA BP 10.10.04 document. 16
The approach builds on the existing AIA G202TM Levels of Development for model elements used in the construction documentation process. The Client will specify the following two criteria's:

·         Level Of Development for the model element to achieve by construction completion (e.g. LOD 300, LOD 350 or LOD 400),
·         As-built element grade verification using a suffix attribute: (VAB – Visual As-Built, or MAB – Measured As-Built).

Potential model element examples:
LOD 350 – VAB                   i.e. Level of development 350 – Visually verified
LOD 300 – MAB                  i.e. Level of development 300 - Measured verified

Leaving the suffix blank, will identify the model element does not require an As-Built grade. The philosophy of this system is similar to the M3; US Army Corps of Engineers framework.

Graphical As-Built Grade Framework:


Visual As-Built (VAB) model element:

Model Element Content Requirements: Model element and its relevant appended documentation are continually updated through construction to reflect all corresponded amendments. Promptly following element installation, it is field verified by visually comparing it against the modelled element with recognisable deviations recorded, and the model element updated.

The Model Element is graphically represented in the model and is correct in terms of quantity and space allocation, relative to its environment in terms of size, shape, location and orientation.

Visual As-Built (VAB) - Authorised Uses:


As-Built Drawings: The model element may be used to generate “as-built drawings” and “record drawings” as per the AIA Best Practices – BP 10.10.04. 16

Facility HSE Management: The model may be used to generate Health Safety and Environment (HSE) documentation and animations to meet the facilities HSE requirements and logistics with the exclusion of operations requiring high dimensional accuracy within the element’s environment.  5

Space Planning and Management: The model may be used to manage space occupancy assignments to departments and employees, plan for future space needs, and report on space utilization. 5

Disaster Management: The model may be used for disaster planning and management, including disaster simulations and the supply of applicable data to authorities for emergency and fire response, flooding and storm management.

Performance Monitoring: The model may be used to monitor and manage Energy Use, Lighting Levels, Thermal efficiencies and other building performance metrics. 5

Asset Management: The model element may be linked to a facilities asset management information data base (CMMS / CAFM system or similar) to graphically navigate, inspect, interrogate, track and report on the facility systems and equipment, excluding inspection analysis requiring high dimensional accuracy. 5

Asset Procurement: The model element may be used to provide a platform for procurement of Assets. This may include valuation, negotiations, tendering, purchasing, stock-take, and asset disposal excluding tenancies requiring NLA (Net Lettable Area) dimensional accuracy. 5

Facility Future Alterations:  The model element may provide designers and professional trades, as-built information to facilitate early design planning and costings for future facility alterations.  A detailed measured survey, with relevant model element updates, are to occur before the main design and documentation works commence.


Measured As-Built (MAB) Model Element:

Model Element Content Requirements: Model elements reaching the VAB grade are checked against an As-Installed digital survey. Model elements are updated to match the survey with agreed representation accuracy. This process will engage the USIBD Level of Accuracy (LOA) Specification with the Client specifying the Model element LOA representation.
The Model element is graphically represented in the model and is correct in terms of quantity, space allocation, size, shape, location and orientation within the specified LOA representation.

Measured As-Built (MAB) Authorized Use:


Measured Drawings: The model element may be used to generate “measured drawings” as per the AIA Best Practices – BP 10.10.04. 16 The measured drawings will contain the following information: Survey date/s, Surveyor name and contact details and a completed USIDB Document C220TM.

Facility HSE Management: The model may be used to generate Health Safety and Environment (HSE) documentation and animations to meet the facilities HSE requirements and logistics, including operations requiring high dimensional accuracy within the element’s environment.

Space Planning and Management: The model may be used to manage space occupancy assignments to departments and employees, plan for future space needs, and report on space utilization. 5

Asset Management: The model element may be linked to a facilities asset management information data base (CMMS / CAFM system or similar) to graphically navigate, inspect, interrogate, track and report on the facility systems or equipment, including inspection analysis requiring high dimensional accuracy. 5

Asset Procurement: The model element may be used to provide a platform for procurement of Assets. This may include valuation, negotiations, tendering, purchasing, leasing, long-term hiring, stock-take, and asset disposal, including accurate tenancies NLA’s  (Net Lettable Areas). 5

Facility Future Alterations:  The model element may provide designers and professional trades as-built information to facilitate early design planning and costings for future facility alterations.  A visual inspection along with check dimensions to occur before main design and documentation works commence. Model element discrepancies will be updated accordingly.


Authorized Uses: Authorized Uses must be agreed during novation with the Model Element Author. Model Element Authors cannot take responsibilities for model elements used in an unforeseen or unpredicted way. Parties may believe the model element is not fit for some of the above Authorized Uses, and thus they should be removed or amended within the agreement. There is potentially an infinite amount of Authorized Use definitions. The client and model element author should give this area due consideration and expand, or add to the above definitions to ensure all parties are satisfied.

Graphical As-Built Prerequisites: Model elements may only be capable of achieving an as-built status; if it was directly used in the construction working documentation. Thus, graphical elements of LOD 100 and LOD 200 will not have reached an appropriate development level to be used for construction and, must be excluded from an as-built grade.

Graphical As-Built & Level of Detail:  Clients must understand how model elements Level of Detail (LoD) may affect software performance and future uses of the BIModel. Clients may want model elements reaching LOD 350 and LOD 400 to be simplified to a Level of Detail similar to LOD 300’s graphic appearance, as per the BIMForum LOD Specification element graphic images.  In this case, the Main Contractor will supply the model elements in both the higher and simplified requested Level of Detail. Refer to reference 25: Penn State - Planning Guide for Facility Owners for more guidance in this area.

Measured As-Built Surveys: Survey outputs used to validate MAB (Measured As-Builts) model elements are to be supplied to the client along with the As-Built BIModel.

Graphical As-Built Example Use:  May engage a model element table in a similar approach as to per AIA® Document G202TM 1.  Below is a fictional example completed Model element table using the BIMForum LOD Specification 2015 draft template. It shows the LOD (Level of Development) and MEA requirements for Tender stage, Construction stage and at building handover including some custom notes.  As with LOD, As-Built Grades will vary for different elements. 

Above:  A Possible example of the Model Element Table, with the As-Built Grade information identified.

Note: from above example table:
  • Measured As-Built grade is likely to occur in specific elements: (e.g. only tenancy perimeter walls)
  • “NM” indicates Not Modeled.
  • Some items which go through a shop drawing process, depending on the client requirements may not need to be brought to an As-Built status. E.g. Secondary steel.




Ideal As-Built Modelling Strategy:
One thing that everyone can agree on: producing an As-Built BIModel, even As-Built drawings are not an exact science. There may be a time in the future; when there is a technology solution, but currently we need to rely on: human participation, processes, and technologies. It also is becoming evident, if clients just request outcomes; the result is unlikely to reach its potential. Requesting key requirements along the development process, specific outcomes and model authorized uses will have the best result. In the future, with more powerful technology solutions, this may not be necessary.



Best practice to achieve a practical As-Built BIModel outcome:  Below is a suggested best practice approach, which is applicable for medium to large size commercial projects. It should be adjusted for complex or simple projects to meet the client needs. The process will provide the client with a quality As-Built graphical record set of documentation which can be leveraged for future uses.

  1. All project participants to engage in a model-centric collaboration and coordination approach (i.e. paper and 2D processes take second place).
  2. All design models, construction models and shop drawing reviews to pass model clash detection before fabrication/construction approval.  Clash detection shall continue during the construction process as the model elements are updated.
  3. Identified building components to be set-out using digital layout technologies (e.g.: Total Robotic Station). These components are identified in the Client EIR (Client Information Requirements). Examples may include: Substructure, Superstructure, In-ground services, Walls and partitions, doors and openings, Major bracket fixing points for mounted equipment, major pipes, cable trays and ducts. Below reference 15; contains valuable information in a considered approach to capturing as-built geometry information.
  4. Digital laid out (set-out) element deviations are logged and the as-planned model element updated.
  5. At identified construction milestones, Laser scanning point clouds will capture key components such as Footings / foundations, in-ground services, slabs on grade, superstructure, post-tensioning reinforcing, services first fix and building close out.
  6. The point clouds will be purged to remove temporary construction activities captured, and the result visually compared against the model elements to check the model completeness.
  7. Visual onsite inspections, including digital photographs to occur monthly. This will include comparing recently completed works against the model element with deviations updated in the BIModel. This will especially focus on areas not covered by the point cloud capture process.
  8. All model elements in the As-Built BIModel to contain data attributes, identifying:
    • final construction Level of Development,
    • Level of Development graphical As-Built grade,
    • Level of Accuracy (if applicable),
    • name of verifier and date verified.
  9. The As-Built BIModel, laser scan point clouds, and digital photographs are to be supplied to the client at the building handover stage.  Files are to use the current version of their native file format, and supplied in an open neutral format, such as IFC (BIModel format) and an E57 file (point cloud) format. Digital photographs are to be cataloged, including; date taken, floor and space/room location details.



As-Built Package:  It is still standard practice for an As-Built BIModel to be handed over along with As-Built 2D PDF Drawings and Documentation which have been directly generated from the As-Built BIModel.

Cost Impact: If the above As-Built requirements are identified up front in the contract, the result will impose no additional costs on the client. Assuming the Design team and Contractor actively engage in the process, they should incur cost savings, deliver the project with greater efficiency, greater site safety, reduce construction waste and achieve an outcome closer to the Design Intent. Failure to clearly identify As-Built requirements in the contract “may” result in variations and additional costs to the client.


LOD 500 Conclusion:

LOD 500 appears a poor approach in specifying As-Built graphical data for BIModel elements. It lacks clarity, lacks authorised uses, and will cause project confusion and poor outcomes when engaged. Approaches similar to the above-identified (Graphical As-Built grade) will enable clarity and provide the Client with the As-Built certainty they desire.



Requiring measured As-Builts may be a pointless exercise unless the Client is directly engaging the BIModel elements on a dimensional level. Clients unwilling to maintain and update measured as-built BIModel geometry must question this deliverable.

Fundamental BIModel As-Built Framework Requirements:

  • Identify model elements final Level Of Development reached.
  • Allow various grades of field verification grades. Such as Visual or Measured.
  • Measured field verification to specify the Model Element Level Of Accuracy
  • Identify model element’s As-Built Authorized Uses.
  • Identify the name of the person who carried out the verification and the date.
  • The above data to be embedded into Attributes of the Model Elements.
  • Contain other sources of As-Built references, such as As-Built: point clouds, photos and Drawings/Documentation.



Close: The AIA should retire LOD 500, and replace it with a clear and concise As-Built grade specification which provides certainty and value to BIModel users. I propose the above approach “Level of Development graphical As-Built” replace the LOD 500 section of the AIA G202TM framework.


Open Discussion:

As always, I encourage open debate on the above conclusions, outcomes and proposed processes. Without debate, we never get real progress. I am happy for individuals to use the above content with prior permission from the Author; Brian Renehan. Use of some of the definitions above will also require appropriate licences from BIMExcellence (Reference 5).

I would like to thank Bilal Succar for the use of the BIMExcellence definitions, and for providing comments on an early draft of this article.


References:

3 –AIA® Document E202TM-2008 – Building Modeling Information Protocol Exhibit – withdrawn and replaced by AIA® Document G202TM – 2013 Building Modeling Inform2ation Protocol Form 1
4 – BIMExcellance – BIM Dictionary – Change Agents AEC Pty Ltd - Bilal Succar
5 - BIM Uses and Authorized uses. The definitions for Authorized uses have been partly derived from the “BIMExcellence” website - Change Agents AEC Pty Ltd (CA) based on the academic research of Dr Bilal Succar. These include: Asset Maintenance, Asset Procurement & Space management.
7 - BS 1192- 1 - 2007 Collaborative production of architectural, engineering and construction information –Code of practice -
8 – PAS 1192-2 – 2013 Specification for information management for the capital/delivery phase of construction projects using building information modeling
9 – Designing Building Wiki – Great source of detail on the UK BIM approach and definition.
12 Comparison of photogrammetric point clouds with BIM building Elements for construction progress monitoring - S. Tuttas , A. Braun, A. Borrmann, U. Stilla - September 2014, Zurich, Switzerland
Bosche, Frederic Nicolas; Ahmed, Mahmoud; Turkan, Yelda; Haas, Carl; Haas, Ralph. 2015
14 Tracking MEP installation works.  Frédéric Bosché, Yelda Turkan, Carl Haas, Tiziana Chiamone, Giorgio Vassena, Angelo Ciribini - 2013
16 AIA Best Practices - BP 10.10.04 Terminology: As-Built Drawings, Record Drawings, Measured Drawings. June 2007.
17 AIA Best Practices - BP  10.10.05 Certifying As-Built or Record Drawings. February 2007
19 The Penguin – Dictionary for Building – James H.Maclean & John S. Scott. First published in 1964, Reprinted in 1995
23  AIA - The Architect's Handbook of Professional Practice.  – Fourteenth Edition - By Joseph A. Demkin, American Institute of Architects - 2008
24 US Army Corps of Engineers – Minimum Modelling Matrix (M3) – Scope-LOD-Grade - USACE_M3_v1.3_20140919.xlsx
25- BIM – Planning Guide for Facility Owners. A Building SmartTM alliance project. Version 2.0 June 2013. BIM.PSU.EDU. Penn Stage - Minimum As-Built/Record Model Deliverable

Former article comments on LOD 500 or As-Built BIModels:
26 – BIMFix Blog - Developing LOD (Level of Development) - LOD 500 - July 09, 2013 – Brian Renehan
27 – Practical BIM – “LOD, are we there yet” - LOD 500 - confused? - 25 August 2013 - Antony McPhee 
28 – The case for BIM - ‘AS BUILT’ MODELS? I THINK NOT… - Feb – 2013 – Casey Rutland

2 comments:

  1. Congratulations on a great article - thorough, clearly expressed, well-argued and with constructive proposals to address the issues identified - a valuable contribution to advancing the informed use of BIM.

    ReplyDelete
  2. Great article Brian, definitely a lot of food for thought and see it being immediately applicable to projects we are currently developing.

    ReplyDelete

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