Clash detection – Design Stage – All projects

Clash detection is one item which many industry people lump together with BIM deliverables. But is it something which can be part of all typical projects at design stage irrelevant of being a BIM deliverable?

The below article is based on the current workflow configuration of the authoring software Autodesk® Revit® and clash analysis software Autodesk® Navisworks® (2013 products). The article is however written in a vendor neutral format. In directly applying any below mythologies to clash detection software, please contact your preferred software vendor to decide if their software solution is capable of the below approaches.

I have only come across a handful of standard projects (non-BIM  deliverable projects) which included digital virtual clash detection.  Generally it is only employed if it is a client or contractor deliverable. Within design contracts, it is a requirement of building design consultants to “coordinate and integrate” their designs with other consultants (refer to below contractual clauses **). Many believe clash detection software tools are beyond the coordination requirements and resource intensive. This is however a misconception. When the philosophy and approach is well planned, the outcomes can be tailored to meet the desired needs.

During Design Development, Contract Documentation and Contract Admin; the Architectural team spend considerable time coordinating the design consultants and answering construction queries. Large projects often contain a dedicated Architectural role to manage and coordinate the consultant’s work. Building coordination comes in many forms, and can depend on the building type and aspects precious to the design team. Architects are well aware, poor coordination leads to poor building outcomes. Architects are typically the “Lead Consultant”, thus fingers inevitably are pointed their way when things go wrong.

Traditional means of coordination is far from scientific. Visual checks and overlays are carried out at periodic times. Checks focus on the ceiling voids and end up being hit and miss. Risers, under structure services, internal storm water pipe reticulation and component height clearances, are often missed. I once worked with a senior coordinator whom I had great respect for. He would describe coordination as the process of, working through the services/structure from below the foundations, up the building to the plant room; then working the coordinated back down the building to the foundations. For manual coordination this was very thorough, but still leaves a large scope for error.

Coordination communications traditionally consist of the manual generation of screen captured images, or marked-up prints. These are then issued to consultants as items are found. On receipt of new drawings/models the previous conflict resolution are navigated to, and checked. The new drawings/models also need a complete re-checked to identify new issues. You can see, this quickly becomes very time consuming and monotonous. Unfortunately design teams just don’t have time to do the desired level of coordination. A 3D model authoring software environment does help; but again, I have yet to come across a team whom comprehensively overlays and visually checks each consultants model on receipt of new models. You still have the issues of is being a “Visual” (hit and miss) and there is no tracking. So surely, if the design consultants are generating 3D models; we can use them to digitally manage the process.

If we are to use a managed virtual digital coordination and allocate the same resourcing time, we should be able to get a better outcome!

Clash detection software is known for returning to mush information/data, when the designer only wants to focus on key items. A strategic planned approach should be adopted.

Key areas to consider:
  • Prioritise building components/assemblies by their function, movability and risk
  • Use reliable meta data to identify specific systems, assemblies and parts
  • Use Object-oriented rules
  • Predefined strategic clash tests and processes
  • Quickly identify, consolidate, mark-up and report/communicate issues
  • Track issues and resolution outcomes

Prioritise building components/assemblies by their function, movability and risk:
We will create a scale from 1 to 4 (1 being the highest priority and 4 the lowest). List all building components, and identify priority to each of them. The philosophy is generalised in the below table using an element importance order;

Element Importance Order
Priority Definition:
Potential examples:
Elements are virtually immovable.
Primary structure, large duct runs & gravity fed services
Elements can be moved but will require a high degree of difficulty and, or coordination.
Services primary equipment
Non-Gravity fed services > 100mm Ø, secondary structure & penetrations
Elements can be moved with little difficulty.
Pipes < 100mm Ø, fixtures and fittings
Elements has the lowest priority and will be moved without question if found clashing.
Suspended ceiling hangers, pipes < 50mm Ø, linings, dressings, finishes

Element priority is defined by the lead consultant. They can decide what is precious for the preferred outcome. Take into account, some traditional coordination methods will continue along anyway despite formalised clash detection (e.g. fittings in a reflected ceiling plan).

Below is a sample “possible” priority table for Hydraulics:

Hydraulic Services:
Clash Priority 1-4
Piping systems – Gravity-fed services ≥ 100mm Ø (pipes, fittings, & insulations)
Piping systems – Non Gravity-fed services ≥ 100mm Ø (pipes, fittings, accessories & insulations)
Piping systems – Gravity-fed services < 100mm Ø & ≥ 55mm Ø (pipes, fittings, accessories & insulations)
Piping systems – Non Gravity-fed services < 100mm Ø & ≥ 55mm Ø (pipes, fittings, accessories & insulations)
Piping systems – Gravity-fed services < 55mm Ø (pipes, fittings, accessories & insulations)
Piping systems – Non-Gravity fed services < 55mm Ø (pipes, fittings, accessories & insulations)
Plumbing Fixtures
Plumbing Equipment

During design stage clash detection; the decision may be made to only test items with a priority 1 and 2. The method clearly identifies what needs to be resolved first.

Reliable meta data to identify specific systems, assemblies and parts:
I have come across many professionals whom believe clash detection is not BIM; your just clashing 3D geometry. Clash detection is a prime example of “rubbish in; rubbish out”. To carry out “effective and efficient” clash detection; quality and reliable data is needed from the BIM. When carrying out clash detection, I request the models to have the following element data from the consultants:

Authoring identification
Who created the element? Many consultants model pipes (can be with the file name)
Element Classification
Specific identification of category
Pipe/Fittings Diameter
Pipe and pipe fitting sizes
Insulated pipe identification
Ability to identify pipes with insulation
Duct Size
e.g. identify of Duct sizes e.g. ≥750mm in size
Insulated duct identification
Ability to identify ducts with insulation
Structural material type
Identify; steel, precast, concrete etc…
Service system type
Distinguish between, supply, return, cold, hot, gravity-fed & non gravity-fed pipe systems
Service System name
Identify group of components creating the unique system. i.e. Supply are for level 2.
Element Room Data
Identify the room/space name and number equipment is within. This assists in reporting the location of clashes.

None of the above is onerous, and most competent firms (claiming BIM knowledge) are producing BIM’s with this Meta data all ready. Much of the above is automated by the authoring applications if used correctly.

Object-oriented rules;
There are very few true construction “Object-oriented” clash detection software’s available (the computer gaming industry has used it for several years now).
Object-oriented is where classified objects have specific associated rules. E.g. in many BIM compatible authoring applications,
       Walls: can have penetrations, define room extents and cannot be horizontal,
      Furniture: cannot have penetrations, can be allotted to a room and are always vertical

Within Clash Detection, rules can remove irrelevant clashes and create a pseudo object-oriented environment. Some examples:
  • Ignore clashes of parts, if a previous clash is found within the parent assembly: i.e. A beam is clashing with a door assembly (both leaf and frame geometry), only report one clash
  • Ignore clashes between parts, if they are within the same unique system: i.e. In a service system, if due to poor modelling a duct branch intersects with the parent duct, ignore it
  • Ignore clashes if an element has a specified value: i.e. ignore duct clashes, if the duct is a flexi-duct.
  • Ignore parts which have an external wrapping: i.e. ducts and pipes are often wrapped in insulation. If it is modelled with the insulation, ignore the wrapped component
  • Ignore parts if a specific numerical parameter value is less than a specified number: i.e. Ignore pipes less than 90mm diameter in size

I do look forward to the day when clash detection is truly object-oriented.
E.g. a pipe is clashing with a floor slab:
the algorithm determines the slab is horizontal and the pipe vertical. A role states a slab core drill penetration size up to 150mm is acceptable; thus the clash is not reported.
However if the pipe run is parallel to the slab the clash is reported.

Predefined strategic clash tests and processes;
Comprehensive clash test templates are prepared and documented, allowing all team members to clearly understand outcomes. Sample clash test:

Structural Elements
Hydraulic Elements
Rules – Ignore items in:
Floor Slab >= 350mm Thickness
Framing & trusses
Mechanical Equipment
Gravity-fed piping systems <= 100mm Ø
Same File
Same Assembly object
Previously found pair of assembly objects
have Insulation Defined

Explanation of above test:
      Name – Clash test name. Identifies discipline, priority of component and clash tolerance
      Clash Type – is it a clearance test or physical intersection
      Rules – Rules to remove false positives and irrelevant objects.

Quickly identify, consolidate, mark-up and communicate issues:
Following running the test and identification of clashes; they are to be quickly consolidated into specific issues (groups). E.g. a run of two parallel pipes clash a single perpendicular duct. Most software applications will report two separate clashes. The consolidation of this into one reportable item is somewhat manual, but it must be a quick and easy process.

Following clash consolidation; an ideal viewpoint is captured and the clash area marked up.
The report needs to be concise. It should include:

  • Marked up Image of clash, clearly showing context and adjacencies
  • ID number and name of conflicting components
  • Location of clash – Level, Grid coordinates and room number where possible
  • Identify disciplines involved and identify party to lead the issue resolution
  • Identify priority of components involved
  • General Comments

Track issues and resolution:
All BIM authoring software applications generate a unique identification (ID)  number for each component. When components are modified, the ID number should remain unchanged. Clash detection applications use and track this ID number; thus, when models are updated, the application reports the updated clash status.

Another BIM myth is 100% of all clashes will be resolved. This is just not necessary at design stage. The point of the tool is to test the design and ensure proof of concept. Thus; if systems clash and there is ample adjacent free space to easily relocate then (and will not affect design requirement), the clash is approved. If there is no quick/simple fix, then the clash is to be addressed.
Bear in mind we are in the design stage.  The approach at construction stage is slightly different. During the construction, the subcontractors will:

  • convert all the generic equipment to manufactured components
  • tweak solutions to better fit their approach
  • value manage
  • apply construction and OH&S tolerances

Thus, the design intent model and constructed building are two different things. Like everything a balanced approach is always best. Clash detection tools are quite simple to use. Strategically planning the approach is another thing. When implemented at design stage correctly, it will greatly improve all outcomes. 

The next item is; how do you get buy-in from the design team? Again remember, we are just using a tool to more efficiently find and track what is already occurring. Below is a part sample “Request for Tender” (These will vary, and thus please refer to your project specific contract). The sample below also specifies: Finalise design with full coordination with all other design team members”. Monthly reports are commonly now part of projects. The clash detection summary report (including resolution status) can be an attached appendix. Clients love to see these and are well able to act when adequate design resolution is perceived to be not occurring. From a legal point; if a design issue is raised, but not addressed, and this in-turn leads to costs incurred by the client; the client may have the right to pursue the negligent party.

When it comes to BIM deliverables, clash detection is one of the easiest a client can specify. All the above methods are 100% scalable, so when the client does require a “high level” Clash Detection deliverable at design stage; it has minimum impact on resourcing, workflows and could potentially be very profitable for the lead consultant. The above text is just scraping the surface in regard to “strategic clash detection”. But is should provide ample information to start your investigation and seek potentially further help.


References: (all direct quotes are in italics)
Client and Architect Agreement – AN10.01.131 – Australian Institute of Architects - 2009
Clause A. Core Architectural Services: (i.e. required professional services)
-Coordinate and integrate the work of other specialist consultants
- Coordinate the construction services provided by other specialist consultants
The architect must.
d.  coordinate and integrate the work of all specialist consultants engaged for the project;

Below extract from a "Sample Part" design consultants Request for Tender I have come across;
Request for Tender (RFT): Hydraulic: (N.B. please refer to your project specific contract documentation)

General Services
 Allow for attendance and participation at fortnightly consultant coordination meetings during the schematic design, design development and documentation phases of the project. During peak periods of the project these meetings may be weekly.

Design Development
 Expand and develop schematic up to Design Development status. Prepare design development drawings in CAD format. Allow for coordination with the Consultant team during the design development process.
Finalise design with full coordination with all other design team members. Allow for peer review and cross referencing. Provide evidence of this taking place if requested by the Project Manager.

Full Documentation and Tender
Provide full, complete, coordinated set of design documentation relevant to the consultant’s discipline. 

COBie Challenge 2013 Results

Every so often, the buildingSMART alliance (the body which manages COBie - Construction Operations Building Information Exchange), invites BIM (Building Information Modelling) software vendors to take part in a test project to determine how well their applications offer a robust transfer to COBie data. So did they stack up?

The Challenge: This covers several forms of software types which included:
  • Software for Planning (Programming)
  • Software for Design (Model Authoring)
  • Software for Construction (BIM Field & Construction Management)
  • Software for Facility Management (Asset Management & Facility Management)

A full list of details can be found here:
The 2013 tests carried out in January; were using the COBie 2.4 format. Each Vendor along with buildingSMART had developed a COBie “Toolkit” (plugin application) to streamline the export and comply with the COBie XML table format (eg MS Excel). Vendors were expected to have zero formatting errors, therefore, any row containing a formatting error was given a one-minute penalty (i.e. the time it would take to fix it manually).
For this Article, we will just look at "Software for Design". Any below text in "Italics" are direct exerts from the builidngSMART website.

Software for Design: “COBie Challenge events starting in 2013 checked software to determine
(1) if the format of the COBie file is correct, and
(2) if the content of the COBie file matches the content of the standard drawings.”

Below is the conclusion section of the results. A full detailed report is available on the buildingSMART Website (links below). Please read the full reports to truly understand the results.  

AutoDesk – Revit 2013

"Format Compliance: This company successfully completed the construction COBie challenge by producing the handover COBie file of the Medical Clinic model. Based on the quality control report, there was only one small error that incurred a one-minute penalty with respect to the internal consistency of the output format that would require an estimated 5 minutes to correct.

Content Quality: The vendor did not produce the 100% of the sample data; however the produced data was very accurate to expected sample data found on the project drawings. Based on the content quality criteria a 4 minutes penalty was applied as described in the session above. In sum, a total of 5 minutes was applied for the submitted file. This means that a user utilizing Autodesk Revit 2013 software is estimated to have to spend 9 minutes cleaning/fixing the COBie file for a facility of comparable size and complexity."

Bentley Systems - AECOsimBuilding Designer (beta) PDF

"Format Compliance: This company successfully completed the construction COBie challenge by producing the handover COBie file of the Medical Clinic model. No errors were encountered based on the quality control report; therefore, no penalty was applied for the data format, delivery of required fields, and proper referencing across the worksheets.

Content Quality: The quality of the produced data did not match 100% to the sample data provided and penalties were applied as described above. A total of 218 minutes (3.6 hours) penalty was applied for the data mismatch. This means that a user utilizing Bentley software would have to spend 3.6 hours fixing/cleaning the COBie file.

GraphiSoft - ArchiCAD17 (beta) PDF

"Format Compliance: This company successfully completed the construction COBie challenge by producing the handover COBie file of the Medical Clinic model. Based on the quality control report, were zero errors identified.

Content Quality: The vendor produced the architectural data of the model for a portion of the original clinic model. However, the provided data was inconsistent with the sample data which resulted in a penalty of 503 minutes (8 hours). This means that a user utilizing this product is estimated to have to spend 8 hours cleaning/fixing the COBie file for a facility of comparable size and complexity."

What is COBie: The below is an extract from Wikipedia
Construction Operations Building Information Exchange (COBie) is a data format for the publication of a subset of building model information focused on delivering building information not geometric modelling. It is closely associated with building information modelling (BIM) approaches to programming, design, construction and management of built assets, and was devised by Bill East of the United States Army Corps of Engineers, who authored a pilot standard in June 2007. COBie is currently managed by the buildingSMART alliance.

In short, COBie is a recognised process to specify, manage and record building asset data for hand over to the building facility management. Full information on COBie available here:

BIM - Protecting IP (Intellectual Property)

Intellectual Property: When working in a collaborative design and construction environment, protecting Intellectual Property (IP) has to be considered. If the collaboration includes an advanced level of Building Information Modelling (BIM), the potential loss IP can be very high. But there are some good information sources available to assist professionals.

Within this article where possible, I will quote (in italics) official sources and let you (the reader) determine the outcome. All information should be read in context with the original source.
NOTE: the comments below are in reference to Australian sources, thus readers outside Australia should be aware the implications may be different depending on local laws.

Quote sources:
IP Australia -
AIA BIM & IPD Steering group -
Australian Copyright Council -

IP Meaning: Let’s identify the Australian meaning of IP. Extract from the government “IP Australia” website:
Intellectual property (IP) is the property of your mind or proprietary knowledge and can be an invention, a trade mark, a design or the practical application of your idea.”

To get started in getting your head around IP and BIM, I would suggest referring to the Australian Institute of Architects (AIA), BIM/IPD Steering Group’s document titled: “L1 - BIM and Intellectual Property”. This was made publicly available in August 2012 from the website: This is a very informative, short and concise document. I’m just going to cover a few other items not elaborated in the above document:

IP Ownership: (extract from IP Australia)
Ownership is based on being able to show that you are the 'author' or 'creator' of the IP. You may also become the owner by having the IP rights assigned to you.
Absolute title to an IP right cannot be guaranteed…………  IP is always open to a challenge in court from another person who believes that they can show that certain criteria were not met in the original application process. The best defence against this is proper planning and management.”
IP Types: IP can come in many forms, each with different legal protection and meanings. Below is another very useful abstract from the IP Australia website

NOTE: It is recommended readers, thoroughly investigate and understand the contents of the IP Australia website. It was updated in December 2012 and is very useful for this topic.

What's protected
Type of IP protection
What it means
Product designs
Registered design
The visual appearance of a product is protected, but not the way it works.
kitchen appliances footwear
fashion items
Logos, words letters, numbers, colours, a phrase, sound, scent, shape, picture, aspect of packaging or branding - or any combination of these
Trade mark
A trade mark identifies the particular goods or services of a trader as distinct from those of other traders.
Lonely Planet®
Inventions and new processes
A patent protects how an invention works or functions.
Polymer bank notes
Anti cervical cancer drug, Gardasil
Drawings, art, literature, music, film, broadcasts, computer programs
The owner's original expression of ideas is protected, but not the ideas themselves.
Typefaces and fonts
Trade secrets and confidential information
These types of IP rights give creators certain rights and privileges depending on the type of IP protection.
Coca Cola has used trade secrets to keep its formula from becoming public for decades.
New plant variety
Plant Breeder's Rights
Plant Breeder's rights protect the commercial rights of new plant varieties
Cotton plants with insect resistance and the pink iceberg rose

In the building / construction industry, the most applicable “Protection Types” for everyday use is Copyright and what they define as “Other” (i.e. confidentiality agreements). Let’s have a look at them:

“An intellectual property right which protects the original expression of ideas, not the ideas themselves.” Copyrights may include the following:
       Books, films, music, sound recordings, newspapers, magazines, artwork.

Copyright also protects originally created: 

       typographical arrangements, databases, media broadcasts, computer programs, compositions of other people's work such as academic journals or CD compilations

The moment an idea or creative concept is documented, on paper or electronically, it is automatically protected by copyright. Because it is automatic in Australia, there is no official registry or application process for copyright protection

So how does this relate to our industry? Original Drawings, Sketches & Texts are also covered (just not directly mentioned above). Below are some court transcriptions freely available on the Australian Copyright Council website:

“Copyright in building plans

The Full Federal Court observed that in order for there to be an infringement it is not necessary to show there has been direct copying. Indirect copying is sufficient for an infringement to occur. It said for example, that copyright in a two-dimensional drawing may be infringed where the copying is carried out from a three-dimensional version of the drawing. It also accepted that copyright may be infringed where a person conveys information to anther person, who then carries out the copying.”

Databases and Copyright: Below is an extract from “Databases, Compilations, Tables & Forms” – “INFORMATION SHEET G060v11, February 2012” published by the Australian Copyright Council.

As much of BIM is database driven, the below is very relevant:

Court transcription:
“a 2009 decision by the High Court of Australia concerning Channel Nineʼs television schedules (known as “electronic program guides”) casts a great deal of doubt on the extent to which copyright will subsist in compilations that essentially contain only information.
In order for copyright to subsist in a work, the Copyright Act requires that the work be “original”. The judgments in the High Court case note that, in copyright terms, originality means that the literary work “originated” with the author – the author must not have copied it from someone else. The Court went on to say that the amount of skill, labour or expense expended by an author is not necessarily indicative of an “original” work.”

The document then concludes:
“the following broad principles indicate that a compilation is protected by copyright:

• the individual or individuals who created the compilation can be identified;

• the creators used sufficient intellectual effort and creativity; and
• the creatorʼs intellectual effort and creativity is expressed in the resulting compilation.”

Trade Secrets and Confidentiality: When it comes to ideas, processes, workflows; i.e. “secret trade knowledge”; if a patient is not an appropriate method of securing IP, a confidentiality agreement may be considered. This is a legal signed agreement between parties, to not disclose specific information outside the confinement of a defined group.

Anyone in the industry whom has worked on Defence work or large tender bids may have had to sign a confidentiality agreement. One of the most famous trade secrets is the recipe for Coca Cola, and to date this method has worked in keeping the ingredients a secret. Confidentiality agreements can be used on specific projects or within an organisation. More information on Trade Secrets is available here: IP Australia

Conclusion: To claim IP Protection on an item it must be “Original”. You need to be able to identify exactly who created it (having the original IP item archived, including authored date will also help).  If it was created by multiple parties, it then becomes the IP of the authoring parties, and no one individual party can claim ownership (unless there is a predefined agreement).

From the above you can see there is no Black and White with IP law. As it is so grey, in the event there is an infringement, going to court may be the only way to resolve it. Thus weighing up the monetary value of the IP is essential in your IP protection plan. Even if the claimant wins the legal case, there are costs incurred. 

Other useful links: