Category: Design Management

Pre-design site information

A search for “Site” under the resources section of the NZACS website brings up several articles highlighting the necessity of getting a firm grip on site information before pencil hits paper (or mouse is engaged).  A couple of recent claims has prompted a list of some (not all-inclusive!) things to think about:

  • Overhead power lines including Transpower lines
  • Internal legal boundaries subdividing a site
  • Boundaries which may be in doubt or ill-defined
  • Flood plains and overland flow paths – is your site vulnerable to flooding?  Where is surface water coming from, where does it go, what affect will your building have on it?
  • Underground services, including unmapped and unregistered public SS and SW lines, gas pipes, electrical cables, private services.
  • Regional overlays on your site – Check with regional authority.  May override local council requirements.
  • Set-backs due to specific regional/local conditions such as railway lines, power lines or transmission towers
  • Possible redundant offal pits and/or aquifers on site, or other ground contamination.
  • Cross-lease, ROW restrictions and easements
  • Check site coverage, HIRTB, etc. Recent changes may have affected your site.
  • Unstable land – by definition if sloping.  Do the trees on site look unusual?  Does the vegetation suggest dampness or recent re-establishment?
  • Localised or site-specific vegetation/subgrade/wind/rain/drainage issues which may or may not be recorded on publicly available information.
  • Protected or notable trees.
  • Covenants on the land protecting views etc. 
  • Nearby properties or activities which may require specific design in relation to privacy or environmental issues (smells, noise, irregular activities, animals, and others not necessarily subject to regulatory control)
  • Coastal land instability.  For example, Auckland Council has mapped the coastline that could be affected by coastal erosion and instability under a range of climate change (sea-level rise) scenarios and timeframes (2050, 2080, 2130).  This Area Susceptible to Coastal Instability and Erosion (ASCIE) mapping has been done at a regional-scale but is refined depending on site-specific assessments.  This will have significant implications on coastal properties.  Other regions will have similar issues.
  • Some of the things members can do to ensure a successful project:
  • Visit the site in person and record everything you can
  • Be satisfied that the site setout is as designed (or if not, is as it should be!)
  • Have a survey done showing all legal boundaries, topo levels, easements, services
  • If justified, have a GRP survey done for all underground services.  Map LL and ILs
  • Check local council GIS maps for all property information including any encumbrances or local council requirements which are outside the legal boundary but which might affect your site.  
  • Download the local council Property File
  • View all official or historical information with a critical eye, and reconcile it with your observations and common sense.  Information at a macro level may not provide the detailed information required for the specific site.
  • Obtain the Certificate of Title to confirm any legal constraints, and if necessary seek legal interpretation of them.
  • If appropriate, check with any architect or fellow professional who may have worked on the site previously.
  • If appropriate, have a geotech assessment completed.

Engineered Stone Risks

The risks of working with engineered stone have recently been in the media, and compared with asbestos risks.  Whilst the current PI cover does not include asbestos risks, there is no such exclusion for engineered stone.  But that might change in the future.

Engineered stone is widely used in benchtops, and usually machined off site, but there could also be some machining on site.  The risks, as now known, are that the machining process produces a fine dust that contains high levels of silica crystals, and this can cause the deadly lung disease silicosis.

A competent architect is likely to be held to know of that problem, and thus to have a responsibility and duty of care to ensure safety measures are taken if the product is being used, as defined by accepted practice.  Worksafe outlines such measures, so an architect has an obligation – to the extent within their control – to see that these are carried out.  

https://www.worksafe.govt.nz/topic-and-industry/dust/accelerated-silicosis/engineered-stone-and-exposure-to-respirable-crystalline-silica/

Obviously an architectural practice has a responsibility to ensure that its employees are aware of the risks and take the necessary precautions on site.  But in addition the architect is in a position to make clients aware of those risks:  that may be relevant in both selecting the product and during its installation.  Whilst the architect might not be able to control the off-site machining of the product, there would be an obligation to select and specify it in a way which recognises the risks and requires them to be addressed both on and off site.

NZACS suggests that engineered stone benchtops are fully pre-templated in MDF to avoid any site cutting;  that all off-site manufacture has to use wet-cutting;  and that a sticker is put on the product to identify the risks.  It is known that some practices have put the product on their prohibited list.

Further information about fabrication guidelines is available at https://impac.co.nz/rcs-accreditation/home/

BIM – PROJECT RISK MANAGEMENT

Before having anything to do with BIM, members should acquaint themselves with the New Zealand BIM Handbook https://www.biminnz.co.nz/nz-bim-handbook and its appendices.

These are very useful documents and contain more detail than the NZCIC guidelines.  More detailed information is also in the international standard ISO 19650.  These documents are a reminder that BIM is much more than a fancy parametric CAD model, and that during the life of a project there are many ways in which ‘information’ might be used.

One of the key aspects of BIM is that the work you do is generally used by and relied upon by numerous downstream parties (e.g. construction, operation) so it’s very important that what you input into a BIM model is correct and so, before you even start, you need good internal modelling standards, templates, and systems.  Also make any limitations about the model/information clear.  A good BIM model is much more valuable than a simple set of drawings and so you should charge appropriately for this.

There are various views of how you can protect your intellectual property rights but, assuming the use of an NZIA AAS, the licence to use the model is similar to the drawings and belongs to them.  The IP also lies in how you model things and carry out Quality Assurance but this will largely remain within your team and not be passed on.

As the lead consultant the architect is often also looked upon to provide BIM Management Services.  Only provide these if you are confident that you have, and can maintain, this skillset.

The following identifies some of the hazard and risk areas by typical workstage.

Request for Proposal (RFP)

  • Dealing with poorly written RFPs.  These can contain broad requirements like ‘a clash-free BIM model is to be provided to the contractor as part of the construction documentation’ or have a requirement to provide ‘a complete as-built BIM model to LOD 300’.  These can be very onerous or impractical, and to manage this risk it is important to review the RFP documents looking for these requirements, seek clarification if possible, and respond clearly with what your proposal includes.
  • If you are part of a consultant team bid then it’s worth doing a pre-contract BIM Execution Plan (BEP) so that everyone knows what they’re committing to and what is covered by the fee.  BIM is typically highly collaborative and such a BEP clearly sets out what everyone is expected to deliver.  This minimizes the risk of disagreements later and, if included in your bid, can make it clear what is in scope.
  • Make sure that you identify and charge accordingly for managing the BIM process if you have that role.  This will include the BIM manager’s time but can also include project related costs like a Common Data Environment (CDE) where the BIM model is hosted, and licences for BIM collaboration and model-checking software.  This can all add up to a considerable sum.
  • Ensure that proper protocols are in place (with all participants) to manage cyber security risks, and make sure you have the appropriate Cyber Liability insurance in place in case something goes wrong.

Briefing

  • It is important to get a BIM brief that is signed off by the client.  The NZ BIM Handbook Appendix E shows an example of such a brief.  On more than one occasion we have had to assist the client with writing the brief.  Confirm that the client understands what they are getting and that you can deliver it.  Getting an agreed brief reduces the risk of the client coming back later with additional information requirements.

Design Stages

The primary risks for this stage of the project are those associated with inefficiencies, poor coordination, and tension with your consultants.

Working with a consultant team during the design stages

  • The foundation for a good consultant team producing good BIM is a well-executed and monitored BEP which is led by the BIM Manager.
  • The BEP makes it clear what is required at each workstage and where responsibility sits, so take the time to properly review and input into this document, and ensure it is agreed upon by all parties as soon as possible.
  • It is important for future users that the project uses OpenBIM (i.e. a non-proprietary format).  Revit is quite dominant with consultants, but ArchiCAD is popular with architects so ensure that consultants are committed to exchanging models in an open format like IFC (International Foundation Class) rather than their preferred CAD programme.
  • Make sure that your hardware can deal with the large file sizes that you will end up with.  For example, curved pipes and ducts can make these very large.
  • Carry out testing prior to the actual execution of exchanges and clash detection.

The Design Process

  • To have a decent BIM model you should have an internal model-coordinator on your team.  This is different to the BIM manager, which should be regarded as an independent role, even if you are providing those services.
  • Focus on clashes that are appropriate to the workstage.  For example large clashes are important to resolve at early design stages but don’t sweat the small stuff as this will be very time consuming.
  • Be careful of letting the ‘CAD people’ be the only team members engaged in the process.  A successful BIM project needs buy-in from all disciplines and levels, and good transparency to avoid silos developing.

Procurement

The main risks with this project stage are getting tenders/prices that don’t properly take account of the contractor’s BIM responsibilities, and have the potential to generate later claims.

It is very important that tenderers for the construction are aware of the following:

  • The status of the model that they will be provided with, including the level of development of the various BIM Model components.
  • Any limitations or qualifications about the model being provided.
  • What the contractor will be required to do with the model and who will do this work. For example, who will be responsible for updating the model as a result of variations or shop drawings, and what LOD will be required?
  • How will shop drawings be reviewed – drawings only or models only or both?  And don’t forget that you don’t approve these drawings/models, but are reviewing them so you can be in a position to issue the response as suggested in NZIA Practice Note PN 4.206.
  • Are as-builts required and what is the level of accuracy of these?
  • Is any BIM reporting needed during the construction phase?

Tenderers should be required to submit a construction BEP to confirm that they properly understand and have included for all BIM aspects.

Construction/Handover/Operation

  • Responsibility during the construction stage will rest largely with the main contractor and sub-contractors.  There may be some risk to the architect if they have a role of updating the model and do this poorly.
  • Like non-BIM projects there is also the obvious risk of variation claims arising from poorly executed design, coordination and documentation in the earlier stages.
  • To enable a smooth handover from contractor to client/user, the defects liability period can be used for a ‘soft landing’.  The BIM Manager is likely to have a role in monitoring this.
  • There are likely to be fewer risks to the design team members during the building operation stage but it’s important to ensure that the client has the necessary skills and software to make proper use of the BIM model.  This will reduce the risk of an operational failure and any possible resultant claim.

Summary

The best way to mitigate BIM risks is the usual combination of good communication, thoroughness, and quality assurance.

You need to think carefully about the fees necessary to do it properly.

BIM – LEGAL & ENGAGEMENT CONSIDERATIONS

The following points address some issues which may affect the conditions of engagement and fees, and PI cover, for BIM.  They are drawn from an Australian legal paper which dealt with BIM across the whole project life.

  • The BIM model is dependent on multiple contributors and will be relied upon by others for future unknown decisions.  How do you confine your liability to your input only?  This is likely to require specific terms of engagement. 
  • If an “issue” (or dispute) arises out of the use of the BIM model, there is the potential that you may incur costs and resources regardless of the relevance of your contribution to the problems.  How do you “ring-fence” or allocate liability to the respective inputs by the various contributors or users?
  • If there is some ambiguity or conflict between the BIM model and the other responsibilities you have under your engagement – or have described in your design/specification – which takes precedence?
  • The definition of quality standards may require amendments to address the standard BIM guidelines and consistency across all contributors.
  • Is there a “BIM protocol” which specifically deals with liability and responsibility, order of precedence, and the resolution of conflict?
  • There need to be protocols to trace work carried out in BIM and establish what occurred, who did what to whom and when, and to establish causation in the event a dispute arises.
  • What are the intellectual property rights and ownership issues?  Who “owns” the BIM model and controls access and use?  To what extent does it affect your copyright on design elements?
  • Insurance:  NZACS Professional Indemnity does not specifically exclude BIM design, as this is regarded as within the scope of architectural business practice.  But the insurance contract does have some provisions in respect of liability which would make it prudent for members to discuss the BIM contract terms and possible fish hooks with Aon, the insurance brokers for the NZACS scheme.  Also consider Cyber Liability, and the additional protection it provides.
  • The operation of BIM on a project may inadvertently allow parties to access information which is otherwise confidential.  Parties may consider restricting access to different areas of BIM.

Balustrades and Barriers

For some reason, balustrade failures – especially glazed ones – have been prominent over the past year or so. 

  • there seems to be plenty of room for a difference of opinion about the type of glass, fixings, rails and supports. 
  • the long-term durability of elements has been an issue in respect of paint finishes and metal treatment; 
  • support fixings into the structure have been the source of leaks; 
  • cost-issues have driven design solutions which are incompatible with the potential risk; 
  • minimum balustrade heights have not accounted for the deck falls and finishes; 
  • inconsistencies between a “generic” design, or the designer’s details and those of a specialist trade design/install contractor.
  • poor workmanship or inadequate quality control has led to sudden or potential failures
  • spontaneous failure of toughened glass as a result of:  poor edge finishing or hole formation, damage in delivery or installation, uneven shading, localised fixing or shape issues, imperfections and inclusions in the glass at the time of manufacture, and unknown or a combination of all of these, perhaps beyond the control of the designer or contractor.

At the heart of the matter is the functional purpose of a barrier:  irrespective of compliance minima, if the human consequences of barrier failure are significant, then that is the first priority for design, installation, and site observation.

Guides to the design of balustrades and barriers:

•             The Building Code (primarily sections B1, B2, F2 and F4) and relevant determinations

•             New Zealand Standards (e.g. NZS 4223 Glazing in Buildings Part 3)

•             Determinations

•             MBIE Guidance Documents

•             Specific Design (usually by the sub-contractor)

•             Rules for barriers around swimming pools.

The Building Code:

Section B1 (Structure), clause 22.4.3 amends what is set out in NZS 4223, and so it’s worth familiarising yourself with this if you are designing structural glass barriers.  Also watch out for any change of use that might impact on the loads that your structural engineer uses.  The MBIE Guidance on Barrier Design is a useful document to accompany B1, and Figure 3.1 in the Guidance document sets out a useful design flowchart.

Section B2 (Durability) accepts a 15-year durability for a barrier infill but there is a 50-year requirement for the handrail and its supporting structure.  We can sometimes think of barriers as part of a cladding system but this makes it clear that the structural aspects need to match the life of the building.

Section F2 (Hazardous Materials) references NZS 4223: Part 3.  A word of warning here is that if you apply some decorative film – say for graphics or privacy purposes – to toughened glass, you may be inadvertently turning the glass into something more hazardous than if it were able to break into many small pieces.

Section F4 Safety from Falling is obviously the most relevant part of the code and it’s worth re-reading this to make sure you don’t miss something.  A few aspects to note include the following.

Table 1 sets out minimum barrier heights, however it would be a good idea to dimension your documents with extra height to take care of falls, finishes, construction tolerances, unexpected build-ups etc.  There is no obvious provision in the code for inspectors to allow for “tolerances” when they check measure on site.    Preferably dimension the height as a minimum in relation to the finished floor/deck level.  (It’s not unknown for owners to change deck finishes without informing the designer!)

A commentary in F4 notes that there are more relaxed requirements where a building won’t be frequented by children under 6.  But you cannot control who uses the building and how:  we recommend caution before relying on this exemption, and drawing the issue – and inherent responsibility – to the client’s attention.

Figure 3 shows that any projecting lip of greater than 15mm in a barrier design is considered a foothold, and therefore the barrier height needs to be measured from this projection.  It’s easy with a parapet flashing build up to get caught out by this rule and have to measure the barrier height from an upstand rather than a terrace level.

Figure 4 shows the requirements for stair barriers.  Don’t be caught out by the 150mm diameter rule – it’s tested in 3 dimensions by a 150mm diameter sphere:  if the handrail is set out from the stairs it may need a smaller opening than a 150mm elevational diameter.

Figure 5 is a reminder of the importance of preventing a barrier from being able to be used as a seat.  This requirement does not apply to housing but in all other cases something like a top edge wider than 100mm could be considered a seat and so would not be code compliant, as well as being hazardous.

There are a number of requirements in situations where there is a toilet pan or any other fixed feature (e.g. seating) within 500mm of a window.  It would be easy to forget about including a restrictor or barrier in these situations.

Landscaped areas may require a barrier.  MBIE Determination 99/012 notes that “Barriers are required above retaining walls exceeding 1 metre in height, where people, particularly those unfamiliar with the area, would frequently be expected to be close to the top of the wall in the course of their normal activities.”

Some detailing issues:

  • Try to avoid barriers going across backgrounds with different light reflectance that may create temperature differentials that cause stresses in the glass, leading to breakages.  (East elevations can produce rapid temperature rises).
  • Detailing and dimensions should allow for generous construction tolerances.  Glass fixings where there is little to no gap are more prone to breakage.
  • Conservatively detail the base plates of stanchions bearing in mind the potential risks from corrosion and surface water:  consider the B2 50-year durability requirement.
  • Make your compliance pathway clear in your building consent documentation, so that an inspector on site interprets things the same as the consent processing officer.

BIM Risks

Some members have expressed an interest in understanding the risks associated with BIM – Building Information Modelling.  I don’t claim any particular BIM expertise but the following is drawn from my personal experience on medium to large commercial projects, and is therefore by no means exhaustive.

Before having anything to do with BIM, members should acquaint themselves with the New Zealand BIM Handbook https://www.biminnz.co.nz/nz-bim-handbook and its appendices.

These are very useful documents and contain more detail than the NZCIC guidelines.  More detailed information is also in the international standard ISO 19650.  These documents are a reminder that BIM is much more than a fancy parametric CAD model, and that during the life of a project there are many ways in which ‘information’ might be used.

One of the key aspects of BIM is that the work you do is generally used by and relied upon by numerous downstream parties (e.g. construction, operation) so it’s very important that what you input into a BIM model is correct and so, before you even start, you need good internal modelling standards, templates, and systems.  Also make any limitations about the model/information clear.  A good BIM model is much more valuable than a simple set of drawings and so you should charge appropriately for this.

There are various views of how you can protect your intellectual property rights but, assuming the use of an NZIA AAS, the licence to use the model is similar to the drawings and belongs to them.  The IP also lies in how you model things and carry out Quality Assurance but this will largely remain within your team and not be passed on.

As the lead consultant the architect is often also looked upon to provide BIM Management Services.  Only provide these if you are confident that you have, and can maintain, this skillset.

The following identifies some of the hazard and risk areas by typical workstage.

Project Establishment/Briefing

Request for Proposal (RFP)

  • Dealing with poorly written RFPs.  These can contain broad requirements like ‘a clash-free BIM model is to be provided to the contractor as part of the construction documentation’ or a have requirement to provide ‘a complete as-built BIM model to LOD 300’.  These can be very onerous or impractical, and to manage this risk it is important to review the RFP documents looking for these requirements, seek clarification if possible, and respond clearly with what your proposal includes.
  • If you are part of a consultant team bid then it’s worth doing a pre-contract BIM Execution Plan (BEP) so that everyone knows what they’re committing to and what is covered by the fee.  BIM is typically highly collaborative and such a BEP clearly sets out what everyone is expected to deliver.  This minimizes the risk of disagreements later and, if included in your bid, can make it clear what is in scope.
  • Make sure that you identify and charge accordingly for managing the BIM process if you have that role.  This will include the BIM manager’s time but can also include project related costs like a Common Data Environment (CDE) where the BIM model is hosted, and licences for BIM collaboration and model-checking software.  This can all add up to a considerable sum.
  • Ensure that proper protocols are in place (with all participants) to manage cyber security risks, and make sure you have the appropriate Cyber Liability insurance in place in case something goes wrong.

Briefing

  • It is important to get a BIM brief that is signed off by the client.  The NZ BIM Handbook Appendix E shows an example of such a brief.  On more than one occasion we have had to assist the client with writing the brief.  Confirm that the client understands what they are getting and that you can deliver it.  Getting an agreed brief reduces the risk of the client coming back later with additional information requirements.

Design Stages

The primary risks for this stage of the project are those associated with inefficiencies, poor coordination, and tension with your consultants.

Working with a consultant team during the design stages

  • The foundation for a good consultant team producing good BIM is a well-executed and monitored BEP which is led by the BIM Manager.
  • The BEP makes it clear what is required at each workstage and where responsibility sits, so take the time to properly review and input into this document, and ensure it is agreed upon by all parties as soon as possible.
  • It is important for future users that the project uses OpenBIM (i.e. a non-proprietary format).  Revit is quite dominant with consultants, but ArchiCAD is popular with architects so ensure that consultants are committed to exchanging models in an open formation like IFC (International Foundation Class) rather than their preferred CAD programme.
  • Make sure that your hardware can deal with the large file sizes that you will end up with.  For example, curved pipes and ducts can make these very large.
  • Carry out testing prior to the actual execution of exchanges and clash detection.

The Design Process

  • To have a decent BIM model you should have an internal model-coordinator on your team.  This is different to the BIM manager, which should be regarded as an independent role, even if you are providing those services.
  • Focus on clashes that are appropriate to the workstage.  For example large clashes are important to resolve at early design stages but don’t sweat the small stuff as this will be very time consuming.
  • Be careful of letting the ‘CAD people’ be the only team members engaged in the process.  A successful BIM project needs buy-in from all disciplines and levels, and good transparency to avoid silos developing.

Procurement

The main risks with this project stage are getting tenders/prices that don’t properly take account of the contractor’s BIM responsibilities, and have the potential to generate later claims.

It is very important that tenderers for the construction are aware of the following:

  • The status of the model that they will be provided with, including the level of development of the various BIM Model components.
  • Any limitations or qualifications about the model being provided.
  • What the contractor will be required to do with the model and who will do this work. For example, who will be responsible for updating the model as a result of variations or shop drawings, and what LOD will be required?
  • How will shop drawings be reviewed – drawings only or models only or both?
  • Are as-builts required and what is the level of accuracy of these?
  • Is any BIM reporting needed during the construction phase?

Tenderers should be required to submit a construction BEP to confirm that they properly understand and have included for all BIM aspects.

Construction/Handover/Operation

  • Responsibility during the construction stage will rest largely with the main contractor and sub-contractors.  There may be some risk to the architect if they have a role of updating the model and do this poorly.
  • Like non-BIM projects there is also the obvious risk of variation claims arising from poorly executed design, coordination and documentation in the earlier stages.
  • To enable a smooth handover from contractor to client/user, the defects liability period can be used for a ‘soft landing’.  The BIM Manager is likely to have a role in monitoring this.
  • There are likely to be fewer risks to the design team members during the building operation stage but it’s important to ensure that the client has the necessary skills and software to make proper use of the BIM model.  This will reduce the risk of an operational failure and any possible resultant claim.

Summary

The best way to mitigate BIM risks is the usual combination of good communication, thoroughness, and quality assurance.

You need to think carefully about the fees necessary to do it properly.

Risk management issues

  • The BIM model is dependent on multiple contributors and will be relied upon by others for future unknown decisions.  How do you confine your liability to your input only?  This is likely to require specific terms of engagement. 
  • If an “issue” arises out of the use of the BIM model, there is the potential that you may incur costs and resources regardless of the relevance of your contribution to it.  How do you “ring-fence” or allocate the respective inputs by the various contributors or users?
  • If there is some ambiguity or conflict between the BIM model and the other responsibilities you have under your engagement – or have described in your design/specification – which takes precedence?
  • The definition of quality standards may require amendments to address the standardisation of BIM guidelines.
  • Is there a “BIM protocol” which specifically deals liability and responsibility, order of precedence, and the resolution of conflict?
  • There need to be protocols to trace work carried out in BIM and establish what occurred, who did what to whom and when, and to establish causation in the event a dispute arises.
  • What are the intellectual property rights and ownership issues?  Who “owns” the BIM model and controls access and use?  To what extent does it affect your copyright on design elements?
  • Check that your professional indemnity insurance covers failures due to BIM design, and what additional provisions you may need to make.  Your duty to disclose material facts to your insurer may require you to disclose that BIM is implemented on a project.
  • The operation of BIM on a project may inadvertently allow parties to access information which is otherwise confidential.  Parties may consider restricting access to different areas of BIM.

A Grim Tale About Piggies and Wolves

Once upon a time there were three designer pigs:
The first designer pig designed a house of straw, but along came a shower of rain and because the walls weren’t protected by eaves, and the window details were appalling, and the waterproofing system comprised only paint over dodgy plasterwork, the walls rotted and the house fell down. Along came a wolf, and the design pig was roasted.
The second designer pig designed a house of timber, which was all very well and good, but the pig did not stick around to see if the house got built properly, and the piggies who lived in the house closed all the windows to stay warm in winter, and didn’t venture outside to clean out the gutters or even stop the weeds growing up very close to the walls. The insulation and building wrap ensured that the walls were always wet inside and before very long the house was a great place for growing mushrooms, many of which were not found until the wall linings were removed. Along came a wolf who was keen to see that the piggies who lived in the house grew big and fat instead of being weak and sick from the dampness. He made sure that the design pig paid the costs of making the piggies and the house better again.
The third designer pig was much smarter and more stylish. Of course, a brick chimney was out of the question because of the earthquake risk, and possibly because a wolf could fall down it. Instead, one of those very stylish metal fireplaces was put in to keep the piggies who lived in the house healthy and happy. And everyone was. Well, for a couple of years, anyway. Because what happened then was that the house suddenly burst into flames. The wolf was not at all happy that the piggies were overcooked and he asked a wise old owl what could have possibly happened. The owl yawned and said (in a doleful way) “pyrophilia” which the wolf looked up on Google (with some surprise!) and found should have been “pyrophoric carbonization”.
And the moral of this story?

  1. Whenever an aspect of design or construction is critical to the performance of the completed building, both design and installation are critical activities. In these cases, proper detailing and specification, observation during construction, and review of manufacturer’s installation requirements may have saved the designer pigs’ bacon.
  2. Any hot surface in proximity to timberwork has the long-term potential dry out the timber to the point that spontaneous ignition may occur at temperatures less than would happen by the application of a direct flame.
  3. If reliant on intumescent products for fire protection, do not ignore the need to provide specific fixing details, clearances for expansion, and installation conditions applicable to that product.
  4. If the ongoing satisfactory performance of an element of a building – or its continued warranty cover – is reliant on maintenance, then it is in the interests all concerned that the need for that maintenance is made clear.
  5. Wolves can be scary and hungry

Balustrades and Barriers

For some reason, balustrade failures – especially glazed ones – have been prominent over the past year or so.
• there seems to be plenty of room for a difference of opinion about the type of glass, fixings, rails and supports.
• the long-term durability of elements has been an issue in respect of paint finishes and metal treatment;
• support fixings into the structure have been the source of leaks;
• cost-issues have driven design solutions which are incompatible with the potential risk;
• minimum balustrade heights have not accounted for the deck falls and finishes;
• inconsistencies between a “generic” design, or the designer’s details and those of a specialist trade design/install contractor.
• poor workmanship or inadequate quality control has led to sudden or potential failures
• spontaneous failure of toughened glass as a result of: poor edge finishing or hole formation, damage in delivery or installation, uneven shading, localised fixing or shape issues, imperfections and inclusions in the glass at the time of manufacture, and unknown or a combination of all of these, perhaps beyond the control of the designer or contractor.
At the heart of the matter is the functional purpose of a barrier: irrespective of compliance minima, if the human consequences of barrier failure are significant, then that is the first priority for design, installation, and site observation.

Guides to the design of balustrades and barriers:
• The Building Code (primarily sections B1, B2, F2 and F4) and relevant determinations
• New Zealand Standards (e.g. NZS 4223 Glazing in Buildings Part 3)
• Determinations
• MBIE Guidance Documents
• Specific Design (usually by the sub-contractor)
• Rules for barriers around swimming pools.

The Building Code:
Section B1 (Structure), clause 22.4.3 amends what is set out in NZS 4223, and so it’s worth familiarising yourself with this if you are designing structural glass barriers. Also watch out for any change of use that might impact on the loads that your structural engineer uses. The MBIE Guidance on Barrier Design is a useful document to accompany B1, and Figure 3.1 in the Guidance document sets out a useful design flowchart.
Section B2 (Durability) accepts a 15-year durability for a barrier infill but there is a 50-year requirement for the handrail and its supporting structure. We can sometimes think of barriers as part of a cladding system but this makes it clear that the structural aspects need to match the life of the building.
Section F2 (Hazardous Materials) references NZS 4223: Part 3. A word of warning here is that if you apply some decorative film – say for graphics or privacy purposes – to toughened glass, you may be inadvertently turning the glass into something more hazardous than if it were able to break into many small pieces.
Section F4 Safety from Falling is obviously the most relevant part of the code and it’s worth re-reading this to make sure you don’t miss something. A few aspects to note include the following.
Table 1 sets out minimum barrier heights, however it would be a good idea to dimension your documents with extra height to take care of falls, finishes, construction tolerances, unexpected build-ups etc. There is no obvious provision in the code for inspectors to allow for “tolerances” when they check measure on site. Preferably dimension the height as a minimum in relation to the finished floor/deck level. (It’s not unknown for owners to change deck finishes without informing the designer!)
A commentary in F4 notes that there are more relaxed requirements where a building won’t be frequented by children under 6. But you cannot control who uses the building and how: we recommend caution before relying on this exemption, and drawing the issue – and inherent responsibility – to the client’s attention.
Figure 3 shows that any projecting lip of greater than 15mm in a barrier design is considered a foothold, and therefore the barrier height needs to be measured from this projection. It’s easy with a parapet flashing build up to get caught out by this rule and have to measure the barrier height from an upstand rather than a terrace level.
Figure 4 shows the requirements for stair barriers. Don’t be caught out by the 150mm diameter rule – it’s tested in 3 dimensions by a 150mm diameter sphere: if the handrail is set out from the stairs it may need a smaller opening than a 150mm elevational diameter.
Figure 5 is a reminder of the importance of preventing a barrier from being able to be used as a seat. This requirement does not apply to housing but in all other cases something like a top edge wider than 100mm could be considered a seat and so would not be code compliant, as well as being hazardous.
There are a number of requirements in situations where there is a toilet pan or any other fixed feature (e.g. seating) within 500mm of a window. It would be easy to forget about including a restrictor or barrier in these situations.
Landscaped areas may require a barrier. MBIE Determination 99/012 notes that “Barriers are required above retaining walls exceeding 1 metre in height, where people, particularly those unfamiliar with the area, would frequently be expected to be close to the top of the wall in the course of their normal activities.”
Some detailing issues:
• Try to avoid barriers going across backgrounds with different light reflectance that may create temperature differentials that cause stresses in the glass, leading to breakages. (East elevations can produce rapid temperature rises).
• Detailing and dimensions should allow for generous construction tolerances. Glass fixings where there is little to no gap are more prone to breakage.
• Conservatively detail the base plates of stanchions bearing in mind the potential risks from corrosion and surface water: consider the B2 50-year durability requirement.
• Make your compliance pathway clear in your building consent documentation, so that an inspector on site interprets things the same as the consent processing officer.

Passive Fire Design – Intumescent paint systems

Passive Fire Design – Intumescent paint systems

In October 2020, a “Code of Practice for the Specification and Application of Intumescent Coatings for the Fire Protection of Structural Steel” was published by the Fire Protection Association of New Zealand.

It includes a requirement to keep all structure clear of the steel by a distance of 50x the dry film thickness of the coating. It is no longer acceptable to fix timber directly to coated structural steel to accommodate the protective foaming of the intumescent paint during a fire or for the fixing of linings. It will also be a requirement to have access to the steel to inspect the state of the coating when ‘life to first maintenance’ inspection is required.