Suspended ceilings

This Issue This is a part of the Resilience feature

By - , Build 148

A proposed new Code of practice aims to improve the seismic performance of suspended ceilings. This follows the surprisingly poor performance of many non-structural building components in recent earthquakes.

THE EXTENT OF DAMAGE to non-structural building components in recent earthquakes took many people by surprise.

High cost of non-structural damage

During the 2013 Seddon earthquake, collapsing ducting, pipework, sprinklers and ceilings were responsible for over $10 million in damage in a large significant Wellington building.

This was more than 10% of the building’s total 2009 construction cost. Nobody was injured by the falling components – the earthquake happened on a Sunday evening – but burst pipes caused extensive water damage, soaking carpets, furnishings and electrical wiring.

Collapsing ceilings and building services within the ceiling space also affected commercial and institutional buildings across the Canterbury region in the 2010–11 earthquakes.

In some buildings, the structure was left virtually intact, but the extent of the damage to the services tipped the repair cost over the edge, and the building ended up being demolished. Some estimates place non-structural damage as high as 65% of the total repair cost in Canterbury.

MBIE called on the industry

In response to these types of failures, the Ministry of Business, Innovation and Employment (MBIE) tasked the construction industry with improving the performance of systems in the ceiling space. MBIE’s preference was that change be driven from within the industry itself rather than through legislation.

As a result, the last 18 months has seen a flurry of activity regarding the seismic performance of non-structural systems and buildings services. To date, one of the key pieces of work is the Code of Practice for design, installation and seismic restraint of suspended ceilings from the Association of Wall and Ceiling Industries of New Zealand (AWCI).

‘We are aiming to to produce a guidance document for the seismic design and installation of suspended ceilings and their interaction with other systems,’ says John Parkin, Executive Officer with AWCI, ‘so we ran meetings around the country to talk to our members and find out about the issues they have regarding the seismic performance of ceilings. We wanted to know why ceilings in Wellington and Christchurch had failed.’

Piecemeal installation

From a technical standpoint, the reason for the failures is clear. Ceilings were often poorly restrained and failed along with the building services they were supporting or were compromised by poorly restrained or unrestrained building services and partitions. In other words, they were noncompliant. But why were systems installed like this in the first place?

‘The industry faces a big issue with the interaction and lack of coordination of services in the ceiling space,’ says John. ‘A lot of work goes into the structural design of a building to make sure that it performs, but very little detail goes into how the fit-out is going to occur.’

This leads to situations where the first trade in the ceiling space installs their system in the most convenient location, often occupying the best fixing points available. Each subsequent trade in the ceiling takes the same approach, installing in the easiest available location. At the end of the job, the ceiling installer is left trying to install a compliant ceiling system where there are no available ceiling fixings at the designated spacings.

Many cases non-compliant

The Building Code and standards like NZS 4219:2009 Seismic performance of engineering systems in buildings and NZS 1170.5:2004 Structural design actions – Part 5: Earthquake actions – New Zealand control the seismic design of building services and ceilings. Among other things, they ensure restraints can withstand the likely seismic loads and sufficient clearance is in place to prevent the ceiling and services from interacting with each other during an earthquake.

‘The standards cover how the design takes place and what clearances should be met, but the reality is that, in many cases, it is simply not happening,’ he says.

Proposed code of practice supports coordinated approach

To address these issues, the proposed code of practice advocates a much more coordinated approach to design. An integrated design should be carried out early in the design so all the trades in the ceiling space – eight different trades is not uncommon – can install in a structured way.

‘The more coordinated services in the ceiling space, the better the outcome is going to be. There’s going to be less conflict between the trades, greater chance of compliance and lower costs because the job’s going to be done once and done right,’ he says.

It also recommends a project process where contractors tendering for suspended ceilings must consider and allow for the cost of seismic design and installation and identify the provisions that have been made.

Code uses seismic grade

The proposed code of practice also introduces a new concept to classify the seismic performance of suspended ceilings.

‘The seismic grade is a convenient way for designers, building owners and services installers to identify the seismic forces that a ceiling must be able to withstand. It’s a key element of the new code,’ he says.

Measured on a scale from 1–4, each step in seismic grade represents incremental increase in grid strength, seismic restraint, the requirement for specific engineering design and the involvement of seismic specialists (see Table 1).

For example, a ceiling in a simple, single-storey commercial building with low public use might be a level 1 seismic grade, while a ceiling in a more structurally complex building with higher public use might have level 4 ceilings in public meeting areas and on access or egress routes.

Table 1
Seismic grade of suspended ceilings


SEISMIC GRADEDESCRIPTION
1 Basic ceiling in a building with low seismic performance requirements with ceiling component category P7 and serviceability limit state 1 (up to Building Importance Level 3).
Lightweight ceiling in areas that (other than ceilings less than 3 m above floor level or items weighing less than 10 kg) are not public spaces and do not form part of an emergency egress way or support life safety systems, generally in small areas (under 100 m²).
Not requiring specific engineering design.
2 Ceiling in a building with low seismic performance requirements with ceiling component category P7 and serviceability limit state 1 (up to Building Importance Level 3).
Lightweight ceiling in areas that (other than ceilings less than 3 m above floor level or items weighing less than 10 kg) are not public spaces and do not form part of an emergency egress way or support life safety systems, but may be in larger areas.
Within design parameters of relevant manufacturers’ standard type-tested designs but not requiring specific engineering design.
Producer statement 3 with supporting documents.
3 Ceiling in a building up to Building Importance Level 3 or component category P4 where ceilings must be installed to ultimate limit state, in public spaces, forming part of an emergency egress way, supporting life safety systems or at high level.
May be within design parameters of relevant manufacturers’ standard typetested designs, but specific engineering design is required.
Minimum of producer statements 1 and 3 with supporting documents.
4 Ceiling in a building up to Building Importance Level 4 or component category P4 where ceilings must be installed to ultimate limit state, in public spaces, forming part of an emergency egress way, supporting life safety systems or at high level.
Specific engineering design is required.
Minimum of producer statements 1 and 3 with supporting documents and producer statement 4.

Feedback encouraged

John Parkin anticipates a mid-2015 release for the code of practice, but AWCI opened the working draft for comment as early as last year.

‘For the code to be accepted and used, it’s important that all the industry players have the opportunity to see the code and comment on what it proposes,’ he says. ‘They don’t have to agree with everything, but they have to have the chance to comment.

‘So far, we’ve received some very positive feedback from the industry.’

For more

The AWCI Code of practice for design, installation and seismic restraint of suspended ceilings is available at www.awcinz.org.nz.

Download the PDF

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Articles are correct at the time of publication but may have since become outdated.

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