Are we building durable buildings?

by Biju Balakrishnan FIEAust CPEng NER
Principal Structural Engineer at Intrax PROJECTS

No one wants to demolish their new home within four years of construction due to durability issues. That is what happened to a homeowner in Tasmania whose family dreams were shattered because of a poorly designed home. This would never have happened if the building team had been copetent to design and construct the house for the required durability.

Durability is something that is often forgotten in the design and construction process and ends up with disastrous consequences for developers, builders, and house owners.

Australia is a country with a large land mass, extensive coastlines, and aggressive environments. Designing and constructing buildings requires knowledge, expertise, and experience, Intrax has these. According to the Australian Corrosion Association (ACA), around 4.35%($78 billion) of GDP per annum is being spent on remediating assets affected by corrosion.

This article reviews the current requirements under the National Construction Code (NCC) for durability, Australian Standard requirements, and acceptable industry practices.

What is durability?

“Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair when faced with the challenges of normal operation over its design lifetime.”
The above definition from Wikipedia sums up durability well. The important element in durability design is to establish the “design life” of a structure.Many external factors reduce the durability of a structure, such as the sun, rain, chemicals, aggressive environment, and various life forms.

Durable structures can be designed with maintenance interventions if the structural element is accessible for maintenance. For example, an exposed steel beam in a veranda can be designed for 25 years of durability even though the structure demands 50 years of life. The structure needs to be re-coated after 25 years to cover the rest of its life.

 

How do I ensure durability for building materials?

Residential construction mainly uses concrete, steel, timber, and brick masonry as structural members. All these materials need durability design based on the intended design life. Even though the use of steel is minimal in residential construction, if used uncoated, durability issues in steel are common due to its highly corrosive nature.

Timber is extensively used in residential construction and is non-corrosive. If timber is to be exposed to weather, the right selection of timber and treatment is required. Even though timber is non-corrosive, the timber connections (nails, nail plates, tie downs, screws, bolts) need corrosion protection. Galvanising is the preferred method of protection for connections. Self-drilling screws for the building and construction industries shall comply with AS 3566.1.

Concrete footing hidden in the ground also requires a damp-proof membrane and minimum cover. Footings in aggressive and contaminated soil might also need appropriate concrete strength and additional cover.

Concrete above ground is more susceptible to durability issues and might need closer attention.

Masonry is often used as a cladding element (brick veneer construction) and the components in masonry such as lintels and brick ties create durability issues for masonry, rather than the masonry itself. Compliance with AS/NZS 2699 is essential for masonry components in residential buildings.

 

National Construction Code (NCC)

The NCC is Australia’s primary set of codes for technical design and construction provisions for buildings. For residential construction, NCC Vol 2 is the governing code for design and construction.

Since NCC refers to other Australian Standards as referred documents, compliance to relevant Australian Standards is also required to comply with NCC. For example, compliance with AS 2870 and AS 3600 will ensure durability requirements for footing, and compliance with AS 4100, AS 4600, and AS 2312 will ensure durability requirements for steel.

For timber, compliance with AS 1720, AS 1684, AS 1604, and AS 5604 are required to meet the durability requirements.Masonry shall comply with AS 3700 and AS 4773. Light gauge steel structures shall comply with NASH standards.

Buildings near the beach, what are the additional requirements?
This question is raised by many builders and homeowners. The quick answer is to comply with the NCC and referred Australian Standards. The defining parameter for concrete members (footings in this case) is exposure classification to AS 3600.

Steel is more corrosive near beaches due to saline atmospheric conditions. Special consideration shall be given to exposed steel members and hidden masonry components such as lintels and brick ties. Defining an appropriate durability rating for building components will ensure durable structures.

In certain cases, the minimum requirements in NCC are not sufficient to meet the durability and practitioners shall refer to other industry guidelines such as galvanizers association technical manuals to design for durability.

 

Do I need treated timber?

Timber is a durable material if it is not exposed to alternate wet and dry weather conditions. While timber is susceptible to attack from living organisms (termites, borers, fungus, and insects), we can avoid such durability issues by enclosing members sufficiently or by selecting a durable species/treated timber.

Since frames, roof trusses, and floors in residential buildings are protected from moisture and attack from living organisms, even softwood will last for more than 50 years. Therefore, timber within building elements doesn’t require any additional treatment other than seasoning. Machine Graded Pine (MGP10) which is a common stud material, is commonly used untreated within wall frames, floors, and roofs.

This is not the case if your timber is used in the ground or above ground. In such a scenario compliance with AS 1684, AS 1604 and AS 5604 is necessary based on what timber is used.

For example, IronBark, a hardwood species, has more than 40 years of durability when used outside whereas untreated softwood species Radiata Pine will last only 0-7 years.

Treating timber is an effective way to increase its durability. Hazard classification to AS 1604.1, Table 1.1, and appropriate preservative treatment is required. Copper Chromium Arsenic (CCA), a common treatment option for timber, is not suitable for public places and schools due to health hazards. Light Organic Solvent-Borne Preservatives (LOSP) are to be specified in such instances.

Close coordination between structural engineers and architects is necessary to select the appropriate species and treatment options.

What coating should I use, galvanising or painting?

Steel is highly corrosive due to the oxidation of iron into its oxides. There are three strategies we can adopt to increase the durability of steel 1. Painting 2. Zinc coating (Galvanising) and 3. Cathodic protection.

In residential applications, Galvanising is common due to its high effectiveness and offsite application. Based on the durability requirements Galvanising thickness can be varied to achieve life up to 50 years.

Paint coating is more effective than Galvanising in highly corrosive environments due to its flexibility in designing to specific requirements. It is important to design the Dry Film Thickness ( DFT) to provide enough durability based on the external atmospheric conditions.

Galvanising and painting (also known as duplex systems) are also common for lintels in coastal areas.

Cathodic protection is more suitable for infrastructure construction such as bridges and tunnels.

How to make durable buildings?

It is important to work with a competent design team who are experienced in the durability of materials, to design and construct buildings that can last for their intended life.

With the right material selection, design, detailing, and maintenance, the building structure can perform satisfactorily to its intended use. It is not rocket science!

Architects, engineers, and specifiers shall design for durability and specify the right material specification and coating requirements. Concrete and mortar strengths, timber durability rating, steel coating thickness, and maintenance regime, the strategies are many.

Durability is not just for the structural performance of buildings but also encompasses the functional aspects as well. For example, a steel structural beam stained due to corrosion may still function as a structural member but may not be acceptable in a living room.

Therefore, it is critical to understand the various functional uses and performance requirements. Structural engineers need to work closely with architects to design appropriate durability requirements.

Compliance with NCC and referred Australian Standards will ensure durable buildings. We don’t want anyone thinking of demolishing their building because of durability issues. Engage Intrax to ensure the longevity and quality of your project.

Phillip Campbell

Chairman of the Board – Non-Executive Director and member of the risk committee

Phillip Campbell is the Non-Executive Chairman of the Board of the Intrax Consulting Group.

Phillip is an experienced company director with a demonstrated history of successful transformations of public and private organisations by focusing on the intrinsic value of the business, working behind the scenes to improve the effectiveness of management and building strong foundations for growth.

Graduating from Queensland University with a Bachelors’ degree in Electrical Engineering, Phillip has been CEO/MD of a number of public and private companies in the manufacturing and engineering services sectors.

He is a Graduate Member of the Australian Institute of Company Directors.

Phillip has an abiding belief that a stable and safe family home environment is critical for children to achieve a sound education and establish the foundations of a productive life. This is one of the reasons he joined Anchor Inc and is currently its Chairman.

Danny Borzillo

Executive Director

Danny Borzillo is an Executive Director.

Danny has a broad range of experience gained over 30 years of working in the construction and engineering consultancy industries.

Danny is the co-Founder of Intrax Consulting Engineers and was instrumental in the establishment of the Business in 2003. The early success of Intrax was mainly attributed to Danny’s innovation in the volume housing market and positioning Intrax to off its unique end to end service.

Danny Borzillo held the position of Managing Director of Intrax and then joint Managing Director together with Robert Borzillo until March 2011 when Barry Borzillo was appointed.

Prior to establishing and working at Intrax, Danny was involved in several small to mid-sized engineering consultancy businesses. His roles in these companies included Business Owner, Director and Senior Manager, providing consultancy design and construction advice and design services to the building industry.

Danny holds a Bachelor of Engineering (Civil) from Victoria University, is a Chartered Member of the Australian Institute of Engineers and is a Member of several industry technical bodies.

Barry Borzillo

CEO/MD

Barry Borzillo is the CEO/MD of the Intrax Consulting Group

Barry has a broad range of experience in the construction, telecommunications, professional services and government outsourcing industries.

Prior to his appointment in March 2011 as CEO/MD of Intrax, Barry held CEO roles for the ESH group, Tenix Solutions and Ericsson Australia/NZ. He spent nearly four years in the USA in senior roles with Ericsson Inc.

Barry began his career at Ericsson in 1987 as part of the Graduate program. He holds a Masters of Business Administration (Executive) from the Australian Graduate School of Management, a Bachelors’ degree with Distinction in Electrical/Electronic Engineering from Victoria University, is a Fellow of the Australian Institute of Engineers and is a Graduate of the Australian Institute of Company Directors.

Barry is passionate about improving educational outcomes in disadvantaged communities which is one of the reasons he joined the Ardoch Youth Foundation Board for ten years, the last five of which he was also the Chairperson.

Andrew Taylor

CFO & Company Secretary

Andrew has more than 30 years of diverse and progressive senior financial experience in professional services, manufacturing and government industries. He is a trusted and proactive business partner, has developed and led high-performance teams, been a member of executive teams and Boards, and driven organisation change with profitability, working capital and structure.

Prior to his appointment in April 2018 at Intrax, Andrew was regional CFO – Australia and NZ region at Aurecon. He spent 17 years at Aurecon leading the finance team, corporatising the business and driving operations across ANZ and Asia.

Andrew is CPA qualified and holds a Bachelor of Business – Accounting.

Andrew’s career highlights include: aligning and integrating 2 major businesses; the initiation, design and implementation of reporting and budgeting software globally; and development and leadership of a new Finance function for a growing company. Andrew enjoys team leadership, developing and mentoring others to reach their potential, and is passionate about maturing, evolving and improving companies and businesses.

Nigel Guo

Executive Director and CTO

Nigel is the Chief Technology Officer of Intrax.

Nigel joined Intrax in 2007 and rapidly rose through ranks with the business. Nigel completed a Bachelor of Structural and Civil engineer from University of Melbourne, and also earned a  Master of Business Administration from Melbourne Business School.

Nigel has had many roles at Intrax, from engineer, to running the residential engineering and quality departments before being promoted into general management roles.

He has played a key role in continuing process and system improvement at Intrax, developing most of the processes and procedures used in the housing departments today that have enabled Intrax to scale with quality, while consistently delivering to clients..

In his spare time Nigel likes sketching, playing bass guitar and soccer.

Robert Borzillo

Non-Executive Director, member of the risk committee

Robert Borzillo is a Non-Executive Director of the Intrax Consulting Group. Robert has over 40 years’ experience working as an engineer in various capacities within the Australian building Industry.

Robert was a co-founder of Intrax Consulting in 2003 with a vision to establish a dynamic end to end values driven engineering consultancy delivering services into the residential housing and building construction industries in Australia

Prior to the establishment of Intrax Consulting Robert was General Manager of Porta Moulding working within the Australian timber industry; in forestry, manufacture and distribution of timber products for the residential building and construction industries.

In his earlier days, Robert also worked as an engineer for Humes Concrete. Involved in the design, manufacture, supply, and installation of precast concrete components for large scale civil and building infrastructure. Robert spent time working in Sydney NSW, and Far North Queensland on many projects. Prior to that Robert spent time with the Country Roads Board in road design and planning of Victorian road infrastructure.

Robert earned a bachelor’s degree from Victoria University, BE Civil is a Certified Practicing Engineer CPE, is on the National Engineers Register. NER, and an accredited practicing engineer in most Australian states. Robert is also a graduate of the Australian Institute of Company Directors. GAICD.

Robert’s passion outside of work is travel and snow skiing. He has had the privilege to combine these passions traveling extensively and skiing in Australia, New Zealand, USA, Japan, Italy, and Switzerland.