Never has the spotlight been shone so brightly on bushfires in Australia than in recent months where out-of-control fires tore through vast areas in NSW, ACT, Victoria and South Australia. It is estimated that more than 2,000 homes have been lost during the recent bushfire crisis in Australia.
National building requirements for residences in bushfire-prone areas were scaled-up after the “Black Saturday” bushfires in Victoria in 2009, in which 173 people died and more 2,000 homes were destroyed.
Like many regulations in Australia, buildings are regulated by states and territories but governments have recognised the value of nationally consistent building codes through the National Construction Code. This code, among other things, sets minimum standards for the design and construction of new buildings on bushfire-prone land.
A residential building on bushfire-prone land, the code states, must be designed and constructed to “reduce the risk” of ignition from a bushfire, appropriate to the risk from bushfire flames, burning embers, radiant heat and intensity of the bushfire attack.
Bushfire Attack Level rating
Properties are assessed and given a “Bushfire Attack Level” (BAL) rating by inspectors who examine the risk to which a building is potentially exposed on the individual site and conditions such as vegetation type and density, and slope of the land.
There are six BAL levels that classify the severity of potential exposure to bushfire. The highest – BAL FZ – is for buildings exposed to an extreme risk, such as a house surrounded by trees that could produce direct contact from flames.
A house in Rosedale NSW that was rated BAL FZ, known colloquially as flame-zone, survived the recent bushfires when all the surrounding houses were destroyed. It was built in 2017 by Batemans Bay local builders TLC Constructions and aside from some minor damage caused by explosions from nearby houses as they burnt to the ground, it is remarkably untouched.
Even the chocolate biscuits survived
TLC Constructions owner Tim Love says that even the chocolate biscuits in the pantry survived the fiery inferno, and there was no trace of smoke inside the building.
“Although it was built to the highest fire-rating I must admit that I was skeptical about its chances of surviving such a ferocious fire, but the proof is there.
“There were many products and techniques used to build this house but chief among them was the Spantec flooring system which included posts, joists, and the Ezipier system. We’ve used the Spantec system many times before so we’re confident that it would work well on this job.
“This wasn’t a straightforward build so the architect Thomas Caddaye and TLC worked together to find the right solution for the client that also fitted their budget. It took longer than our usual design and approval phase but it was well worth the effort.
“We’ve built a number of houses in the flame-zone so understood the general concepts, but every new home is different so we needed to custom design it to suit the client and the site,” said Love.
Worked closely with Spantec to find the right solution
We’ve worked with Spantec for about 15 years so are very familiar with the product range. On this project, we worked closely with the Spantec team to ensure the product was utilised in the correct way to gain the maximum benefit. I find the Spantec flooring systems to be easy to use for lots of applications,” added Love.
He said that complying with the bushfire rating meant construction costs increased by about 20 to 25 per cent, but it was still an affordable house.
Construction details for each BAL cover building elements such as floors, walls, roofs, doors, windows, vents, roof drainage systems, verandahs, water and gas supply pipes.
In the Rosedale home key elements that worked alongside the Spantec flooring system were the boundary wall cladding, hebel power floor and the approved fire-rated windows and shutter system.
The rebuilding phase begins
The fires on the NSW south coast have now been brought under control which means many people need to rebuild their homes that were lost.
TLC Constructions has received an increase in the number of enquiries as a result of the destruction. “I certainly didn’t want to increase our workload in this way we are more than happy to be involved in the rebuilding process our knowledge of the fire-rating system will certainly make this more streamlined for everyone at this difficult time.
“As a local builder, I get a huge amount of satisfaction and pride from creating homes for people that they really love. We recently spoke with a couple who said they wanted to replace their home with something really similar but when we got them talking they realised that this is an opportunity to gain the things that their previous home lacked. And while they will take a long time to recover they are now excited about a brand new home and creating new memories.
“And I’m sure we’ll be working closely with Spantec to ensure the new homes meet the BAL requirements,” added Love.
For nearly 30 years Spantec Systems has been pioneering the use of steel for building professionals, owner-builders and DIY-ers. To find out how we can help with your next build, contact us on (02) 4860 1000 or by sales@spantec.com.au. Already have plans and engineer’s drawings? Then get a quote now.
It’s hard to not think about bushfires at the moment, regardless of where you live in Australia. Given our typically hot and dry climate, bushfire concerns are a very real part of the conversation during Spring and Summer.
Just like wind classification and soil classification, there are building guidelines and standards that govern the construction of residential homes in bushfire prone areas that need to be met when building your new home.
Referred to as “bush fire prone land” in NSW and “bushfire prone areas” in Victoria, the NSW Rural Fire Service classifies this as, “land that has been identified by local council which can support a bush fire or is subject to bush fire attack”. Bush fire prone land maps are prepared by local councils and certified by the relevant state or territory fire authority.
Understanding Bushfire Attack Level categories
There is no one size fits all designation for determining what is and isn’t classified as bush fire prone land. But if your building site is surrounded by bush, or located close to grassland, paddocks or the coastline, then you may be on bushfire prone land.
If your site is determined to be on bush fire prone land, it will be assessed as falling into one of six categories of Bushfire Attack Level (BAL). Each level measures (in kilowatts/m2) the severity of a building’s potential exposure to ember attack, radiant heat and direct flame contact. Which BAL your site will be classified in will be determined by:
- the region where you site is located;
- the type of vegetation surrounding your property;
- the distance from your home to individual vegetation types; and
- the slope on your property.
The six BAL categories, as covered in Australian Standard AS 3959 – 2009, Construction of buildings in bushfire-prone areas, are:
- BAL – Low: Insufficient risk to warrant specific construction requirements.
- BAL – 12.5: Ember attack with heat flux of up to 12.5kW/m2.
- BAL – 19: Increasing levels of ember attack and ignition of debris with a heat flux of up to 19kW/m2.
- BAL – 29: Increasing levels of ember attack and ignition of debris with a heat flux of up to 29kW/m2.
- BAL – 40: Increasing levels of ember attack and ignition of debris with a heat flux of up to 40kW/m2 and increased likelihood of exposure to flames.
- BAL – FZ: Direct exposure to flames from the fire front, in addition to heat flux and ember attack greater than 40kW/m2.
Critical requirements for building on bush fire prone land
If you’re building in a bushfire prone area, there are additional requirements that you and your builder need to consider regarding the building materials that you use on your project. This includes critical structural aspects of your home, such as piers, decks, floors and roofs. These requirements are outlined in two Australian building industry standards:
- Australian Standard AS 3959 – 2009, Construction of buildings in bushfire-prone areas; and
- NASH STANDARD Steel Framed Construction in Bushfire Areas – 2014.
The onus is on both the property owner and their builder to ensure that these standards are met. In order to build the home that you want to in a bushfire prone area, you may need to modify the style, plans and construction material used in your build.
Spantec building supplies for bushfire prone sites
At Spantec, our proprietary range of steel piers, decks, suspended floors and roofs can be incorporated into designs to meet the requirements for all six
BAL categories. Spantec steel building components comply with the above-mentioned Australian building industry standards and, with few limitations, are equally suitable for inclusion in designs prepared using either AS 3959 or the NASH Bushfire Standard.
For more information on how Spantec’s steel building materials can enable you to build the home that you want on your bushfire prone site, visit our building in bushfire prone areas page now.
Need help with building on a bushfire prone site?
For nearly 30 years Spantec Systems has been pioneering the use of light steel flooring systems, including structural steel beams and adjustable steel piers under sub-floors, for building professionals, owner-builders and DIY-ers. To find out how we can help with your next build, contact us on (02) 4860 1000 or by sales@spantec.com.au. Already have plans and engineers drawings? Then get a quote now.ß
No two building sites are exactly the same. Even when two sites look similar on the surface, what’s going on underneath may well tell a different story. Even building sites on the same street can have very different properties. These are things that engineers need to consider when designing building projects and building components such as frames.
As such, part of every building project includes analysing and assessing the site in order to define the engineering and design parameters required to deliver a safe and long-lasting finished product.
The term builders and architects use to describe this is Site Specific Engineering. Site Specific Engineering delivers a set of detailed engineering documents pertaining to a specific building site. These documents will detail critical design requirements for your project and may include information regarding footings, bracing, and requirements for fixing to existing structures. They may also include regulatory requirements, such as Form 11 – Interim Certificate of Classification (Victoria) and Form 15 – Compliance Certificate for Building Design or Specification (Qld/SA).
What does Site Specific Engineering cover?
Every building and every location is unique, so it goes without saying that every frame must also be unique. Site Specific Engineering considers location, shielding and terrain, building classification, soil classification and wind region to accurately determine design requirements for the following:
- Footings: Not the pier itself, but rather the formation that will be supporting the pier. Footings reinforce support to individual columns while transferring the load into the soil.
- Bracing: Diagonal members that provide stability, which also help make the structure stiffer in response to lateral movement.
- Fixing to existing: While all frames can be designed as free standing, if there is an existing structure that you want to fix your frame to, then an engineer will need to determine if the existing structure can safely support the added frame.
Why Site Specific Engineering matters
Why is Site Specific Engineering so important? Because these documents provide you and your builder with assurance and peace of mind in knowing that a qualified engineer has inspected your site and certified your project.
Also, it’s worth noting that many local authorities will not accept engineering documents unless they are site specific. After all, there is no room for generalisation and ‘guesstimation’ when it comes to building, where precision and accuracy are mandatories for a successful build that will stand the test of time.
Site Specific Engineering with Spantec
When you choose Spantec Systems for your designed roof and floor frames, you’ll get peace of mind knowing that all Spantec frames are designed using engineered and certified span charts to adhere to site specific engineering requirements.
Some building suppliers may provide you with generic engineering for your frame, but with Spantec Systems you will always receive site specific engineering to ensure that your frame stringently meets the design requirements of your specific site.
Our in-house engineer can inspect your site and certify your project. We will ask you a lot of questions, but we do this because every Spantec frame is site specific and designed specifically for your site. This means it will be designed to endure the environment in which it will sit, which enables your Spantec frame to stand the test of time.
If you have your own engineer, or if you are an engineer yourself, we are happy to receive Site Specific Engineering documents from you.
Spantec for your next project
For nearly 30 years Spantec Systems has been pioneering the use of light steel flooring systems, including structural steel beams, frames and adjustable steel piers under sub-floors, for building professionals, owner-builders and DIY-ers. To find out how we can help with your next build, contact us on (02) 4860 1000 or by emailing sales@spantec.com.au.
The type of soil on your block will determine the design of your footings. Soil classification can differ from block to block, even on the same street, as it can be impacted by variables such as the removal or trees as well as surrounding buildings.
Soil classification relates to the soil material that your piers will be sitting on, and how much that soil material is likely to be affected by moisture content, which causes the soil material to shrink and swell.
Determining soil classification is important for all projects requiring footings because in order for your footings to effectively achieve their purpose – i.e., supporting your foundation and preventing settling – they need to be designed with the integrity of the surrounding soil taken into account.
Soil classification classes explained
There are six different soil classification classes:
- Class A – stable non-reactive: Rock or sand sites featuring little or no movement.
- Class S – slightly reactive: Clay sites featuring slight ground movements due to moisture changes.
- Class M – moderately reactive: Clay sites featuring moderate ground movements due to moisture changes.
- Class H –highly reactive: Clay sites featuring high ground movements due to moisture changes.
- Class E – extremely reactive: Clay sites featuring extreme ground movements due to moisture changes.
- Class P – problem: Irregular sites with existing issues such as soft soils, loose sands, landslip, mine subsidence, collapsing soil, erosion, fill, abnormal moisture conditions, water courses, or existing structures.
Soil classification is determined by conducting an inspection and compiling a geotechnical report of your site. The geotechnical report will detail your soil bearing capacity, which is a measurement of the weight the soil can support. The engineer then uses the information in the geotechnical report to design the size (usually in terms of diameter) and the depth of the footings that your project will require.
Why geotechnical reports and soil classification matter
It is important that a geotechnical report is compiled for your site, because if this information isn’t provided the engineer may only be able to make an assumed classification. Assumed classifications, by necessity, are typically conservative and may be based on a more reactive soil type than what is actually on your site. Assumed classifications can result in your pier depths being deeper – and more expensive – than what is actually required to meet building and safety standards.
Spantec uses the information contained in the geotechnical report when designing your floor. If your site has a high chance of movement (Class H), or if there is a problem site with the site (Class P), we will consider reducing the number of piers need. This will bring down your site excavations costs, but this reduction in site costs may result in an increase to your floor frame cost due to the need to use larger members for the floor frame.
Spantec Systems carefully considers all details regarding your site when determining the most cost-effective and most appropriate design for your project. At Spantec, our design and engineering team works with you to understand your building site and to determine its soil classification. From there, our experts will advise on the most appropriate footing design for your project.
Need help with your next building project?
For nearly 30 years Spantec Systems has been pioneering the use of light steel flooring systems, including structural steel beams and adjustable steel piers under sub-floors, for building professionals, owner-builders and DIY-ers. To find out how we can help with your next build, contact us on (02) 4860 1000 or by sales@spantec.com.au. Already have plans and engineers drawings? Then get a quote now.
The wind classification for your site will play a critical role in determining what your overall design can look like. The wind classification of your site determines the amount of bracing, as well as the type of bracing, that your project will require. Wind classification covers three key areas of your build:
- roof bracing;
- wall bracing; and
- floor and sub-floor bracing.
It can also influence the type of tie-down between your:
- roof frame to wall frame;
- wall frame to floor frame;
- your floor frame to the sub-floor structure; and
- the sub-floor structure to your pad/strip footing or slab.
Defining wind classification
But what exactly is wind classification? And why does it matter in building projects?
Wind classification is the term used by building engineers and other construction professionals to measure the gust wind speeds (m/s) that affect a given site. Wind classification is determined by the wind speed at a structure, which in turn is influenced by the terrain the wind flows over as it approaches the structure.
Wind classification of a building site is critical for every building project as it helps to ensure that a building or structure is designed and built to a level that is appropriate to safely withstand the wind forces it will be subjected to.
Assessing and determining the wind classification for your site ensures that your project is designed and built to the installation standard that will ensure it is not structurally compromised in instances of high wind.
How your wind classification is determined
There are four key areas that your building engineer or designer will take into consideration when determining the wind classification of your site: wind region, terrain category, shielding, and topography.
- Wind region
Your designer will locate your site in relation to its wind region. The different wind regions in Australia are defined as:
- Region A (Normal): Coffs Harbour and south NSW.
- Region B (Intermediate): North of Coffs Harbour (NSW), Gascoyne Junction (Western Australia).
- Region C (Tropical Cyclones): Bundaberg, Hervey Bay (Queensland), Northern Territory, and parts of Western Australia.
- Region D (Server Tropical Cyclones): Port Headland to Carnarvon, Western Australia.
- Terrain category
The terrain category describes the surrounding area 500m from your building site. The wind speed when it reaches your structure will be affected by what obstructions it flows over as it approaches your house. Terrain categories range from TC1 (very exposed open terrain – no obstructions) to TC3 (suburban housing to light Industrial – lots of obstructions).
- Shielding factor
The shielding factor takes into consideration the surrounding area 500m from your building site, and can be influenced by obstructions such as other houses or thick tree or wooded areas. Shielding factors range from full shielding (in the middle of suburban housing) to no shielding (no surrounding permanent structures).
- Topography
The final key factor in determining the wind classification of your site is topography. Your topography classification is determined by the effect the wind has on your house according to its location on a hill, and the hills height and slope.
Combining these four categories will determine the wind classification for your site, which in turn will determine both the type of bracing and the amount of bracing that your project will require.
At Spantec Systems, our design and engineering team works with you to understand your building site and to determine its wind classification. From there, our experts will advise on the bracing that your project requires.
Need help with your next building project?
For nearly 30 years Spantec Systems has been pioneering the use of light steel flooring systems, including structural steel beams and adjustable steel piers under sub-floors, for building professionals, owner-builders and DIY-ers. To find out how we can help with your next build, contact us on (02) 4860 1000 or by sales@spantec.com.au. Already have plans and engineers drawings? Then get a quote now.
