Floor Bearers and Joists Australian Standards: A Comprehensive Guide 

When building a new home or renovating an existing one, it’s essential to ensure that it meets the floor bearers and joists Australian standards. These structural elements provide the foundation for the flooring system, ensuring it is safe, stable, and durable. Compliance with Australian standards is crucial to ensure that the floor can support the weight of furniture, appliances, and people without sagging or cracking.

The Australian building code mandates that all floor bearers and joists meet specific requirements in terms of their size, material, spacing, and installation. For example, the standard specifies the minimum thickness and width of floor bearers and joists, depending on their length and the load they must support. It also outlines the maximum spacing between joists and bearers, which varies depending on the type of flooring material used. Additionally, the standard provides guidelines for the installation of bearers and joists, such as fixing them to the foundation and ensuring they are level and straight.

Understanding Floor Bearers and Joists

When it comes to building a timber-framed structure, floor bearers and joists are essential components. Bearers are horizontal members that run perpendicular to the joists and rest on stumps, piers, or a foundation wall. Joists are the horizontal members that run parallel to each other and are supported by the bearers. Together, bearers and joists form a subfloor system that provides a solid base for the flooring material to be laid on.

In Australia, the AS 1684 Residential Timber-framed Construction standard provides guidelines for designing and constructing bearers and joists. The standard specifies the maximum allowable spans for bearers and joists based on the size and spacing of the timber used. The span tables for bearers and joists are divided into different grades of timber, such as MGP10, MGP12, and F17, and are based on the loads that the subfloor system will be subjected to.

When designing a subfloor system, it is important to consider the type of timber that will be used for the bearers and joists, as well as the spacing between them. The spacing of the bearers and joists will depend on the size of the timber used and the loads that will be placed on the subfloor system. The AS 1684 standard provides tables that specify the maximum allowable spans for different timber sizes and spacings.

It is important to note that the subfloor system must be designed to withstand not only the weight of the flooring material and the contents of the room but also any additional loads that may be placed on it. For example, if the room will be used for heavy equipment or furniture, the subfloor system must be designed to support the additional weight.

When constructing a subfloor system, it is also important to ensure that the bearers and joists are level and straight. Any variations in the levelness or straightness of the bearers and joists can cause problems with the flooring material, such as squeaks or unevenness.

Australian Standards for Floor Bearers and Joists

When it comes to constructing floors for buildings, there are specific Australian standards that must be followed. These standards ensure that the floors are safe, durable, and able to withstand the weight of the building and its occupants. The primary Australian standard for floor bearers and joists is AS 1684 – Residential timber-framed construction. This standard outlines the requirements for designing and constructing timber-framed buildings, including the floors.

The National Construction Code (NCC) also contains performance requirements for floors, including Performance Requirement P2.1.1. This requirement specifies that floors must be designed and constructed to support the weight of the building and its occupants, and to resist lateral forces such as wind and earthquake loads.

To meet the performance requirements of the NCC, acceptable construction practices must be followed. These practices are outlined in AS 1684 and include requirements for the size, spacing, and grade of floor bearers and joists. The standard also specifies the maximum allowable spans for timber floor joists based on their size and spacing.

It is important to note that the requirements for floor bearers and joists may vary depending on the specific building design and location. For example, buildings in high wind or earthquake zones may have different requirements than those in low-risk areas. It is essential to consult with a qualified engineer or builder to ensure that the floor design meets all relevant standards and requirements.

Materials Used in Construction

When it comes to building a floor, there are several materials to choose from. The most commonly used material for residential floors is timber. Timber is a popular choice due to its flexibility and versatility. It is also relatively easy to work with, making it a popular choice for DIY projects.

Steel is also a popular material for building floors. Steel frame homes are becoming increasingly popular due to their durability and strength. Steel is often used for buildings with additional weight requirements. Structural steel members are commonly used in commercial and industrial buildings due to their strength and load-bearing capabilities.

Plywood is another material used in construction, particularly in flooring. Plywood is a strong and durable material that is resistant to warping and shrinking. It is often used as a subfloor material and can be used in conjunction with other materials such as timber or steel.

Copper is another material that is used in construction, particularly in plumbing. Copper pipes are durable and long-lasting, making them a popular choice for water supply lines. However, copper is not commonly used in flooring construction.

Masonry veneer construction is a method of building where a layer of brick or stone is used as a decorative covering over a structural frame. This method is commonly used in commercial and industrial buildings and is not commonly used in residential flooring construction.

Key Components and Their Functions

When it comes to constructing a floor, there are several key components that must be considered. These include the bearers, joists, stumps, posts, footings, and plates. Each of these components plays an important role in ensuring that the floor is structurally sound and can support the weight of the building and its occupants.

Bearers

Bearers are horizontal beams that run parallel to the ground and are supported by stumps or posts. They are designed to transfer the weight of the building to the stumps or posts, which in turn transfer the weight to the footings. The bearers must be level and have a sufficient cross-sectional area to support the load they will bear.

Joists

Joists are horizontal beams that run perpendicular to the bearers and support the floorboards or decking. They are typically spaced at regular intervals and must be level and have a sufficient cross-sectional area to support the load they will bear. The spacing of the joists will depend on the size and spacing of the bearers, the span of the joists, and the load they will bear.

Stumps and Posts

Stumps and posts are vertical supports that are used to support the bearers. They are typically made of timber or steel and must be anchored securely to the footings. The size and spacing of the stumps and posts will depend on the load they will bear and the span of the bearers.

Footings

Footings are typically made of concrete and are used to transfer the weight of the building to the ground. They are designed to spread the load over a larger area and prevent the building from sinking or settling. The size and depth of the footings will depend on the load they will bear and the soil conditions.

Plates

Plates are horizontal beams that are used to connect the stumps or posts to the bearers. They are typically bolted or nailed to the stumps or posts and provide additional support for the bearers. The size and spacing of the plates will depend on the load they will bear and the size of the stumps or posts.

Framing Techniques

When it comes to floor bearers and joists, Australian standards dictate specific framing techniques that must be followed to ensure structural integrity and safety. Here are some of the framing techniques you should keep in mind:

Timber Framing

Timber is a popular choice for framing floors due to its strength, durability, and versatility. When using timber for framing, it is important to use timber that is graded and treated to meet Australian standards. The size and spacing of timber bearers and joists will depend on the load they need to support.

Wall Framing

Wall framing is an important part of floor framing, as it provides lateral support and stability. The walls should be properly braced to prevent movement and ensure they can withstand any horizontal forces that may be exerted on them.

Floor Framing

Floor framing involves the use of bearers and joists to support the weight of the floor and any loads that may be placed on it. The size and spacing of bearers and joists will depend on the load they need to support, as well as the span of the floor.

Roof Framing

Roof framing is similar to floor framing, but it involves the use of rafters and purlins to support the weight of the roof. The size and spacing of rafters and purlins will depend on the weight of the roof and the span of the roof.

Steel Framing

Steel framing is becoming more popular in Australia due to its strength and durability. When using steel for framing, it is important to use steel that is graded and treated to meet Australian standards. The size and spacing of steel bearers and joists will depend on the load they need to support.

Spacing and Spanning

When it comes to floor bearers and joists in Australia, spacing and spanning are crucial factors to consider. The spacing of the floor joists depends on the spanning capacity of the flooring being supported. The maximum allowable spacing of joists supporting tongue and groove strip and sheet flooring relates to the species of wood, grade, and thickness.

For example, if you are using particle board or 15mm compressed FC sheet, the standard floor types, the dead load is 0.75 kPa. In this case, joists supporting floor loads only (or decks less than 1m above ground) should be spaced. Similarly, bearers supporting floor loads only (or decks less than 1m above ground) should be spaced.

The bearer span is another important factor to consider. The effective bearer spacing is a measure of the width of the load area being supported by the member. The top flange of the lintel must be laterally restrained at the loading points.

Cantilever is another factor that needs to be considered when it comes to floor bearers and joists. Cantilever refers to the unsupported overhanging length of the bearer or joist. The maximum allowable cantilever for floor bearers and joists depends on the species, grade, and size of the timber. 

Finally, continuous spans are another important factor to consider. Continuous spans refer to the length of the bearer or joist that is supported at both ends. The maximum allowable continuous span for floor bearers and joists depends on the species, grade, and size of the timber. 

Fixings and Fasteners

When it comes to installing floor bearers and joists, it is important to use the correct fixings and fasteners to ensure the structural integrity of the floor. The Australian Standards provide guidelines for the types of fixings and fasteners that can be used.

Nails

Nails are commonly used to fix floor bearers and joists together. The Australian Standards specify the size and length of nails that should be used for different types of timber and for different applications. For example, for softwood bearers and joists, a 75mm x 3.75mm nail should be used, while for hardwood bearers and joists, an 80mm x 4.0mm nail should be used.

Coach Screws

Coach screws can also be used to fix floor bearers and joists together. The Australian Standards specify the size and length of coach screws that should be used for different types of timber and for different applications. For example, for softwood bearers and joists, a 10 gauge x 75mm coach screw should be used, while for hardwood bearers and joists, a 12 gauge x 100mm coach screw should be used.

Fixings and Fasteners

The Australian Standards also provide guidelines for other types of fixings and fasteners that can be used to fix floor bearers and joists together. These include bolts, washers, and nuts. The size and length of these fixings and fasteners depend on the type of timber, the size of the floor, and the load that the floor will bear.

Adhesives

Adhesives can also be used to fix floor bearers and joists together. The Australian Standards provide guidelines for the types of adhesives that can be used and the application process. It is important to follow these guidelines to ensure that the adhesive is applied correctly and that it provides a strong bond between the timber components.

External Walls and Cladding

When it comes to building an external wall, it is important to ensure that it is structurally sound and complies with Australian standards. The external wall must be designed to resist wind loads and provide adequate support for the cladding system.

Wall bracing is an essential component of external walls. It helps to resist lateral forces and provide stability to the building. The Australian standard AS 1684.2-2010 provides guidelines for wall bracing design and installation.

Wall cladding is the external material that covers the wall frame. It can be made of various materials such as timber, metal, brick, or stone. The cladding must be installed in accordance with the manufacturer’s instructions and comply with the relevant Australian standards.

If you are using timber cladding, you must ensure that it is treated to protect against decay, termites, and fire. The Australian standard AS 1604.4-2012 provides guidelines for timber treatment and preservative treatment levels.

When designing the wall frame, it is important to consider the spacing of the floor bearers and joists. The Australian standard AS 1684.2-2010 provides guidelines for the maximum span and spacing of floor bearers and joists. The maximum span and spacing depend on the type of timber used, the load capacity, and the distance between the bearers.

Subfloor Ventilation and Clearance

When it comes to constructing floor bearers and joists in Australia, it’s important to consider subfloor ventilation and clearance. Adequate ventilation and clearance can help prevent moisture buildup, which can lead to structural damage and pest infestations.

According to the Australian Standard 3660, there are minimum clearance requirements between the ground and the underside of a subfloor. This standard is called “Termite management,” and it outlines good building practices for avoiding termite attack and maintaining adequate subfloor ventilation. The minimum clearance requirements vary depending on the type of construction and the climate zone.

To ensure proper subfloor ventilation, the National Construction Code (NCC) specifies the minimum amount of subfloor ventilation openings and height of subfloor framing members above ground level for the three climatic zones in Australia. Generally, the season with the highest relative humidity is used to determine the minimum requirements. Table 3.4.1.1 and Table 3.4.1.2 in the NCC specify these requirements for southern and northern Australia, respectively.

It’s essential to ensure that subfloor ventilation openings are not blocked or obstructed by any materials or debris. Crossflow ventilation is also crucial to the performance of structural timber products, including timber flooring. Most dwellings constructed over joists and bearers are “bricked in or cladded in” from finished floor height down and lack sufficient cross flow ventilation. This can lead to moisture buildup and structural damage.

Maintenance and Durability

When it comes to floor bearers and joists, it is important to ensure that they are maintained properly in order to maximize their durability. Regular maintenance can help to prevent corrosion and other forms of damage that can compromise the structural integrity of your flooring system.

One of the most important things you can do to maintain your floor bearers and joists is to ensure that they are properly ventilated. Poor ventilation can lead to moisture buildup, which can cause corrosion and other forms of damage over time. It is also important to keep the area around your flooring system clean and free of debris, as this can help to prevent damage from occurring.

In addition to regular maintenance, it is also important to choose high-quality materials that are designed to withstand the test of time. When selecting floor bearers and joists, it is important to choose materials that are in compliance with Australian Standards for Structural Exterior Products, such as AS 5068-2006.

It is also important to consider the soil conditions and floor clearance when selecting your flooring system. Bearers and joists that are too small or spaced too far apart can lead to structural instability and compromise the overall durability of your flooring system.

Specific Requirements for Single-Storey Constructions

When it comes to single-storey constructions, the Australian Standards have specific requirements that need to be followed for the floor bearers and joists. Here are some of the key points to keep in mind:

Floor Joists

Floor joists are horizontal structural members that support the floor and transfer the weight of the floor to the bearers. The following are some of the specific requirements for floor joists in single-storey constructions:

• The spacing between the floor joists should not exceed 450mm.
• The maximum span of floor joists should not exceed 3.6m, and the minimum size of the joist should be 150mm x 50mm.
• The size of the joist may vary depending on the type of timber used, the spacing of the joists, and the load that they are expected to carry.

Floor Bearers

Floor bearers are horizontal structural members that support the floor joists and transfer the weight of the floor to the foundation. Here are some of the specific requirements for floor bearers in single-storey constructions:

• The size of the floor bearer may vary depending on the type of timber used, the spacing of the bearers, and the load that they are expected to carry.
• The spacing between the floor bearers should not exceed 1.8m.
• The maximum span of the floor bearer should not exceed 3.6m, and the minimum size of the bearer should be 150mm x 50mm.

Subfloor Ventilation

Subfloor ventilation is an important aspect of single-storey constructions, as it helps to prevent moisture buildup and protect the structural integrity of the floor. Here are some of the specific requirements for subfloor ventilation in single-storey constructions:

• The subfloor should be ventilated to provide at least 5,000mm² of ventilation per linear metre of external wall.
• The vents should be evenly distributed around the perimeter of the building, with a minimum of two vents on each side.
• The vents should be located no more than 1.5m from the corners of the building.

Considerations for Suspended Floors

When designing a suspended floor system, there are several considerations that need to be taken into account to ensure that the floor is structurally sound and meets Australian standards. Here are some of the key factors to consider:

Load Area

The load area is the width of the area being supported by the floor bearer. The effective bearer spacing is a measure of the width of the load area being supported by the member. It is important to ensure that the load area is evenly distributed across the floor system to prevent any one area from being overloaded.

Floor Joists and Bearers

Floor joists and bearers are critical components of a suspended floor system. The Australian Steel Institute provides detailed information on the design and installation of floor joists and bearers in Chapter 4 of their Handbook. The Stramit Residential Floor Framing System is a popular option for residential construction, combining Stramit structural members with Steel-MAX™ brackets and accessories.

Vibration

Vibration can be a concern in suspended floor systems, particularly in multi-storey buildings. The NASH Handbook provides guidance on vibration design for residential and low-rise steel framing. It is important to consider the potential sources of vibration, such as foot traffic, and to design the floor system to minimise the effects of vibration.

Connections

The connections between the various components of the suspended floor system are critical to its overall structural integrity. The NASH Handbook provides detailed guidance on the design and installation of connections for residential and low-rise steel framing. It is important to ensure that the connections are strong and secure, and that they are installed correctly to prevent any potential for failure.

Understanding Floor Systems and Decking

When it comes to building a floor system, it is important to understand the Australian Standards for decking bearers and joists. These standards provide guidance on the appropriate timber sizes, spans, loads, and connections for your project.

The first step in building a floor system is to determine the required span and spacing for your bearers and joists. This will depend on the size and load of your decking, as well as the type of timber you are using. You can use online calculators or consult the relevant Australian Standards to determine the appropriate sizes and spans.

Once you have determined the required sizes and spans, you can begin constructing your floor system. This will involve setting out the sub-floor frame, installing the timber bearers, and then installing the timber floor joists. It is important to follow the relevant work instructions, including plans, specifications, quality requirements, and operational details.

When it comes to decking, there are a variety of timber species to choose from, each with their own unique characteristics and properties. You should choose a timber species that is appropriate for your project, taking into account factors such as durability, strength, and appearance.

Weatherproofing and Stress Grade

When it comes to building floor bearers and joists, it’s important to consider the weather conditions they will be exposed to. The Australian climate can be harsh, and untreated timber is vulnerable to fungal and termite attacks. That’s why it’s recommended to use chemically treated timber that is resistant to these types of attacks. The Weatherproof range is a ready-to-use building product that is chemically treated using an organic H3 LOSP preservative for resistance against termite and fungal attack. It is intended for use in Australia’s toughest conditions and meets Australian Standards AS 1604.

Another important factor to consider when building floor bearers and joists is the stress grade of the timber. Stress grading is a measure of the strength and stiffness of the timber and is essential for ensuring the safety and durability of the structure. The Australian Standard AS 1720.1 specifies the stress grades for different types of timber used in building construction.

The stress grade of timber is determined by testing a sample of the timber to measure its strength and stiffness. Timber is graded from F1 to F34, with higher grades indicating higher strength and stiffness. The most commonly used stress grades for floor bearers and joists are F11 and F17. F11 is suitable for smaller spans and lower loads, while F17 is suitable for larger spans and higher loads.

It’s important to choose the right stress grade for your project to ensure the safety and durability of the structure. Using timber with a lower stress grade than required can result in structural failure and safety hazards.

Additional Tips for Construction

When constructing a subfloor system, it is important to adhere to the Australian Standards for floor bearers and joists. Here are some additional tips to ensure that your construction is up to par.

Thickness

The thickness of the flooring joists will depend on what is going on top of them. For example, joists that sit below end-matched joints must be at least 35mm thick. It is important to consult the relevant Australian Standards to determine the appropriate thickness for your specific application.

End Matched

End matched joints are a type of joint where the ends of the boards are cut to fit together tightly. This type of joint is commonly used in flooring applications. When using end matched joints, it is important to ensure that the joists below are strong enough to support the weight of the flooring.

Member Sizes

The size of the members used in the construction of your subfloor system will depend on the span and spacing of the bearers and joists. The Australian Standards provide span tables that can be used to determine the appropriate member sizes for your specific application.

Spacing

The spacing of the bearers and joists is also important in ensuring the structural integrity of your subfloor system. The spacing will depend on the size of the members used and the span of the bearers and joists. The Australian Standards provide guidelines for the maximum spacing of bearers and joists based on their size and span.

Fasteners

The fasteners used in the construction of your subfloor system are also important. It is important to use the appropriate size and type of fasteners to ensure that the members are securely fastened together. The Australian Standards provide guidelines for the appropriate size and type of fasteners for different applications.

Frequently Asked Questions

What are the recommended floor bearer sizes according to Australian standards?

According to the AS 1684.2-2010 Residential timber-framed construction standard, the recommended sizes for bearers depend on the maximum span, live load, and dead load. The standard provides tables that show the recommended sizes for bearers made of hardwood, softwood, and LVL. The tables also show the maximum spans for each size and the load capacity.

Where can I access the AS 1684 Timber Framing Code in PDF format?

The AS 1684 Timber Framing Code is a comprehensive guide for timber framing in Australia. You can access the code in PDF format from the SAI Global website. The code provides detailed information on timber framing for residential and commercial buildings, including floors, walls, roofs, and other structural elements. The code also covers design, construction, and maintenance requirements.

What are the span tables for floor joists in Australia?

The span tables for floor joists in Australia depend on the type of timber, the size of the joist, and the spacing between the joists. The AS 1684.2-2010 Residential timber-framed construction standard provides tables that show the recommended sizes and spans for floor joists made of hardwood, softwood, and LVL. The tables also show the maximum spans for each size and the load capacity.

What are the requirements for roof bearers and joists according to Australian standards?

The AS 1684.2-2010 Residential timber-framed construction standard provides guidelines for roof bearers and joists. The standard specifies the sizes of bearers and joists based on the maximum span, live load, and dead load. The standard also provides tables that show the recommended sizes and spans for bearers and joists made of hardwood, softwood, and LVL.

What are the standard sizes for timber floor joists in Australia?

The standard sizes for timber floor joists in Australia depend on the type of timber, the spacing between the joists, and the load capacity. The most common sizes for floor joists made of treated pine are 90x35mm, 120x35mm, and 140x45mm. The AS 1684.2-2010 Residential timber-framed construction standard provides tables that show the recommended sizes and spans for floor joists made of hardwood, softwood, and LVL.

Wrapping Up

Understanding the Australian standards for floor bearers and joists is crucial for ensuring structural integrity and compliance with building regulations. To have your questions answered and to receive expert guidance on this topic, reach out to SQM Architects. Our team of professionals is ready to provide you with the necessary information and assistance. Contact us and let us help you ensure a safe and robust flooring system for your project.