There are multiple elements to consider when selecting the correct external sheathing board for a building project – factors such as safety, durability, stability and cost need to be carefully researched, tested and validated to ensure maximum performance.
What is racking strength?
Racking strength (or racking resistance) is the ability of a structure to withstand horizontal pressure, most commonly wind force. Other factors such as environmental or seismic activity or thermal contraction and expansion, should be taken into consideration when testing. The racking strength is a determining factor in the safety and structural stability of a building.
The racking resistance of a build can be determined by a number of elements – including size, shape, design and location of the structure. Superior racking strength is particularly important when a building is in an environment subject to unpredictable climate change or where it may suffer exposure to extreme weather conditions. Racking strength is highly influential in determining a building’s longevity, and consideration should be given to the building’s intended use both immediately and in the future.
The racking strength of a structure or system is determined via performance testing, considering the various conditions and different product and component compositions. This forms part of the system that determines the structural stability and loadbearing capacity of the building overall, making it an integral part of the safety features of the structure. This is particularly important in high-risk buildings, including those with multiple residential units or a higher number of storeys.
How does the importance of fixing correctly factor into racking strength?
The correct fixing of external sheathing boards forms an important part of the continuous load path for any structure, which will determine and influence overall racking resistance. The external sheathing boards also provide the base for siding and finishing products, meaning a strong and risk-free fixing system is integral to ensuring each product component remains in place and performs as part of the whole system in cohesion with the internal structure of the building.
Incorrect or poorly connected fixings or interfaces can open the structure system up to the risk of failure at specific points which may weaken the building’s structural stability and strength. As external sheathing also determines the weatherability and performance of the building against the elements, it is important to ensure correct fixings to negate any failures or weaknesses in relation to weather tightness and insulation and energy performance.
Klasse C-Board is the ultimate high-performance, A1 non-combustible cement external sheathing board, suitable for numerous applications. Offering high-impact resistance, Klasse C-Board can be utilised for facade solutions, as well as many roof and flooring requirements. Due to its exceptional strength, impact resistance and performance qualities, C-Board is ideal for use in offsite and modular constructions.
The exceptional dimensional stability of C-Board makes it a particularly sound choice for builds requiring a high level of racking resistance and can be used in buildings over 18m. Designed for high-impact resistance, C-Board offers an impact strength of over 2100 J/m2.
According to BS 5268-6.1 9mm C-board achieved calculated basic test racking resistance values of 3.01 kN/m, with no vertical load and a value of 2.42 kN/m with 5 kN per stud applied vertical load.
C-Board also offers thermal conductivity of 0.18 W/mK and holds an EN13501-1 Class A1fire classification, rated as a Category A board to BS EN 12467:2012+A2 2018 (where the board may be subjected to heat, high moisture and severe frost). Following extensive testing against extreme weather conditions and hot and cold environments, Klasse C-Board passes freeze/thaw tests up to 100 cycles. In heat/rain tests, C-Board passes 50 cycles.
C-board is primarily used as an external sheathing board on both metal and timber structures of all types of facade solutions. The board is manufactured using cement, cellulose fibres with performance-enhancing special additives. It is then laminated and cured using autoclaving, under high steam and pressure to give a stable crystalline structure. C-board is fully recyclable, comes with minimal packaging and the pallets are made of recyclable material. C-board boards have the capacity to hold nails and screws and do not require any backing frame to hang light-weight objects like picture frames.
With risk management at the forefront of factors to consider when specifying a build, Klasse understands the importance of making and offering products that provide practical solutions that are thoroughly tested for performance when interfaced with different components and third-party products. Klasse offers clear and transparent data regarding all testing results, including racking resistance, when applied to other products in both function and practice.
Klasse external sheathing boards are quick to install, manufactured offsite and delivered by our delivery team, requiring less time on site and minimising disruption to workflow. All our products exceed the new building safety regulations – designed with safety and quality at the forefront of everything we do.
Find out more about Klasse External Sheathing Boards here.
Download technical documents here.
