How to install Hardieflex fibre cement boards for exterior wall?

[jefff]

Hi 

I am planning to use Hardieflex for the exterior wall of my house extension project at the back of my house.
The wall is 5.5m long x 3m high. I am planning to use 1200x3000x4.5 sheets , laid vertically so that there is no horizontal joints. 

This will be my first project using fibre cement sheets, so I have a few questions:
What spacing gaps, if any, is required for the vertical joints?

And what is the best way for the joints - sealant or jointing tape/compound?
Do I need to have flashing behind the joints?

Thanks

[JacobZ]

Hi @jefff,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

External walls can be fairly complex as there are a number of requirements under the National Construction Code, the Australian and New Zealand Standards and the manufacturer's technical specifications to ensure a compliant, insurable and warrantable installation. I'd recommend you look through the requirements set out in NCC Part 3.5.3 Wall Cladding and the James Hardie External Cladding Technical Specifications. As there is considerable complexity, you may need to seek the assistance of a carpenter or builder to ensure everything is up to standard.

Vertically oriented Hardie Flex Sheets are normally jointed with PVC straight joint moulds or timber battens such as this 42 x 11mm 5.4m H3 Treated Pine FJ DAR Primed LOSP. For installation methods outside of those mentioned in the External Cladding Technical Specifications, I'd encourage you to get in touch with James Hardie on 13 11 03 in Australia and 0800 808 868 in New Zealand for their assistance. This ensures your installation method is within the terms of their warranty and is up to construction standards.

A suitable water control membrane must be installed under Hardie external cladding in accordance with the AS/NZS 4200.2 ‘Pliable building membranes and underlays – Installation’ and NCC requirements. James Hardie offers their Hardie™ Wrap Weather Barrier system that can be ordered through your local Bunnings' Special Orders desk. I can't find mention of a requirement for additional flashing beneath joints; however, it is likely required by the Australian Standards.

Let me know if you have further questions, I am happy to point you in the right direction and help where I can.

Jacob

[jefff]

Thanks, Jacob.  That's useful information - I will digest this first and let you know if there are any other questions.  Thanks