I have vinyl siding on my ICF home and one section of it is waving and being distorted by the reflections of of my neighbours skylights heating up the siding. I want to replace a section of the wall with Hardie board panels 4 x 8, but I'm not sure about the need for strapping. I'm in a cold climate, Ottawa, Ontario, Canada. This will cover a section 4 feet down and about 32 feet across right below the eaves of the roof line.

In Ontario we are required to strap behind Hardi siding

Thanks Chris for the response. I thought that would be the answer. how much of an air space is needed for pre-finished panels?

John

1x strapping is fine

Posted By Chris Johnson on 05 May 2015 09:30 AM
1x strapping is fine

Since 1x is 3/4" thick, using 3/4 inch pressure treated plywood ripped 2" wide is a good idea or is any of the available strapping OK to use outside? John

We have always used cheap 1x without issue

The air gap can be much smaller if you are going to the trouble of ripping plywood. Here is a link that addresses this issue from a leading authority. http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh . He suggests as small as 1/16" depending on what your trying to do (drainage and diffusion redistribution) or 3/16" (drainage, ventilation and diffusion).

If you are going to rip plywood as Johny suggests, a 3/16" dimension would cheapen the material cost and should hold as well. I would also use an exterior rated plywood (CDX) in this instance.

Thanks, I'll read the link! John

9.27.2.2.1) of the Alberta Building Code mandates a minimum of 10mm space. I assume the Ontario code is the same.

Plywood is less prone to splitting and you can rip it in wider sections if you need to address corner issues where the plastic nailing strap in the ICF does not come where you need it.