How Building Code Permits Cladding To Be Installed Over Halo Exterra (with 10 psi compressive strength)

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Section R703.15 (Cladding attachment over foam sheathing to wood framing) of the International Residential Code for One-and Two-Family Dwellings (IRC) outlines the options for installing cladding over top of foam sheathing or with wood furring.

The clause also notes that the cladding manufacturers’ approved instructions must be followed as well as any limitations they specify for applications on top of foam sheathing.

In addition, the attachment of cladding or furring overtop of the foam sheathing shall adhere to the fastening requirements laid out in section R703.15.1 for direct attachment or section R703.15.2 for a furred cladding attachment. These tables are below:

Figure 1: Cladding minimum fastening requirements for direct, and furring overtop foam sheathing (IRC)

To use these tables, the foam sheathing must have a minimum compressive strength of at least 15 psi (103 kPa) in accordance with ASTM C578 or ASTM C1289.

This limitation to the minimum compressive strength was established simply because that was a minimum limit that applied to all the main foam sheathings at the time the testing was done, and this testing was to develop the prescriptive building code requirements (specifically the engineering procedures using connection design methodology in wood construction design standards).

However, also per section R703.15.1, a foam sheathing with a different compressive strength can also be permitted, provided it has similar testing done. 

This clause also notes; “Where the cladding manufacturer has provided approved installation instructions for application over foam sheathing, those requirements shall apply”.

Logix Brands Halo® Exterra® has a compressive strength of 10 psi (70 kPa) and uses the exception within the IRC to permit the fastening of cladding directly or with furring overtop of it.

Exterra wall with WRB Outside
Example of wall insulated with Halo Exterra

And here is the testing that has been provided:

BC Housing Research Centre worked with leading industry consultants such as RDH Building Science Inc. and Morrison Hershfield Limited, as well as other industry professionals, in the development of the guide, “Illustrated Guide R22+ Effective Walls in Residential Construction in British Columbia”.

Within the guide it notes extensive research and engineering on cladding support and fasteners through foam sheathing. There is a complete fastener table found on page 27 of 57 that notes acceptable fastening solutions for foam sheathing with a minimum compressive strength of 10 psi (70 kPa) for light, medium, and heavy weight claddings (Figure 2).

Therefore these tables can be used to achieve compliance with securement of cladding with furring over top of Halo® Exterra® to meet the requirements of section R703.15.1. in the IRC.

Figure 2: Cladding support and fasteners through foam sheathing (Illustrated Guide – R22+ Effective Walls in Residential Construction in British Columbia)

If there are any further questions, please contact the Logix Brands technical department at [email protected].  

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