Exterior Wood sheathing / furring in Type 2-B Const

[mpd-architect]

This pertains to a siding renovation project to an existing type 2B building / A4 Use group. FSD is well over 30 feet so no exterior wall ratings required. Applicable Codes are 2015 IBC & 2015 IEBC. The existing building (1977 const) is partially sided with wood 1 x 8 t&g siding over gypsum sheathing over 2 x 4 furring 24" OC over the exterior masonry bearing wall. The original siding and substrate are damaged and need full replacement. We are proposing a Pac-Clad metal siding to replace the original wood siding and would like to install over FRTW 1/2" plywood substrate over the existing 2 x 4 furring. Is this allowed or are we required to use non-combustible such as gyp sheathing? We prefer the plywood due to the more solid backing it will provide.

 

[classicT]

Wood is generally not allowed for Type II-B buildings. See IBC 602.2 and 603.1.

 

[Tim Mailloux]

This pertains to a siding renovation project to an existing type 2B building / A4 Use group. FSD is well over 30 feet so no exterior wall ratings required. Applicable Codes are 2015 IBC & 2015 IEBC. The existing building (1977 const) is partially sided with wood 1 x 8 t&g siding over gypsum sheathing over 2 x 4 furring 24" OC over the exterior masonry bearing wall. The original siding and substrate are damaged and need full replacement. We are proposing a Pac-Clad metal siding to replace the original wood siding and would like to install over FRTW 1/2" plywood substrate over the existing 2 x 4 furring. Is this allowed or are we required to use non-combustible such as gyp sheathing? We prefer the plywood due to the more solid backing it will provide.

are all the existing exterior walls masonry bearing walls? If so I am not sure you have IIB construction, sounds more like type III

 

[mpd-architect]

are all the existing exterior walls masonry bearing walls? If so I am not sure you have IIB construction, sounds more like type III

Yes all exterior walls are masonry bearing walls w/ steel bar joist roof structure. I did speak with an ICC technical staff member and they seem to say that fire retardant treated wood (FRTW) is allowed in 2B buildings under the specific circumstances as noted in Section 603....which includes non-rated & non-bearing exterior walls. Thank you for your input.

 

[mpd-architect]

Wood is generally not allowed for Type II-B buildings. See IBC 602.2 and 603.1.

Fire retardant treated wood (FRTW) is allowed in Type II construction under specific circumstances as outlined in Section 603. Thank you for your input.

 

[Paul Sweet]

IBC 1404.5 & 1405.1.1 allow wood veneers on exterior walls of buildings of Types I, II, III and IV up to 40 ft. in height. 603.1.13 refers to chapter 24.