Cover Fire-retardant Treated Wood with untreated wood

[manifold]

IBC 2012, Type II-B
In a small exterior canopy structured with fire-retardant treated wood, can the treated wood structure (beam, ledger, purlins) be covered with 1x wood that is not fire-retardant treated?

 

[classicT]

Nope.... see IBC Section 603.

 

[manifold]

Nope.... see IBC Section 603.

Right, one of the items that I am curious about is if the canopy falls under "balconies and similar projections" listed in 603.1 #13 that would allow some combustible material per 1406.2.1

 

[classicT]

Right, one of the items that I am curious about is if the canopy falls under "balconies and similar projections" listed in 603.1 #13 that would allow some combustible material per 1406.2.1

#13 is "Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14."

Is the 1x wood an exterior finish, or is it structural? If simply the exterior cladding, then I would take a look at IBC Section 1406.2.1 #4, which pushes you to IBC Section 1405.5.

1405.5 Wood Veneers
Wood veneers on exterior walls of buildings of Type I, II, III and IV construction shall be not less than 1 inch (25 mm) nominal thickness, 0.438-inch (11.1 mm) exterior hardboard siding or 0.375-inch (9.5 mm) exterior-type wood structural panels or particleboard and shall conform to the following:

1. The veneer shall not exceed 40 feet (12 190 mm) in height above grade. Where fire-retardant-treated wood is used, the height shall not exceed 60 feet (18 290 mm) in height above grade.
2. The veneer is attached to or furred from a noncombustible backing that is fire-resistance rated as required by other provisions of this code.
3. Where open or spaced wood veneers (without concealed spaces) are used, they shall not project more than 24 inches (610 mm) from the building wall.

 

[manifold]

#13 is "Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14."

Is the 1x wood an exterior finish, or is it structural? If simply the exterior cladding, then I would take a look at IBC Section 1406.2.1 #4, which pushes you to IBC Section 1405.5.

The 1x would be an exterior finish, non-structural. Seems like 1405.5 might allow it, though would a canopy beam and purlins that extend 8 feet from the face of the building really be considered as an exterior wall?

 

[cda]

IBC 2012, Type II-B
In a small exterior canopy structured with fire-retardant treated wood, can the treated wood structure (beam, ledger, purlins) be covered with 1x wood that is not fire-retardant treated?

1 ground level ??

2 Is it attached to the building?

3 Fire sprinkler system I’m building?

 

[manifold]

1 ground level

2 Is it attached to the building?

3 Fire sprinkler system I’m building?

1. Yes
2. Yes
3. The building has a sprinkler system. The canopy is not sprinklered. Nothing is stored under the canopy, it is primarily a decorative element at the entry.

 

[Mark K]

You do not want to expose treated lumber to the weather because it will corrode the fasteners and metal in contact with it. Since this is a commercial project there should be an engineer involved and the engineer should be able to find the industry recommendations. I seem to recall that the Simpson catalog deals with this issue.

 

[Tim Mailloux]

I am dealing with this very issue right now on a project. If the canopy projection is greater than 4 feet you need either sprinklers or a non combustable / limited combustible structure. Per NFPA 13 any treated wood will require a minimum flame spread index of 25 or less and comply with ASTM E86 testing.

 

[Ana]

Just came across this although it's an old post, so just incase someone is looking for an answer, I recently found and exterior fire retardant treated wood that can be used for canopies, it's an exterior pressure impregnated fire retardant wood, that has flame spread index of less than 25 and non-corrosive. Just search on google exterior Fire-X.