NJ IBC 2018 AZEK as an Exterior Finish for Fire Rated Walls in Type 5B Construction

[nickedemus]

We have a type 5 building with exterior walls within 0 – 5’-0” of the property line. All of the fire rated walls are symmetrical at the exterior. According to this report, can AZEK be applied to the outside of the walls?

I’ve read two reports that say AZEK can be used as an exterior wall cladding on fire-rated exterior wall assemblies. These reports APPEAR to say this is true even in in Type 5 construction. But I’m having trouble pinpointing exactly where this is substantiated in the code.

Both of the reports I’ve read (ESR-4508 by ICC Evaluation Service, CCRR-0266 by Intertek) reference IBC section 1405.1.1.1 which states that combustible exterior wall coverings for exterior walls having a fire separation distance of 5 feet or less shall not exhibit sustained flaming as defined in NFPA 268. There is a table (1405.1.1.1.2) that shows minimum fire separation distance for different levels of sustained flaming. However, this entire section seems to apply only to Type I, II, III, and IV Construction. It does not say anything about Type V construction.

The exception to 1405.1 is “Plastics complying with Chapter 26.” Section 2603.5 says that “Exterior walls of buildings of Type V construction shall comply with Sections 2603.2, 2603.3 and 2603.4.” But these sections seem specific to foam plastic insulation and foam plastic insulation components. Vinyl is not mentioned.

Where does the code specifically say that AZEK siding may be part of a fire rated wall assembly in Type 5 construction? Or is this simply not permitted?

Yes, I am aware of 703.2.4/IBC, which states that materials, systems or devices that have not been tested as part of a fire resistance-rated assembly are incorporated into the building element, component or assembly, sufficient data shall be made available to the building official to show that the required fire-resistance rating is not reduced. But what constitutes "sufficient data?" How do you prove that something reduces a fire rating?

 

[nickedemus]

According to this report, can AZEK be applied to the outside of the walls?

Oops--didn't mean to include this part in my post. It's from an email to ICC-ES and "this report" refers to ESR-4508.

 

[steveray]

How tall is the wall? NFPA 268 in play? Nevermind, that is only 1-4...Not type V

 

[adekom]

Exterior walls in types I, II, III, and IV construction are required to be constructed of noncombustible materials per 602.2, 602.3, and 602.4. I read section 1405.1.1.1 as establishing the conditions under which combustible exterior facings can be used on an exterior wall that is otherwise required to be noncombustible. Given that type V exterior walls are permitted to be constructed of combustible materials, I would think that per 602.5, 2605.3, and 1403.9, vinyl siding would be allowable in type V construction. I'm assuming that AZEK is just vinyl siding, but perhaps I'm overlooking something about this specific product.

 

[nickedemus]

Exterior walls in types I, II, III, and IV construction are required to be constructed of noncombustible materials per 602.2, 602.3, and 602.4. I read section 1405.1.1.1 as establishing the conditions under which combustible exterior facings can be used on an exterior wall that is otherwise required to be noncombustible. Given that type V exterior walls are permitted to be constructed of combustible materials, I would think that per 602.5, 2605.3, and 1403.9, vinyl siding would be allowable in type V construction. I'm assuming that AZEK is just vinyl siding, but perhaps I'm overlooking something about this specific product.

There's no question that it's allowable in Type V construction. The question is, is AZEK allowable as part of a fire-rated exterior wall assembly (rated at the interior and exterior sides) within 5 feet of a property line? Or does it diminish the overall rating of that assembly?

 

[nickedemus]

So, I guess a follow up question is, if a material has a Class A flame spread rating, can I assume that it does not diminish the rating of a fire-rated assembly?

 

[adekom]

Your rated assembly, whether that be a UL design or a design from a proprietary test report, should specify which exterior facings are acceptable. Some will say "vinyl siding with a flame spread rating of X or less". If your walls are 1-hour rated and if you're using wood studs, then you can use the calculated fire resistance provisions in 722.6 and in that case vinyl siding is permitted outright per table 722.6.2(3).

 

[nickedemus]

Unfortunately, it looks like 722.6.2(3) only applies to exterior walls that are more than 10 feet away from a property line. My walls are within 5 feet.

722.6.2.3 Exterior walls.
For an exterior wall with a fire separation distance greater than 10 feet (3048 mm), the wall is assigned a rating dependent on the interior membrane and the framing as described in Tables 722.6.2(1) and 722.6.2(2). The membrane on the outside of the nonfire-exposed side of exterior walls with a fire separation distance greater than 10 feet (3048 mm) shall consist of sheathing, sheathing paper and siding as described in Table 722.6.2(3).

Any other suggestion?

 

[adekom]

Much of 722.6 is related to walls that are rated from both sides. I interpret 722.6.2.3 as laying out the requirements for walls that are rated from one side only (ie, exterior walls with a FSD > 10'). I don't read 722.6.2.3 as saying that the provisions of 722.6 only apply to exterior walls with a FSD > 10'.

The following is excerpted from Design For Code Acceptance #5 published by the American Wood Council:

If the wall is assumed to be exposed to fire from both sides (e.g., for interior fire rated partitions and exterior walls with a fire separation distance of 10 feet or less), each surface of the framing member would be required to be fire protected with a membrane or combination of membranes having an assigned time of at least 40 minutes, as shown in the example, in order to achieve a one-hour fire-resistance rating from either side. If the proposed wall is assumed to be exposed to fire from one side only, as is required of an exterior wall having a fire separation distance greater than 10 feet, the fire exposure is assumed to be from the interior, which would require protection on the interior side with a membrane or combination of membranes having an assigned time of at least 40 minutes in order to achieve a one-hour fire-resistance rating. For this latter case, it should be noted that to achieve the assigned fire resistance rating for the interior side, the exterior side must be protected in accordance with IBC Table 722.6.2(3) or any membrane that is assigned a time of at least 15 minutes as listed in IBC Table 722.6.2(1).