How to Achieve a Higher Fire Rating on Gypsum, Metal and Wood

• During building construction or renovation, a significant challenge that can arise is ensuring that the building is based on a design that meets the required standards for fire safety. Having a structure recognized as fire resistant requires, among other things, a good understanding of the building’s fire protection system and the tests certificates? that the building must have in order to function. The following example is a common phenomenon that many building officials face: floor-ceiling fire separation of the building is only 1 hour, but the IBC now requires it to be 2 hour-fire rated. More so, the commercial building is now required to have residential units on the 2nd floor.
• Those looking to upgrade 1 hour- to 2 hour-fire rating have several options to consider. One solution is to add more drywall, which increases the thickness of the separation. However, many may perceive this approach as time-consuming and not particularly cost-effective; it is also messy and problematic for installed lighting, ductwork, conduit, etc. Another option is foundation-to-roof masonry to separate the units. And yet another option is to spray a layer of intumescent paint, which gives 45 to 75 minutes more. Upgrades ½” gyp from 15-20 mins to 1 hour. Upgrades 5/8” Type X gyp from 45 mins to 2 hours, depending upon the thickness.
• Businesses may find fire resistant paint as a method that as easier, cheaper, and one that provides a better aesthetic look. However, as a new method, many parties involved either don’t understanding intumescent products or don’t totally trust them as reliable fire-resistant products. A careful review of relevant building codes and fire resistance rating standards may provide the needed insight before upgrading a building’s fire rating.

Fire resistance ratings are used by UL, ASTM, and building codes such as IBC to determine the capacity of construction elements to contain fire within a zone comprised of floor, ceiling, and fire-resistance rated walls.

Ratings for fire resistance are given in accordance to the time a structure can contain a simulation fire. More specifically, if a wall is constructed in a manner that closely resembles a tested wall which has shown to contain flames and high temperature for one hour, it is eligible to receive a 1-hour rating. Similarly, a wall resembling a tested wall that has shown to contain flames and heat for two hours can receive a 2-hour rating.

Drywall is a very popular construction material in the United States, which makes it almost impossible to discuss fire-resistance rating without mentioning the material. Drywall is made of calcium sulfate dihydrate (gypsum) and may or may not contain additives. Gypsum drywall can be regarded as an effective barrier against fire, as the product is combined with water, which is released as steam if the drywall is exposed to fire. Fire rated gypsum drywall shows fire resistance to a higher degree due to its glass fiber reinforcement.

Fire rated drywall has to be certified by a third party. The certification is usually obtained by independent testing which establishes whether a company meets the fire performance required by regulation. The most common fire rated drywall is known as type X, which is 5/8 inches thick, placed on each side of 2 by 4 or 2 by 6 inch wood studs and has a minimum fire rating of 1 hour.

When a building contains several occupancies, it is necessary to assess whether they can be considered non-separated or separated occupancies. Exceptions only apply when occupancies can be considered as accessories in accordance with IBC Section 508.2.

IBC has specific provisions for mixed occupancies. Non-separated occupancies, as defined in Section 508.3, require no separation between different occupancies in terms of rated assemblies such as walls, except for hazardous occupancies, with a few exceptions such as the separation between dwelling and sleeping units. Separated occupancies, as defined in Section 508.4 require different occupancies to be separate using rated walls and floors/ceilings. Section 508.4 contains a table which shows the required hourly ratings for assemblies that separate occupancies. The required hourly rating can sometimes be reduced if the building includes an NFPA 13-compliant automatic sprinkler system.

While fire-resistive cementitious coatings are an option to consider when seeking to increase fire ratings of gypsum boards, they are not typically regarded as aesthetical. Intumescent paint, on the other hand, cannot be visually distinguished from regular paint and provides the needed fire-resistive function.

Intumescent paint responds to fire by swelling to several times the original thickness. The gained insulating char protects the elements composing the substrate from fire. When exposed to heat, an intumescent product expands or swells, which makes it act as a barrier and protect the substrate. Regular 5/8" gyp board only gives 30 minutes of rating while gypsum type X can give 1 hour.

Intumescent paint can upgrade the structure to 2-hour rating. Products based on intumescent paint can typically be applied to steel, sheet material, sheetrock, composite panels, and interior woods. Intumescent products can be used on several wood surfaces, including doors, claddings, paneling, soft and hardwoods, gypsum, and other combustible substrates.

Regulations for the built environment meant to protect against fire and restrict its spread take the form of codes, standards, and laws. A code is a law or regulation that establishes the minimum requirements where something must be done while a standard typically specifies the methods for achieving the objective. The private-sector standards development system that exists in the United States is mostly self-administered and oversight and coordination are provided by the American National Standards Institute (ANSI)- a federation of codes and standards developers, company organizations and government users of the standards. ANSI represents the interests of several organizations, including private-standards-development organizations such as the ASTM.

IBC is developed by the International Code Council (ICC) and serves as the base code standards by most jurisdictions in the United States. The code addresses both safety and health concerns for buildings based upon performance and prescriptive requirements and is compatible with all other published ICC codes.

It is worth noticing that intumescent paint cannot be regarded as fireproof paint. Fire resistance rating is establishing according to a product’s ability to limit temperature rise on the unexposed side when tested with fire resistance test standards such as CAN/ULC S101. Flame-spread measures the spread and flammability of flames along a sample as well as the amount of smoke products when a product is exposed to an ignition source. Common used flame-spread classifications include Class I or A, with a 0-25 FSR c; Class II or B with a 26-75 FSR; and Class III or C with a 76-200 FSR.

The mentioned Section 703.2 specifies the methods used for determining fire resistance. The application of any of the methods included in the section must be based on the fire exposure and acceptance criteria specified in ASTM E119 or UL 253. The required fire resistance of a building element includes the following method: 1. Fire-resistance designs documented in approved sources; 2) Prescriptive designs of fire-resistance-rated building elements prescribed in Section 721 of the same code; 3) Calculations in accordance with Section 722; 4) Engineering analysis based on a comparison of building element as determined by test procedures established in ASTM E119 or UL 263 (these test standards are meant to evaluate the duration for which the types of specific building elements contain a fire, retain their structural integrity, or exhibit both properties during a specified test exposure; for a summary of these tests, see ); 5) Alternative protection methods as specified in Section 104.11; and 6) Fire-resistance designs certified by an approved agency.

The fire-resistance rating of building elements is established in accordance to test procedures specified in the ASTM E119 standards or UL 263 standards or in accordance with Section 703.3. The fire-resistance rating of penetration and fire-resistant joint systems are determined in accordance with Sections 714 and 715.

The provisions only apply to structural steel beams and girders protected with sprayed fire-resistant materials. Larger or smaller beam or girder shapes can be substituted for beams specific in approved unrestrained or restrained fire-resistance-rated assemblies as long as the thickness of the fire-resistant materials is adjusted according to the mathematical formula (Figure 1).

Special inspections and test for intumescent fire-resistant coating applied to structural elements and decks must be performed in accordance with AWCI 12-B. Special inspections and test are based on the fire-resistance framework as designed in the approved construction documents.