Fire rated interior walls at roof

[RWright80]

IBC section 706.6 states that fire rated walls may terminate at the roof if protection is added at the roof 4'-0" each way from the wall on parallel framing and for the full distance to the next supporting member if the framing is perpendicular to the wall. What is unclear is how much protection under the roof framing is required. Does it have to match the rating of the wall? (i.e. a 2 hour wall requires 2 hour protection under the roof framing)

 

[classicT]

Which Exception to 706.6 are you considering? Read exceptions #2-4, they tell you exactly what to do.

2. Two-hour fire-resistance-rated walls shall be permitted to terminate at the underside of the roof sheathing, deck or slab, provided that:

2.1 The lower roof assembly within 4 feet (1220 mm) of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour.​

2.2 Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.​

2.3 Each building shall be provided with not less than a Class B roof covering.​

3. Walls shall be permitted to terminate at the underside of noncombustible roof sheathing, deck or slabs where both buildings are provided with not less than a Class B roof covering. Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.
4. In buildings of Types III, IV and V construction, walls shall be permitted to terminate at the underside of combustible roof sheathing or decks, provided that all of the following requirements are met:

4.1 Roof openings are not less than 4 feet (1220 mm) from the fire wall.​

4.2 The roof is covered with a minimum Class B roof covering.​

4.3 The roof sheathing or deck is constructed of fire-retardant-treated wood for a distance of 4 feet (1220 mm) on both sides of the wall or the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by not less than 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a distance of not less than 4 feet (1220 mm) on both sides of the fire wall.​

 

[RWright80]

Which Exception to 706.6 are you considering? Read exceptions #2-4, they tell you exactly what to do.

2. Two-hour fire-resistance-rated walls shall be permitted to terminate at the underside of the roof sheathing, deck or slab, provided that:

2.1 The lower roof assembly within 4 feet (1220 mm) of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour.​

2.2 Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.​

2.3 Each building shall be provided with not less than a Class B roof covering.​

3. Walls shall be permitted to terminate at the underside of noncombustible roof sheathing, deck or slabs where both buildings are provided with not less than a Class B roof covering. Openings in the roof shall not be located within 4 feet (1220 mm) of the fire wall.
4. In buildings of Types III, IV and V construction, walls shall be permitted to terminate at the underside of combustible roof sheathing or decks, provided that all of the following requirements are met:

4.1 Roof openings are not less than 4 feet (1220 mm) from the fire wall.​

4.2 The roof is covered with a minimum Class B roof covering.​

4.3 The roof sheathing or deck is constructed of fire-retardant-treated wood for a distance of 4 feet (1220 mm) on both sides of the wall or the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by not less than 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a distance of not less than 4 feet (1220 mm) on both sides of the fire wall.​

Thanks for your reply. My question involves item 4. Does the drywall un the underside of the framing have to match the drywall on the wall or is a single layer of drywall sufficient if all of the other requirements are met?

 

[classicT]

Thanks for your reply. My question involves item 4. Does the drywall un the underside of the framing have to match the drywall on the wall or is a single layer of drywall sufficient if all of the other requirements are met?

Following Exception #4, you can just go with any 5/8" Type X. I would presume that you'd use the same gyp as that used on the walls just for simplicity.

"...the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by not less than 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a distance of not less than 4 feet (1220 mm) on both sides of the fire wall."

 

[RWright80]

Following Exception #4, you can just go with any 5/8" Type X. I would presume that you'd use the same gyp as that used on the walls just for simplicity.

"...the roof is protected with 5/8-inch (15.9 mm) Type X gypsum board directly beneath the underside of the roof sheathing or deck, supported by not less than 2-inch (51 mm) nominal ledgers attached to the sides of the roof framing members for a distance of not less than 4 feet (1220 mm) on both sides of the fire wall."

Thank you.

 

[classicT]

Thank you.

Your welcome!

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[Jay Smith]

706 refers to fire walls as opposed to fire rated walls. I would suggest confirming that your condition requires a fire wall before doing what it takes to comply with that requirement.

 

[redeyedfly]

Thanks for your reply. My question involves item 4. Does the drywall un the underside of the framing have to match the drywall on the wall or is a single layer of drywall sufficient if all of the other requirements are met?

FRT ply is the easiest way to meet exception 4. But please verify what type of fire rated wall you have. 706 is for fire walls. They are the most restrictive type of fire rated walls and are used to essentially create separate buildings within a larger building for fire compartmentalization. If you have a fire barrier, fire partition, or other type of fire rated wall, there will be different requirements.

 

[Yankee Chronicler]

706 refers to fire walls as opposed to fire rated walls. I would suggest confirming that your condition requires a fire wall before doing what it takes to comply with that requirement.

Good catch. I missed that.

Too many people (including design professionals) refer to any fire-resistance rated wall as a "firewall," but most are either "fire barriers" or "fire partitions" rather than actual firewalls.