09-25-2007, 08:38 AM
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Member
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Join Date: Mar 2007
Location: Ormond Beach, Florida
Posts: 7,720
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Re: Roof deflection/truss rafters
705.6 Vertical continuity. Fire walls shall extend from the
foundation to a termination point at least 30 inches (762 mm)
above both adjacent roofs.
Exceptions: 1. Stepped buildings in accordance with Section
705.6.1.
2. Two-hour walls shall be permitted to terminate at the
underside of the roof sheathing, deck or slab provided:
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 Type III, IV and V construction, walls
shall be permitted to terminate at the underside of
combustible roof sheathing or decks provided:
4.1. There are no openings in the roof within 4 feet
(1220 mm) of the fire wall,
4.2. The roof is covered with a minimum Class B
roof covering, and
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 a minimum of 2-inch (51 mm) ledgers attached
to the sides of the roof framing members
for a minimum distance of 4 feet (1220
mm) on both sides of the fire wall.
5. Buildings located above a parking garage designed in
accordance with Section 508.2 shall be permitted to
have the fire walls for the buildings located above the
parking garage extend from the horizontal separation
between the parking garage and the buildings.
705.6.1 Stepped buildings. Where a fire wall serves as an
exterior wall for a building and separates buildings having
different roof levels, such wall shall terminate at a point not
less than 30 inches (762 mm) above the lower roof level,
provided the exterior wall for a height of 15 feet (4572 mm)
above the lower roof is not less than 1-hour fire-resistance-
rated construction from both sides with openings protected
by assemblies having a 3/4-hour fire protection rating.
Exception: Where the fire wall terminates at the underside
of the roof sheathing, deck or slab of the lower roof,
provided:
1. The lower roof assembly within 10 feet (3048 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. Openings in the lower roof shall not be located
within 10 feet (3048 mm) of the fire wall.
Read the sections which related to fire walls in Chapter 7.
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