FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

9 DESIGNING THE BUILDING Volume II
Figure 9-31.
House being constructed
with a steel frame on
wood piles
9.4.4 Fire Safety Considerations
Designing and constructing townhouses and low-rise multi-family coastal buildings to withstand natural
hazards and meet the building code requirements for adequate fire separation presents some challenges.
Although fire separation provisions of the 2012 IBC and 2012 IRC differ, they both require that the common
walls between living units be constructed of materials that provide a minimum fire resistance rating. The
intent is for units to be constructed so that if a fire occurs in one unit, the structural frame of that unit would
collapse within itself and not affect either the structure or the fire resistance of adjacent units.
For townhouse-like units, the common framing method is to use the front and rear walls for the exterior
load-bearing walls so that firewalls can be placed between the units. Beams that are parallel to the front and
rear exterior walls are typically used to provide support for these walls as well as the floor framing. Figure
9-32 illustrates a framing system for a series of townhouses in which floor beams are perpendicular to the
primary direction of flood forces. Design issues include the following:
5. The floor support beams are parallel to the shore and perpendicular to the expected flow and may
therefore create an obstruction during a greater-than-design flood event.
6. The fire separation between townhouse units limits options for structural connections between units,
making the transfer of lateral loads to the foundation more difficult to achieve.
7. The exposed undersides of buildings elevated on an open foundation (e.g., pile, pier, post, column) must
be protected with a fire-rated material. Typically, this is accomplished with use of fire-resistant gypsum
board; however, gypsum board is not a flood-damage-resistant material. An alternative approach is
to use other materials such as cement-fiber board (with appropriate fire rating), which has a greater
resistance to damage from floodwaters, and fire retardant treated wood. Other alternative materials or
methods of protection that are flood-damage-resistant may be required in order to meet the competing
demands of flood- and fire-resistance.
9-36 COASTAL CONSTRUCTION MANUAL