A parapet wall is a dwarf or low wall that is constructed along the edge of the terrace, roof, balcony, walkway, passage, etc. Parapet Design should be well executed to add aesthetic beauty to the building.

In other words,

The vertical extension of the Wall at the edge of the roof, balcony, terrace, and walkway thereby creating a barrier is known as the parapet wall.

  1. Parapet Design  

Here are a few outstanding parapet designs.

  2. Codal Provisions for Parapet Wall Construction ( IBC)  

IBC Section 705.11 defines the requirements for parapet design.

As a default, the code requires that parapets should be installed on all exterior walls of a building. However, there are several exceptions to this, notably when one of the following conditions exists:

a. The exterior wall does not require a fire-resistance rating based solely on Fire Separation Distance per IBC Table 602 (e.g., most multi-family, wood-frame projects would need a fire separation distance of 30 ft or more; Type VB construction with multi-family occupancies would need a fire separation distance of 10 ft or more)

b. The building area is less than 1,000 sq. ft on any given floor.

c. The entire roof construction is of noncombustible materials or at least 2-hour fire-resistance-rated construction (not common on most wood-frame projects).

d. The building has 1-hour fire-resistance-rated exterior walls that terminate at the underside of the roof sheathing, provided that:

~ Roof construction that spans parallel to the exterior wall is not less than 1-hour rated for 4 ft from the interior side of the wall for Group R/U; 10 ft for other occupancies, or

~ Roof construction that spans perpendicular to the exterior wall is not less than 1-hour rated for its entire span

~ For either of the above cases, openings in the roof are not within 5 ft of the exterior wall for Group R/U or within 10 ft for other occupancies, and

~ The entire building has a class B roof covering

e. For Group R-2 or R-3 occupancies, the building is of Type III, IV, or V construction and has a class C roof covering, provided that:

The roof sheathing or deck is non-combustible or fire-retardant-treated wood for a minimum of 4 ft from the exterior wall, or

5/8″ Type X gypsum board is installed directly to the underside of the roof sheathing or deck for a minimum distance of 4 ft from the exterior wall

f. IBC Section 705.8 allows the exterior wall to have 25% or more of its openings unprotected as a function of fire separation distance.

g. If none of the exceptions applies and a parapet is required, IBC 705.11.1 lists the construction requirements as follows.

705.11.1 Parapet wall construction

Parapet design shall have the same fire-resistance rating as that required for the supporting wall, and on any side adjacent to a roof surface, shall have noncombustible faces for the uppermost 18 inches (457 mm), including counter flashing and coping materials.

The height of the parapet shall be not less than 30 inches (762 mm) above the point where the roof surface and the wall intersect.

Where the roof slopes toward a parapet at a slope greater than 2 units vertical in 12 units horizontal (16.7 percent slope), the parapet shall extend to the same height as any portion of the roof within a fire separation distance where protection of wall openings is required, but in no case shall the height be less than 30 inches (762 mm).

This section notes that the parapet shall have the same fire resistance as the exterior wall below it. Although it is not stated, it is common to interpret this as applying to fire rating requirements for both the inside and outside faces of the wall. For Type V construction, IBC Table 601 requires a 1-hour rating for exterior bearing walls, while no rating is required for non-bearing walls.

Type III construction requires a 2-hour rating for exterior bearing walls. Fire separation distance should also be checked to determine the most restrictive requirements between Tables 601 and 602.

Note that IBC 705.5 only requires exterior walls to be rated from both faces when the fire separation distance is 10 ft or less. Otherwise, the required rating only applies to the inside face of the exterior wall.

The minimum height of a parapet wall above the roof surface is 30 inches. However, when a roof slopes down toward an exterior wall and parapet with a slope greater than 2:12, further analysis is required to determine if a taller parapet is necessary.

In Type III construction, exterior walls are required to be non-combustible or framed with fire-retardant-treated wood (FRTW). Under these circumstances, another common question is whether parapets on Type III buildings need to be framed with FRTW.

Although IBC 705.11.1 doesn’t specify the requirements for parapet construction materials, some have interpreted that code intent would imply that the use of FRTW is necessary for parapet wall construction; others have not.

This is a subject that should be discussed with the Authority Having Jurisdiction regarding their interpretation and requirements.

Under certain circumstances, parapets may not be required by code (using one of the exceptions noted above) but are still installed on a building to serve aesthetic functions.

In this case, a common question is whether or not the parapet needs to follow the fire-resistance rating and construction requirements of IBC 705.11.

For this scenario, some designers have successfully designed and constructed parapets without a fire-resistance rating (even when the exterior wall below requires one) by using the rationale that the parapet is similar to a roof member/roof extension or an exterior wall projection as opposed to an exterior wall member.

This is based on the fact that the parapet is not required by code and, therefore, is not required to provide fire containment.

  3. Uses of Parapet Walls  

The uses of parapet walls are as follows:

a. To have an aesthetic look at the structure.

b. To have safety for humans when they are on the rooftop but in the case of bridges to control vehicles from dropping off bridges.

c. To conceal and control the equipment and machinery on the rooftop.

d. To control the entrance of dust through the air on the rooftop.

e. To control the falling of debris gathered on the rooftop.

f. To control high wind loads coming onto the rooftop.

g. Perforated parapets can be valuable for defense actions in military areas.

This was for parapet design.

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