Draftstopping Requirements For Multi-Family Construction

The Problem
A conflict exists between the installation standards and the building codes regarding sprinklers and combustible concealed space separation requirements, specifically in attics and floor/ceiling assemblies. When conflicts occur, what is actually required?

Basically NFPA13 requires sprinklers in combustible concealed spaces, including attics and floor/ceiling assemblies, other than as excluded by Section 4-13.1 (1996 edition). NFPA13R, however, in Section 2-6 Exception 4 specifically exempts sprinkler requirements from attics, penthouse equipment rooms, crawl spaces, floor/ceiling spaces, elevator shafts, and other concealed spaces that are not used or intended for living purposes or storage. The building code requires that sprinklers be installed according to the applicable standard (NFPA 13 or NFPA 13R).
 

Installing in Accordance With the Standard
The sprinkler contractor sprinklered the building according to NFPA 13R but the AHJ then said to either install attic sprinklers or provide the required draftstopping. What’s the problem and how can we solve it?
 

The problem starts with the fact that the model building codes limit the maximum areas of these spaces for both sprinklered and non-sprinklered buildings. This means even when fully sprinklered according to NFPA 13, draftstopping requirements may be required. This results in confusion between the sprinkler and the framing/drywall contractor. What is required and who includes it in their price?

What is Fully Sprinklered?
The building codes provide basic draftstopping requirements based on the non-sprinklered building. These requirements limit the combustible concealed spaces to specific sizes even though the permitted allowable areas can be increased up to 300 percent with open space and sprinklers. Trade-offs or sprinkler advantages are permitted for fully sprinklered buildings.

A second problem is related to confusion over what is considered a fully sprinklered building. Some codes do not consider 13R as a fully sprinklered building and therefore do not permit deletion of the draftstopping. They will permit draftstopping deletions if sprinklers are also installed in the spaces. As an area outside the dwelling units, however, the attic would need to be protected according to NFPA 13 even if the balance of the building uses NFPA13R.
 
 

What Do The Codes Require?
This publication will provide a summary of the different code requirements regarding draftstopping and sprinklers for the model building codes. If in question, it is always better to consult the AHJ before submitting the bid or final plans for approval. Find out what is required before you sign the contract.

Example building (used for determining the following code requirements):

Two-story multi-family apartment building, 8 units per floor, each apartment 800 sq ft. The building footprint is 82 ft x 87 ft or 7134 sq ft per floor. The building has a center-loaded corridor serving all units, with two stairways. Construction is unprotected wood frame. There is an approved 30 ft wide open space along two of the 87 ft sides.
 
 

BOCA National Building Code
R-2 occupancy classification, multi-family

Sprinkler Requirements: Sprinklers are not required based on occupancy or type of construction.

Allowable area per floor:
Type Construction 5B basic allowable area non-sprinklered 4,800 sq ft plus street frontage increase = 7,296 sq ft per floor.
 
 

Sprinkler Requirements:
Sprinklers are not required based on occupancy or type of construction.

Attic Separations:
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls (721.7.2.1) or when area exceeds 3,000 sq ft (721.7.2).

Sprinkler Advantage: Draftstopping is not required when sprinklers are installed in concealed spaces (721.7.2.1). Floor/Ceiling Assemblies:
Draftstopping is required floor system above and in line with tenant separation walls and on one side of corridor walls (721.7.1.1). Sprinkler Advantage: Draftstopping is not required when sprinklers are installed in the concealed space (721.1.1). Proposed International Building Code:

R-2 occupancy classification apartment houses

Sprinkler Requirements: Sprinklers are not required based on occupancy or type of construction.

Allowable area per floor:
Type Construction 5B basic allowable area non-sprinklered 7,000 sq ft plus street frontage increase = 8,820 sq ft per floor.

Sprinkler Requirements:
Sprinklers are not required based on occupancy or type of construction.

Attic Separations
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls and attic space is greater than 3,000 sq ft (716.4.2).

Sprinkler Advantage: Draftstopping is not required when sprinklers are installed in the concealed space (716.4.2). Floor/Ceiling Assemblies:
Draftstopping is required in floor system above and in line with tenant separation walls and on one side of corridor walls and when areas exceed 500 sq ft (716.3.2). Sprinkler Advantage: Draftstopping is not required when sprinklers are installed in the concealed space (716.3.2). Standard Building Code:
R-2 occupancy classification apartment houses

Sprinkler Requirements: Sprinklers are not required based on occupancy or type of construction.

Allowable areas per floor: Type VI-UP basic allowable area non-sprinklered 7,000 sq ft
non-sprinklered plus street frontage increase = 11,760 sq ft allowable areas.

Attic Separations:
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls (2305.2.3).

Sprinkler Advantage: Draftstopping is not required when sprinklers are installed in the concealed space up to 9,000 sq ft (2305.2.3). Floor/Ceiling Assemblies:
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls (2305.2.2).

No exception for sprinklers.

Uniform Building Code:
R Division 1 occupancy classification hotels and apartment classifications.

Sprinkler Requirements:
Sprinklers are not required based on occupancy.

Allowable Areas:
Type Construction V-N allowable area 6,000 sq ft non-sprinklered plus open space increase
= 11,812 sq ft per floor.

Sprinkler Requirements:
Sprinklers are not required based on occupancy or type of construction.

Attic Separations:
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls and areas greater than 3,000 sq ft, and a maximum separation of 60 ft (708.3.1.2.1).

Sprinkler Advantage: When sprinklers are installed in concealed spaces maximum size to 9000 sq ft and an increase in separation to 100 ft. Floor Ceiling Assemblies:
Draftstopping is required above and in line with tenant separation walls and on one side of corridor walls and in areas greater than 1,000 sq ft and over 60 ft separation (708.3.1.1.2). Sprinkler Advantage: When sprinklers are installed in concealed spaces the maximum area is increased to 3,000 sq ft and the maximum spacing increases to 100 ft. Firewalls
Firewalls are used to divide overall structures into allowable areas permitted by the building code. Firewalls are also used to divide a building containing different types of construction. Firewalls extend through the attic and therefore must also be considered in the design. Firewall separations are not included in information shown above.

The model building codes are currently revising the terminology of draftstopping, firestopping, smoke barriers, etc. This article uses the single term "draftstopping" to describe all of the various separation requirements. Consult the specific building code for actual construction requirements.
 

Avoid the Problems
To avoid construction delays and possible increased costs, it is imperative that you apply the codes correctly. It is not enough to comply only with the installation standard. Be sure you understand all the requirements and identify errors when you find them. Check out the plans with the AHJ, do not rely completely on the plans and specifications.