Applying NFPA 13D Residential Sprinkler Omission Rules

Before laying out sprinklers, classify the spaces on the residential plan that require coverage and the spaces that qualify for omission. Doing this first prevents time from being spent designing coverage in spaces where a sprinkler is not required and gives you a clearer starting point for the rest of the sprinkler layout.

NFPA 13D 2025 provides specific conditions for when sprinklers can be omitted. These requirements need to be applied exactly. A space may meet a size threshold but still fail another condition in the same provision, so the complete omission requirement needs to be checked before removing a sprinkler from the design.

Classify Spaces Before Placing Sprinklers

Work through the plan room by room and determine whether each space requires sprinkler protection or qualifies for omission. Common omission conditions include:

This classification should happen before the main sprinkler pattern is developed. A small closet that qualifies for omission changes the coverage needed around that portion of the plan. A bathroom that does not qualify has to be included in the sprinkler layout and coordinated with the adjacent spaces just like any other area requiring sprinkler protection.

Apply Size Thresholds Exactly

Bathrooms may be omitted when they are 55 square feet or less. A 55-square-foot bathroom meets the size threshold; a 56-square-foot bathroom does not.

Closets, linen closets, and pantries may qualify for omission when the area does not exceed 24 square feet and the required wall and ceiling surface conditions are satisfied. A 24-square-foot closet therefore meets the size condition, while a 25-square-foot closet does not.

Meeting the size condition alone does not mean the space qualifies for omission. For a closet, linen closet, or pantry, the required wall and ceiling surface conditions must also be verified. If the architectural plans do not provide enough information to confirm those conditions, the omission should not be assumed.

Measure these spaces using the dimensions provided on the architectural plans rather than estimating from the drawing or relying on the visual size of the room. When a bathroom, closet, or pantry is near the applicable threshold, verify the dimensions before finalizing the omission.

Design principle: Omission thresholds are specific limits, not rules of thumb. Check every condition in the applicable provision before deciding that a sprinkler can be omitted.

Handle Garages, Attics, and Concealed Spaces Separately

The omission rules for garages, attics, and concealed spaces are different from the size-based requirements for bathrooms, closets, and pantries.

Garages are omittable regardless of size. Attics and concealed spaces are omittable when they are not used for living purposes. Unlike bathrooms and closets, there is no room-area calculation used to determine whether these spaces qualify based on size.

Instead, identify these spaces on the plan and verify the condition that allows the sprinkler to be omitted. For attics and concealed spaces, that means confirming that the space is not being used for living purposes.

These spaces should still be identified deliberately when reviewing the plan. Omitting a sprinkler should be a design decision based on the applicable condition, not an area that simply disappears from the layout because it is outside the primary living spaces.

Use Omissions as Part of the Overall Layout

Omission decisions affect the sprinkler layout in the surrounding spaces. An omittable closet may remove the need to fit a sprinkler into that space, but the adjacent bedroom still has to satisfy its own coverage and spacing requirements. A bathroom that does not qualify for omission becomes another area that needs to be included when developing the sprinkler layout.

The most effective approach is to review the plan and establish which spaces require sprinkler protection before developing the main sprinkler pattern. Once the omission review is complete, the remaining spaces define where sprinkler coverage needs to be developed and where the spacing and positioning requirements need to be applied.