Porches, balconies, and roof decks: when a DC sprinkler system has to reach outside

The drawings come back for a three unit conversion on Capitol Hill and there is a head on every rear balcony and one under the roof deck, and the owner wants to know who asked for that. The answer depends on which standard the building is designed to and what the building is made of. This article covers which exterior spaces on a DC rowhouse or small condo building the sprinkler code reaches, and what a head that lives outside has to do to survive a District winter.

Two standards, two answers

A single house or a two unit building in the District gets its sprinklers under NFPA 13D. A building with three or more dwelling units is Group R-2 under the DC Building Code, and the sprinkler system is designed to NFPA 13R, or to full NFPA 13 once the building gets tall enough. The 13D versus 13R article explains how a building lands on one or the other. For exterior spaces the split matters more than almost anywhere else, because the two standards point in opposite directions.

NFPA 13D lists open attached porches, carports, garages, and similar structures among the spaces where sprinklers are not required. The standard is built around the idea that a house fire that matters starts inside and the system buys the family time to get out. An open porch with air on three sides is not where that fire starts. So on a single rowhouse, the back porch, the front stoop roof, and a rear deck are outside the system unless the designer chooses otherwise. The rooms 13D can skip article has the full list of indoor spaces that get the same treatment.

NFPA 13R goes the other way. After a run of apartment fires that started on wood balconies and ran up the outside of the building past every indoor head, the standard added a rule that exterior balconies, decks, and ground floor patios of dwelling units get sprinklers when the building is wood frame construction. A three unit rowhouse conversion with a wood rear balcony on each floor is exactly the building that rule was written for.

What the building is made of decides it

The 13R rule turns on construction type, and this is where DC rowhouses get interesting. A rowhouse with brick bearing walls and party walls, wood floor joists, and a wood roof is usually classified as Type III construction on the permit drawings. Exterior walls of masonry, interior of wood. A building classified Type III is not the wood frame building the balcony rule names, so a wood balcony hung off the back of a brick rowhouse may fall outside the requirement even on a 13R system.

A rear addition framed in wood, or a pop up that adds a floor in wood framing, can change that classification for the whole building or for the addition, depending on how the architect draws it. That is a conversation to have with the architect before the sprinkler drawings start, because the construction type on sheet one of the architectural set is what the sprinkler designer reads. The pop up article and the rear addition article cover how those projects pull the sprinkler system along with them.

Roof decks follow the same logic. A wood deck on a wood framed pop up is a deck on a Type V structure. A roof deck on pedestals over a masonry building is a harder call, and the plan reviewer at DOB will ask the question rather than let it slide. The designer answers it on the drawings, in writing.

What an outdoor head has to survive

A standard sprinkler head holds water right up to the seal. Put that outside in the District and the first hard freeze in January splits the fitting. The usual fix is a dry sidewall head. The seal sits back inside the heated wall, and a barrel reaches through to the outside with no water in it until the head opens. The barrel length is specified to the wall thickness, which is why the designer needs a wall section, not a guess. Dry heads cost more than wet ones, so three balconies and a roof deck add a line to the bid that a 13D house never sees.

The second issue is coverage. A balcony head is usually a sidewall, mounted high on the wall and throwing water out over the deck. The ceiling above it, if there is one, is what makes the head work, because heat has to collect somewhere to open the bulb. An open roof deck with no cover has nothing to trap heat, and the standard is written around covered or partly covered spaces for that reason. Where a deck has no roof over it, the designer and the reviewer may agree there is nothing for a head to do, and that agreement belongs in writing on the drawings.

The freeze protection article covers the pipe that feeds the head. For an exterior head the short answer is that the pipe stays inside the heated envelope and only the dry barrel goes out.

The question to ask before the bid is signed

Ask the sprinkler contractor to point to the exterior heads on the drawings and say why each one is there. The answer is one of three things. The standard requires it on this building, and here is the construction type that triggers it. The designer added it as a judgment call, and you can decline it. Or nobody is sure, which means the question goes to the plan reviewer before the bid is final rather than as a change order after the balconies are framed. The heads themselves are cheap next to the cost of running pipe to a wall that was closed up without them. Retrofit pricing on this site runs $2 to $7 per sprinklered square foot, and exterior heads sit at the high end of that band because of the dry barrels and the wall work.

Quick answers