#210 – Explaining Sidewall Sprinkler Heads, Both Horizontal and Vertical

Slight differences between two less-common fire sprinkler types give designers and installers much-needed flexibility

There are plenty of good reasons why most fire sprinklers are mounted in pipes above or just below ceilings, including:

• Fire sprinklers are heat-activated, and heat rises
• Higher sprinklers can cover wider areas
• For the most part, heads placed near the ceiling face fewer obstructions (like furniture, cabinets, and other large objects) that might get in the way

But there are also good reasons to mount sprinklers along walls—and plenty of ways to do it, too, thanks to the sidewall sprinkler head. In this article, we look at what these fire sprinklers do and how horizontal and vertical models play slightly different roles in active fire protection.

Not interested in the finer points of sidewall sprinkler heads? Browse our full selection of sidewall sprinklers.

Sidewall sprinkler heads go where pendent and upright sprinklers can’t (or shouldn’t)

We’ve explained much of what separates one kind of fire sprinkler head from another in our in-depth look at fire sprinkler head types. But basically, each sprinkler is designed to point in a direction. Pendent sprinklers (the most common type) point downward and to the sides from a ceiling or beam. Horizontal sidewall sprinklers, on the other hand, install horizontally, often in a wall. They may or may not stick out, depending on the sprinkler’s construction and the way it’s mounted, but each of these heads relies on piping along or behind a wall for a supply of water.

There are two big reasons to use sidewall sprinklers:

• Access to ceiling piping is limited or unavailable
• Ceiling-mounted sprinkler heads would somehow detract from the building’s aesthetics

By and large, most sidewall sprinkler heads are horizontal sidewall sprinklers. They’re designed to point parallel to the floor.

However, most sprinkler manufacturers also offer vertical sidewall sprinklers. These heads point perpendicular to the floor and can be installed either facing up (a classic upright orientation) or down (a classic pendent orientation). That flexibility makes them unusual. Upright and pendent sprinklers, for example, can face only one way—and will likely fail to keep a fire in check if installers choose the wrong orientation.

A short sidewall case study: apartment fire protection

For a great example of when these sprinklers do what others can’t, let’s watch one in action:

This isn’t a typical use, as sidewalls are usually indoors. Residential buildings like hotels use the lion’s share of sidewall sprinklers, and they’re also common in dining rooms, offices, and other spaces where running overhead pipe is impractical or ceiling aesthetics are a high priority.

But the design in the video—which features a horizontal sidewall head placed beneath an outdoor walkway on an apartment complex—embodies many of the benefits offered by sidewall heads. Neither upright nor pendent sprinklers make much sense here, for several reasons:

• Running pipe for pendent sprinklers in the outside wooden deck is impractical.
• This configuration connects an outdoor sprinkler to protected, climate-controlled indoor pipes, reducing the risks of vandalism, impact, and freezing.
• The sidewall is used “For the protection of exterior projections and similar structures,” one of NFPA 13’s nine permitted use cases.

Sidewall sprinklers do have certain limits (as we’ll see in the next section). Still, as an alternative to pendent or upright heads, they support designs that work where other orientations wouldn’t.

Vertical and horizontal sidewall sprinkler models look similar but are easily distinguished by their deflectors

To tell a sidewall sprinkler head from another type, look at the deflector. These small plates rest between the sprinkler’s orifice and the space it protects, shaping the water pattern as it sprays. While most (upright and pendent) sprinklers have a spoked circle, sidewall heads have a deflector that usually combines a semicircle and a flat plate that runs perpendicular to it. That shape guides water away from one direction and toward the intended direction.

The deflector holds the key to telling these sprinklers apart—and to installing them properly. Horizontal models are marked with the word “top,” indicating the side of the deflector that should face the ceiling. In contrast, vertical models feature an arrow and the word “flow.”

Horizontal and vertical models have slightly different installation requirements

In 1996, professor and fire protection engineer Glenn Corbett described sidewalls—with more than a trace of irony—as “superhuman” sprinkler heads. His article for Fire Engineering drew attention to a concerning trend in fire protection to install sidewall sprinklers in ways that simply weren’t safe. Installers, he said, often overestimated their abilities, placing them too close to obstacles or otherwise putting them in places that don’t work.

That’s a big problem, and for a simple reason: like other fire sprinkler types, sidewall heads activate when they get hot. But tests have shown that some parts of buildings—particularly, those where a wall and ceiling meet—manage to lock cooler pockets of air in place. This phenomenon, called “dead air,” can cause heads to start spraying too late, allowing a fire to spread.

As such, sidewalls and other heads need clearance from dead air. The 2022 edition of NFPA 13: Standard for the Installation of Sprinkler Systems requires the following clearances for vertical and horizontal sidewall sprinklers:

• At least four inches of clearance between deflectors and ceilings or end walls for all models
• No more than six inches of clearance from the ceiling for vertical sidewall models only
• No more than 18 inches of ceiling clearance for horizontal sidewall models specifically listed for that use, when placed below non-combustible and limited-combustible ceilings
• No more than six inches of ceiling clearance for all other horizontal-type models

NFPA 13 also prescribes a minimum distance from the deflector to the wall where the sprinkler is installed:

• Vertical models: four to six inches
• Horizontal models: zero to six inches

With globally recognized manufacturers competing for a share of the fire protection market, sidewall sprinkler purchasers have a wide array of options

Sidewall sprinklers open up design possibilities in a wide variety of buildings. They’re certainly not “superhuman”—but they’re an impressive and helpful addition to any designer’s toolkit.

QRFS carries more than 40 sidewall sprinkler models from industry-leading manufacturers Victaulic, Viking, Senju Sprinkler, and Tyco. With a variety of temperatures, finishes, and orifice sizes for residential and commercial heads—both quick and standard response—our selection has sprinkler heads suited to almost any project.

All of our residential models are UL-listed and ready for installation in NFPA 13D and 13R fire sprinkler systems. Each of our commercial models is UL-listed, FM-approved, and ready for installation in NFPA 13-compliant systems.

Browse our selection of sidewall sprinklers.

Questions about sidewall sprinklers? Call us at +1 (888) 361-6662 or email support@qrfs.com.

This blog was originally posted at blog.qrfs.com. If this article answered your questions about these useful heads, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.