A sidewall fire sprinkler

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 ceilings or on pipes just below them. Among them:

  • 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 selection of commercial sidewall sprinklers, or our selection of residential sidewall sprinklers.

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

We've explained what separates one kind of head from another in our in-depth look at fire sprinkler head types. But basically, each head is designed to point in only one direction. Pendent sprinklers (the most common type) point down from a ceiling or beam. 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 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.

Horizontal sidewall sprinklers installed in a wall

The white sprinklers along this decorative trim under the ceiling take advantage of pipes concealed within the walls. Source: A.L. Fire Protection

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

A window fire sprinkler

Specialized vertical models cool interior glass when a fire strikes, eliminating the need for fire-rated glass. Source: Tyco Fire Products

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 probably isn't a typical use. Residential buildings like hotels use the lion's share of sidewall sprinklers, largely in an effort to reduce the number of sprinklers needed. They're also common in dining rooms, offices, and other spaces where aesthetics are a high priority.

But this design—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:

  • Ice builds up in (and can break) pendent sprinkler heads exposed to low temperatures
  • Running pipe for upright sprinklers, which resist freezing, would reduce overhead space
  • This configuration connects an outdoor sprinkler to protected indoor pipes, reducing the risks of vandalism, impact, and freezing

These sprinklers do have limits (as we'll see in the next section). Still, as an alternative to pendent or upright heads, they can produce designs that are prettier and less costly and risky in the long run.

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

To tell a sidewall sprinkler head from another type, look at their deflectors. These small plates rest between the sprinkler's orifice and the space it protects, shaping water as it sprays. While most 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 ceilings or walls and toward the open space nearby.

Victaulic v2709 fire sprinkler

Not all deflectors look exactly like this, but Victaulic’s V2709 head embodies a style common to horizontal sidewall heads.

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. Vertical models feature an arrow and the word "flow."

Flow label on a sidewall sprinkler

Deflectors on all modern fire sprinklers are stamped with need-to-know information. Among other things, these stamps (“Flow” and “Top” above) tell installers which direction heads like these should face.

Horizontal and vertical models have slightly different installation requirements

In 1996, professor and fire protection engineer Glenn Corbett described them—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 installing 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.

Diagram of smoke detector installation

This illustration shows smoke detectors and the dead space nearby—but the principle is the same for sidewall sprinklers, which won't work properly if placed in dead air space. Source: Drewprops

As such, these and other heads need clearance from dead air. The 2019 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

Horizontal and vertical models share most things in common, but a few differences are worth noting

These sprinkler types are very alike—so much so, that most manufacturers offer both styles with the same materials, finishes, and lists of approvals.

Purchasers won't find any concealed vertical sidewall sprinklers, and for an obvious reason: vertical models hang from exposed pipes beneath the ceiling. Horizontal sidewall models, on the other hand, rest flush against a wall. That leaves installers the option of concealing the sprinkler—using a heat-sensitive cover plate—or placing it in a recessed escutcheon.

Viking concealed sidewall sprinkler

Behind the white disc (cover plate) on this Viking VK4800 is a fully-functional horizontal sidewall sprinkler.

For similar reasons, manufacturers don't offer institutional versions of vertical sidewall sprinklers. Those are designed for prisons, hospitals, and other environments where vandalism, self-harm, and other concerns make fire sprinklers a liability. Because vertical sidewalls aren't installed flush with any surface—wall or ceiling—there's no effective way to protect against somebody ripping the head off a pipe (or misusing the pipes themselves).

Beyond these differences, manufacturers' offerings for these sidewall heads are almost identical. We found only a handful of other distinctions worth mentioning, including these:

  • Tyco offers a range of corrosion-resistant "poly-stainless" sprinklers designed as a cost-effective alternative to stainless steel. While their offerings are almost identical for both sprinkler types, they don't provide poly-stainless construction for some vertical sidewall heads.
  • The vast majority of modern sprinklers have approvals or listings to vouch for their suitability in fire protection. One that doesn't is a dry vertical sidewall from Viking designed for use in areas subject to freezing. There is no obvious horizontal equivalent in Viking's catalog.

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

Sidewall sprinklers open a range of possibilities in a wide variety of buildings. They're not quite "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 like 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.

Viking VK305 sidewall fire sprinkler

QRFS has commercial sidewall heads rated for temperatures including 286 degrees Fahrenheit, 200 degrees, and 155-degree models like this Viking VK305.

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

Senju flush horizontal sprinkler.

Our line of horizontal heads includes Senju's decorative flush sidewall sprinklers for residential buildings, which offer a balance of aesthetics and function.

Browse our selection of commercial sidewall sprinklers.

View our selection of residential sidewall sprinklers.

Questions about sidewall sprinklers? Call us at +1 (888) 361-6662 or email [email protected].

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