Tread strips: on stairways, fools rush in, when angels fear to intervene.

Back in March, I stuck my leg out with an article that I expected to generate a “much ado about nothing” or “marking a mountain out of a molehill” response.  I do have that tendency.  I had stumbled upon an unusual stairway configuration during a visit to the North Dakota State Capitol complex in Bismarck.  The geometry of it tripped me up, because it was unequivocally dangerous, yet also mundane enough that I could easily see engineers replicated this stairway design tens of thousands of times without anyone raising much of a stink.  I hurtled headlong into the North Dakota article, and—lo and behold!—pretty much all the commentariat agreed with me. These stairs were an accident waiting to happen.  It wasn’t just the layout but of the inconspicuousness of it: the absence of any visual cues meant that I (and no doubt many others) were blithely unaware of a six-foot drop onto an uneven surface until we were inches away from the ledge, flapping our arms wildly to maintain balance.  What could the State of North Dakota do to fix it without weakening the appearance with bannister clutter?  At least a few commenters provided effective if somewhat opulent solutions.  The best fix may be no more complicated than a long, thin strip of sandpaper and some really strong glue—what I will call “tread strips”.

This photo, from an interior in Washington DC, makes it obvious.  I will leave the building anonymous, though the full photo series here will likely reveal what type of building it is.  (And, for some readers, the photo will offer enough of a clue to identify the exact building by name and address.)  But there, on the final stair before ground, is the visual—and, to a lesser extent, tactile—cue needed to signify a change in planar surface.  In the conclusion of the previous paragraph, I indicated that “I will call” them tread strips, primarily because they operate under a variety of of names: stair safety strips, anti-slip stair treads, stair nosing strip, grip stair strips, step warning strips, step edge strips.  In fact, virtually every manufacturer has its own name; no industry standard exists that I can see.  They can serve any variety of functions based largely on the color, size, material, and precise location within the tread of each stair, unified by a goal of improving safety.

So what’s the function here?  The placement is close to the nosing of the stair tread, which is the term for the front edge, which often projects or overhangs solidly beyond the vertical riser portion below it, like a nose.  The nosing absorbs the majority of shock within a staircase, since it is the first place most human feet contact when ascending, and it is the most critical portion of a stair tread in promoting safety and visibility.  In the stairwell to the right, the gritty finish to the strips probably helps reduce slipping on these staircases when they are muddy or wet from people carrying the outdoor elements indoors on their feet.  But they are not tactile in the same way as the now-omnipresent kenji blocks, the raised bumps that indicate to significantly visually impaired (legally blind) people that they are approaching a hazard in the form of a busy street or train platform.  Those raised bumps, usually made of rubber, essentially function as Braille for feet and are much more detectable than the black strips seen here.  As mere strips of an abrasive surface with good traction rather than a protective coat, the tread strips here do not protect the nosing from deterioration, which is a major detriment to safety, especially in outdoor stone or concrete stairwells, where nosings tend to deteriorate.  Interior nosing, not subject to the elements, tends to last much longer.

Most importantly, however, is the seemingly willy-nilly placement of the tread strips.  Why are the only on some treads but not all of them?  Investigating further, these tread strips only seem to exist at the top-most stair and the final tread before a landing or the ground floor, so they don’t intend to protect against the hazard of stairs in general; no single stair tread is more or less dangerous than the others.  Rather, they alert users of a change in condition signified through the entrance or exiting of a flight of stairs.  They are moderately useful at protecting against slipping, though not as much as if they existed at each tread….but they are highly useful as a visual cue toward a change in conditions where the ascent or (especially) descent begins and ends.

Now that it’s clear which function the tread strips serve at the stairwells in this particular building, do they pass the building code sniff tests?  Well, in most respects, yes.  The Americans with Disabilities Act (ADA), the nationwide standard for maximizing safety and accessibility for those with mobility or sensory impairments, strongly recommends builders to “consider providing visual contrast on tread nosings, or at the leading edges of treads without nosings, so that stair treads are more visible for people with low vision”.  Diction is essential here: the choice of a verb “consider” reveals this to be advisory and not mandatory.  Then again, some jurisdictions in the US perceive the ADA as a bare minimum that specifically targets improving the built environment for persons with access and functional needs, but building codes cover far more manifestations of safety than accommodations for the disabled.

The ADA is not a proxy for the full array of building codes that most municipalities deploy; it informs some practices but does not speak at all on many others.  The International Building Code (IBC) is the most comprehensive set of minimum standards intended to unify construction industries through a goal of consistent building safety, but the IBC has not informed federal policy in any capacity remotely close to the ADA, which is federal law.  Thus, individual jurisdictions retain the right to craft their own building codes, with the IBC serving as one of many guiding tools. Washington DC largely adopted the 2015 IBC in its 2020 update to the District of Columbia Construction Codes, amendments notwithstanding.  And IBC Section 504.6 (on Visual Contrast) does mandate a stark visual contrast (light-on-dark or dark-on-light) at every tread and landing in stairwells, not just the top and bottom.  While this suggests the building here is non-compliant, it predates these new building codes by many decades, and, unless the building undergoes a significant renovation that includes alterations to the stairwells, it should enjoy relief from DC’s building code amendments through the grandfather clause.  Additionally, I can assert that this structure has sought to comply with ADA in recent years by investing heavily in a fully functional elevator that accommodates any and all wheelchairs, meaning that individuals whose disabilities (visual or mobility) prevent them from using stairs—which are necessary to reach the core functions that take place in this structure—have an alternative that is many degrees safer than this stairwell, which predates almost all codified safety standards over the past sixty years.

Ultimately, tread strips are so site-specific that I do not foresee a consistent naming scheme ever coming into place.

Less than two miles from the previous building, once again in DC, the photo below offers a markedly different condition that still prompts a similar remedy.  It it weren’t for my one thousand words that already precede this photo to the left, it would be tricky to tell what I’m trying to single out.  But, given the context, it’s obvious!  Here is a cornershop in DC’s prestigious, largely 19th century Capitol Hill neighborhood, where the elegant brick sidewalk presents an anomalous condition.  The mere slope to get from the street level to the doorway involves a change of grade of probably a foot.  As recently as four years ago, this entryway was concrete, and the business (Union Kitchen) treated the terraced steps as a decorative element, with potted plants at each deep, barely vertical tread.  Since then, the owners bricked over the entryway, as my recently-taken photo proves.  Bricks look better than concrete in most people’s estimations, but, as I’ve noted before, create more edges and interstices and opportunities for things to go wrong.

Somewhere along the way, one of the parties decided that the nosing of these steps needed tread strips.

This bricking/repaving may constitute enough of a renovation that the IBC element of DC’s building codes comes into effect, and the owner must comply with Section 504.6.  But it’s a tricky judgement: when the grade change is this slight, is it really a stair or is it merely an “unevenness”?

Since these tread strips offer no traction improvement, they do not aid mobility; they are exclusively a visual cue.  It’s still easy to discern why they’re useful.  Without the significant color contrast of white-on-red, the only indicator that a nosing exists is the deviation from the herringbone status quo pattern.  One can imagine how hard it might be to see an edge or nosing, because it’s uncustomary and only exists because the terraced tread was already there under the previous concrete conditions.  Thus, the white tread strips help signal a step that wheelchairs must avoid—they can use the nearby ramp and sloped area—and it also helps the able-bodied avoid tripping injuries.  Building code mandate or not, it is in the best interest of Union Kitchen (or the property owner if Union Kitchen is a tenant) to avoid liability by making this weird irregularity as visible and safe as possible.

Ultimately, whether indoors or outdoors, tread strips can improve safety on stairways through a multitude of solutions, each belonging to a gradient of differences significant enough to warrant different names (and probably discrete patents).  Stairs must be as safe as possible, not only because they are so ubiquitous but also so banal.  Significant numbers of serious injuries—broken femurs or hips—occur due to slip-and-falls along stairs, affecting the elderly to such proportions that it can shorten their life spans.  Even in private homes, many people (young and healthy) use some sort of aesthetic tread strip or a special material at the nosing to avoid sliding, which we’ve all done when going down a flight of stairs in our socks.  (Carpet and hard wood stairs are equally slippery, it seems.)  Ascending or descending a flight of stairs should be almost involuntary; the more one has to think about it, the more problems one will encounter if a stairway’s design involves something abnormal or irregular. 

Better to regularize it with predictable railings, visual cues, and traction.  Ugly as tread strips may be, an unsightly stairwell won’t elicit quite as many lawsuits. Both fools and angels can proceed with confidence.