Cable railing, South Seaport New York City (C) Daniel FriedmanBuilding Code Rules & Installation Specifications for Guardrail Cables: Wire Rope Railings

  • CABLE RAILINGS & GUARDRAILS - CONTENTS: What's a cable or wire rope railing? What's the difference between a guardrail and a handrail? Specifications for Installing Cable-Type Guard Railings along Balconies or Stairways. Cable Railing Specifications: railing height, cable diameters, cable spacing, cable support & cable tensioning. Maximum Sphere Passage Rule vs. Cable Type Guardrails & Stair Rails - Importance of Proper Cable Railing Spacing, Tension & Cable Railing Rigidity. The Ladder Effect of Horizontal Cable Railings - climbing children & Safety Issues
  • POST a QUESTION or READ FAQs about Building Code Rules & Installation Specifications for Guardrail Cables: Wire Rope Railings, spacing, tensioning, support, cable diameters, inspection, safety hazards, applications, & code approvals
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Guide to cable railings or wire rope guardrails:

This article describes and includes illustrations of cable or wire rope railings or guardrails used along decks, balconies, walkways and stairways. We include definitions of guardrail, a handrailing or stairway handrail, and other terms that assist in understanding the building code, construction, and safety requirements that wire cable type railings must meet.

We describe the key installation features necessary for cable railings and we explain both the 4-inch sphere rule problem faced by cable railings and the ladder-effect or climbability problem that these systems must also address. Installing a cable railing according to the manufacturer's specifications for spacing, tension, support, and other parameters (described here) improve the safety of cable railings.

Where the presence of children argues against any sort of horizontally-run guard railing member, cable railing manufacturers can provide vertical cable railing designs.

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Building Code & Manufacturer Specifications for Cable (Wire Rope) Used in Stair & Guardrail Installations

What's a Railing? What's the difference between a guardrail and a handrail?

Guardrail unsafe (C) Daniel Friedman

While cable "railings" are permitted under some building codes and by local building Inspectors we find that people speak a bit loosely about the definition of "railing" - and "cable railing".

It is important to be clear in our terminology as building codes specify different requirements for handrailings than for guardrailings in terms of construction, height, and graspability. [48][49][50][51][52]

Definition of Guard railings

Properly, questions about cable railings or wire rope rails are asking about a guard rail, a type of safety "fencing" or "railing" used along the outer side of balconies and stairways, not a "hand railing". Below in this article we discuss the installation and safety of cable-type guardrailings.

Our photo at left illustrates a home-made (and unsafe) cable guardrailing around the top of a stairwell opening in a New York home inspected by the author. The cables were visibly slack, incomplete, and the entire assembly so wobbly that it would easily collapse if leaned-on or stumbled-against.

At Guardrails on Balconies & Landings we provide details about all types of guard railings.

Definition of Hand Railings

Wire cable hand railing at the Pyramids, Mexico City, Mexico (C) Daniel Friedman

A handrail is a horizontal or sloping rail intended to be grasped by a person's hand for support when using a stairway and importantly, instinctively grasped in an attempt to arrest a fall.

Our photo (left) illustrates use of a wire cable "hand railing" along steps ascending the Pyramid of the Sun outside Mexico City.

Watch out: A wire rope or wire cable in the typical dimensions used at railings (1/8-inch to 3/8-inch in diameter) is not a graspable handrailing by any of the building code standards because of its small diameter.

1003. Handrail grasp ability. Handrails with a circular cross section shall have an outside diameter of at least 1.25 inches (32 mm) and not greater than 2 inches (51 mm) or shall provide equivalent grasp ability. If the handrail is not circular, it shall have a perimeter dimension of at least 4 inches (102 mm) and not greater than 6.25 inches (159 mm) with a maximum cross-section dimension of 2.25 inches (57 mm). Edges shall have a minimum radius of 0.125 inch (3.2 mm). - 2000 BOCA, ICBO, SBCCI

See HANDRAILS & HANDRAILINGS for details about hand railing building codes, construction, inspection, & safety concerns.

Specifications for Installing Cable-Type Guard Railings along Balconies or Stairways

Cable Railing Specifications: railing height, cable diameters, cable spacing, cable support & cable tensioning

Cable tensioning devices for residential cable or wire guardrail, Tivolin NY (C) Daniel Friedman RA

If you take a look at cable "railing" specifications provided by a company that sells components for cable railing construction [such as Atlantis Rail, Keuka Studios, or Wagner Companies, three suppliers of cable railing systems, you'll see that the "railing" is really a guardrail comprised of stainless steel horizontal cables of diameters of 1/8", 5/32", 3/16", and 1/4" depending on the application.

Horizontal cables are stretched tight, 3" o.c. to form a barrier and are supported by a combination of structural posts and intermediate posts spaced 42" o.c. to 48" o.c. depending on the manufacturer's recommendations.

At left a wire guardrail installed at a private residence in Tivoli, NY uses individual cable tensioning devices at each end of a three-sided cable railing. Each of these little cable guardrail tensioners is secured to the wooden post with three wood screws. I'm uncertain just how much rail tension can be achieved without pulling the tensioning device right off of the post to which it was attached.

Wire Rope or Cable Guardrail / Railing Height - Balconies & Walkways vs Stairs

The International Residential Code (IRC) requires a minimum 36-inch-high guardrail for all decks, balconies, or screened enclosures more than 30 inches off the ground. [48][49][50][51][52]

The guardrail top height is in most jurisdictions 36" high (or more) in residential applications and 42" high in commercial installations. Along a stairway the railing height is governed by different rules because of the need to grasp the railing during use of the stairs.

Handrails are required on all stairs more than four risers in height. Handrails cannot be less than 30 inches nor more than 42 inches above the nosing of the treads

Maximum Sphere Passage Rule vs. Cable Type Guardrails & Stair Rails - Importance of Proper Cable Railing Spacing, Tension & Cable Railing Rigidity

Unsafe railing in New York City (C) Daniel Friedman Child safe guardrail on a Seattle Ferry (C) Daniel Friedman

For child safety, the balusters or other decorative infill must be spaced less than 4 inches apart (a 4-inch-diameter ball should not pass between the balusters). [48][49][50][51][52]

At above left is an unsafe guardrailing in New York City. In comparison, the guardrailing shown at above right happens to be on a Seattle ferry and resists even active jumping climbing children. The mesh guardrail infill is small enough that little toes and shoes don't easily climb the rail.

Companies selling cable guardrailings point out that building codes (IBC and IRC) specify that the opening between vertical balusters or between horizontal railings (if the local code official will permit them) must be close enough together that a 4-inch sphere won't pass between them. [45][46][47]

Watch out: For horizontal guardrailing in-fill cables we point out that if the cable can be stretched or is not properly tensioned, the guardrail system may fail this 4-inch sphere test.

Also the largest opening between the bottom-most horizontal cable or guardrail member and an individual stair tread should not pass a 6-inch sphere.

Cable or Wire Rope Spacing & Tension Are Critical for Safe Guardrails

Unsafe railing in New York City (C) Daniel Friedman

Our photo at above left shows an attractive railing with horizontal cables intended to permit a nice view of the Brooklyn NY skyline. We also demonstrate how easily the cables can be separated as well as how attractive this guard railing is to children.

To have a chance of meeting the 4" sphere rule (maximum sphere passage <= 4 3/8") the cables must be installed with adequate tension and rigidity to prevent deflection by climbing or playing children or other forces that might be anticipated.

If the cable spacing is more than 3" o.c.) or the cable horizontal span is too great, if the intermediate posts spaced too far apart (more than 42" of horizontal distance o.c.), or if the cables are not adequately tensioned, the system may fail this safety test. Using a heavier gauge cable (3/16" diameter instead of the minimum 1/8" diameter) can also add rigidity.

The supporting structural posts and intermediate bracing also need to be strong enough to handle the forces created by properly tensioned horizontal cables. Wagner points out that

An incredible amount of tension is generated on an end post when you have ten or more lines, each tensioned at 400 lbs. over a height of 36" to 42". Often designers and fabricators inexperienced in cable railings will not recognize the amount of the tension applied to the posts.

The end result all too often is end posts which will bend considerably as the cables are being tensioned…or with a railing where the cables cannot be properly tensioned without an unacceptable amount of post deflection. The posts to which hardware is mounted must be constructed so that they will not deflect perceptively as the cables are tensioned. [46]

Cable railing tension demonstration (C) Daniel Friedman

And where we have seen cable "guardrailings" installed, indeed a graspable and solid top rail was always provided. The top rail also provides a rigid horizontal support that prevents the whole system from collapsing as vertical posts would bend inwards as the horizontal cables are tightened.

Also, regular inspection of the tension and security of the cables is something I'd recommend, particularly in public areas where the system may be subjected to climbers and pushers.

At left we illustrate that these horizontal cables were very resistant to opening, and considerable force was required to cause enough deflection to pass a 4-inch sphere. Notice that a heavier gauge cable diameter was used (3/8"), adding to the cable rail's rigidity.

But below we illustrate another (residential) cable or wire guardrailing system that was easily deflected and opened and whose tensioners appear to be of limited ability.

Atlantis points out that using a cable tensioner such as their RailEasy™ device permits on-site cable cutting to proper length and adjustment to proper tension without risking slack sagging cables due to mis-cuts or mis-measurement. The company also describes the proper order of tightening the tension on the horizontal cables, starting at the center cable and then alternating above and below that point as each cable is tensioned. [45]

Just below I illustrate how easily some cable guardrail wires can be deflected with a bit of foot or hand pressure. My opinion is that even tightening these cables to a specified tension cannot predict how wide an opening might occur when children climb on the cables unless the tension specification also includes factors for both vertical post spacing intervals and the total length of wires or unsupported wires that are used in the cable guardrail. The cable tensioners illustrated earlier in this article were part of this deflected, cable guardrail.

Deflection in a cable guardrail system cannot preserve the 3-inch spacing (C) Daniel Friedman

Other tensioning troubles occur: seeking very high tension in an effort to prevent spreading of the cables by children who may then might pass through the guardrail can bend posts or dislodge them unless the posts are of sufficient strength.

The Ladder Effect of Horizontal Cable Railings - Safety Issues

Unsafe railing in New York City (C) Daniel Friedman Climbable horizontal infill of a guard railing (C) Daniel Friedman

Our concern with any horizontally-run guardrail structure is that it is climbable, and also that often we find the cables are loose enough that a child can easily slip between the cables - an installation or maintenance error, not a conceptual error.

In our cable guardrail at above left the tension on the guardrail cables was pretty high but a child standing on the cable can often increase the opening size to more than 4-inches. For researchers who argue that the "ladder effect" is not a useful construct and that children are not attracted to climbable structures, take another look at this photograph.

At above right where in the distance is a nice view of Seattle's Lake Washington, the horizontal guardrailing members are constructed of metal pipe and do not stretch or deflect, but they are more than 4" apart and as they are horizontal, a child could easily climb the guardrailing at this Seattle.

The stretch and opening of horizontal guard cables can be minimized by placing intermittent posts at suitable intervals between the supporting posts. Atlantis suggests no horizontal space between posts should be 4 feet on center - a spacing that I usually see has been violated by the installer.

Unsafe cable or wire guard along a stair, Queretaro (C) Daniel Friedman Cable guardrail and stair guard, FDR Estate (C) Daniel Friedman

Above left we can see by casual observation (sagging and wide-open wire cables) that this cable type stair guard does not protect children using the stairs. This installation is in a coffee shop in Colonia Sur in Queretaro, Mexico. At above right is a closely-spaced, highly-tensioned guard rail and stair guard at the FDR estate in Hyde Park, New York.

At least some of the cable railing suppliers offer vertical cable railings for installations where a horizontal railing is not approved or not suitable.

In our OPINION, a vertical cable guardrail adequately addresses the climbability question (the ladder effect) and if properly tensioned, might pass the opening spacing requirements.

The Atlantis company's opinion is that because of their small diameter and lack of rigidity, horizontal cables are thin and not easy to climb. [46] Indeed in our photo where kids were tugging on the horizontal cables installed in a cable railing in New York City, the cables appeared rigid enough that there was not much visible deflection.

Our field experience is that children enjoy climbing horizontal cables and other horizontally run guardrailings. Perhaps due to playground practice, it's apparent that kids have little difficulty ascending the cables. OPINION: We do not recommend any type of horizontal guardrail intermediate members that can be climbed in locations where children may be present.

Stairway Lighting requirements (C) Carson Dunlop Associates

Stairway handrail & stair balusters & guard details are in this sketch.

Balusters (vertical posts comprising the barrier in guards and railings)

Hand-railing heights are given:

Sketch above was provided courtesy of Carson Dunlop Associates and is used with permission.

Research on Child Safety vs Cable Guardrails or Stair Railings

Reader Question: are there really safety or security issues for children with cable railings on decks and stairs?

15 August 2015 Barbara said:
Are there any data or feedback on security issues for children with cable railing (deck and staircase)? I am concerned that they might want to climb on the horizontal cables, but not sure if it is a serious issue.


Horizontal cables or any horizontal member in a guardrail are a child hazard as children can and are tempted to climb such a guardrail - a hazard often described as the ladder effect.

The ladder effect hazard at guardrails and stair guards remains a common opinion among safety experts (cited below) and some code officials and home inspectors, regardless of whether or not the railing was approved by local code officials. In our opinion, the aesthetic desire for cable railings and the marketing objectives of vendors may be a factor in the removal of the ladder effect hazard from some building code restrictions on guardrail design and there may be both inadequate fall and injury reporting data as well as conflicting interests between safety and and industry vendors.

For example, Hedge (2007) completed a under the auspices of the National Association of Home Builders' Research Center (NAHBRC) and funded by and prepared for the National Ornamental and Miscellaneous Metals Association (NOMMA), an industrial association that includes vendors of cable railing systems that did not find data which supported the need for additional code language.

Readers concerned only with code violation and "legality" of cable guardrailings should check with their local building code enforcement official. Readers concerned with child safety should also review the safety articles cited below. Istre (2003) makes clear that guardrail openings spaced or capable of being spaced more than 4 inches apart are a significant fall and injury hazard for children.

Typically there are other hazards such as the ability of the cables to be stretched or moves such that the 4-inch safety opening size can be increased so that a child could also pass through the guard. For this reason some builders and code enforcement officials specify a 3 1/4" spacing between horizontal cables rather than the 4-inch rule of thumb used for solid balusters. Other sources we found (Ellis 2011) suggest that cable manufacturers suggest a 3-inch spacing.

Allowable Openings Code Citations pertinent to Cable Railings

Exceptions to the spacing rules given above:

Triangular openings formed by the riser, tread and bottom rail of a guard at the open side of a stairway should be such that a sphere 6 inches (152 mm) cannot pass through.

Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches (107mm) to pass through.

Exceptions: 21" sphere for elevated walk for electrical, mechanical and plumbing systems and Group I-3, F, H, or S occupancies, balusters, horizontal intermediate rails or other construction.

References discussing cable guardrailings, cable railing safety, design, construction & spacing specifications

Note: the deck building citations below are generally quiet or have little to say about child hazards, climbability, and building code compliance for cable railing systems but they do offer good construction practices and discuss cable tension, spacing, post security and strength and similar cable railing design considerations.


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Or see GUARDRAIL & HANDRAIL STRENGTH for a description of guardrail types, strengths, testing specifications

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