Metal railing and guardrail fabrication and installation field guide

Metal railing work, and why the anchorage is the job

Metal railing work is fabricating and installing a fall barrier or a graspable rail to the heights, loads, and infill the building code sets, then anchoring it to a structure that can actually carry those loads. A guardrail keeps people from falling off an edge. A handrail gives a hand something to hold on stairs and ramps. Both are life-safety elements, not trim, and the code sizes them for specific numbers.

Here is the part the pretty rendering never shows. The rail is the easy half. Anyone with a saw and a welder can build a guard that looks right and meets the height. The half that decides whether someone gets hurt is the post anchorage, the connection between the post and the floor, the slab edge, the steel, or the framing. A beautiful rail bolted to a substrate that cannot take the load fails the day someone leans into it, and that is the worst possible day for it to let go.

So the work has two jobs that have to stay in step. Build the rail to the code geometry, the heights and the 4-inch sphere infill. And anchor the posts to a structure that takes the load and the overturning moment at the base. The posts often land on the same concrete the foundation crew left or the steel the erection crew set, which ties this work to the structural-steel guide and, on roofs, to the rooftop fall-protection guide.

The anchorage carries the load, not the rail

This is the one truth to carry out of this guide. When a guard fails, it almost never fails because the top rail snapped or a picket pulled loose. It fails at the base, where the post meets the structure, because the anchorage could not carry the load the code requires. The rail stays in one piece and goes over the edge with the post still bolted to it.

The reason is the long arm. A horizontal push at the top of a 42-inch post is a small force, but that arm turns the push into a large prying moment down at the anchor bolts or the embed. The metal of the rail handles its share without much trouble. The four small bolts and the concrete around them at the base are where the demand concentrates, and that is where the chain is only as strong as its weakest link.

Treat the anchorage as an engineered connection, not a detail you eyeball. The fabricator can guarantee the rail. The thing that has to be designed for the actual substrate, the load, and the moment is the attachment, and on a real project the engineer of record or a delegated engineer signs off on it. Build the most elegant rail in the city and bolt it to a thin slab edge with two wedge anchors at the wrong spacing, and you have built a hazard with a nice finish.

What is the difference between a guardrail and a handrail?

A guardrail is the fall barrier. It goes where there is a drop-off over the height the code cares about, more than 30 inches under the IBC and IRC, a deck, a balcony, an open stair side, a mezzanine, a landing, and its job is to keep a person, and a child, from going over the edge. The IBC and IRC require it at those drops, and they size it for a height and a load and an infill that closes the gap.

A handrail is the graspable rail you hold while you climb or descend a stair or walk a ramp. Its job is steadying and catching a stumble, so it has to be the right height for a hand and the right shape to actually grasp. The code wants a handrail on stairs and ramps regardless of whether there is a drop, because the fall it prevents is the fall down the stair, not over the edge.

They are different elements with different rules, and the confusion costs money. People build a 42-inch guard, call it a handrail, and fail inspection because nothing at 42 inches is graspable for someone going down the stair. On an open stair you frequently need both: a guard at the open side to stop the fall over the edge, and a handrail at the right height, mounted to or inside that guard, for the hand. Build them as two jobs and you stop fighting the geometry.

What load must a guardrail resist?

A guardrail in commercial work has to resist a 200 lbf concentrated load applied at any point along the top, in any direction, and a 50 plf uniform load applied horizontally at the top rail. The two are checked separately, not added, and the structure does not have to resist both at the same time. These are the live-load provisions in the IBC structural chapter, and the IRC sets the same 200 lbf concentrated load for residential guards.

The infill carries its own load. The pickets, the glass panel, the cable, or the mesh that fills the guard between posts has to resist a 50 lbf load applied horizontally on a 1 square foot area, so a person leaning, falling, or pushing against the infill does not break through it. This is a separate check from the top-rail load and it is the one that catches undersized pickets and weak panel clips.

The handrail is sized for the same 200 lbf concentrated load and the 50 plf uniform load, because a person catching a fall on a stair loads it hard and suddenly. The 200 lbf number sounds modest until you remember it acts at the top of the post and the anchorage has to carry the moment it creates. Confirm the exact load cases and any factors against the adopted code edition and the project structural drawings, because the engineer designs to those, not to a rule of thumb.

How high should a guardrail be?

A guard in commercial occupancies has to be at least 42 inches high, measured vertically from the walking surface or the stair nosing line to the top of the rail. In one- and two-family residential work the IRC drops the guard minimum to 36 inches. That difference, 42 versus 36, is the single most common height mix-up between commercial and residential jobs, so confirm which code governs the building before you cut a post.

A handrail is set between 34 and 38 inches above the stair nosings and the ramp surface. That band is fixed because it is where a hand naturally falls when someone steadies on the rail, and it is narrower than people expect, so the handrail height and the guard height almost never coincide. On an open stair you carry the guard at its height and run the handrail inside the 34 to 38 inch window, which is exactly why both rails exist.

Measure to the right datum. Guard height on a stair is taken at the nosing line, not the tread, and handrail height is to the top of the gripping surface. The numbers above are the common code minimums, but the adopted edition, the occupancy, and local amendments control, and some uses and some jurisdictions require more. Verify the heights against the IBC or IRC the AHJ has actually adopted before you commit the layout.

The infill: pickets, glass, cable, and mesh

The infill is whatever fills the guard between the posts and the top and bottom rails. It can be vertical pickets, a glass panel, horizontal cable, perforated or woven mesh, or a solid panel. Its job is to close the opening so a person, especially a small child, cannot fall or slip through, and to resist the 50 lbf infill load without giving way.

The geometry is governed by the 4-inch sphere rule, covered in the next section, and the spacing of the infill is what makes or breaks it. Vertical pickets are the simplest to keep compliant because the spacing is fixed by the fabrication. Horizontal infill, cable in particular, is harder, because it deflects under load and the gap opens up when someone pushes on it. Glass and solid panels close the opening outright, but they trade the sphere problem for a structural-glass problem.

Pick the infill for the load and the spacing first and the look second. A guard that passes the height and the top-rail load can still fail inspection because the infill lets the sphere through or flexes under the 50 lbf push. The infill is not decoration sitting inside a structural frame. It is part of the fall barrier, and the code treats it that way.

What is the 4-inch sphere rule?

The 4-inch sphere rule says no opening in a required guard can let a 4-inch-diameter sphere pass through. It exists to keep a small child from slipping through the infill and falling, and it is the single most-cited number in railing code. It applies to the gaps between pickets, the gap under the bottom rail, and any opening in the barrier up to the height the code specifies.

There are two stair exceptions that trip people up. At the open side of a stair, the triangular opening formed by the tread, the riser, and the bottom rail is allowed to be larger, up to a 6-inch sphere, because the geometry of a stair makes the strict 4-inch limit impractical at that triangle. And on the stair guard itself, the IBC permits openings up to a 4-3/8-inch sphere rather than the 4-inch limit used on level guards. A separate exception lets guards in some occupancies not open to the public pass a 4-3/8-inch sphere in the zone from 36 to 42 inches, but the base zone stays at 4 inches.

Check the gap under the bottom rail as carefully as the picket spacing, because that is the opening crews forget. A guard with perfect 3-inch picket spacing still fails if the bottom rail sits 5 inches off the deck. Confirm the exact sphere sizes, the height zones, and the stair exceptions against the adopted IBC or IRC edition, because the details differ between the level guard, the stair guard, and the stair triangle.

Materials: steel, aluminum, stainless, glass, and cable

The material decision is driven by where the rail lives, what it has to resist, and how it has to look. Steel is the strongest and cheapest per pound and takes any finish, but it rusts and has to be coated or galvanized, especially outdoors. Aluminum is light, does not rust, and is easy to extrude into pickets and shoes, but it is softer, so sections run heavier to carry the same load. The structural design uses the metal's actual strength, so a swap is never free.

Stainless steel is the corrosion choice for coastal and harsh exposure and for the clean architectural look, at a real cost premium, and the grade matters: 316 holds up near salt where 304 will eventually tea-stain. Glass and cable are infill systems hung on a metal frame, each with its own code and structural rules covered later. Match the material and the gauge or wall thickness to the load the engineer calculated, not to what is on the rack, because a thinner-wall post that looks identical can fail the moment check at the base.

Finish and corrosion

The finish is what keeps a steel rail from rusting back to nothing, and outdoors it is not optional. Hot-dip galvanizing dips the fabricated steel in molten zinc and gives the longest-lasting exterior protection, including the inside of tube where rust starts unseen. Powder coat is a baked-on finish that comes in any color and holds up well, and the durable exterior detail is to galvanize first and powder coat over it, so a chip in the coating does not start a rust bloom. Paint is the least durable and needs maintenance.

Coastal and wet exposure is where finishes get tested. Salt air drives corrosion hard, so stainless steel, hot-dip galvanizing, or a galvanized-plus-powder system earns its cost near the water, and a shop paint job does not. Seal the tube ends and provide weep holes, because water that gets inside a sealed tube and cannot drain rusts it from the inside.

Dissimilar metals are the quiet failure. Put bare aluminum in direct contact with steel or stainless in a wet location and galvanic corrosion eats the aluminum at the joint, and stainless fasteners in aluminum or aluminum posts on a steel base plate do the same. Isolate the metals with an inert barrier or a coating, or specify compatible fasteners. The job looks fine at handover and the connection corrodes out of sight over a few seasons.

The attachment: the number-one failure

The attachment of the post to the structure is where railings fail, and it is the part most often built by feel. There are a handful of ways to do it, and each one has to be matched to the substrate and designed for the load and the moment at the base.

A base plate bolts the post to the top of a slab or a steel beam with anchors through the plate. It is the most common and the easiest to inspect, but it depends entirely on the anchors and the substrate beneath them. A core-drilled post sets the post into a hole drilled in the concrete and grouts or epoxies it in place, which buries the moment connection in the slab and looks clean, but it needs enough slab depth and edge distance. A cast-in embed or sleeve is set before the concrete is poured, the strongest option because it is locked in, but it has to be located right the first time. A fascia mount bolts a plate to the vertical face of a slab edge or a rim, and it is the most demanding of all, because the load and the moment both hang off the face of the concrete.

Whatever the method, the substrate has to take the moment. A base plate is only as good as the slab it sits on, and a fascia mount is only as good as the slab edge it hangs from. This is the connection to engineer, not to copy from the last job, because the last job's slab is not this job's slab.

The substrate and the overturning moment

The number that governs the anchorage is the overturning moment, the load times the height. The 200 lbf code load acting at the top of a 42-inch post is a moment of roughly 700 lbf-ft at the base, and that moment tries to pry the anchors out on the tension side and crush the concrete on the compression side. The taller the post and the longer the post spacing, the bigger the moment and the demand at every anchor.

Concrete carries that demand only if there is enough of it in the right places. Edge distance is the one crews underestimate: an anchor set close to the edge of a slab or a stair has a cone of concrete that can break out sideways well below the anchor's rated capacity, and a post on a thin slab edge has very little concrete to resist the pull. Slab thickness, edge distance, anchor spacing, and the concrete strength all feed the calculation, and a fascia mount adds the worst case because the moment pulls directly on the edge.

On wood-framed decks the substrate problem is the same in a different material: the post load has to make it into solid framing and blocking, not into decking or a single rim board, or the post racks. This is squarely engineering territory. Hand the load, the height, the spacing, and the real substrate to the engineer and let the anchorage be designed, because the edge-distance and breakout checks are not something to carry in your head.

Anchor types and how they grab

Anchors into concrete come in two families. Cast-in anchors, bolts or embeds set in the wet pour, develop the most capacity because the concrete is cast around them, but they demand accurate layout before the slab goes down and there is no second chance once it cures. Post-installed anchors go into a hole drilled in cured concrete, and they split into mechanical anchors, wedge and screw types that grip by expansion or threads, and adhesive anchors, where an epoxy or acrylic bonds a threaded rod into the hole.

Adhesive, or epoxy, anchors are common on railing retrofits because they can develop real tension capacity in a drilled hole, but they live and die on installation. The hole has to be drilled to the right diameter and depth, cleaned of dust by the manufacturer's method, the adhesive injected from the bottom up with no voids, and the rod set and left undisturbed for the full cure. Skip the hole cleaning and the bond strength drops sharply, which is why the qualification of adhesive anchors is governed by standards like ACI 355.4 and the design by the concrete code's anchoring provisions in ACI 318.

Edge distance and embedment depth set the capacity as much as the anchor itself. An anchor too near an edge or too shallow gives a fraction of its rated pull, and core-drill-and-grout posts depend on the same slab geometry. Use the anchor the engineer specified, install it to the manufacturer's instructions and the evaluation report, and do not substitute a wedge anchor for an epoxy anchor because it is what is in the truck.

Fabrication: shop drawings and layout

Fabrication starts with shop drawings, not at the saw. The shop drawing takes the architect's intent and the engineer's loads and turns them into a buildable rail: the post spacing, the heights, the infill spacing that satisfies the sphere rule, the base detail, and the connections. It is also where the anchorage gets coordinated with the structure, so the embed or the base plate matches the slab or the steel that is actually there. Getting this right on paper is cheaper than fixing it in the field.

From the drawing the work is layout, cut, fit, weld, and grind. Accurate layout sets the post spacing and the pickets so the sphere rule holds across every bay, and a careful cut and fit makes the welds easier and stronger. The same connection discipline that governs structural steel applies here, and the structural-steel guide covers the bolting and welding fundamentals in depth, so this guide does not repeat them.

There is a real choice between welded and modular construction. A fully welded rail is the strongest and cleanest looking and is fabricated to the exact geometry, but it is heavier to handle and harder to adjust in the field. A modular or bolted system assembles from manufactured components and installs faster with less field skill, but the connections are only as good as the fittings and they have to carry the same code loads. Pick the method for the project, and either way the anchorage still has to be engineered.

Welds that carry the load

On a welded rail, the welds are structural connections, not cosmetic beads. The weld at the base of the post and the welds joining the rail to the posts carry the load and the moment into the connection, so they have to be sized, made, and finished to do that. An undersized or cold weld at the post base is a hidden version of the anchorage failure: the rail looks complete and lets go under load.

Welding to a structural standard means a qualified procedure and a qualified welder, the weld type and size the drawing calls for, and clean fit-up so the weld fuses instead of bridging a gap. The grind and finish that follow are partly for looks, but over-grinding a structural weld down to nothing for appearance removes the very metal that carries the load. Finish the weld, do not erase it.

Architectural metal carries the AWS welding requirements the same way structural steel does, so the welding details, the procedure and welder qualification, and the inspection live in the structural-steel guide rather than here. The point to hold onto is that the weld at the connection is load-carrying, and it gets the same care as any structural joint.

Cable railing: tension and the 4-inch deflection

Cable railing runs horizontal stainless cables as the infill, and it is governed by deflection. A cable is not a rigid picket. Push on it and it bows, and the gap between cables opens up, so a spacing that passes the 4-inch sphere at rest can let the sphere through once someone leans on it. The code does not care what the gap is when nobody is touching it. It cares what the gap is under load.

Two things keep cable compliant. First, the cables are spaced closer than the 4-inch limit, commonly around 3 inches on center, so even after deflection the opening stays under 4 inches. Second, the cables are tensioned hard, often in the range of 200 to 300 lbf each depending on the system, and intermediate posts or spacer pickets are added every few feet between the structural posts to stop the cables from bowing on long runs. Without the intermediate supports a long cable run deflects no matter how tight you crank it.

The end posts take the worst of it. All that cable tension pulls the two end posts inward, so the end-post anchorage on a cable system has to resist the combined cable tension on top of the code rail load, and it is a frequent failure point. Tension the cables to the manufacturer's spec, retension after the cable relaxes, and verify the deflection by pushing on the middle of a run and checking that the 4-inch sphere still will not pass.

Glass railing and the structural glass

Glass railing uses the glass itself as the infill, and sometimes as the structural baluster, which puts it under the glass and glazing rules as well as the railing rules. The glass has to be safety glazing, and for guards the IBC calls for laminated glass made of fully tempered or heat-strengthened glass, complying with the safety-glazing standards, so that a broken panel holds together on its interlayer instead of falling out of the opening.

How the glass is captured decides the structure. A base shoe is a continuous channel that clamps the bottom edge of the glass and cantilevers the panel up as a structural baluster, which carries the rail load into the shoe and then into the anchorage. Point clamps or standoffs bolt the glass to posts or a fascia. The IBC generally requires a top rail across glass balusters, attached to enough panels that the loss of one panel does not drop the guard, with an exception for laminated glass that has been impact-tested as a barrier.

Glass guards are designed to a safety factor on the glass strength, commonly a factor of four, which is why the glass is thicker than it looks like it needs to be. The base shoe anchorage is the same problem as any post base, only continuous, and it has to carry the rail load and the moment into the slab. Glass railing is an engineered system: the glass thickness, the capture, the top rail, and the anchorage all come off the structural design, not the catalog picture.

ADA handrails: graspability, extensions, and returns

An accessible handrail has to be graspable, which is a specific shape, not just a rail at the right height. For a circular section the ADA standards call for an outside diameter of 1 1/4 to 2 inches. A non-circular section has to have a perimeter of 4 to 6 1/4 inches with no cross-section dimension over 2 1/4 inches, so a hand can close around it. A flat bar or an oversized architectural section that nobody can grip fails this even when it is the right height.

Extensions are where ADA handrails go beyond the basic code rail. At the top of a stair the handrail extends horizontally at least 12 inches beyond the top nosing. At the bottom it continues to slope for the depth of one tread past the bottom nosing, then runs level. The extension is there so a person has the rail before the first step and after the last, which is exactly where stair falls happen.

The returns close the ends so nothing snags. The ends of the handrail return to a wall, a guard, or the floor, so a sleeve, a strap, or a bag does not catch on an open end and pull someone down. The handrail also has to be continuous along the flight, with a consistent gripping surface and the right clearance to the wall. Confirm the dimensions against the current ADA Standards for Accessible Design and the adopted IBC accessibility provisions, because the graspability, the extensions, and the returns are all checked at inspection.

Stair and ramp rails

Stairs and ramps are where the guard and the handrail both show up, on the rake, and the geometry gets busy. On an open stair you typically need a guard at the open side to stop the fall over the edge, and a handrail at 34 to 38 inches for the hand, and on many stairs a handrail on both sides. The guard follows the 42-inch commercial or 36-inch residential height; the handrail follows the rake at its own height. They are not the same line.

The guard height on a stair is measured along the nosing line, and the handrail height is measured vertically from the nosings to the top of the grip, so on the rake the two rails diverge and the layout has to account for it. The infill on the stair guard follows the sphere rules, including the 6-inch triangle exception at the tread, riser, and bottom rail.

Ramps add the handrail wherever the rise crosses the threshold the accessibility rules set, with the extensions at the top and bottom, and a guard at any drop-off along the ramp. The mistake is treating the stair or ramp rail as one element doing two jobs. Lay out the guard and the handrail as separate runs with their own heights, and the geometry resolves instead of fighting you.

Field layout: measure, space, and plumb

Layout in the field is where the shop drawing meets the building as it was actually built, and the building is never exactly the drawing. Measure the real opening, the real stair, and the real slab edge before you set anything, because a post spacing that worked on paper can drop a post right on a slab joint or off the edge.

Set the post spacing to carry the load and to keep the infill within the sphere rule across every bay, then mark each post location, snap the lines, and check the slab depth and edge distance at each one before drilling. A post that lands too close to the slab edge has to move or the anchorage has to change, and that is a decision to make with the layout, not after the holes are drilled.

Plumb and level are not cosmetic on a rail. A post out of plumb throws the rail height off and stresses the connection in a direction it was not designed for, and a rail that is not level reads as sloppy from across the room. Use a template or a jig for repetitive post spacing, set the posts plumb, and string or laser the top rail so the height holds the full run. Get the layout right and the install goes fast; get it wrong and you are re-drilling anchors in cured concrete.

The install: set, anchor, infill, and check

The install runs in an order, and the order is the anchorage first because everything hangs off it. Set the posts to the layout, anchor them to the engineered detail, the base-plate bolts, the epoxy anchors, the core-drill grout, or the cast-in embed, and let any adhesive or grout reach its cure before the posts take load. A post leaned on before the epoxy cures is a post that never reaches its rated capacity.

Then hang the rail and the infill. Connect the top and bottom rails, set the pickets, panels, or cable, and tension cable systems to spec. Hold the heights as you go, 42 or 36 inches at the guard, 34 to 38 inches at the handrail, and keep the infill within the sphere rule across every bay including the gap under the bottom rail.

Close out by checking load-tightness, not just appearance. Every anchor torqued, every connection made, every weld complete, and a hand-push on the rail to feel for movement at the base. The rail should feel solid when you lean into it. If it racks or the base moves, the anchorage is not done, and finding that with your hand at handover is far better than the inspector or a tenant finding it later.

What does the inspector check on a railing?

The inspector checks the same short list every time, and it maps to the code: the height, the infill, the load, and the anchorage. Height comes first because it is fast, a tape on the guard at 42 or 36 inches and on the handrail in the 34 to 38 inch band, taken to the right datum on the rake. A rail at the wrong height is an instant rejection no matter how well it is built.

The infill gets the sphere. The inspector runs a 4-inch sphere, an actual gauge or a calibrated tool, through the picket gaps, under the bottom rail, and across any opening, plus the 6-inch sphere at the stair triangle. On cable rail they push on the run and re-check, because the gap that matters is the gap under load. Then the load and the anchorage: the rail gets pushed, and on engineered or larger projects the anchorage falls under special inspection of the post-installed anchors, with the installer's adherence to the evaluation report verified.

The push test is the moment of truth, and it is where the anchorage either holds or shows itself. Prove it before the inspector does. Verify the heights, run your own sphere gauge, confirm the anchors were installed per the report, and push every run yourself. The inspection should confirm what you already know, not surprise you. Confirm the inspection scope and any special-inspection requirement with the AHJ, because what triggers special inspection varies by jurisdiction and project.

What to document

A railing that passes inspection and a railing nobody can prove passed are two different things a year later when a tenant leans on a guard and asks who built it. The record is what answers that, and it is exactly the kind of thing a field tool like FieldOS is for: capture the shop drawing, the materials, the anchorage detail, the anchor installation, the load verification, and the inspection sign-off against each run, with photos, so the file exists when it is needed.

Capture the shop drawing and the engineering for the anchorage, the material and finish of the rail, the anchor type and the substrate it went into, the manufacturer's instructions and evaluation report for post-installed anchors, the cure for any epoxy or grout, the cable tension if it is a cable system, the height and sphere checks, the push test, and the inspection result with who signed it. If the anchorage was a delegated design, keep that engineering with the file.

Common mistakes

• Anchoring the post to a substrate that cannot carry the load, a thin slab edge, too little edge distance, or unblocked deck framing.
• Infill that fails the 4-inch sphere rule, usually the gap under the bottom rail or the picket spacing.
• Building the wrong height, 36 in where 42 in is required, or a guard called a handrail with nothing graspable at the right height.
• Sizing the rail or the anchorage below the 200 lbf concentrated load and the moment it makes at the base.
• Cable rail not tensioned, or no intermediate posts, so the cable deflects past the 4-inch sphere under load.
• Corrosion from the wrong finish for the exposure, or dissimilar metals in contact with no isolation.
• Substituting a wedge anchor for the specified epoxy anchor, or skipping the hole cleaning so the adhesive never bonds.
• Over-grinding a structural weld at the post base for looks until it can no longer carry the load.

Field checklist

Standards and references

The heights, the loads, and the infill come from the building code. The IBC sets the commercial guard and handrail requirements, with guards in the means-of-egress provisions and the structural loads in the live-load chapter, and the IRC sets the residential versions, with guards and handrails in its means-of-egress sections. Those are where the 42-inch and 36-inch heights, the 34 to 38 inch handrail band, the 200 lbf load, and the 4-inch sphere live. The exact section numbers shift between code cycles, so confirm them against the edition the jurisdiction has adopted and any local amendments.

The anchorage is engineering. The design of anchors to concrete falls under the concrete code's anchoring provisions in ACI 318, with post-installed anchor qualification under standards such as ACI 355, and the structural design of the rail and its connection belongs to the engineer of record or a delegated engineer, not to a rule of thumb. Glass guards add the glass and glazing provisions of the IBC and the safety-glazing standards. Welding follows the AWS structural welding requirements, covered in the structural-steel guide.

Accessible handrails follow the ADA Standards for Accessible Design and the IBC accessibility provisions for the graspability, the extensions, and the returns. Across all of it, the AHJ is the final word on what the adopted code requires and what triggers special inspection. Cite the standard that governs the point, design the anchorage with an engineer, and verify the heights, loads, infill, and anchorage against the IBC, the IRC, ADA, and the AHJ before you commit.

Units and terms

Railing work mixes life-safety terms that get used loosely on site, so the same word can mean different things across a drawing set, a spec, and a code section. Pin them down before they cause a height or load mistake.

A guardrail, or guard, is the fall barrier at a drop-off. A handrail is the graspable rail on stairs and ramps. The code load is the force the element has to resist: 200 lbf concentrated at any point in any direction, plus a 50 plf uniform load. The infill is whatever fills the guard between posts and rails, and it resists 50 lbf on a 1 square foot area. The 4-inch sphere rule is the opening limit that keeps a child from passing through. The post anchorage is the connection of the post to the structure, and the overturning moment is the load times the height that the anchorage has to resist.

Guardrail (guard)

The code-required fall barrier at a drop-off over the height threshold, sized for a height, a load, and the infill

Handrail

The graspable rail on stairs and ramps, set at 34 to 38 inches, sized for the hand and for the catch of a stumble

Code load (200 lbf concentrated)

The 200 lbf load applied at any point on the top in any direction, plus a 50 plf uniform load, checked separately

Guard / handrail height

42 in commercial and 36 in residential for guards; 34 to 38 in for handrails, to the right datum

4-inch sphere rule

No opening in a required guard may pass a 4-inch sphere; 6-inch at the stair tread-riser triangle

Infill

The pickets, glass, cable, or mesh filling the guard, which must resist 50 lbf on a 1 sq ft area

Post anchorage / base plate

The connection of the post to the structure that carries the rail load and the overturning moment

Overturning moment

The load times the height of the post, the prying force the anchorage at the base must resist

Cable rail deflection

The bowing of a tensioned cable under load that opens the gap, controlled by spacing, tension, and intermediate posts

ADA graspability / extensions

A 1 1/4 to 2 in graspable handrail with extensions past the top and bottom nosings and returns to wall or floor

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