Metal Siding Specification Guide: Cable Railing, Stair Systems, and the Cost of Getting It Wrong

Here's the conclusion up front: the cheapest way to buy metal siding, cable railing, or stair systems is to specify it correctly before you send the purchase order—not to chase the lowest quote and make up for it with expediting later. I've coordinated 200-plus rush orders for architectural and structural metal products at McNichols, and the ones that crater almost always fail on the spec sheet, not the supplier. A $400 "savings" on the initial quote routinely becomes $1,200 in rush fees, rework, and inspection failures. The most expensive sentence in construction isn't "change order." It's "I thought that's what I ordered."

In my role coordinating emergency fulfillment and specification support, I'm the person contractors call when they're 48 hours from a deadline and the cable railing doesn't meet code, or the siding panels are the wrong gauge. In March 2024, a client called at 4:30 PM needing 1,600 feet of stainless wire mesh infill for a hotel stairwell—36 hours before the city inspection. Normal fabrication lead time was two weeks. We sourced the correct mesh, got it certified, fabricated the infill panels, and had it on a truck by the next morning. The client's alternative was a $50,000 penalty clause.

I'm sharing this because I've seen the same pattern enough times to write this guide: the "emergency" in a rush order is usually the result of an under-specified product, not an under-performing vendor.

Start With Total Cost, Not Unit Price

When I ask a customer why they picked a certain quote, the answer is usually "it was cheaper." But the unit price is maybe 60% of the real cost of an architectural metal product. The total cost includes freight, lead time, fabrication, rework, and the cost of a failed inspection. I had a customer who chose a $500 quote for perforated panels. After freight and a hole-pattern mismatch, the total was $810—and he lost six days. The $650 quote that included the right pattern and pre-fitting would have been cheaper, and he would have made the schedule.

So now I calculate total cost before comparing any vendor quotes. Put another way: the number on the quote isn't the number you'll actually pay. We didn't have a formal approval chain for rush orders for the first few years—cost us when an unauthorized expedite fee showed up on a client's invoice. Now every rush order gets a written sign-off before we move.

Cable Railing: The 4-Inch Sphere Gets Everyone

If I had a dollar for every rush order involving cable railing that didn't meet the infill spacing requirement, I could retire. The rule is simple: no gap larger than 4 inches. A 4-inch sphere, to be precise. What gets people is cable deflection. Even properly tensioned stainless cable will move when pushed, so the gap you measured in the shop isn't the gap you'll have on site.

What I tell customers now:

• Use 1x19 stainless cable, not 7x7. It's stiffer, which means less deflection under the code-specified 50-pound horizontal load.
• Keep post spacing tight. The farther apart the posts, the more tension you need and the more deflection you get between them.
• Remember that cable is not the guardrail. Most commercial applications require a top rail, per IBC Section 1015.4. Calculate the load path from the top rail down through the posts—not through the cable.
• On stairways, the 4-inch spacing requirement applies to the vertical projection of the cable run. This fails inspection more than any other railing detail I know.

And specify the right alloy from day one. Grade 316 stainless for coastal or industrial environments; 304 for most interior work. I recently handled a rush order where the spec called out 304 components on 316 cable—a corrosion mismatch that showed up within months. To be fair, the customer didn't know the difference: the catalog just said "stainless."

Looking back, I should have pushed that hotel client to verify his post spacing before we fabricated the infill panels. At the time, I assumed the structural engineer had checked it. He hadn't. Now I ask for the stamped drawings before quoting anything structural.

Wire Mesh Infill: The Fix Nobody Plans For

When cable railing spacing is too tight, or the design needs something more opaque, wire mesh is the answer. Actually, mesh infill has one advantage over cable that gets overlooked: deflection is minimal. Rigid panels pass the 4-inch sphere test much more easily than tensioned cable. McNichols wire mesh—whether welded, woven, or expanded—can be framed into infill panels or tensioned between posts.

The spec points that matter: wire diameter, opening size, and material. The clear opening has to be less than 4 inches in the installed condition. And here's a mistake I made in my first year—I assumed "standard" meant the same thing to every vendor. Cost me a $600 redo when a customer's "standard" mesh turned out to be a special weave with a 4-month lead time. Now I always ask for the exact opening size in inches and millimeters, in writing.

Stair Systems: Egress Comes First

Metal stair systems are code-critical in a way that decorative products aren't. A stair that fails inspection holds up an entire building. The things I check before recommending a system:

• Egress width and capacity per IBC Chapter 10
• Riser height and tread depth consistency—the tolerances are tight
• Nosing profile and slip resistance
• Guardrail height: 42 inches for most commercial applications (IBC 1015.4)
• Handrail height: 34 to 38 inches, measured from the nosing

Now the total-cost angle for stairs. Cheap prefab stair pans from a catalog look like a bargain until they arrive too shallow, or with a pan gauge that won't take the concrete fill, or a nosing profile that doesn't meet code. The rework cost on stairs is brutal because it's labor-intensive. By the time a crew on site has modified, welded, and re-coated, you've spent more than a proper fabricated system would have cost.

That said, prefab stairs are completely fine for utility applications—mechanical rooms, maintenance access. For anything in a public building, I'd spec a fabricated system with drawings and certified materials.

Metal Siding Specification Guide: What I Actually Check

This is the part people ask for by name, so here's what I verify on a siding spec, in order:

1. Substrate and coating. "Steel siding" isn't a spec. You need the substrate thickness (24-gauge vs 26-gauge matters) and the coating weight (G90 vs G60, or galvalume). I've seen contractors buy 26-gauge because it was cheaper, only to find the required span called for 24-gauge. Rework costs more than the material difference ever would.

2. Finish system. Exterior panels should specify a PVDF finish (70% Kynar 500 or Hylar 5000), not just "painted." The UV performance difference between PVDF and polyester is an order of magnitude. And per FTC guidelines (ftc.gov), manufacturers have to be able to substantiate performance claims—so ask for the test data.

3. Fastener system. Hidden fastener systems cost more per square foot, but they prevent oil-canning and the fastener staining that shows up on exposed-fastener walls within a few years. Exposed fasteners are fine for industrial buildings, but they need the right washer system. When a siding problem shows up, it usually starts at the fastener.

4. Moisture management. A proper vented rainscreen detail prevents the "leaking metal building" calls that are actually condensation. Not glamorous, but it's the spec point I see missing most often.

I want to say the most common emergency siding order is the gauge issue, but don't quote me on exact percentages. It's up there.

Where McNichols Fits In

Full disclosure: I'm biased. I work here. But I see the value of a supplier that carries both the architectural products and the structural ones, because the specification goes through one set of technical hands. When you're ordering cable railing and stair systems for the same project, you don't want to coordinate three vendors. And when you need mcnichols wire mesh because your cable infill failed inspection, you want someone who can answer "what's the clear opening?" without putting you on hold.

We're not always the cheapest. But the catalog is genuinely deep—mcnichols steel grating, perforated panels, stair pans, handrail components, even elevator parts—and the specification support is where the value shows up. You tell us the code requirement, we tell you what's available to meet it. In my experience, that's pretty rare in this industry.

When Cheap Makes Sense (and When It Doesn't)

I don't want to sound like the guy who insists every project needs the premium option. Some honest guidelines:

• If the application is non-code-critical, non-visible, and low-traffic—mechanical rooms, storage areas—a standard economical product is fine.
• If the price difference is under 10% of the installed cost but the better spec saves a week of lead time, take the better spec. Every time.
• Expediting is worth every dollar when the alternative is a penalty clause. Just don't pretend rush is a procurement strategy. Rush fees are a symptom, not a solution.

One more caveat: my experience is in architectural and structural metal products. A residential cable railing deck has different design loads and inspection requirements than a commercial stair system. Local amendments to the IBC vary, and they seem to be getting stricter, not less. Verify the codes for your jurisdiction before you order—don't take my word for it.

Bottom line: the spec sheet is the cheapest place to solve your problems. The time you spend on it up front is the best return on investment in the entire project.