Modular & prefab steel stairs. Bolt-together kits, engineered, repeatable.

Where it fits

Bolt-together when site time matters.

"Modular" and "prefab" cover the same idea: stair components fabricated in the shop, finished, shipped to site, and bolted together rather than welded. The stair is just as engineered as a fully welded one — but the install crew doesn't need to bring a welder, and the site time drops to a few hours per stair instead of a day. The trade-off: tighter shop tolerances and a slightly higher unit cost vs. fully welded site work.

When modular wins

• Multi-site fit-ups — same stair geometry across multiple sites means one engineering package, repeated.
• Tight shutdown windows — bolt-together installs don't need hot-work permits, fume extraction, or fire-watch.
• Relocatable layouts — modular mezzanines often need modular stairs to match.
• Limited access for welding — interior food-grade or clean-room sites where welding is impractical.

When fully welded wins

• One-off geometry — single-stair projects rarely justify the modular tooling.
• Heavy load classes — bolted connections are fine to most industrial loads but welded joints are cleaner above 250 psf.
• Architectural visibility — bolt heads are visible; welded stairs are smoother.

Detail decisions

• Connection type — A325 structural bolts at primary frame; ASTM A307 at non-structural connections.
• Stringer splice — bolted gusset plate at flight-to-landing splices; engineered as moment connection where needed.
• Tread attachment — bolted bar-grate or grip-strut treads to angle clip stringers.
• Guard rail — bolted post connections with structural angle baseplates.

Typical parameters

• ConnectionA325 structural bolts (primary frame)
• Site assembly time4 – 8 hours per typical stair
• Component weighteach piece < 200 lbs (forklift-installable)
• Treadbar-grate / grip-strut (bolted)
• Guard height42" (OBC §3.3.1.18)
• Finishpowder-coat or galvanized (shop-applied to all components)
• Lead time4 – 6 weeks from sign-off