Z-Stack™ Modular Stair TowersBolt-together aluminum stair towers that stack to the height you need and lift into place by crane. Standard 36" and Compact 24" sizes, same-day quotes and nationwide shipping from ATI.
Z-Stack™ is a modular, pre-engineered stair tower made by SafeSmart and supplied by ATI Construction Products. Each module is a welded aluminum frame with two flights of stairs and a landing. Modules bolt together and stack on top of each other, so one system can reach a single roof edge or climb with a building as it goes up. SafeSmart built it as a faster, more stable alternative to scaffold stair towers, ladders and cage ladders.
Enter the height you need to reach. The calculator stacks Standard and Compact stair modules up to your height, adds the top module that forms the guardrail around the top landing, and picks the AdaptaStep™ bridge or AdjustaStairs™ that connects the landing to the roof. It also shows tie-off brackets and the footprint. Pick a tower to send the setup to ATI for a quote.
Planning estimate based on module heights published by SafeSmart. ATI confirms the final layout, anchoring and tie-off points for your site.
4 modules
3 stair modules + 1 top railing module
Wider stairs for crews carrying tools and materials. Footprint 9' 4" x 6' 10".
4 modules
3 stair modules + 1 top railing module
Smaller footprint for roof and equipment access. Footprint 7' 7" x 4' 11".
Two stair flights per module Top railing module Bridge or stairs to the roof Roof at your height
Both sizes use the same bolt-together module system. Standard towers have wider stairs for crews moving tools and materials. Compact towers fit where space is tight and work as a true ladder replacement for roof and equipment access.
| Stair width | 36" |
|---|---|
| Module footprint | 9' 4" long x 6' 10" wide |
| Base module top landing | 9' 1 1/2" (with base jacks) |
| Each added module | 8' 8 3/4" more height |
| Load rating | Up to 1,100 lbs per module, per SafeSmart |
| Stairs per module | 2 flights with a 4-plank deck |
Common uses: construction site access, emergency egress towers, large crews, multi-level construction, industrial roof access and infrastructure projects.
| Stair width | 24" |
|---|---|
| Module footprint | 7' 7" long x 4' 11" wide |
| Base module top landing | 8' 7 1/4" (with base jacks) |
| Each added module | 8' 1 1/2" more height |
| Step rise | 8 7/8" per step |
| Frame material | 6061-T6 aluminum, with Grade 5 and Grade 8 bolts |
Common uses: roof access, ladder replacement, mechanical equipment and utility platforms, facility service access and confined sites.
Module heights are planning figures from SafeSmart. The base module includes its adjustable base jacks, which also level the tower on uneven ground.
Every tower uses three module types: one base module, as many middle modules as the height needs, and one top module. Each module is lifted into place and lowered onto four joiners that stick up from the module below. The male-to-female joiners seat the module, and the supplied bolts and locknuts lock it into one rigid tower.
Four height-adjustable base jacks anchor the tower to an approved surface and level it on uneven ground. Castors and a mobile chassis are available for indoor sites.
Repeat middle modules to gain height. Each one adds two stair flights and a landing. Tie the tower to the structure with a tie-off bracket every third module.
Every tower gets one more module above the top landing. It has no stairs and works as the guardrail around the landing, with the top handrail and gate. Add joiners and a lifting bar there if the whole tower will be craned.
Yes. Because every connection is fully bolted and locknut-secured, a Z-Stack™ tower holds its shape when it is lifted. The joiners on each module double as crane hooks for lifting single modules, and lifting bars spread the load across the tower so it doesn’t twist when you lift the whole thing.
For repeated trips between levels, usually yes. Scaffold stair towers take a crew and time to build piece by piece, and ladders make workers climb hand over hand without tools. Here is how they compare.
| Feature | Z-Stack™ tower | Scaffold stair tower | Ladder or cage ladder |
|---|---|---|---|
| How workers move | Walk up stairs with landings | Walk up stairs | Climb vertically, hands full |
| Carrying tools and materials | Yes, on stairs with guardrails | Yes | Difficult and tiring |
| Setup | Pre-engineered modules bolt together in hours | Built piece by piece, often over days | Fast |
| Changing height | Add or remove a module | Rebuild or extend by hand | New ladder |
| Moving it | Crane the whole tower | Take it down and rebuild | Carry it |
| Reuse | Reusable aluminum modules | Reusable parts, rebuilt each time | Reusable |
| Permanent installs | Yes, can be fully enclosed | Rarely | Cage ladders, with a vertical climb |
For the full list of rules, read OSHA stairway requirements for construction sites. Comparing short-term options for a single roof? See how to choose temporary roof access.
Modules come in fixed heights, so the top landing rarely matches the roof or platform exactly. Every tower finishes with a transition from the top landing to the roof: an AdaptaStep™ bridge when the difference is 24" or less, and AdjustaStairs™ from 24" to 48". If 48" or more would be left, the tower gets another stair module. The height calculator above picks the right one for your height.
A modular bridging platform that bolts onto the Z-Stack™ and spans to the destination surface. It can run up to 30 feet long and joins AdaptaStep catwalks for rooftop and equipment access. AdaptaStep™ brochure (PDF).
Self-leveling stairs connect the top landing to a higher or lower level, with no unsafe step-downs or site-built steps. See AdjustaStairs™ specs and sizing.
Add-ons adapt a tower to the site, the people using it and how long it will stay.
Lift the whole tower by crane without twisting. Required for lifting 4 or more modules together.
Telescopic brackets tie the tower to a nearby structure to reduce sway. Required every third module.
Control who enters the tower at the base module. Available in aluminum or mesh.
Panels along the tower help contain tools and debris and stop unauthorized climbing.
Heavy-duty lockable castors let low towers roll to a new spot inside controlled facilities.
Extends the working platform past the tower footprint to reach equipment or structures.
Stair access between floors that grows as the building goes up, replacing scaffold stair towers.
Stable stairs into deep excavations for utility, infrastructure and foundation work.
Permanent stairs to rooftop mechanical equipment, enclosed if access must be controlled.
Aluminum towers adapt to dock heights and stand up to marine environments.
Standard towers support larger crews moving between levels.
Compact towers replace ladders at utility and service platforms.
Z-Stack™ on Real ProjectsTwo project profiles from SafeSmart, the manufacturer of Z-Stack™.
With PCL Construction, a Compact Z-Stack™ tower was set on a custom steel rostrum that projected off the face of the building. It was the first Z-Stack fitted to a rostrum.
A fully enclosed Standard Z-Stack™ tower replaced outdated ladder access for rooftop equipment maintenance.
“We used it during the excavation phase, and now it’s climbed with the project - almost 10 stories tall!”Superintendent, confidential project (SafeSmart brochure)
Full module layouts, component lists, accessories, landing solutions and project profiles, in one PDF. The AdaptaStep™ brochure covers the bridging platforms, catwalks and crossovers that connect a tower to the roof.
BrochureZ-Stack™ Modular Stair Tower BrochureDownload the Brochure (PDF)
BrochureAdaptaStep™ Access Platform BrochureDownload the Brochure (PDF)ATI Construction Products also supplies AdjustaStairs™, AdaptaStep™ and AdaptaSpan™ access systems, debris and safety netting and aluminum scaffolding. See everything ATI offers.
Z-Stack™ is a modular, pre-engineered aluminum stair tower made by SafeSmart and supplied by ATI Construction Products. Bolt-together modules, each with two stair flights and a landing, stack to the height you need and can be craned into place as one tower.
There is no fixed limit. Middle modules repeat to add height, about 8' 8 3/4" each for Standard and 8' 1 1/2" for Compact, and towers have climbed almost 10 stories on SafeSmart projects. Taller towers need a tie-off bracket every third module.
For 28 feet, a Standard tower uses 4 modules: 3 stair modules with the top landing at 26' 7", plus the top railing module. An AdaptaStep™ bridge covers the last 1' 5" to the roof. A Compact tower also uses 4 modules, with the top landing at 24' 10 1/2" and AdjustaStairs™ for the last 3' 1 1/2". Try any height in the Z-Stack height calculator.
Standard modules have 36" stairs and a 9' 4" x 6' 10" footprint, for larger crews carrying tools and materials. Compact modules have 24" stairs and a 7' 7" x 4' 11" footprint, for roof access, ladder replacement and tight sites.
Yes. Module joiners double as crane hooks for single modules, and lifting bars let you lift the whole tower as one structure without twisting. Lifting bars are required to lift 4 or more modules together.
Adjustable base jacks anchor and level the base on an approved surface, and telescopic tie-off brackets secure the tower to the nearby structure every third module to reduce sway.
Z-Stack™ is engineered with integrated stairs, landings and guardrails to provide compliant stair access. OSHA requires a stairway or ladder at any break in elevation of 19 inches or more under 1926.1051, and your site's competent person still confirms the setup for each job.
Both. Contractors reuse Z-Stack™ towers from job to job, and facilities install them as permanent roof and equipment access, often enclosed in security mesh with an entry gate.
ATI Construction Products supplies Z-Stack™ towers, accessories and transitions with same-day quotes and nationwide shipping. Call (800) 360-6115 or use the calculator on this page to send your setup for a quote.
Send your height and site details for a same-day quote, or call (800) 360-6115.
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