Picture a hyperscale data center nearing a critical milestone. Twelve hundred workers from 40 different subcontractors share a single floor. Electricians pull high-voltage cable while HVAC crews test ductwork overhead. Sprinkler fitters squeeze past drywall installers. Everyone has a deadline, and everyone needs to be in the same place.
The schedule says this is the plan, but the physical space limitations say otherwise.
This is trade stacking. On large data center builds, it’s one of the biggest threats to safety, productivity, and deadlines. When too many trades compete for too little space, efficiency drops, quality can suffer, and the likelihood of a serious incident goes up. Once that happens, insurance premiums (usually OCIP or CCIP plans) can skyrocket, resulting in a poor reputation for the managing general contractor and potential loss of work.
The data center construction boom makes this even more pressing. McKinsey projects that companies will invest nearly $7 trillion globally in data center infrastructure by 2030, with more than 40% of that spending in the United States. Over 400 new data centers are expected in the U.S. over the next five years. Each of these builds will face the same challenge: coordinating dozens of specialty contractors in a confined, high-pressure environment without creating chaos.
In this guide, we’ll discuss what trade stacking is, why it’s hazardous on data center projects, what OSHA expects from general contractors, and some practical strategies to keep crowded jobsites moving safely.
What Is Trade Stacking?
Trade stacking is when multiple trades are scheduled to work simultaneously in the same area of a construction site.
On paper, trade stacking might seem efficient… and it can be under the right conditions. More crews in the space should mean more work getting done. In reality, the opposite often happens. Workers compete for the same square footage, tools pile up, and crews have to wait on each other to finish their tasks before they can start. The result is slower progress, more mistakes, and greater risk.
The 200-Square-Foot Rule
Construction workers need at least 200 to 250 square feet of space each to maintain full productivity, depending on the complexity of their work. In an indoor space, you lose the space you need to get the job done, which reduces efficiency.
Let’s break down how reduced workspace limits productivity:
- At 191 square feet per worker: no efficiency loss
- At 90 square feet per worker: 50% loss of efficiency
- This applies to projects ranging from 2,000 to 150,000 person-hours
Adding more workers to a crowded area without proper organization doesn’t accelerate the schedule. It slows everyone down, leading to delays and increased risk.
Why Trade Stacking Happens
Trade stacking rarely happens because someone planned it that way. It usually results from a combination of pressures that push trades into the same space at the same time. Here are just a few things that might make trade stacking a necessity.
- Schedule compression. When a project falls behind, the instinct is to add more crews to catch up. The schedule says there’s time to recover. The physical space says there’s nowhere to put everyone.
- Upstream delays. When early trades fall behind, downstream crews get compressed into tighter windows. What was supposed to be a phased sequence becomes a scramble.
- Change orders and rework. Scope changes disrupt the original work sequence. Rework brings crews back into areas where other trades are already active.
- Client acceleration. A request for earlier delivery forces fast-tracking, which means parallel work in spaces that were designed for sequential handoffs.
- Poor initial planning. Sometimes the original schedule assigns multiple trades to the same zone without realistic sequencing. The problem is baked in from the start.
Rework and Trade Stacking
When trades compete for space, workmanship suffers. Crews rush to finish before the next trade moves in, tools become harder to access, and precision work becomes nearly impossible in chaotic conditions. Oftentimes, subcontractors will need to return to previous work to fix quality issues caused by trade stacking.
The financial impact is significant. A PlanGrid and FMI study found that construction companies worldwide spend approximately $178 billion annually on rework. Trade stacking is a leading contributor, especially on complex projects where electrical wiring, plumbing, and finishing work require careful attention.
Subcontractors can file disruption claims when they’re forced to work less efficiently than planned due to factors outside their control. Reduced or restricted site access is one of the leading causes of delay claims. When a GC’s scheduling decisions create trade stacking, they may face financial liability for the resulting inefficiencies.
Why Data Center Construction Is Different
Trade stacking is a challenge on any large commercial project. On hyperscale data center builds, it’s an especially acute risk because of the scale, speed, and technical complexity involved.
Massive Footprints, Aggressive Timelines
Hyperscale data centers can span hundreds of thousands to millions of square feet. A single campus might include multiple buildings under construction at once. These projects cost billions of dollars, and speed-to-market is critical. Hyperscalers also need to get online fast to meet demand from AI and cloud computing. That pressure compresses schedules and increases trade overlap.
When an accident happens or efficiency drops, one of a GC’s worst nightmares can occur — a delay in schedule. Delays can cost millions per day in lost revenue, adding pressure that pushes teams to stack trades rather than wait for space to clear.
Workforce Density at Peak Construction
According to McKinsey, a typical large data center of around 250,000 square feet can have up to 1,500 workers on site during peak construction. These workers include site developers, equipment operators, electricians, HVAC technicians, plumbers, fire protection installers, network infrastructure specialists, and security system contractors.
When you’re managing dozens of specialty subcontractors across a site of that scale, coordination becomes exponentially harder. Contractors could also pull workers from multiple projects to make up for lost time in an area, making consistent safety oversight even more difficult.
Critical Sequencing Dependencies
Data centers have tighter handoff requirements than typical commercial construction projects. Cooling systems must be installed and tested before server racks can be deployed. Electrical infrastructure needs to be energized before commissioning can begin. High-voltage work, backup generators, and uninterruptible power supply (UPS) systems require precision that trade stacking might not allow.
When one trade falls behind, the downstream trades can’t just wait for their turn — otherwise everyone will be late. Their tasks get compressed into the same window as other trades. As various specialties and tasks collide, order of operations can get muddled if you’re not highly coordinated.
Safety Risks of Trade Stacking
Overcrowding increases the likelihood of workplace accidents. The mechanisms are straightforward: more activity in a confined space means more opportunities for things to go wrong. Here are a few issues that trade stacking can cause if your job site isn’t properly coordinated.
- Struck-by incidents: More workers in the same space means more tools, materials, and equipment in motion. Dropped tools and falling objects become more likely when crews are stacked on top of each other.
- Trips, slips, and falls: Congested areas accumulate cords, hoses, debris, and equipment, creating fall hazards. Workers navigate around each other instead of focusing on their footing.
- Equipment conflicts: Forklifts, scissor lifts, and cranes operating near multiple crews increase caught-between and struck-by risk.
- Communication breakdown: Noise, dust, and movement make it difficult to warn nearby workers of hazards. When crews from different contractors don’t share the same safety language or protocols, miscommunication spikes.
- Lockout/Tagout: When everyone has different procedures and tasks, locking out energy to one side of a job site can negatively affect another team’s work.
- Stress and fatigue: Overcrowding increases worker stress and distraction, both of which contribute to incidents.
Connection to OSHA’s Focus Four
Construction accounts for nearly 20% of all workplace fatalities. The leading causes, commonly called OSHA’s “Focus Four (or Fatal Four),” are falls, struck-by incidents, electrocution, and caught-in/between hazards. Trade stacking amplifies all four.
Falls become more likely when elevated work areas, scaffolding, and ladders are crowded. Struck-by risk rises when more objects are in motion in a confined area. On data center builds, where high-voltage electrical work is constant, non-electrical trades working nearby face electrocution risk. Heavy equipment, materials, and structural elements in close quarters also create pinch points for caught-in/between incidents.
Stronger safety policies and coordination can often help prevent these common incidents. Why? Because one contractor’s work can directly endanger another’s crew if they aren’t properly informed about what’s going on. For example, a crane lift by one sub might create a drop zone for another. Demolition or cutting by one team can expose workers from a different company to silica, fumes, or debris. Without coordination, no single contractor has full visibility into all the hazards in their work area.
What OSHA Expects from GCs on Multi-Contractor Sites
General contractors have specific responsibilities when multiple employers share a construction site. OSHA’s regulations and recommended practices make clear that coordination is not optional.
Under OSHA’s multi-employer citation policy, both general contractors and subcontractors can be cited for violations on the same site. GCs who have the authority to coordinate work and correct hazards can be cited even if their own employees aren’t directly exposed to the hazard.
OSHA’s construction regulations establish that the prime contractor assumes entire responsibility under the contract, while subcontractors share joint responsibility for their portion of the work. This means that when trade stacking creates unsafe conditions, the GC is accountable for failing to coordinate.
Coordination Requirements
OSHA’s recommended practices for multi-employer construction sites highlight these key responsibilities:
- GCs, contractors, and staffing agencies must provide the same level of safety protection to all employees on site.
- All parties must communicate hazards present at the worksite.
- Prior to work, GCs and subs must coordinate on planning and scheduling to identify and resolve conflicts that could impact safety.
- GCs must establish specifications and qualifications for contractors working on site.
The General Duty Clause
OSHA’s General Duty Clause establishes the precedent for keeping construction sites organized and safe. Section 5(a)(1) of the Occupational Safety and Health Act requires employers to provide a workplace “free from recognized hazards that are causing or are likely to cause death or serious physical harm.” Overcrowding and trade stacking can violate this standard when GCs fail to coordinate work safely.
Strategies to Manage Trade Stacking
Trade stacking is predictable, which means it’s controllable. While it could be eliminated, massive data center builds often require multiple trades to work in close proximity with each other. The key to working in harmony is to identify the conditions that lead to overcrowding before they become dangerous. Here are a few areas to focus on to help make trade stacking work.
Planning and Scheduling
- Target the 200-square-foot rule: Plan work sequences so no area exceeds one worker per 200 square feet of workable space. This may require extending timelines, but the productivity gains often offset the schedule impact.
- Phase work by zone: Assign different trades to designated areas at different times. Trades follow each other through zones rather than competing for the same space.
- Build in buffer time: Schedules that assume everything goes perfectly will fail. Buffer time absorbs delays without forcing trades to stack.
- Coordinate Proactively: Weekly coordination meetings should identify potential conflicts two to three weeks out, not the day before.
Communication and Coordination
- Daily coordination meetings: Short, focused meetings with all trade foremen to review the day’s work areas, sequences, and potential overlaps.
- Standardized safety orientation: All contractors receive the same site-specific training so everyone understands the same hazards, signals, and protocols.
- Shared hazard communication: When one contractor creates a hazard through hot work, crane lifts, or energized work, nearby crews must be notified immediately.
- Clear escalation paths: Workers need to know who to contact when they see trade stacking becoming dangerous. Empower anyone to raise concerns without fear of retaliation.
Technology and Visibility
- Real-time workforce tracking: Know where crews are working and identify overlaps before they become problematic.
- Digital scheduling tools: Replace static spreadsheets with tools that update in real time as conditions change.
- Centralized safety data: When all contractors report into the same system, GCs can see leading indicators across the entire site, not just their direct employees.
- Contractor performance tracking: Monitor which subs are completing Pre-Task Plans (PTPs), reporting observations, and following your safety program. Spot problems before they become incidents.
How Safety Mojo Helps GCs Manage Trade Stacking
When 20, 50, or 100+ subcontractors share the same site, general contractors lose visibility over safety and operations. Each sub often uses different safety tools, different forms, and its own reporting cadence. Unfortunately, this creates a massive visibility gap. The GC ends up chasing paperwork instead of identifying and mitigating risk. By the time a problem surfaces, it can be too late to prevent an incident.
Safety Mojo addresses this visibility gap with a platform designed for managing safety on complicated multi-contractor jobsites.
One Platform for All Subcontractors
Safety Mojo gives GCs one system to see safety data from every contractor working through Safety Mojo on the project. No more chasing spreadsheets or waiting for weekly reports. Contractor Scorecards show which subs are completing pre-task plans, submitting observations, and completing corrective actions on time. You can identify at-a-glance the contractors who need more oversight before trade stacking puts their crews at risk.
Field-First Data Collection
Safety Mojo’s Flex PTP and Conversational Forms let crews complete standardized safety tasks on phones or tablets without slowing down. Instead of filling out forms by hand, you can take a picture of a form or whiteboard to quickly transcribe and submit the data. On average, forms can be completed 80% faster, with less room for error.
When forms are fast and easy to interact with, crews actually complete them. The platform supports voice-to-form input and bilingual workflows, which is critical for the diverse workforces common on large data center projects.
Higher completion rates also mean better data. More PTPs, observations, and near-miss reports give you the information you need to spot trade stacking problems before they become incidents.
Leading Indicators for High-Risk Work
Safety Mojo surfaces trends across all contractors. Which areas are generating the most hazard observations? Which high-risk activities are happening in the same zones on the same day? For example, when you can see that three different trades are planning hot work in adjacent areas, you can intervene before the situation becomes dangerous.
OSHA also expects GCs to coordinate work and communicate hazards across contractors. Safety Mojo gives you the data and documentation to demonstrate you’re meeting those responsibilities. From PTPs to permit approvals at a glance, you have everything you need to meet and exceed compliance. The best part? Safety Mojo’s digital forms are compliant with OSHA’s online reporting guidelines, which means you can collect data without needing to worry about extra administrative work.
Ready to level up your safety program? Request a demo to see how Safety Mojo helps GCs maintain visibility across all subcontractors.
