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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteAt Eleven Times Square, the reinforced-concrete elevator and service core was built ahead of the surrounding steel frame with self-climbing formwork. That sequence let the project team run core concrete work separately from steel erection, then connect the steel to embedded plates and welded shear tabs as the lower formwork cleared each level.
Project participants reported better control of concrete quality, schedule and logistics, along with completion on time or a couple of months early and under budget. Those outcomes are project claims, not an independently audited comparison: the available accounts do not establish a dollar saving, a percentage reduction, a controlled schedule baseline or a comparative accident-rate result.
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What “core-first” means on a high-rise
A conventional steel-and-concrete tower often advances several trades in a tightly interdependent sequence. Core-first construction changes that relationship. The reinforced-concrete core rises as its own operation, while the perimeter and floor steel is fabricated and erected behind it. The core supplies the building’s principal vertical spine and much of its lateral stability; steel crews then attach beams and framing to connection points deliberately cast into the concrete.
At Eleven Times Square, Plaza Construction used a self-climbing form system. The formwork was erected on the footings, reinforcing steel was placed, concrete was poured, and the entire form-and-platform assembly was raised hydraulically after the concrete had set. The cycle was repeated floor by floor. Embedded plates and welded shear tabs in the core provided the attachment points for the steel beams that followed.
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The approach is not simply “pour concrete first.” It is a coordinated structural, access and labor plan in which the core, its climbing equipment, connection details, cranes, steel fabrication and safety controls are designed to work as one production system.
Eleven Times Square: project facts and historical context
| Item | Reported detail |
|---|---|
| Building | Eleven Times Square, a New York City office tower |
| Size | 40 stories and approximately 1.1 million square feet, according to the 2014 Building Design + Construction case account |
| Height and completion | 640 feet; completed in 2010, according to the construction manager’s project page |
| Core-first sequence | Reinforced-concrete core advanced before the surrounding structural steel |
| Cranes | One crane served the concrete-core operation and two served steel erection, according to the project page |
| Formwork | Customized self-climbing forms supplied by PERI |
| Historical claim | The construction manager describes the tower as the first New York City building constructed with this core-first system; that is a project claim, not a citywide independent survey |
Building Design + Construction’s case account, published December 28, 2014, presented the method as new to the New York City market at that time, while noting that similar concrete-first work had been used elsewhere, including Europe. That is historical framing for the project, not evidence that the system remains unusual or dominant in New York today.
How the construction sequence worked
1. Start the core before the rest of the foundation work was finished
The foundation contractor began the concrete core while foundation work was still under way and while the structural steel was being fabricated. Starting these activities in parallel created the opportunity for the core to gain a lead instead of waiting for the complete foundation and steel package to be ready.
2. Erect the climbing form on the footings
The self-climbing form was installed on the core’s initial support. Its platforms were part of the working system, not merely temporary shuttering. They moved with the form and provided protected work areas and places to store materials during the core cycle.
3. Install reinforcement and embedded steel
Reinforcing bars were placed inside the form. Connection hardware was coordinated at the same time: embedded plates and welded shear tabs had to be located accurately so later steel beams could be attached without rework. This detailing is one of the reasons a core-first plan must be resolved during design and fabrication rather than improvised in the field.
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4. Pour and cure the concrete
Concrete was placed in the core form and allowed to set sufficiently for the next lift. Plaza president Richard Wood said the system was advantageous because the forming system allowed the team to control concrete quality and keep the pour schedule from depending on other work. That is a statement from the project participant, not an independently measured performance result.
5. Hydraulically climb the form
Once the concrete reached the required condition, hydraulic equipment raised the form and its platforms. The cycle then repeated at the next level. The core’s straight vertical configuration was described as particularly suitable for this self-climbing arrangement; a tower with major setbacks, transfers or changing core geometry would require a different engineering and formwork strategy.
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Steel framing followed after the lower formwork cleared the embedded connections. This allowed steel crews to work below or behind the advancing core rather than waiting for the entire concrete structure to finish. One crane was assigned to the core operation and two to steel erection, a division that had to be integrated into the site logistics plan.
Why separating the core and steel work can help
Independent control of concrete production
Core pours can be planned around concrete placement, testing, curing and climbing-form cycles instead of being held up by steel deliveries or perimeter-crew progress. The reported benefit is control: the team can manage the quality and timing of the core operation as a distinct production line.
Earlier release of the steel sequence
Steel fabrication can proceed while the core rises. Once embedded connections and working clearances are ready, erection can begin without waiting for a conventional, fully synchronized frame sequence. At Eleven Times Square, that overlap was part of the project’s reported time advantage.
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A stable vertical spine for follow-on work
Wood described the concrete core as providing lateral stability and a protected area with egress functions. A completed section of core can therefore serve as the organizing element for steel erection and later interior work, although the exact structural role depends on the engineer’s design.
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The 2014 case account reports cost savings and completion a couple of months ahead of schedule. The construction manager’s project page instead describes the building as completed on time and under budget. Those descriptions are not reconciled by the sources, and neither supplies a baseline schedule, a dollar amount or a percentage. The defensible conclusion is that project participants reported a favorable outcome, not that core-first construction produces a predictable saving on every tower.
Safety was a design requirement, not an afterthought
The central New York labor concern was the possibility of workers operating below other trades. Richard Wood said, “Before this job, it was believed by many that you couldn’t do a concrete core first in New York because certain trades wouldn’t work below other trades.” The project therefore required agreement among the owner, unions, site-safety specialists and subcontractors before the sequence could proceed.
Dedicated egress from the climbing system
- A dedicated hoist served access and egress for the core operation.
- A temporary stair hung from the formwork and moved with the climbing system.
- Permanent stairs were installed up to the underside of the form system at each lift, extending reliable access as the core rose.
These arrangements addressed a practical problem: a self-climbing platform changes location repeatedly, so workers cannot rely on a completed permanent stair tower alone during the early phases.
Protection from simultaneous work above and below
The platforms supplied protected working and material-storage areas. The broader safety plan had to control falling objects, equipment movement and interaction between core and steel crews. Plaza assigned two full-time safety managers to monitor the core and steel operations and used a safety reward program, according to the project accounts.
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Labor coordination
Wood said Plaza worked with the Local 40 Ironworkers to establish an acceptable safety plan. In an Engineering News-Record project account, he characterized the result as the “antithesis” of predictions that the approach would be a disaster. Those are Wood’s contemporaneous statements; the sources do not provide an independent accident-rate comparison or a quantified safety improvement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What had to be true for the method to work
- Suitable geometry: The reported straight, vertical core was well matched to a climbing form. Irregular plans, transfer levels and major setbacks can interrupt a repetitive climb.
- Connection certainty: Embedded plates and shear tabs had to be located, inspected and protected so steel could connect when the form cleared.
- Customized formwork: The climbing system was project-specific. PERI supplied customized forms; the sources do not establish a standard kit or universal configuration.
- Crane and delivery planning: Separate crane assignments for the core and steel required clear lift paths, material staging and a sequence that avoided conflicts.
- Concrete production capacity: The contractor needed dependable reinforcement, placement, curing and testing operations to maintain the climbing cycle.
- Trade buy-in: Unions and subcontractors had to accept work occurring below other activities and follow agreed exclusion, access and communication rules.
- Protected access: Hoists, temporary stairs and permanent-stair extensions had to keep pace with each lift.
- Baseline discipline: Any claimed saving must be compared with a defined conventional sequence, including the same design, labor market, procurement conditions and site constraints.
Core-first versus a conventional synchronized frame
| Decision point | Core-first approach at Eleven Times Square | What must be checked on another project |
|---|---|---|
| Concrete and steel sequence | Core advanced independently; steel followed as connections became available | Whether the core can gain a useful lead without creating idle steel crews |
| Formwork | Self-climbing, hydraulically raised form with working platforms | Core geometry, lift height, tie locations and engineering of the climbing system |
| Connections | Embedded plates and welded shear tabs received later steel beams | Tolerances, inspection access, fireproofing interfaces and correction procedures |
| Logistics | One crane for the core and two for steel, according to the project page | Crane capacity, swing conflicts, hoist locations and delivery timing |
| Safety | Dedicated hoist, hanging temporary stair, permanent stairs to the form underside, two safety managers and coordinated labor plan | Protection from falling objects, egress during every lift and rules for work above and below |
| Outcome evidence | Reported on-time or early completion and under-budget delivery; no quantified independent audit | Agreed schedule and cost baseline plus measured results |
This comparison does not establish that one sequence is universally better. It shows where the advantages and liabilities arise. A core-first plan can shorten an interface between trades, but it also concentrates risk in the formwork cycle, connection accuracy, access system and coordination agreement.
A later New York example: 7 Bryant Park
Thornton Tomasetti describes 7 Bryant Park as a 30-story office tower completed in 2015 whose basic structural system used a core-first concrete core with surrounding steel framing. A separate project account reports a self-climbing formwork system and one floor poured every four days.
That reported rate belongs to 7 Bryant Park. It is not a benchmark for Eleven Times Square and should not be treated as a general production promise. The two projects can be compared only after accounting for core and floor-plate geometry, concrete and steel sequencing, formwork customization, crane logistics, embedded connection details, labor agreements, work-at-height exposure, egress and falling-object controls, and the schedule and cost baselines used to judge success.
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How to evaluate a core-first proposal
- Map the geometry. Confirm whether the core is sufficiently repetitive and vertical for a climbing system. Identify setbacks, transfer floors, outriggers and openings that could interrupt the cycle.
- Model the connection handoff. Set the elevation, tolerance and inspection requirements for every embedded plate and shear tab, then define how steel crews will access each connection after the form clears.
- Build a two-stream schedule. Show core reinforcement, concrete, curing and climbs on one track and steel fabrication, delivery and erection on another. Mark the exact handoff levels.
- Test crane and hoist logistics. Allocate lifting capacity, swing areas, storage platforms and delivery windows. Check that the core crane does not block steel cranes or emergency routes.
- Design egress for every lift. Specify hoists, temporary stairs, permanent-stair extensions and rescue access before work starts; do not defer them to a generic site-safety plan.
- Secure trade agreements. Review the rules for workers below other trades, exclusion zones, communications, weather stoppages and simultaneous operations with unions and subcontractors.
- Set measurable baselines. Compare the proposal with a defined alternative using the same scope. Track cycle time, concrete quality results, steel-release dates, rework, incidents, labor hours and actual cost.
- Define stop and recovery points. Establish what happens if concrete strength, embedded-plate tolerances, crane availability or form hydraulics fall behind. A recovery plan is part of the method, not evidence that the method failed.
What the available evidence does—and does not—show
The project accounts support a clear description of the method and its reported operational advantages. They do not support a universal percentage saving, a specific dollar reduction, a quantified acceleration that can be transferred to another tower, or a comparative safety statistic. The “couple of months ahead of schedule” statement comes from the 2014 case account, while the construction manager’s page says the building finished on time and under budget.
Accordingly, the strongest conclusion is conditional: at Eleven Times Square, a straight concrete core, customized climbing formwork, advance steel fabrication, dedicated cranes, embedded connections and a negotiated safety plan allowed the team to run core and steel activities in parallel. The reported result was favorable, but the method’s value on another project depends on geometry, logistics, labor coordination and a credible baseline for measuring performance.
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