REGISTRO DOI: 10.69849/revistaft/dt10202507311929
Rafael Feldmann1
ABSTRACT
The U.S. multifamily housing market has traditionally relied on wood-frame structures or reinforced concrete frames with concrete masonry unit (CMU) infill. These methods require specialized labor, break the project into sequential stages and hinder the overlap of trades, leading to extended schedules and high indirect costs. By contrast, the cast-in-place monolithic concrete wall system—widely used in Brazil—combines structure and enclosure in a single pour, allowing crews to progress in repetitive cycles and to release interior trades early. This paper compares the performance of these systems through three projects managed by the author between 2022 and 2024. Two projects in Florida and Georgia used monolithic concrete walls; a third project in Florida followed a conventional method. The study compares weekly productivity, construction schedules, logistics and financial impacts. Although nominal output per week appears similar across methods, the monolithic wall system dramatically shortens the time to a dry-in condition, which speeds up interior work and accelerates revenue generation. Faster delivery reduces indirect costs, lowers construction loan interest and enables leasing several months earlier. We conclude that the monolithic concrete wall system is both technically competitive and financially advantageous for multifamily housing in the United States.
Keywords: monolithic concrete wall; multifamily construction; productivity; schedule; return on investment.
1. INTRODUCTION
Demand for rental housing has expanded across the United States over the past decade, driven by demographic shifts and rising interest rates. At the same time, contractors face labor shortages, material inflation and pressure to deliver projects with a strong return on investment. Wood framing and concrete frames with CMU infill remain the dominant construction systems because they are familiar to builders and lenders. These methods segment the process: the structural skeleton is completed before masonry walls are erected; only then are mechanical, electrical and finish trades allowed to start. As a result, projects take longer and accumulate overhead costs for field offices, crane rentals and site management.
An alternative developed in Brazil in the 1970s and later popularized by the country’s low-income housing programs, is cast-in-place concrete walls. The system uses reusable metal forms to cast walls and slabs together, eliminating masonry infill and plasterwork. Because the structure and enclosure are poured simultaneously, crews can follow repetitive cycles with smaller teams, greater logistical flexibility and earlier release of interior trades. Despite these advantages, the technology began to gain traction in the United States only recently. This article examines why adoption has lagged, evaluates the technical competitiveness of monolithic walls and discusses their impact on productivity and financial viability for multifamily developments.
2. METHODOLOGY
The study adopts a qualitative, applied approach. We selected three workforce-housing projects managed by the author in Florida and Georgia between 2022 and 2024. Two projects were built with in-situ concrete walls using modular aluminum forms, weekly productivity tracking and staggered sequencing of buildings. The reference project used a conventional system: a five-story building with reinforced concrete beams and slabs and CMU infill walls. For each site we collected schedule data (dates of concrete pours, topping-out milestones and dry-in events), weekly productivity per floor and weather conditions. We also observed site logistics, handoffs between disciplines (structure, enclosure, MEP and finishes) and the timing of interior work. The analysis compared the duration of structural and enclosure cycles, the potential for overlapping trades and the effect of these choices on physical progress. In parallel we reviewed documents from the American Concrete Institute (ACI), the Portland Cement Association (PCA) and the National Association of Home Builders (NAHB) to contextualize multifamily construction in the United States.
3. RESULTS AND DISCUSSION
3.1 Florida Project – 372 units
The first case comprised eight three-story buildings with a total of 372 apartments. A single set of metal forms advanced from building to building in five-week cycles. Each week about ten units—roughly 8,000 sq ft of floor area—were cast. The entire structure of all buildings was completed in 37 weeks. The crucial metric, however, was the dry-in milestone: within about five weeks of starting a building, the roof slab and exterior walls were in place, allowing windows to be installed and the roof to be waterproofed. At that point, electrical, plumbing and HVAC crews could work under cover while the formwork moved to the next building. This staggered, linear sequence created parallelism between structural and finish activities, shortened the overall schedule and maintained consistent productivity even with a single formwork crew.
3.2 Georgia Project – 476 units
The second case involved five residential towers of seven stories, totaling 476 units. The same monolithic wall system was used, but average production was slightly lower—about eight units per week (roughly 6,500 sq ft/week)—and the complete structure of the five towers required 60 weeks. Frequent rain and greater heights reduced productivity. Nevertheless, the methodology proved robust: each floor was completed sequentially and dry-in was achieved floor by floor, releasing interiors before the tower was topped out. Each topping-out occurred as scheduled, indicating that even in taller buildings and under adverse weather, the concrete wall system maintains schedule predictability and allows overlaps between trades.
3.3 Conventional Florida Project – 125 units
The reference project was a five-story building with 125 apartments built using reinforced concrete slabs, beams and columns with CMU infill. Casting each structural floor took 12–14 days, after which crews erected masonry walls in 7–10 days. The building’s skeleton was finished in about 15 weeks, but a fully weather-tight condition was reached only eight weeks later, around week 23. Because mechanical and finish trades depend on the exterior closure, these crews waited for the masonry to catch up. The result was a linear schedule—structure, then enclosure, then interior trades—with few parallel work fronts. This sequencing limited integration between trades and led to idle periods for equipment and labor.
3.4 Productivity and Schedule Comparison
Although the numerical productivity of the concrete wall projects (8–10 units/week) was close to that of the conventional building (about 8 units/week), the integrated structure-and-enclosure system altered the schedule dynamics. In the 372-unit project, each building was started and enclosed in about five weeks, allowing interior crews to begin almost immediately. In the 125-unit conventional project, enclosure occurred only after the entire structure was finished and required several additional weeks, delaying the start of finishes. In larger developments, the difference grows: with concrete walls, multiple buildings can be constructed in a “cascade” using a single set of forms; a conventional approach would require larger masonry crews and accept longer wait times. Thus, even if the rate of concrete casting appears similar, the monolithic system shortens the critical path and improves site logistics.
3.5 Financial Impact of Schedule
Accelerating the schedule has a direct effect on economic viability. Each month saved reduces overhead, general conditions and financing costs. Studies from the Terner Center for Housing Innovation show that faster methods can save up to 2 percent of a project’s total cost in construction loan interest alone. More importantly, rental revenue begins sooner. Consider a development with 150 units renting for an average of $1,800 per month. At 90 percent occupancy, gross revenue would be roughly $243,000 per month. If the project is delivered four months earlier, investors collect almost $1 million in additional rent. To understand the investment more deeply, it helps to apply real estate finance metrics. Suppose each unit costs $200,000 to build and generates gross annual rent of $21,600. Deducting operating expenses of roughly 30 percent yields a net operating income (NOI) of $15,120 per unit per year. Yield on cost—the NOI divided by total cost—equals about 7.5 percent (15,120 ÷ 200,000). For a 150-unit project the annual NOI is around $2.27 million. Delivering four months early effectively brings in about one-third of that NOI sooner, or roughly $756,000 in additional cash flow. This advanced income improves the internal rate of return and adds roughly 2.5 percentage points to the investor’s annual return without increasing project cost. In a high-interest environment, such time and cash-flow gains become critical to a project’s feasibility.
3.6 Interpretation of the Results
The three cases indicate that cast-in-place concrete walls offer significant schedule and organizational advantages over the conventional method. Across different climates and building heights, concrete walls maintained steady production, produced weather-tight buildings within weeks and released interior trades early. This flexibility reduced idle time and allowed simultaneous work by multiple trades, optimizing resource use. Financially, the schedule gains translated into lower indirect costs and earlier rental revenue. The evidence suggests that adopting this technology aligns with the needs of multifamily investors seeking short schedules, reliable delivery and quick return on capital. While cultural and regulatory barriers remain, the Brazilian experience demonstrates that industrializing concrete walls is viable and scalable, especially for repetitive developments.
4. CONCLUSIONS
The comparative analysis of three projects shows that cast-in-place concrete walls can transform multifamily construction in the United States. By integrating structure and enclosure, the system significantly reduces the time to dry-in, allows concurrent trades and increases schedule reliability. The projects studied reveal that, with similar weekly productivities to the conventional method, buildings can be delivered months earlier, generating earlier rental income and reducing financing costs. In an environment of labor shortages, rising costs and high interest rates, these benefits make the system particularly attractive to developers of workforce housing and to investors aiming to maximize return on investment. Adoption of monolithic concrete walls in the United States is therefore likely to grow, especially in repetitive, build-to-rent projects, and future research should explore environmental impacts and learning curves associated with industrialized systems.
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1Civil Engineer / Sr Project Manager