Monolithic Concrete Floors Made Possible by LevelFlor

Self-leveling underlayment provides the foundation for an award-winning affordable housing transformation in Harlem.
Posted on 11/11/2022

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Opening its doors in 2020, The Smile is an 11-story apartment building in East Harlem that slopes inward as it rises upward, allowing more sunlight to hit the street and providing residents with incredible views of New York City's East River and Central Park. Previously known as E126, the building's interiors feature white monolithic concrete floors and exposed concrete ceilings and columns that provide an ideal framework for industrial and minimalist design themes.

Before final flooring could be installed in the lobby and more than 200 apartments, M.O.G. Contracting of Nyack, N.Y., had to address the building's uneven concrete floor substrates. The flooring contractor used Rapid Set® LevelFlor self-leveling underlayment to flatten them.

LevelFlor is an advanced hydraulic cement-based underlayment that can be used indoors and outdoors to produce a flat, strong surface with high bond strength. It can be applied from featheredge to 2 inches thick, and up to 5 inches thick when extended with aggregate. The underlayment is often specified when a fast, durable, and economical solution is required.

The contractor first primed the concrete substrate with Rapid Set® Acrylic Primer, a concentrated primer that improves the adhesion of self-leveling flooring products. Acrylic Primer seals porous concrete to prevent pinholes from forming in the finished surface. One gallon covers 400 to 600 square feet when properly diluted.

Next, the crew applied LevelFlor to build up the lower areas and produce an even, flat surface suitable for the final flooring. For the ground-floor lobby, the underlayment was mixed with a continuous pump that enabled enough material to fill deep areas (around 2 inches) in the substrate. For all other floors, the crew used a Hippo mixer and placed elevation pins in a grid pattern to achieve the desired elevation depth, which varied by floor anywhere from zero to ¾ inch.

LevelFlor was placed via gauge rakes and finished with smoother trowels. Designed for fast-track applications, the underlayment was ready for foot traffic in two to four hours and for covering with the finished flooring in four to 16 hours.

M.O.G. Contracting completed the project in less than four months. In all, 150 gallons of Acrylic Primer and 5,000 bags of LevelFlor were used to cover 60,000 square feet.

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M.O.G. Contracting’s crew placed elevation pins in a grid pattern to achieve the desired elevation depth of apartment floors, which varied from zero to ¾ inch.
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Before mixing and placing the LevelFlor® self-underlayment on lobby and apartment floors, crews primed the concrete substrate with Rapid Set® Acrylic Primer to promote adhesion and prevent pinholes from forming in the finished surface. This is after application of the LevelFlor.
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And this is the sleek, finished product: a high-gloss, high-strength, even floor.
Project at a glance
  • Type: Residential
  • Application: Flooring
  • Products: Rapid Set® Acrylic Primer (150 gallons), LevelFlor® (5,000 bags; 125 tons)
  • Location: 158 E. 126th St., New York City
  • Size: 60,000 square feet
  • Dates: Jan. 29 – April 10, 2020
  • Owner: Blumenfeld Development Group
  • Contractor: M.O.G. Contracting Inc.
  • Architect: Bjarke Ingels Group
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