M id A tlantic Real Estate Journal — Owners, Developers & Managers — June 2023 — 13A
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O wners , D evelopers & M anagers
By Jigar Desai, PhD, P.E., ECS Mid Atlantic Thinking about floor coverings over concrete floor slab? Consider this too
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F1869 and internal relative humidity of concrete testing F2170) testing before install- ing the concrete flooring is required for almost all floor - ing systems. In addition, for old slabs used for applications that led to exposure to oily and greasy substances, sampling of the concrete floor for chemi - cal analysis is recommended. Since moisture transmits from underneath the floor slab, it is a good practice to sample and test soils of the floor slab subgrade for moisture content. For old concrete slabs that show signs of cracks, discoloration, or a white powdery substance
along the cracks, a laboratory petrographic examination of concrete core samples from the floor slab to look for any harm - ful reactions within the con- crete is highly recommended. 3. Vapor barriers: Check for an effective vapor barrier’s presence (or absence) beneath the concrete slab. Older build- ings may not have a vapor bar- rier under the slab, or if they have one, it may be so thin and disintegrated that it would be ineffective to serve as a barrier. Consider a moisture mitigation system before installing the new floor covering if a vapor barrier doesn’t exist. For new
These additives help reduce the need for water (and subsequent moisture), and some additives also provide additional water resistance capabilities. Consult with a professional to determine the most suitable admixture for your project. 6. Moisture mitigation sys- tems: In cases with high mois- ture (moisture vapor emission rate or high concrete inter- nal relative humidity) levels, consider installing moisture mitigation systems such as moisture vapor barriers over the slab or epoxy-based coat- ings. These systems provide continued on page 14A
construction, ensure a vapor barrier is part of the design and guidelines of ACI 360R-10 are followed for floor slab design. 4. Proper drainage: Ensure proper site grading and drain- age to direct water away from the concrete slab. Poor drainage can lead to water accumulation and moisture-related problems. Implement appropriate slopes and install drains if necessary. Ensure that roof downspouts do not dump water near the exterior walls and foundation of the building. 5. Water-reducing admixtures: Consider using water-reducing admixtures in the concrete mix.
ave you ever heard of words used for flooring over concrete slabs
like vapor barrier, sweating, blistering, musty odors, peel- ing, moisture, and high inter- nal relative humidity? If you have, I can empathize with you since you may have dealt with a flooring failure situation that may have cost you a dear penny. Thoughtful planning is critical to any project’s design to avoid flooring failures. Do your homework and ask the right questions. Consider this scenario for a 20-year-old mid-rise build- ing with concrete floor slabs on the ground and elevated composite concrete slabs on a metal deck. A renovation for a new tenant includes a new interior build-out and a variety of floor finishes with a combination of luxury vinyl tile (LVT), carpet, ceramic tiles, and some polished con- crete floor. Each of these floor finishes has a different sur - face preparation requirement. Still, one thing in common is that the concrete floor slab must meet a particular mois- ture requirement to install any new floor covering over it, i.e., the concrete must be dry enough when tested un- der specific standard ASTM test methods. When proper surface preparation, includ- ing assessment of the existing substrate, is not performed, the failure of flooring sys- tems becomes inevitable. To prevent flooring over concrete surfaces from failing due to moisture-related issues, be- low are some guidelines: 1. Hire a Consultant to Eval- uate Existing Floor Condi- tions: A flooring consultant is not a salesperson from the flooring materials vendor or a flooring installer, but rather an independent consultant with experience in materials science, knowledge of how flooring systems work (or fail), experience in construction and sequence of construction ac- tivities, understanding of how ambient conditions contribute to the performance of flooring systems and focused on ensur- ing that the new floor covering is compatible to the existing floor while being able to evalu - ate the flooring installation requirements. 2. Testing of Existing Con- crete Floor and Soil Subgrade: Conduct moisture (vapor emis- sion rate testing per ASTM
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