Concrete Evaluation and Core Testing: A Critical First Step in Resin Flooring Success
When it comes to installing high performance resin flooring systems, what happens beneath the surface can make or break the outcome. Even the most advanced coatings will fall short if applied over compromised concrete. At Sherwin-Williams, we know that long-lasting, durable floors begin with a deep understanding of the substrate they’ll adhere to. That’s why concrete evaluation and core are essential first steps in the process.
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Understanding the Jobsite Environment
Most resin flooring systems are designed for application in controlled environments. However, many real-world jobsites don’t meet those ideal conditions.
Before any installation begins, it’s important to assess the environmental variables that could affect the project. These environmental factors can have a significant impact not only on installation but also on the long-term integrity of the floor system.
Temperature
Temperature directly impacts curing. If it falls outside the manufacturer’s recommended range, delays or product adjustments may be necessary. Excessive cold can slow down curing and reduce adhesion, while extreme heat may accelerate the reaction beyond workable limits. In both scenarios, performance suffers.
Humidity
Humidity plays a role too. Low humidity may require alternate formulas or additional environmental controls to ensure full cure, while high humidity can lead to coating defects like improper bonding or bubbling.
Dew Point
Dew point proximity to the slab temperature is another key metric. If the dew point is close to or matches the slab temperature, there is a risk of condensation forming on the surface. This invisible layer of moisture can lead to amine blush, bonding failure and delamination if coatings are applied prematurely.
Ventilation and Lighting
Other considerations include ventilation, especially for chemistries like methyl methacrylate (MMA) systems that require airflow for curing, and lighting. Installing floors under similar lighting conditions to their final use ensures a consistent appearance and finish quality. Uneven or poor lighting during application can hide trowel marks or roller lines that become visible once the space is occupied.
Reviewing Site Logistics and Layout
Resin flooring installation is a logistically demanding process, often requiring a tightly choreographed schedule and coordinated access to tools, people and materials. Evaluating the layout of the space and planning accordingly can prevent avoidable setbacks and costly downtime.
Mixing Area
Start by identifying a mixing area close to the install zone. This area should be large enough to stage materials, house mixing equipment and protect contents from temperature or humidity extremes. If outdoor mixing is necessary, ensure it can be enclosed or conditioned to avoid material failure from temperature swings or contaminants.
Material Storage
For material storage, determine if products can be delivered early to acclimate to the environment. Temperature-sensitive materials must be kept within manufacturer-specified ranges to maintain their shelf life and performance characteristics.
Power Access
Assess power access for equipment such as grinders, vacuums, mixers and heat units. Confirm the facility has the correct voltage and amperage. Will temporary panels need to be installed? Will generators be required? These questions should be answered well before the day of install.
Equipment Logistics
Understand equipment logistics in advance to avoid day-of surprises. For instance, clarify whether elevators or lifts are available for transporting heavy machinery to elevated spaces. Something as simple as limited door clearance can halt a project if not identified ahead of time.
Material Delivery
Lastly, plan for material delivery. Are there loading docks available? Will deliveries require a forklift, liftgate or ramp? Knowing the answers to these questions helps align delivery times and prevent last-minute scrambling.
Inspecting the Concrete Slab
Before installing any resin flooring system, you must evaluate the existing concrete substrate. This evaluation provides a clearer understanding of whether the slab can support the selected system and what, if any, remediation is needed.
Inadequate surface preparation or underlying slab issues can lead to adhesion failure, blistering or early system breakdown. Whether you’re working with a new pour or an aged substrate, a comprehensive slab assessment lays the groundwork for long-term performance.
Pre-Pour Specifications
If the slab hasn’t been poured yet, there’s an opportunity to influence its quality. Properly specified concrete can reduce risks associated with moisture movement, surface defects and poor bonding.
Recommended specifications include the following:
- 3500 psi compressive strength
- Water/cement ratio of < 0.45
- Light steel trowel finish to maintain surface texture
- Wet curing for a minimum of seven days to ensure strength development
- No curing or sealing compounds that may leave residues
- A 15-mil vapor retarder (ASTM E1745-09) below the slab to prevent ground moisture intrusion
Discussing these standards with the project team ahead of the pour ensures compatibility with future flooring systems and saves time down the road.
Existing Slab Assessment
For existing slabs, start with a thorough visual inspection. Look for cracks, spalling, delamination and surface irregularities. These can be signs of larger structural or environmental issues and should be documented for further evaluation.
There are several simple yet effective field tests you can use to assess the existing slab:
- Chain drag test: Dragging a metal chain across the surface can help identify voids or delamination based on the sound it makes. A sharp, consistent sound is expected; hollow tones can reveal underlying flaws.
- Golf ball test: Bouncing a golf ball across the surface can reveal inconsistencies. A sharp bounce and sound indicate solid areas; dull sounds and low bounces may point to voids.
- Rebound hammer: This tool measures surface hardness and provides a relative gauge of compressive strength. It’s not a replacement for lab testing but can help identify weak zones on site.
Testing for Moisture and Contaminants
Concrete is porous and can retain or emit moisture long after it has cured. Water used in mixing the concrete and potential groundwater vapor can affect resin coatings if not properly accounted for. In unsealed slabs, moisture vapor transmission is less of a concern. However, once a coating is applied, especially a non-breathable one, the presence of moisture and contaminants can compromise the entire system.
Excess moisture or soluble salts can cause osmotic blistering, delamination and premature failure of the coating system. It is critical to detect and quantify this before installation begins.
ASTM F2170 in-situ RH testing is the preferred method due to its reliability in varied ambient conditions. Probes are inserted into drilled holes in the slab and provide moisture readings within the concrete’s internal environment. Calcium chloride testing (ASTM F1869), while still in use, measures only surface-level moisture emissions. It is more prone to error due to environmental fluctuations during testing.
Visual signs like slab discoloration, darkened crazing and efflorescence can suggest issues with moisture or contamination. If detected, further analysis is strongly advised to confirm the presence and severity.
Going Below the Surface with Core Testing
When RH testing reveals elevated moisture, or the history of the concrete is uncertain, core testing becomes a crucial next step.
Sherwin-Williams partners with advanced laboratories to perform core analysis and evaluate for soluble salts such as chlorides, sulfates and nitrates. These salts can lead to osmotic blistering and bond failure when resinous coatings are applied.
Core samples, extracted via core drill, are recommended at one per 1,500 square feet, or five total for smaller areas (four corners and one center). The process is non-invasive relative to the cost of potential flooring failure.
Core testing can also identify several issues:
- Improper curing compounds
- Surface densifiers that inhibit bond
- Chemical contamination from previous tenants or uses
- Hidden structural deficiencies
In one case, a facility manager in Texas spent approximately $4,000 on core testing prior to a planned $90,000 installation. The results showed high moisture and salt levels that would have caused premature coating failure. By investing upfront in testing, she avoided costly downtime, replacement and reputational risk.
Checking for Joints, Cracks and Terminations
Cracks and joints are inevitable in concrete, but they must be treated appropriately during flooring installation. Structural cracks may require flexible sealants or reinforcement. Static cracks can be filled and coated. All movement joints must be honored in the resinous system to prevent reflection cracks.
Terminations, such as where flooring meets walls, drains or other finishes, also need proper planning. These areas can be vulnerable to delamination if not detailed correctly. Sherwin-Williams provides detailed technical documentation and application guides for joint and termination treatments to ensure durable and clean results.
Interpreting the Data to Choose the Right Flooring System
Not all floors are created equal—and not all are compatible with every concrete condition. Based on core and moisture testing, one of the following may be recommended:
- Breathable epoxy systems: Ideal for allowing some vapor transmission
- Epoxy with moisture vapor primer: Designed to handle elevated RH levels
- Polyurethane or hybrid systems: Tolerant of higher moisture and salts
Another recommendation may be postponement of installation or reconsideration of the flooring system. Sometimes, the best solution is to wait or use an alternate flooring solution. Choosing not to install may seem counterintuitive, but it can prevent a far more costly failure.
Sherwin-Williams prioritizes long-term performance over short-term gains. Our goal is to build trust and ensure each installation is a success for years to come.
Communicating and Documenting the Results
Clear, proactive communication can save projects. Document findings with photos, sketches and site surveys. Share results with contractors, architects or facility managers as soon as possible. Early coordination ensures that moisture issues, overlooked joints or logistical constraints are addressed before install day.
Use standardized forms and digital tools to track data and notes. Sherwin-Williams provides flooring professionals with convenient documentation resources to streamline this process and support transparency with stakeholders.
Partner with Sherwin-Williams for a Successful Flooring Install
Successful flooring systems begin with successful substrate evaluation. Environmental factors, slab conditions and potential contaminants all influence the long-term performance of a resinous flooring system. Through proper site assessments, moisture testing and core analysis, we help our partners make informed decisions that lead to better, longer-lasting results.
Investing in concrete evaluation and core testing early on allows facility managers, architects and installers to avoid costly errors and ensure optimal performance from their chosen flooring system.
For more guidance on concrete evaluation and core testing, contact a Sherwin-Williams representative today. We’re here to help you get it right from the ground up.
"This article is a consolidated rewrite of two earlier works by Jes Grant: 'Initial Space & Concrete Evaluation' and 'Importance of Core Testing.'"
Author: Jes Grant
Jes Grant serves as the Marketing Engagement Manager for Sherwin-Williams Protective & Marine and High Performance Flooring. With over two decades of experience in content creation across various technical industries, Jes has earned recognition for her writing and design expertise, being featured in numerous publications.