For professional installers, a new flooring project often begins with an old problem. Existing coatings or adhesives on a concrete slab present one of the most common and critical challenges in surface preparation. Improper removal can lead to adhesion failure, delamination, and costly callbacks that damage your bottom line and reputation.
Thorough removal isn’t just a best practice; it is essential for the long-term performance of any new flooring system. Failing to create a clean, properly profiled substrate puts the entire installation at risk. This guide provides a systematic approach for assessing and removing old materials, ensuring your surface is ready for a durable, high-performance coating.
Why Old Coatings and Adhesives Compromise New Floors
Old coatings, sealers, and adhesive residues act as bond-breakers. They prevent new flooring systems from achieving the deep mechanical bond needed to withstand traffic, abrasion, and other stressors. Even a thin, nearly invisible layer of old material can compromise the adhesion of a new coating.
The risks of incomplete removal include:
Poor Adhesion: The new system bonds to the old coating instead of the concrete, leading to peeling and delamination.
Chemical Incompatibility: Residual chemicals from old materials can react with the new coating, causing blisters, discoloration, or curing issues.
Uneven Finish: Leftover adhesive ridges or thick coating patches create an uneven surface that telegraphs through the new floor.
Taking the time to remove these old materials completely is a direct investment in the success and longevity of your project.
Step-by-Step Guide for Removal
A successful removal process starts with a clear plan. Follow these steps to efficiently and effectively prepare a concrete slab for its new system.
Step 1: Assess the Existing Material
Before you start any mechanical work, you must identify what you’re dealing with. Different materials require different removal methods.
Identify the Coating or Adhesive: Is it a thin-mil epoxy, a thick elastomeric membrane, or old carpet adhesive? Epoxies are hard and brittle, while urethanes can be tougher and more flexible. Mastics and glues are often soft and gummy.
Determine the Thickness: Measure the coating’s thickness. Thicker systems may require more aggressive removal methods or multiple passes.
Check for Bond Strength: Use a scraper to test how well the old coating is bonded. A poorly bonded coating might come up easily, while a well-adhered system will require significant mechanical effort.
Step 2: Choose the Right Removal Method
Your assessment will determine the most effective removal strategy. The three primary methods are mechanical grinding, shot blasting, and chemical stripping.
Mechanical Grinding: Diamond grinding is a versatile and widely used method for removing coatings up to 1/8-inch thick. Grinders use rotating diamond-tooled discs to abrade the surface, removing the old material and profiling the concrete simultaneously.
Best for: Thin-mil to high build epoxies, sealers, paints, and adhesives.
Tooling is Key: Use aggressive, low-grit metal-bond diamonds designed for coating removal. For softer coating and adhesives it may be necessary to broadcast the surface with an abrasive material such as silica sand to assist in keeping your diamond tooling open. In the case of thick layers of adhesives it could be beneficial to run a carbide scrape away blade to remove the bulk of the material,followed by metal bond diamonds. PCD (polycrystalline diamonds) are particularly useful for the bulk removal of thick coatings, but special care must be taken not to damage the substrate.
Shot Blasting: Shot blasting is a highly efficient method for removing coatings and creating a robust Concrete Surface Profile (CSP). A machine propels tiny steel shot at high velocity against the surface, fracturing the coating and exposing clean concrete.
Best for: Medium to thick coatings, brittle materials, and large-scale projects where speed is critical. It excels at removing well-bonded epoxies and urethanes.
Considerations: Shot blasting creates a more aggressive profile (typically CSP 3–5), so ensure it’s appropriate for the specified flooring system. It can be less effective on soft, elastomeric materials that absorb the impact of the shot.
Chemical Strippers: For some sensitive applications, chemical strippers may be necessary. These products work by softening the coating, allowing it to be scraped off the surface.
Best for: Thin film sealers and coatings
Safety and Cleanup: Always use strippers in a well-ventilated area and follow all safety protocols. The resulting residue is often considered hazardous waste and requires proper collection and disposal, adding time and cost to the project. After stripping and scraping, the slab may still need mechanical grinding to remove impregnated residue and create a proper surface profile.
Scarifying: scarifier is an aggressive, heavy-duty machine that uses rotating tungsten carbide cutters to remove large amounts of material in a single pass, up ¼ inch.
Best For: Removing thick underlayments, overlayment and flooring systems.
Considerations: Scarifying will produce an aggressive surface texture ( typically a CSP 4-9 ) making them not ideal for thinner systems. If using a scarifier for removal in an application less than an ¼ inch grinding and patching will be required post removal to ensure a satisfactory finish for your new installation.
Step 3: Execute the Removal and Profile the Slab
Once you’ve selected your method, begin the removal process.
Systematic Work: Work in a consistent, overlapping pattern to ensure complete removal across the entire slab.
Dust Control: Use a commercial-grade HEPA vacuum connected directly to your grinder or shot blaster. This is non-negotiable for protecting air quality and ensuring a clean work environment.
Detail Work: Use hand grinders with appropriate diamond tooling and dust shrouds to address edges, corners, and tight areas that larger machines cannot reach.
After removing the bulk of the old material, inspect the slab. If any residue remains, a second pass may be needed. The final goal is a clean, porous concrete surface with the correct CSP required by the new flooring system’s manufacturer.
Tackling Old Coatings and Adhesives: Proven Strategies for Concrete Surface Preparation
Dealing with old coatings or adhesives on concrete is a common challenge but it’s more than just an inconvenience. Missed steps or incomplete removal directly undermine even the best resinous flooring systems. Whether your job site is a manufacturing plant with decades-old epoxy or a regional grocery store undergoing a rebrand, legacy layers can mean delays, unexpected costs, and disappointed clients.
Understanding the Risks and Variables
Every existing floor tells a story. Legacy floor coverings may be hiding beneath layers of dirt or paint, may have been repaired, patched, or re-sealed multiple times, and may react unpredictably to solvents, machinery, and new coatings. Weather impacts the job too—cold temperatures harden adhesives, while summer heat makes some mastics sticky and difficult to extract.
Core risks when removing old coatings or adhesives include:
Bond Breakers: Unremoved coatings prevent mechanical bonding, leading to delamination.
Unknown Chemicals: Residues from industrial adhesives or old sealants may chemically react with new systems.
Substrate Damage: Over-aggressive removal or unsuitable tooling risks gouging the concrete.
Irregular Profiles: Patches of adhesive or coating left behind can “telegraph” through the new surface, creating visual and structural issues.
Moisture Traps: Improper cleaning can leave residues that absorb and emit moisture, leading to bubbles or discoloration.
Best Practices and Practical Solutions
To deliver a reliable, lasting floor, follow a process that puts assessment and control at the forefront:
Enhanced Step 1: Diagnose More Than the Surface
Chemical Testing: In addition to visual checks, simple spot-testing with solvents or pH kits can help identify adhesive or coating chemistry (water-based vs. solvent-based, urethane, or epoxy). This step can reveal adhesion issues before removal begins.
Moisture Testing: Use ASTM F710 guidance to determine if old adhesives have trapped moisture beneath the surface. High vapor emissions should be addressed before install.
Historic Job Records: Ask property managers or facility owners for previous install specs. Knowing what lived on the floor before can prevent surprises.
Enhanced Step 2: Select Proven Tools and Methods for the Task
Tailored Tooling: Select diamond abrasives, scarifiers, or shot blasters based on the adhesive or coating type. For hard, brittle material, aggressive metallic segments work well. For soft mastics, PCD scrapers or carbide-tipped tools are more effective.
Vacuums: Use commercial-grade HEPA vacuums throughout, especially when mechanical removal generates silica dust—a health and compliance must on every site.
Air Quality: Use commercial-grade HEPA air scrubber, especially when mechanical removal generates silica dust—a health and compliance must on every site.
Evaluate Strip Method Carefully: Chemical stripping can be effective, but always account for site ventilation and hazardous waste collection. After chemical removal, follow up with grinding to restore the surface profile and eliminate residual contamination.
Enhanced Step 3: Surface Profile and Cleanliness
Double-Pass Standard: In high-risk areas—such as entryways, food prep, or chemical storage—run a second grinder or blaster pass to ensure all residues are gone. Inspect closely for embedded adhesive in surface pores or along slab joints.
Edge and Detail Work: Assign a crew member to detail edges, joints, and under racks—areas most prone to missed removal.
Confirm CSP: Reference ICRI 310.2R-2013’s Concrete Surface Profile (CSP) charts to hit the right level for your floor system. Many resinous coatings demand CSP 2 or 3 as a minimum.
Enhanced Step 4: Document, Communicate, and Protect
Photograph Substrate Conditions: Before and after photos support warranty claims and offer proof of quality.
Communicate with Stakeholders: Keep GCs and property owners informed about unexpected challenges, especially if removal uncovers slab damage or moisture problems requiring additional steps.
Moisture Mitigation When Needed: In situations with persistent vapor or sub-slab moisture, install a moisture mitigation system approved for your specified resinous flooring.
Pro Tips From the Field
When adhesives become soft due heat created from your tooling. Broadcast silica sand to help clean your tools as you go. Also ensuring that 50% of your grinder head is on open concrete will help prevent your tools from getting clogged.
In facilities with layers of unknown coatings, always wear appropriate PPE. Some adhesives may contain hazardous legacy ingredients.
Finish every removal with a thorough vacuum and inspection under work lights—residual streaks or gloss can signal areas needing further grinding.
The Foundation for Long-Term Performance
Skipping or rushing the removal of old coatings and adhesives is one of the fastest routes to flooring failure. A pristine, well-profiled concrete slab is the only acceptable foundation for a new, high-performance flooring system. By thoroughly assessing the existing materials and choosing the right removal method, you ensure the new coating achieves maximum adhesion. This commitment to proper preparation protects your work, satisfies your client, and reinforces your reputation as a professional installer who delivers durable, reliable results every time.
References
International Concrete Repair Institute (ICRI). Guideline No. 310.2R-2013: Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair.
ASTM International. ASTM F710: Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring.
National Ready Mixed Concrete Association (NRMCA). Concrete Moisture Issues and Vapor Emission Testing. 2022.
ConcreteNetwork.com. Removing Old Adhesive from Concrete Floors. Accessed 2024.
ForConstructionPros.com. Jobsite Profile: Removing Adhesives in Cold Weather. 2023.
