Installing tile over concrete can transform dull, cracked concrete into an attractive and durable flooring surface. With the right materials and techniques, tiling over concrete is a straightforward DIY project. This comprehensive guide provides step-by-step instructions for preparing the concrete substrate, selecting appropriate tiles and adhesives, proper tile layout, and grout installation. With these tips, you can achieve professional-looking results and create a tiled floor that withstands heavy use for years to come.
Assessing the Concrete Floor
Before starting a tile installation, the concrete substrate must be properly evaluated. Check for these factors to ensure successful bonding of the tile:
Cleanliness
The concrete surface must be free of contaminants including dirt, oil, paint, wax, grease, sealers, curing compounds, adhesives, and any other material that could act as a bond breaker. Sweep, mop, or etch the surface with an acidic cleaner to remove debris. Rinse thoroughly.
Levelness
Imperfections and uneven spots on the concrete can telegraph through the finished tile installation. Check for levelness using a straightedge or spirit level. Grind down any high spots greater than 1/8 inch within a 10-foot radius. Fill low areas with an appropriate patching compound.
Cracks
Look for any cracks in the concrete, especially ones that go all the way through the slab. Repair minor cracks with polyurethane or epoxy injection. For cracks wider than 1/4 inch, cut a square notch along the length of the crack and fill with a concrete patching compound specifically designed for binding to the edges of cracks.
Moisture
Excess moisture can damageFloor tiles or cause loss of adhesion. Test the concrete moisture level using a calcium chloride test per ASTMs F1869. Results above 3 lbs per 1000 sq ft in 24 hours indicate the need for a vapor barrier primer.
Compressive Strength
Verify the concrete compressive strength meets the tile manufacturer’s requirements, generally 3000 psi. Concrete should have a minimum cure time of 28 days before tiling.
With proper assessment and preparation, nearly any structurally sound concrete can serve as an excellent substrate for tile.
Selecting Appropriate Tile and Adhesive
Choosing the right tile and adhesive suited to the concrete floor surface will ensure a long-lasting installation. Consider these factors:
Tile Material
Popular options like ceramic, porcelain, and natural stone are all appropriate for concrete substrates. Select a tile that can withstand heavy loads and abrasion. Mosaics and smaller format tiles are not ideal for floors. Check manufacturer specifications.
Coefficient of Friction
The tile must have sufficient texture and glaze hardness to provide slip resistance, especially in wet areas. A coefficient of friction above .50 is recommended.
Water Absorption
Tiles with low water absorption (less than 3%) are preferable for durability. Porcelain tiles are generally near-zero absorption. Natural stone varies – check absorption percentages.
Adhesive Type
Use a high-quality thinset mortar designed for bonding tile to concrete floors. Look for extended open time and non-sag or non-slump properties for large format tiles. Flexible adhesives accommodate subtle substrate movement.
Traffic Rating
Select an adhesive rated for the expected traffic level in the installation area. Heavy traffic areas require a more robust adhesive.
With appropriately selected tiles and adhesives, tiling over concrete provides incredible bond strength and performance.
Preparing the Concrete Surface
Proper preparation is crucial before setting tile. Follow these steps:
Clean and Remove Surface Contaminants
Sweep then mop the floor to remove dust and debris. Use an alkaline cleaner or etching solution to break up and rinse away dirt, grease, oil, and any other contaminants. Allow the concrete to fully dry.
Fill Cracks and Patches
Repair all cracks, chips, holes, and uneven spots as needed per the surface assessment. Allow patching compounds to cure fully before tiling.
Apply Concrete Primer
For bare concrete, apply an appropriate acrylic or epoxy primer to enhance adhesion. Use a vapor barrier primer if moisture testing indicates the need. Follow manufacturer instructions for application and drying time.
Create Movement Joints
Cut clear movement joints to help prevent cracks from telegraphing through the tile. Make cuts at existing control joints, changes in plane, and approximately every 12 feet on center in each direction.
With the concrete blank, smooth, and ready, you can move onto tile layout and installation. Proper substrate preparation gives the tilework the best chance for success.
Laying Out the Tile Pattern
Careful tile layout prior to installation ensures the pattern is aligned, visually pleasing, and utilizes cuts efficiently. Consider these tips:
Select a Tile Pattern
Common layout patterns like grid, brick, or herringbone work well on concrete floors. Choose a pattern style that suits the shape and size of the installation area.
Determine Tile Orientation
Typically tile is laid square to the room or area for the most uniform appearance. Diagonal or horizontal/vertical orientations are options as well.
Find the Center Point
Mark perpendicular center lines across the floor space. Use the room’s central axis or divide the longest dimension in half.
Dry Lay Tiles
Place tiles on the floor along the guidelines without using adhesive. Adjust layout lines as needed to balance cuts at edges.
Check Appearance
Stand back periodically and examine overall pattern alignment, color variation, and cut tile size from all room viewpoints. Make adjustments as needed.
Taking time for thoughtful tile layout helps avoid installation regrets and saves time and materials by minimizing tile cuts.
How to Install Tile Over Concrete
Once layout is complete, you’re ready to start setting the tiles. Follow these step-by-step instructions:
Mix Thinset Mortar
Combine thinset powder with clean water per package directions. Use a paddle mixer on low speed to prevent air bubbles. Allow to slake for 5-10 minutes.
Apply Thinset to Substrate
Use a notched trowel held at a 45-degree angle to spread a thin layer of adhesive on the floor. Apply only enough that remains tacky while installing tiles.
Set Tiles in Place
Place tiles firmly into the fresh thinset one at a time in the pattern layout. Push down and slide back and forth slightly to collapse ridges and achieve maximum coverage.
Check Level and Alignment
Use spacers to maintain even grout joint width. Place a level on tiles periodically to ensure they are flat and aligned. Make adjustments quickly before thinset cures.
Continue Setting Tiles
Work in small sections so thinset doesn’t dry before tiles are applied. Scoop out thinset and re-trowel if needed. Clean excess thinset immediately to prevent hazing.
Cut Border and Accent Tiles
Measure and mark tiles to fit perimeter and obstructions. Use a wet saw for clean cuts. Grind cut edges smooth. Blend cuts into pattern to distribute small tiles.
Allow Thinset to Cure
Wait at least 24 hours for thinset to cure before grouting. Avoid walking on tiles and protect from foot traffic. Verify tiles are fully bonded before continuing.
With care and patience, the tile installation will transform the bare concrete into a beautiful floor ready for grout.
Grouting Tile Joints
Grout fills the joints between tiles, seals the tile surfaces, and completes the installation. Follow these best practices:
Select Grout Type
Choose an appropriate sanded or unsanded grout for the tile joints. Match grout color to tile color for contrast or blending based on design tastes.
Prepare and Mix Grout
Pourmeasured grout powder into a bucket and add the manufacturer’s recommended amount of clean, cool water. Mix thoroughly with a paddle until uniform consistency.
Apply Grout to Joints
Holding a rubber grout float at a 45° angle, forcefully apply grout over all tile joints, filling completely. Take care not to smear grout on tile faces.
Clean Excess Grout
Wait 10-15 minutes until grout becomes firm, then hold grout float edge at a 90° angle and scrape diagonally across tiles to remove excess grout. Rinse float frequently.
Polish Grout Lines
After clearing excess grout, use a damp sponge in a circular motion to smooth and level joints. Rinse sponge and change water frequently to prevent haze.
Allow Grout to Cure
Let grout dry 24-48 hours before light use of floor. Avoid wet cleaning or harsh chemicals for at least 7 days while grout gains strength.
With the grout complete, the tile installation over concrete is finished and ready to enjoy for years to come.
Tips for Achieving Professional Results
Follow these pro tips throughout the installation process to help ensure your tile floor over concrete meets high quality standards:
- Carefully follow all manufacturer instructions for products used.
- Work slowly and methodically. Don’t rush through steps.
- Maintain proper thinset thickness, no more than 3/16 inch under tiles.
- Use tile leveling spacers for even grout lines and flat tile planes.
- Make perfectly square cuts using a proper wet saw.
- Keep tiles faces clean throughout using a damp sponge.
- Allow recommended adhesive and grout cure times before use and cleaning.
- Avoid walking on freshly tiled floors until fully cured to prevent loose tiles.
- Seal grout lines periodically to prevent staining and damage.
With practice and patience, DIYers can achieve floor tile results on par with the work of professional tilers. Planning the details, preparing thoroughly, and adhering to best practices will enable your tile installation over concrete to look fantastic and perform reliably for many years of use.
Tile Over Concrete Flooring FAQ
Still have questions about installing tile floors over concrete? Here are answers to some frequently asked questions:
Is acid etching required before tiling over concrete?
Acid etching is often recommended, but not strictly required in all cases. It improves adhesion by slightly roughening the concrete surface. Proper cleaning followed by an adhesive primer coat may suffice.
Can any concrete flatness issues be fixed just with thinset thickness?
No. Thinset should always be a consistent 3/16 inch thickness under tiles. Larger variations in concrete levelness must be remedied through grinding or patching prior to tiling.
What type of backerboard can I use for the tile underlayment?
Cement backerboard or fiber-cement backerboard are ideal underlayments for a tile substrate over concrete. Avoid paper-faced drywall products as they can degrade from moisture exposure.
Is it okay to tile over control joints in concrete?
No. Existing control joints, expansion joints, or moving cracks in concrete must be maintained through the tile to prevent cracking. Fill them with caulk or a flexible sealant rather than grout.
Can tile adhesive be used to level low spots in the concrete?
No. Thinset should not be used in thick layers for concrete leveling or ramping. Use a quality cement-based patching compound specifically made for concrete repairs.
How long should I wait before grouting tiles after installing them?
Wait a full 24 hours at a minimum to allow tile adhesive to cure before applying grout. Ensure tiles are fully bonded and can’t be lifted out of the thinset before grouting.
Can sanded grout be used for joints narrower than 1/8 inch?
No. Sanded grouts have fine sand particles that could get trapped in very narrow joints and cause hazing on tile surfaces. Use unsanded grout for tile spaced less than 1/8 inch.
Conclusion
Installing tile over an existing concrete slab is a durable and visually appealing way to revitalize the space. With careful surface preparation, product selection, and step-by-step installation, you can achieve a professional quality tiled floor. Planning the layout, maintaining proper thinset thickness, straight grout lines, and allowing for appropriate curing of adhesives and grout will result in a finished floor that exceeds expectations. Tile truly transforms plain concrete into an eye-catching, distinctive, and functional surface able to withstand heavy traffic for many years. With this detailed guide’s tips for success, you can confidently tackle tiling projects over concrete and see fantastic results.