A failing quarry tile floor is not always a demolition project, and a tested urethane cement overlay can often replace the grout joints without removing the tile.
For facility managers, engineers and architects responsible for commercial kitchens and food plants, a failing quarry tile floor raises a costly decision: tear it out, or build a new floor over it. Choosing wrong can mean either unnecessary demolition and downtime or a new floor that inherits the problems of the old one.
This article covers how a urethane cement overlay works over existing tile, when removal is the better choice, and what testing owners and specifiers should require before deciding. For the general case for the chemistry, see Advantages of Polyurethane Cement Floor Coatings.
What Is a Urethane Cement Overlay?
Urethane cement, also called polyurethane modified concrete, is a trowel or slurry applied floor topping. It is built much thicker than a thin-film coating and is formulated for thermal shock, hot washdown and chemical exposure.
In an overlay, the existing quarry tile becomes the substrate. After mechanical preparation, the topping is installed directly over the tile and cures to a monolithic, joint-free surface. Eliminating the grout joints eliminates the place where water and soil collect.
Quarry Tile Failure: Why Grout Joints Give Out First
Quarry tile itself is dense and hard. The weak points are the grout joints and the bond between the tile and its setting bed, and both are exposed to harsh conditions every day.
The common causes of deterioration in wet production areas include:
- Hot Water and Steam: Repeated thermal cycling from washdown stresses grout and the tile bond.
- Sanitizers and Cleaners: Aggressive cleaning chemicals wear away cementitious grout over time.
- Food Acids, Fats and Oils: Organic byproducts attack grout and soak into joints and tile pores.
- Impact and Traffic: Carts, pallet jacks and dropped equipment crack tiles and loosen their bond.
Once joints open, water and soil migrate under the tile. Typical symptoms include eroded grout, cracked tiles, tiles that sound hollow when tapped, standing water and sanitation complaints.
Field experience suggests the grout usually fails long before the tile does (an observation, not a measured rate). Spot replacement of individual tiles rarely matches the existing floor and tends to move the problem rather than solve it.
Overlay or Removal: Reading the Condition of the Floor
An overlay is only as sound as the tile, setting bed and slab beneath it. The choice should follow a documented condition survey, not the appearance of the surface.
Choose an overlay when:
- Tile Bond Is Sound: A sounding survey shows most of the tile is well bonded, with hollow areas limited and repairable.
- The Slab Is Sound: There is no active cracking, settlement or deteriorated concrete at sample removal locations.
- Drainage Works: Existing slope to drain and drain bodies are acceptable and do not need to be rebuilt.
- Elevations Allow It: Doorways, adjacent finishes, drains and equipment can accept the added thickness.
- The Test Area Passes: A prepared test area meets the adhesion requirement with an acceptable failure mode.
Choose removal when:
- Hollow Tile Is Widespread: Loose tile across a large share of the floor suggests the setting bed has lost bond broadly.
- The Setting Bed Is Wet or Contaminated: Moisture or fats have migrated under the tile.
- The Slab Has Problems: Active cracks, settlement, deteriorated concrete or failed drain bodies need repair.
- Slope Must Change: Correcting drainage usually means taking the floor down to the slab.
- Materials Are Untested: Older grout, setting materials or adhesives have not been tested for hazardous materials before grinding.
A floor with only a few of these problems in limited areas can sometimes be handled with local removal and patching, followed by an overlay of the rest. That is a judgment call for the project team after the survey.
Overlay Installation: What the Sequence Should Include
The preparation sequence determines whether the overlay bonds to the tile. Owners and specifiers should expect the scope of work to include the following steps:
- Survey and Remove: Sound every tile, map hollow or loose areas, remove them, and fill the voids with a patching material the topping manufacturer approves.
- Clean and Degrease: Remove fats, oils and cleaning residue from tile and grout. Grinding alone may not remove absorbed contamination.
- Mechanically Prepare: Diamond grind or shot blast the tile to remove the smooth fired face and create profile. For concrete, Tnemec's published application guidance references SSPC-SP 13/NACE No. 6 and concrete surface profile (ICRI 310.2R). Preparation of tile should be confirmed with the manufacturer for each project.
- Key the Terminations: Cut keyed terminations at perimeters, drains, trenches and doorways so the topping is anchored rather than featheredged.
- Install Topping and Cove: Place the topping and integral cove base as one continuous system.
Done correctly, this approach produces less noise, dust, debris and closure time than full removal. Those savings are real only when the tile left in place is sound.
Testing Requirements: What Owners and Specifiers Should Require
The overlay decision should rest on test results. The specification or scope of work should require:
- Condition Survey: A documented sounding map of the tile before design is final.
- Prepared Test Area: A test area on the actual tile, prepared exactly as the full floor will be, with pull-off adhesion testing (ASTM D7234). The failure mode matters as much as the value, since a break at the tile bond or setting bed reveals more than the topping does.
- Slab Moisture: In-situ relative humidity testing (ASTM F2170) at locations where tile has been removed, which gives a more direct reading than tests run on the tile surface.
- Manufacturer Confirmation: Written confirmation from the topping manufacturer that the overlay approach, preparation, primer and terminations are acceptable for the substrate.
- Drawn Details: Terminations, drains, transitions and cove base shown on the drawings.
- Installer Experience: Documented urethane cement experience, as discussed in Elevating Quality: Experience as a Requirement in Coating Specifications.
Tnemec Ultra-Tread: Urethane Cement Options for Overlays
Tnemec's urethane cement line is Ultra-Tread. Tnemec Series N242 Ultra-Tread S is a slurry-applied, flowable mortar floor topping, and Tnemec Series N244 Ultra-Tread M is a mortar-applied floor topping. Both are Polyurethane Modified Concrete.
Tnemec Series N243 Ultra-Tread V is a troweled mortar for vertical surfaces and cove base, used with Series N242 or Series N244. Tnemec lists these products for food and beverage, pharmaceutical, processing and commercial kitchen areas.
Tnemec's published application guidance for these products addresses concrete substrates. For an overlay of existing quarry tile, preparation, priming and termination details should be confirmed with Tnemec on each project.
Conclusion
A failing quarry tile floor is not automatically a demolition project. When the survey shows sound tile, a sound and dry slab and a passing test area, a urethane cement overlay can replace the grout joints with a monolithic surface while reducing demolition and downtime. When the testing says otherwise, removal is the better investment, and we recommend letting the survey make that call early.
The floor beneath the overlay decides whether the overlay succeeds.
Field Verification Before Specifying
The following conditions are to be confirmed in the field with the applicable test before a system is finalized:
- Tile bond: sounding survey of every tile, mapped, with hollow and loose tile marked for removal
- Adhesion of a prepared test area on the existing tile: pull-off testing per ASTM D7234, with failure mode recorded
- Slab moisture: in-situ relative humidity per ASTM F2170 at locations where tile has been removed; ASTM F1869 where the manufacturer calls for it
- Surface profile of prepared tile and exposed concrete: compare to ICRI 310.2R CSP chips as directed by the manufacturer
- Fats, oils and cleaning residue in tile and grout: visual and water-drop absorption check after cleaning, confirmed by test-area adhesion results
- Hazardous materials in grout, setting materials or adhesives: sampling and laboratory analysis before grinding or removal
- Slab, drain bodies and slope to drain: inspection at tile removal locations and slope survey
- Finished floor elevations at doorways, drains, equipment and adjacent finishes: field measurement
We are happy to help. Contact a High Performance Coating Consultant in your region to review your project conditions and specification.