USG Tuf-Skim Floor Patch - 25 lbs
USG Durock Brand Tuf-Skim Floor Patch is a fast-setting, fast-drying, chemically hardening compound specifically designed to bond gypsum-based underlayment but can also be used over interior wood and concrete subfloors.
- Compressive Strength: approx. 6,000 psi
- Coverage: approx. 48 square feet when applied at 1/8 in.
- Working Time: 10 - 25 minutes
- Install Flooring: 30 - 60 minutes
All subfloors must be structurally sound, stable, and solid. If there is any question about the structural soundness of the subfloor, consult with the engineer on the project or request the services of a professional structural engineer.
Subfloors must be clean and free of dirt, tar, wax, oil, grease, latex compounds, sealers, curing compounds, release agents, asphalt, water-soluble adhesives, paint, chemicals, loose gypsum, joint compounds from drywall installation or any other contaminant that might prevent proper bonding of USG Durock Tuf-Skim Floor Patch to the host substrate.
No priming is required for treating concrete, cementitious underlayments or solid existing gypsum underlayments. Treat dusty, soft or compromised weak gypsum underlayments with USG Durock Fusion Primer. Any exposed or bare wood substrates must be primed with either USG Durock Fusion Primer or USG Durock Primer-Sealer. See USG Durock Fusion Primer Submittal (CB836) and USG Durock Primer-Sealer Submittal (CB519) at usgperformanceflooring.com for installation details.
Three parts USG Durock Tuf-Skim Floor Patch to one part water by volume, or 3.0-3.5 quarts (2.8-3.3 L) of water per on 25 lb. (11.3 kg) bag of USG Durock Tuf-Skim Floor Patch.
To mix a 25 lb. (11.3 kg) bag of USG Durock Tuf-Skim Floor Patch, add 3.0-3.5 quarts (2.8-3.3 L) of clean water to a clean 5 gal. (US) (11.3 L) pail. Sift in the entire bag of USG Durock Tuf-Skim Floor Patch and mix with a drill fitted with an appropriate mixing paddle for approximately 1-2 minutes, or until relatively smooth. Scrape the sides of the bucket to get all dry powder incorporated into the slurry. Allow the compound to stand (soak) for 1 minute, then remix the material until consistency is smooth and uniform.
To mix smaller quantities by hand, use 3 parts USG Durock Tuf-Skim Floor Patch to 1 part water by volume. Mix vigorously for 2-3 minutes with a trowel to achieve a lump-free consistency.
Over-mixing or mixing at too high a speed can shorten set times and entrain air in the mixture. Note - The cooler the conditions, the longer the soak-time needed. If the compound thickens during application before setting, allow a longer soak-time. Do not overwater, high-strength compounds thin quickly.
Use USG Durock Tuf-Skim Floor Patch within 15-25 minutes after mixing. Dispose of any USG Durock Tuf-Skim Floor Patch once setting has occurred.
During application and until USG Durock Tuf-Skim Floor Patch is set (typically within 30-40 minutes), close all doors, windows and other openings in the building and turn off HVAC systems to prevent air drafts. Protect installation areas from direct sunlight exposure during setting time. Thereafter, the operation of the HVAC system can resume, as well as the use of doors, windows and other openings.
The subfloor, room temperature and USG Durock Tuf-Skim Floor Patch product - either mixed or in powdered form - must be between 55°F and 95°F (12-35°C) at the time of application and for 72 hours after installation of USG Durock Tuf-Skim Floor Patch. For temperatures above 95°F (35°C), consult USG.
It is recommended to patch several small test areas before conducting full installation of USG Durock Tuf-Skim Floor Patch. The test areas must also include finish flooring to establish suitability of the complete system for intended use.
USG Durock Tuf-Skim Floor Patch has a working time of approximately 15-25 minutes at 70°F (21°C). At higher temperatures the working time is shortened. After application has hardened and as soon as possible after the compound stiffens, shave off tool lap marks and other protrustions using a trowel or a drywall knife as a plane.
USG Durock Tuf-Skim Floor Patch can be applied directly to dry, newly poured USG Levelrock and USG Durock gypsum underlayments without priming the surface. All other gypsum underlayments must be consolidated. Loose, debonded gypsum underlayment must be completely removed until a sound bonding surface remains. Using a stiff bristle broom, sweep the old gypsum surface. This will help to remove some of the old gypsum "scale" from the surface. It is highly recommended that a HEPA filtration industrial vacuum be used after sweeping to remove as much dust as possible. Next, prime the surface with either USG Durock Fusion Primer or USG Durock Primer-Sealer per the application instructions. For more information about the use of USG Durock Tuf-Skim Floor Patch as a repair treatment for compromised gypsum underlayments, please see USG Rehabilitation Guidelines for Damaged Gypsum Underlayments (CB822).
Mechanical floor preparation such as shot-blasting, scarification or other methods of grinding may not be required prior to installation of the underlayment over a well-bonded, sound and clean subfloor. To decide whether mechanical preparation of substrate is required or not, the concrete substrate must be thoroughly assessed for its quality over the entire pour area. Simple visual appearance of the concrete substrate as strong and solid does not necessarily guarantee that the concrete substrate is free of impurities and has the right tensile strength.
Concrete exhibiting signs of laitance (a layer of weak material on the concrete surface either visible or invisible), scaling, spalling, crumbling, or delamination must be mechanically removed to achieve a solid and clean substrate. Prior to installation of the underlayment, remove weak or degraded concrete (as described above) with hammer, chisel, or other simple means. It is not required to mechanically profile the concrete subfloor with methods such as shot blasting, scarifying or diamond grinding.
Concrete subfloors receiving USG Durock™ Tuf-Skim Floor Patch must be cured properly (generally for a minimum of 28 days) prior to underlayment installation. Subfloor Moisture Vapor Emission Rate (MVER) exceeding 5 lbs. (2.3 kg)/1,000 sq. ft. (92.9 m2 )/24 hours per ASTM F1869 or a relative humidity (RH) greater than 80% per ASTM F2170, must be treated with a USG Durock™ Brand Moisture Vapor Reducer.
USG Durock™ Tuf-Skim Floor Patch is not a vapor barrier. Transmission of excessive moisture vapors from the concrete subfloor through USG Durock™ Tuf-Skim Floor Patch can interfere with floor coverings and/or floor-covering adhesives, thus compromising their performance. If the concrete subfloor has been treated with a USG Durock™ Brand Moisture Vapor Reducer, it must be primed with USG Durock™ Primer-Sealer prior to application of USG Durock™ Tuf-Skim Floor Patch.
Cracks in the existing concrete subfloor must be inspected to determine if the crack is due to typical concrete “shrink” or if it is a result of a structural movement. In the case of the latter, remediation of the crack must be addressed or eventually the crack will telegraph through USG Durock™ Tuf-Skim Floor Patch. Consult with the engineer on the project or request the services of a professional structural engineer for all suspected structural cracks.
Repair all non-structural cracks in old and new concrete to minimize and control their ability to telegraph through the layer of USG Durock™ Tuf-Skim Floor Patch. First remove the weak concrete along the length of the cracks by chiseling or other suitable means. Next, remove accumulated dust and debris from the crack cavities using a HEPA filtration industrial vacuum or other suitable means. Various cracks present in the concrete subfloor including shrinkage cracks must be filled with a suitable commercially available crack-repair material designed for concrete flooring applications. To ensure superior resistance to crack growth, use injection crack-repair techniques per industry guidelines to repair cracks that are active or deep. Note that repair of existing cracks in the concrete subfloor only subdues, but does not completely prevent their ability to telegraph through USG Durock™ Tuf-Skim Floor Patch. Growth of existing cracks or formation of new cracks in the concrete subfloor can lead to cracks telegraphing through USG Durock™ Tuf-Skim Floor Patch. Respect existing expansion and control joints (see Notes/Limitations #8, pg. 4).
USG Durock™ Tuf-Skim Floor Patch can be applied over engineer-approved, APA-Rated exterior glue plywood or oriented strand board (OSB) (i.e., APA-Rated Exterior or Exposure 1 panels) wood subfloors. Subfloor must be properly prepared and primed with USG Durock™ Primer-Sealer per the application instructions. See Notes/Limitations, #19, pg. 5 for subfloor deflections.
USG Durock™ Tuf-Skim Floor Patch can be installed over non-water-soluble adhesives on concrete only. The adhesive residue must first be tested to make certain it is non-water-soluble. Any water-soluble adhesive residues must be mechanically removed down to clean concrete. Nonwater-soluble adhesive residues should be prepared to a thin, well-bonded residue using the “wet-scraping” technique as recommended by the Resilient Floor Covering Institute’s (rfci.com) Recommended Work Practices for Removal of Resilient Floor Coverings to remove thick areas and adhesive buildup, as well as any areas that are weak or not well bonded to the concrete. Any existing patches below the adhesive must be completely removed.
Cutback Adhesive Residues
To use USG Durock™ Tuf-Skim Floor Patch over cutback adhesive residue, first remove all loose debris from the cutback. Spread dry USG Durock™ Tuf-Skim Floor Patch over the cutback adhesive, then work the dry powder into the floor with a broom. Next, use a razorblade scraper to scrape the cutback down to a very thin thickness and allow to thoroughly dry prior to the application of undiluted USG Durock™ Primer-Sealer at 450 sq. ft./gal. (11 m2 /L) to the area. Once primer-sealer is dry, patch the area with properly prepared USG Durock™ Tuf-Skim Floor Patch.
All existing coatings must be solidly bonded to the substrate and be cured, clean and sound. A weak or degraded epoxy surface layer must be mechanically removed to provide a solid base.
The surface must first be primed with USG Durock™ Primer-Sealer undiluted at 450 sq. ft./gal. (11 m2 /L). After USG Durock™ Primer-Sealer has dried, USG Durock™ Tuf-Skim Floor Patch may be applied.
- A skim coat application of USG Durock™ Tuf-Skim Floor Patch can be walked on in as little as 30 minutes.
- Floor coverings such as ceramic tile, VCT, sheet vinyl and carpeting can be installed in as little as 30 minutes after USG Durock™ Tuf-Skim Floor Patch application. Non-breathable floor coverings requiring special adhesives that are sensitive to moisture; high-performance adhesives such as urethanes or epoxies; and wood flooring can be installed after 16 hours.
- Drying time is dependent on job site temperature and humidity conditions as well as thickness of application. For example, high humidity and/or low substrate temperatures will extend dry times.
- Check with floor-covering and adhesive manufacturers for installation guidelines and suitability of their manufactured products over USG Durock™ Tuf-Skim Floor Patch.
- Protect the surface of USG Durock™ Tuf-Skim Floor Patch from contaminants and water until installation of floor covering is accomplished.
- Perform field bond test to determine adhesive/flooring performance over USG Durock™ Tuf-Skim Floor Patch. Install floor covering with adhesive and perform field bond test approximately 72 hours after installation.
- For tile applications using Portland cement-based mortars over USG Durock™ Tuf-Skim Floor Patch, an application of USG Durock™ Primer-Sealer is required.
- Follow floor-covering manufacturers’ recommendations for surface-sealing requirements. If the floor-covering or adhesive manufacturer requirements are more stringent, their requirements take precedence.
- Do not use in exterior applications.
- Do not use as a wear surface.
- Do not install over wet surfaces, surfaces likely to become wet, or where continuous exposure to moisture is a possibility.
- Do not install over dimensionally unstable, improperly prepared, weak subfloors.
- Do not install over concrete subfloor less than 28 days old. For untreated (without an approved moisture mitigation system) concrete subfloors less than 28 days old, contact USG.
- For below-grade applications, contact USG.
- Do not apply directly to sound mats.
- Do not use over expansion or isolation joints. Continue all movement joints in the concrete slab up through the layer of floor patch. In areas where the expansion or isolation joints are not present in the floor or where the concrete slab has developed systematic cracks in response to slab movement, consult with an engineer on the project or request services of a professional structural engineer to provide such joints as part of the system in accordance with engineering requirements and industry standards.
- Existing cracks in the new and old concrete must be repaired with an appropriate crack-repair material in accordance with industry recommendations prior to installation of USG Durock™ Tuf-Skim Floor Patch. Note that repair of existing cracks in the concrete subfloor only subdues but does not completely prevent their ability to telegraph through USG Durock™ Tuf-Skim Floor Patch. Growth of existing cracks or formation of new cracks in the concrete subfloor can lead to cracks telegraphing through the floor patch.
- When the MVER exceeds 5 lbs. (2.3 kg)/1,000 sq. ft. (92.9 m2 )/24 hours or an RH greater than 80% per ASTM F2170, treat the concrete subfloor with a USG Durock™ Brand Moisture Vapor Reducer. USG Durock™ Tuf-Skim Floor Patch is not a vapor or moisture barrier. Transmission of excessive water vapor or moisture from the concrete subfloor through the USG Durock™ Tuf-Skim Floor Patch can interfere with floor coverings and/or floor-covering adhesives, thus compromising their performance. Moisture mitigation system may not be needed if a vapor retarder is installed below the concrete slab in accordance to industry specifications and practice (ASTM E1745, ASTM E1993, ASTM E1693) and the MVER value of the concrete slab is below 5 lbs. (2.3 kg)/1,000 sq. ft. (92.9 m2 )/24 hours or has an RH less than 80% per ASTM F2170.
- Do not use acid etching as a method of cleaning and preparing the concrete subfloor. Profiling the concrete surface with USG Durock™ LSP Liquid Surface Profiler should be used in lieu of acid etching solutions.
- Do not use sweeping compounds to clean and prepare the concrete subfloor. Use of such sweeping compounds leaves a film on the surface of the concrete that will interfere with the floor patch's bond development. Use vacuum, compressed air or a dry broom to remove the dust and debris and prepare the subfloor for USG Durock™ Tuf-Skim Floor Patch application. SPECIALTY APPLICATIONS CONT. COATINGS FLOOR-COVERING INSTALLATION NOTES/LIMITATIONS Page 4
- The use of adhesive-removing chemicals or solvents to eliminate contaminants from the concrete subfloor can transport oil, grease and other contaminants further into the concrete pores. These chemicals can leech back to the surface over time thus compromising the bond performance of flooring adhesives to USG Durock™ Tuf-Skim Floor Patch. To remove contaminants from the concrete subfloor, use USG Durock™ LSP™ Liquid Surface Profiler to clean and prepare the surface. See USG Durock™ Brand LSP™ Liquid Surface Profiler Submittal (CB5246) at usgperformanceflooring.com for more information.
- For applications over materials containing asbestos, contact USG. Do not mechanically remove organic adhesives, asphalt, coal-tar-based adhesives or other materials containing asbestos.
- Do not overwater or over mix.
- Do not add non-USG approved chemical additives or polymers to USG Durock™ Tuf-Skim Floor Patch.
- Existing curing compounds on concrete surfaces must be removed. Shot blasting is the only recommended method of removal.
- Do not mix with other cementitious products or self-leveling materials.
- Structure shall be designed so deflection does not exceed L/240 from combined dead and live loads and L/360 from live loads. Certain floor coverings such as marble, limestone, travertine and wood may have more restrictive deflection limits. Consult the appropriate floor-covering manufacturer.
- Existing gypsum underlayments must be solid. First test surface hardness by scratching existing underlayment with a coin. If surface can be gouged, refer to the USG Rehabilitation Guidelines for Damaged Gypsum Underlayments (CB822) before proceeding with the application of USG Durock™ Tuf-Skim Floor Patch.