Does the ambient temperature affect the flow properties or set time of Durock™ Self-Leveling Underlayments?
Higher temperatures will typically cause faster set times and less flow time while cooler temperatures will have the opposite effect. USG recommends that material, concrete subfloor and room temperature must be between 50°F and 95°F at the time of application and for 72 hours after installation. For temperatures above 95°F, follow the American Concrete Institute (ACI) Hot Weather Concrete guidelines to ensure proper installation.
Can I get Durock® Self-Leveling Underlayments top loaded with my Fiberock® and Durock®? Where do you stock these products?
Yes these products can be shipped with Fiberock and Durock. Durock® self-Leveling Underlayments and Fast Finish patch and skim coat are available nationwide.
How soon can I install a floor covering or coating over USG Durock™ Brand Self-Leveling Underlayment?
USG Durock™ Brand EcoCap™ and USG Durock™ Brand Speed™ can be walked on after two hours, non-moisture sensitive products can be installed in as little as four hours, and most other floor coverings in 16 hours.
USG Durock™ Brand UltraCap™ can be walked on in two hours, with light trade traffic in 24 hours and floor covering application in as little as 48 hours.
Additionally always follow the floor covering manufacturer’s recommendations.
How much water do I use per 50 lb. bag of self-leveling underlayment?
Durock™ UltraCap™ – 4.5 – 5.0 quarts (1.0 – 1.25 gallons)
Durock™ Speed™ – 5.0 – 5.5 quarts (1.2 – 1.45 gallons)
Durock™ EcoCap™ – 3.2 – 3.4 quarts (0.8 – 0.85 gallons)
What kind of coverage do you get from each type of self-leveling underlayment product?
Durock™ UltraCap™ — 23 square feet at ¼” for a 50 lb. bag
Durock™ Speed™ — 25 square feet at ¼” for a 50 lb. bag
Durock™ EcoCap™ — 20 square feet at ¼” for a 50 lb. bag
Durock™ Fast Finish — 41 square feet at 1/8” for a 10 lb. bag
What are approved substrates for the USG Durock™ Brand Self-Leveling Underlayment products?
USG Durock™ Brand Performance Flooring products are primarily meant to be used over properly prepared concrete. The products can also be used with metal lath over engineer-approved, APA-Rated exterior glue plywood or oriented strand board (OSB) (i.e., APA-Rated Exterior or Exposure 1 panels) wood subfloors following the Tile Council of North America's F-185-11 specification at a minimum ½ in. depth.
Will your self-leveling underlayment products crack?
All of USG’s self-leveling underlayment products are crack-resistant but it is impossible to state that our products will never crack. Self-leveling underlayments are only as good as the substrate, its preparation, and the applicator.
What kind of drill/mixer and paddle/blade should I use to barrel mix the Durock™ Self-Leveling Underlayment product?
The drill/mixer must have sufficient torque to move the volume of product in your batch. Typically a heavy-duty drill with capacity of 650 or higher RPM will be sufficient.
The paddle/blade will also have a big impact on the mixing energy introduced into the batch. USG recommends paddle type mixers (mixing paddle type 2, 3, 4, 8, or 9 – as outlined in the Technical Guidelines, prepared by the International Concrete Repair Institute, Pictorial Atlas of Concrete Repair Material Mixing Equipment (Guideline No. 320.5-2012)).
How thick can the USG Durock™ Brand Self-Leveling Underlayment be poured in a single lift? Can I pour deeper using pea gravel?
USG Durock™ Brand Self-Leveling Underlayments can be installed from featheredge to a thickness of 2-in. in a single lift. Thicker applications of up to 5 in. can be accomplished with the addition of clean 3/8-in. Surface Saturated Dry (SSD) pea gravel with no standing water. For these pours, the recommended technique is to apply pea gravel to the deep section within ¼-in. of the final grade. Make an initial pour of the USG Durock™ Brand Self-Leveling Underlayment into the gravel and using a garden rake, thoroughly mix the underlayment and pea gravel together. Allow to dry for 24 hours. Prime with USG Durock™ Brand Primer-Sealer as directed in Priming. Complete application by capping with a minimum of ¼-in. of the USG Durock™ Brand Self-Leveling Underlayment.
At SSD, the pea gravel aggregate is wet, thus requiring a reduction in the amount of water in the mixture to prevent overwatering. Ensure there is no bleeding or material segregation (settling of sand) in the final mixture. Use only clean and chemically stable aggregate. Do not use limestone aggregate or other types of potentially reactive aggregate.
What is the maximum RH requirement for installing USG Durock™ Brand Self-Leveling Underlayments over concrete slabs?
The maximum RH requirement is 75-80%.
How long do I have to wait between lifts and how do I prime between lifts?
Use Durock™ Primer-Sealer, a low VOC, high-solids acrylic primer, for sealing the concrete and wood subfloor prior to application of Durock™ self-leveling underlayment. Proper use of Durock™ Primer-Sealer effectively seals the subfloor and prevents formation of pinholes, domes and craters in self-leveling underlayment due to upward migration of the air bubbles from the subfloor. Floors to be primed must be dry, structurally sound and clean. Remove any dirt, tar, wax, oil, grease, latex compounds, sealers, curing compounds, release agents, asphalt, adhesives, paint, chemicals, loose topping, joint compounds from drywall installation or any other contaminant that might interfere with development of good bond.
Apply Durock™ Primer-Sealer in a two-step application. For the first application, dilute 1 part of Durock™ Primer-Sealer to 4 parts of water. Mix the diluted solution with a paddle mixer at slow speed for approximately 1 minute. Next, apply primer solution to the subfloor at a coverage rate of approximately 200-300 sq. ft./gal. using a soft push broom. Apply evenly and do not puddle. The actual coverage of the primer will depend upon the nature and porosity of the subfloor. High absorption concrete will require more primer. Allow the first coat to dry for a minimum of 1 hour prior to the application of the second coat.
For the second application, dilute 1 part Durock™ Primer-Sealer to 1 part of water. Mix gently with a paddle mixer at slow speed for approximately 1 minute. Next, apply the primer solution to the subfloor using a soft push broom. Apply the primer evenly and do not puddle. The coverage rate of the diluted primer is approximately 300 sq. ft./gal. Again, the actual coverage of the primer will depend upon the nature and porosity of the subfloor. Allow the second coat to dry to a clear thin film for a minimum of 3 hours and a maximum of 16 hours before recoating will be necessary. High air relative humidity and/or low subfloor temperature may necessitate a longer drying time. Primer must be completely dry before application of the self-leveling underlayment. Extremely porous concrete subfloors may require an additional application.
For primer application, the temperature of Durock™ Primer-Sealer, the subfloor and the room must be maintained between 50°F and 95°F for a period of 72 hours before and after application.
After applying Durock™ Brand Self-Leveling Underlayment, how soon can trade traffic resume?
Durock™ Speed™ and Durock™ EcoCap™ can be walked on after two hours and covered in 16 hours. Durock™ UltraCap™ can be walked on in two hours, with light trade traffic after 24 hours.
Can I pump Durock® Brand Self-Leveling Underlayment and if so, with what pumps?
Yes. For all pumping applications contact USG Technical Services. Pumping these products must be done by an experienced contractor with approved equipment
Isn’t fly ash bad for concrete and isn’t it a potential hazardous product?
Fly ash often is used as a filler in concrete. When used at excessive levels, fly ash and concrete has been cited as one of the reasons for excessive moisture in concrete slabs.
In Durock™ EcoCap™ Self-Leveling Underlayment, the fly ash is not used as filler but rather as a source of aluminum and silicon in the geopolymer reaction that takes place. In this case, the fly ash contributes significantly to the strength, self drying and setting characteristics of the product due to the geopolymer reaction.
What adhesives work with your Durock™ Self-Leveling Underlayment products? Do you have the manufacturers’ approval?
Ultimately the floor covering adhesive manufacturer must approve use of their products over USG products. Please consult with adhesive manufacturer prior to use over USG products.
How long do I mix the Durock™ Self-Leveling Underlayment products?
Mix for 60-90 seconds. Scrape sides and mix for another 15-30 seconds. Do not re-temper.
Which Durock™ Self-Leveling Underlayment product would be considered “low-prep”?
USG always recommends shot blasting, sand blasting, or scarifying a floor prior to installations of our self-leveling products. To decide whether mechanical preparation of substrate is required or not, the concrete substrate must be thoroughly assessed for its quality and tensile strength over the entire pour area. The assessment of concrete tensile strength must be made in its existing state without the removal of any foreign material that may be present on the concrete surface. Simple visual appearance of concrete substrate as strong and solid does not necessarily guarantee that the concrete substrate is free of impurities and has the right tensile strength.
A weak or degraded concrete surface layer must be removed mechanically to provide a solid base. 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, mechanically profile concrete subfloor to a minimum of CSP 3, in accordance with the industry standards as outlined in International Concrete Repair Institute (ICRI) Technical Guideline No. 310.2 Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays.
Use mechanical removal methods such as shot blasting, scarifying or diamond grinding to clean and prepare the concrete subfloor contaminated with adhesives, asphalt or oil. Shot-blasting is the preferred method of mechanically profiling and preparing the concrete subfloor for the application of USG self-leveling underlayments.
For self-leveling underlayments, when do I use the gypsum-based products and when do I use the cements?
Gypsum-based products can be used in almost every place that Portland cement-based products are used.
Gypsum products are generally less expensive, have superior compressive strengths (in most cases), and require less substrate preparation.
What length hose should I use when pumping Durock™ Self-Leveling Underlayment?
We recommend a minimum of 100 feet of hose when being pumped.
When applying self-leveling underlayment, is shot blasting required?
We recommend shot blasting for two main reasons. First, it is very difficult to determine if there are any contaminants that may affect the bond of the underlayment to the substrate which must be removed prior to application. Secondly, shot blasting assures the best possible physical bond of the product. If you feel that you have a job that does not need to be shot blasted, please call for further discussions.
For Durock™ Self-Leveling Underlayments, what size bags are available and how many bags per pallet?
For Durock™ Self-Leveling Underlayments, USG uses 50 lb. bags stacked 56 bags per pallet. We also can use high volume “super sacks” for larger jobs.
Durock™ Fast Finish Floor Patch is available in 10 lb. bags with 208 bags per pallet.
What is Levelrock® and how do I become an approved applicator?
Levelrock® is a gypsum-based self-leveling underlayment sold to a network of certified applicators. If you are interested in becoming a Levelrock® applicator, please contact your sales rep.
Can Durock™ Fast Finish be used over cutback adhesive?
Yes. By following these instructions.
1. Remove all loose debris from the cut-back.
2. Spread dry Fast Finish over the cutback adhesive and then work the dry powder into the floor with a broom. Then take a razorblade scraper and scrape the cut-back down to a very thin thickness and allow any residual moisture from solubility test or clean up to thoroughly dry prior to the application of Fast Finish.
3. Skim-coat the area with Fast Finish.
What is the recycled content of Durock™ EcoCap™ Self-Leveling Underlayment?
75% of the cementitious binder is recycled material.
What warranty do your USG Durock™ Brand Self-Leveling Underlayment products carry?
We offer a one-year, product performance warranty over approved substrates. Longer warranties may be available on a job-by-job basis
What is the shelf life of your Durock™ Self-Leveling Underlayment products?
Durock™ Self-Leveling Underlayment products are good for six months from the date of production.
What is the tensile strength requirement of the concrete to pour Durock™ Self-Leveling Underlayment products?
The tensile strength requirement of the concrete is 175 psi.
What are the (approximate) compressive strengths of your Durock™ Self-Leveling Underlayment products?
Can the Durock™ Self-Leveling Underlayment products be feather edged?
Which ICRI concrete surface profile do you recommend?
We recommend a CSP of 3 – 5.
Do your Durock™ Self-Leveling Underlayment products have gypsum in them?
Just like the other competitive products in the market today, our self-leveling underlayments do contain a small amount of gypsum that enhances the strength and dimensional characteristics of the products.
USG is a gypsum company. What do you know about cement and self-leveling underlayments?
USG has been manufacturing quality building material products for 110 years. We have been selling cement-based products for more than 30 years and have been making underlayment products since the 1970’s. We have an industry-leading R&D center in Libertyville, Illinois, and have several members of our technical staff who have PhD’s in cement-related fields.
What are the MVER tolerances in the concrete substrate when using your USG Durock™ Brand Self-Leveling Underlayment products?
The MVER tolerances are 5 lbs./1,000 s.f./24 hours.
After applying a self-leveling underlayment, when can I put down the final floor covering?
Durock™ UltraCap™ — 2-3 days, depending on climate and environment
Durock™ Speed™ — Non-moisture sensitive tile in 4 hours, other floor coverings in 16 hours
Durock™ EcoCap™ — Non-moisture sensitive tile in 4 hours, other floor coverings in 16 hours
Durock™ Fast Finish — Depending on thickness, floor covering can be put down in as little as 15 minutes after set
Can the Durock™ Self-Leveling Underlayment products be used as a wear surface?
Durock™ Self-Leveling Underlayments can be used as a wear surface with a tested protective coating system. Coating systems must be tested for adhesion. The bond test and performance of coatings is the responsibility of the coating manufacturer.
What moisture mitigation system is recommended to be used with USG Durock™ Brand Self-Leveling Underlayment products?
Most moisture mitigation products will be compatible with USG Durock™ Brand Self-Leveling Underlayments. It is a good practice to check with the manufacturer of the moisture mitigation product before installing the self-leveling underlayment.
Why are the CO2 emissions lower when producing Durock™ EcoCap™ Self-Leveling Underlayment?
Portland cement is one of the largest contributors of CO2 emissions. For each ton of Portland cement made, one ton of CO2 emissions is produced. The Geopolymer binder of Durock™ EcoCap™ is made using a large quantity of industrial byproduct (fly ash) that is instrumental in keeping the CO2 contribution of the product to very low levels. Compared to Portland cement, the net reduction in CO2 emissions resulting from the Durock™ EcoCap™ binder is approximately 80%.
After applying a self-leveling underlayment, do I need to put down a sealer before the floor covering goes down?
We always recommend following the floor covering manufacturer’s installation instructions.