Technical White PaperSELF-LEVELING UNDERLAYMENTSSubsurface Tolerances andFloor Flatness Requirements —A Case for CementitiousSelf-Leveling UnderlaymentsIt is common knowledge that putting more effort into surfacepreparation will yield benefits in your floor coveringinstallation. Not only will the floor covering be easier toinstall, but a truly flat floor will have an aesthetic quality thatbuilding occupants will appreciate. While there are manyminimal industry standards for achieving a flat floor, thequestion remains: Do they go far enough? As the flooringindustry continues to evolve — and architects and designersbecome more demanding — construction methods mustcontinue to evolve as well.By John D. Gallup, CTC, CSIArchitectural ConsultatntCustom Building ProductsToday, there is a growing demand for larger format ceramicand natural stone tiles. This necessitates proper specificationand execution of floor surface preparation, particularly inrelation to floor flatness, which is critical to any successfulfloor covering installation. To insure a higher qualityappearance and reduced life cycle cost, the ceramic tileindustry has responded to large format tile trends withupdated reference standards and guidelines that providemore specific definitions for large format tile, as well astighter tolerances for substrate flatness.

Technical White PaperSELF-LEVELING UNDERLAYMENTSAt Custom Building Products, we believe substrate flatness is best achieved through theapplication of a flowable and cementitious self-leveling underlayment (SLU) and wehave developed this paper to address: Potential conditions in the floor subsurface and the industry’s requirementsrelated to them Proper specification and installation of a self-leveling underlayment over somecommon flooring conditions and substrate types The benefits of specifying self-leveling underlayment and cement-based patchingand leveling compounds for all hard surface and resilient flooring products The performance and cost efficiencies inherent in using self-levelingunderlayment materialsEnhanced Definitions for Large Format Tile and SubsurfaceFlatness RequirementsThe American National Standards Institute (ANSI) Specification for the Installation ofCeramic Tile stipulates that deviations in sub-floor flatness should be no greater than1/4" in 10' (Ref. ANSI A108.02 – 4.0 / Before the year 2010, the TileCouncil of North America (TCNA) described large format tile units as “ generallyconsidered to be 8" x 8" and greater”, with no provision for enhanced subsurfacetolerances when tiles 8" x 8" or larger had been selected. However, as of 2011,subsurface tolerances for tile installation, based on tile unit size, have been updated inthe TCNA Handbook. For tiles with all edges less than 15", the maximum allowablevariation is 1/4" in 10' and no more than 1/16" in 12". For large format tiles with oneedge greater than 15" and for natural stone tiles, the maximum allowable substratevariation can be no more the 1/8" in 10' and 1/16" in 24". When thin bed epoxymortars are used, the variation can be no more than 1/16" in 36" with no abruptirregularities greater than 1/32" (2011 TCNA Handbook). In some instances, thearchitect/designer will require the more stringent finish tolerance, and the subsurfacespecification or tile specification should reflect this.In response to the new subsurface flatness criteria, a number of tile manufacturersspecializing in large format tile materials have embraced these updated floor flatnessrequirements, and now include references to the new guidelines in their product technicaldata sheets and installation guidelines. It is the responsibility of the architect or designprofessional to include these enhanced floor flatness requirements in the projectspecification. It is equally important for the architect or specifications writer to consult withthe design/interiors team (and vice versa) to insure that the specific installation requirementsand guidelines for the selected tile for the project are reflected in the tiling specification.To achieve the required flatness tolerances, the industry is increasingly relying on selfleveling underlayments. By virtue of the SLU’s working characteristics and performance,a flowable, cementitious self-leveling underlayment will provide flatness tolerances wellwithin 1/8" in 10' maximum plane variation. This provides a finished substrate that canaccept most ceramic and natural stone tile, including tile that maintains any edge of 15"or greater, as well as all types of resilient flooring.Traditional Straightedge Specification vs. F-Numbersfor Rating Floor FlatnessThe American Concrete Institute (ACI) has adopted the so-called “f-number” system, underthe ACI 117 specification, as a way of determining the flatness (and levelness as per F/Lnumbers) of concrete slabs. F-numbers are determined through testing procedures inASTM E-1155. These testing procedures are also referenced in ASTM F-710 for ThePreparation of Concrete Floors to Receive Resilient Flooring. Determining the flatness of aconcrete slab using the ASTM E-1155 method provides more accurate and reliable resultscompared to the conventional “straightedge specification” for 1/4" in 10', and 1/8" in 10'plane variation. Under ASTM E-1155, ACI sets forth guidelines that require specified floorflatness be assessed within 72 hours after concrete installation, to insure accuracy.Photo Courtesy ABW Construction – Woodinville, WA

Technical White PaperSELF-LEVELING UNDERLAYMENTSWhere a typical straightedge method for plane variation indicates only where gaps occurbetween a 10' straightedge and finished floor, floor flatness testing procedures underASTM E-1155 provide a more quantitative method for determining the flatness andlevelness of the entire concrete substrate. While a number of various techniques exist formeasuring concrete to determine f-numbers, perhaps the most common is the “dipstickfloor profiler” method, in which assessments are taken at a frequency of 1 ft., in bothnorth/south and east/west directions. Measurement lines must maintain a minimum of11 ft., and a minimum of 34 readings per 1000 sq. ft. of floor is required. The“dipstick” testing apparatus is broadcast along a line, which measures the variation insurface elevation at 1 ft. intervals. A reading is recorded at a point when the dipstick ispivoted, and the alternate “foot” of the apparatus is placed on the slab.Photo Courtesy ABW Construction – Woodinville, WAProject Specifications Shall Indicate the Corrective Measuresfor Concrete Slabs that are not in Compliance with Projectand Condition Requirements.Appropriate floor flatness requirements for the slab, based on conditions, intendedusage, and service requirements, can be found in ACI 302 section - Guide for ConcreteFloor and Slab Construction. Although there is no exact method of comparing f-numbersto conventional straightedge testing results, the following chart can be used as aguideline to approximate values between the two:F-Number Result (FF)Straightedge Specification Result(Plane Variation in 10')251/4"501/8"1001/16"F-Number Results of Self-Leveling ApplicationsInstalling a self-leveling underlayment makes it easy to exceed the requirements of thefloor covering. Using the testing procedures outlined in ASTM E-1155, floor surfacescovered with a cementitious SLU have rendered f-numbers in the mid to upper 80’s. Thefollowing is one example of field test results for a floor covered with CUSTOM’s highperformance SLU:Minimum Required Flatness/Levelness30 Day Result using SLU35 / 2586.6 / 46.2Lippage, Facial Variation of Tile Units and CraftsmanshipLippage is an unsightly and potentially hazardous defect in a ceramic and natural stone tileinstallation. It is a condition in which one edge of a tile is higher than the adjacent tile,which gives the finished surface an uneven appearance. When tile is selected as a flooringfinish, accessibility is a key consideration, and design professionals should understand thatany plane variation in the subsurface would be reflected in the finished installation. In short,a true and flat subsurface, within the flatness tolerances set forth in ANSI sections A108.01and A108.02, will only minimize lippage conditions and any potential subsequent liabilityissues caused by unexpected changes in the plane of the finished floor.Facial variation of the tile units that are being considered for the installation will alsopresent some challenges. A tile installation with tile units maintaining any facial variationwill be made even more challenging over a subsurface that maintains a change of planeoutside of the ANSI and TCNA flatness guidelines. ANSI A108.02 – Section 4.3.8stipulates that the grout joint width shall be at least three times the actual facial variationof the tile. Proper surface preparation with regard to subsurface flatness tolerances willallow for a much more efficient and less challenging tile installation, particularly whenyou are dealing with non-rectified tile units which maintain a facial variation, as describedin ANSI A108.02 4.3.8. It is important to note that thin-set bond coats are intended solelyto bond the tile to the substrate. They are not formulated for use as leveling agents.

Technical White PaperSELF-LEVELING UNDERLAYMENTSWood and Resilient Flooring Also Need Flat UnderlaymentsJust like ceramic tile, wood and resilient flooring require a high degree of flatness thatcan easily be achieved using a cementitious SLU. Many manufacturers of wood flooringrequire that the variation in floor flatness be no more than 3/16" in 10' and 1/8" in 6'.The installation of wood flooring also requires that the floor be dry. Because of the rapidcuring of cementitious SLU, it is possible to achieve a dry floor that meets the industryrequirements in less than 24 hours. Many of the adhesives used to bond wood andresilient flooring are sensitive to moisture and extreme pH readings, CUSTOM’s SLU isformulated to balance the finished pH to accommodate most common adhesives.Condition Requirements Prior to Application ofSelf-Leveling UnderlaymentIt is typically recommended that SLU be applied in conditions where ambienttemperature is above 50 F, and not more than 90 F. To ensure the integrity of theprimer, the moisture vapor transmissions rate (MVTR) from the substrate should not bein excess of 5 lbs. of water/day/1000 sq. ft., based on a standard ASTM F-1869(Calcium Chloride) test, or 80% rh, based on ASTM F-2170. A moisture content that istoo high will also slow the cure of the SLU and can affect the subsequent floor finish.Most floor covering manufacturers will have acceptable limits for MVTR and theirrecommendations must be followed. Consult with Custom’s technical representatives forspecific recommendations regarding CUSTOM’s SLU and your particular installation.Definition, Formulation, and Performance Values ofSelf-Leveling UnderlaymentSelf-leveling underlayment (SLU) for flooring consists of a blend of Portland and/orcalcium aluminate cements, inorganic aggregates, co-polymers, and chemicalmodifiers, which form a flowable, self-leveling compound for leveling interior subfloors.These components form a high compressive strength and flowable cementitiouscompound, resulting in a flat-level surface that accepts all ceramic and natural stone tilefloor finishes. Many SLU manufacturers state that select self-leveling materials alsoprovide proper surface prep and acceptability under alternative floor finishes, such ascarpet, vinyl, linoleum, resilient, and hardwood flooring. Refer to the manufacturers’published data sheets for compatibility with alternative floor finishes. Virtually all thecementitious SLU sold today is mixed with water only; no liquid acrylic-latex additive isrequired. The dry re-dispersible co-polymers in the manufacturer’s formulas provideimproved bond strength and flexibility. SLU is formulated with proprietary copolymers andcements, which provide ultra high compressive values, in some materials in excess of4000 psi. The high compressive value of SLU materials results in a floor assembly thatconsistently passes all 14 cycles on an ASTM C627 Robinson Floor Test for mostapplications. This ‘Extra Heavy Duty’ rating for the finished floor is crucial for floors thatare subject to heavy foot traffic and large equipment such as scissor lifts and palletjacks. Alternative self-leveling applications, such as those over hydronic tubing or electricradiant heat systems, will provide a moderate service rating. Installations over wood joist/ plywood subfloor installations can provide anywhere from a light commercial to astandard residential service rating, depending on the specific assembly detail.The versatility of cement based self-levelers allows for SLU pours that can be appliedfrom 1/8", all the way up to 1 1/2", or in some cases, up to 2" in total thickness. SLUmaterials can also be feather-edged to transition to other floor finishes. Allowablethicknesses will vary depending upon the manufacturer and the specific formula. Certainproprietary formulas are available that provide an extended set for pumping. These aredesigned for use in high ambient temperature conditions, or over large spans whenmore time to float the material is required.Cure rates of SLU materials provide for a fast setting underlayment that can acceptceramic or natural stone tile set with modified thin set in as little as 4 hours and 12 to14 hours for resilient flooring after the SLU is poured in place. This helps to minimizeproject downtime and allows the work schedule to proceed more expeditiously.

Technical White PaperSELF-LEVELING UNDERLAYMENTSDetails and Guidelines for Self-Leveling UnderlaymentsDetails and installation guidelines for floor systems that include an SLU are outlined inthe Tile Council of North America Handbook for Ceramic, Glass, and Stone TileInstallation. The handbook recommends crack-isolation membranes, such asRedGard , Custom 9240 , or CrackBuster Pro from Custom Building Products overconcrete substrates including SLU in order to isolate existing and new cracks in thesubstrate. Floor systems over SLU need to conform to IBC, IRC, and local buildingcodes. Maximum allowable substrate deflection (prior to the application of self-levelingagent) is not to exceed l/360 under live load. For stone installations, maximumallowable deflection in the substrate is l/720.Common tile assembly including self-leveling underlayment:TCNA F205-11 – Self-Leveling Underlayment over On Grade ConcretePlywood subfloor engineered truss joist (TJI) systems can be encapsulated with a selfleveling agent. When installing an SLU over any wood framed plywood floor system,application of metal or plastic lath mechanically anchored to the plywood sheathing isessential to insure the integrity of the self-leveling installation, with the most commonreinforcement being a 2.5 lb. expanded metal lath. All plywood surfaces that are toreceive self-leveling should be coated with a latex primer that is formulated for use withthe self-leveling material. SLU over plywood sheathing truss joist floors must conform toIBC, IRC, and local building codes. Maximum allowable substrate deflection (prior tothe application of self-leveling agent) should not exceed l/360 under live load. For stoneinstallations, maximum allowable deflection in the substrate is l/720. CUSTOM’s XP-1,LevelQuik RS and LevelLite SLU can be applied to TJI or dimension lumber joist systemscan maintain up to 24" o.c. spans in the joist assembly.GroutCF205Floors, InteriorConcrete SubfloorSelf-Leveling Underlayment, BondedCeramic TileLatex Portland Cement MortarSelf-Leveling UnderlaymentPrimerConcrete SubfloorCompatibility of Self-Leveling Applications as Part of aComplete System Assembly.Generally a cement-based self-leveling underlayment is a suitable surface for mostbonding mortars and adhesives. To assure compatibility, all installation products shouldcome from the same manufacturer. All Custom Building Products cement- or epoxybased thin-set mortar and grouting material are 100% compatible with CUSTOM SLUproducts. So are CUSTOM’s waterproofing and crack isolation membranes, such asRedGard , Custom9240 , CrackBuster Pro , or SpiderWeb Mat . CUSTOM’s ability toprovide a complete system inclusive of SLU (LevelQuik or LevelLite), crack isolation andwaterproofing, uncoupling membrane (RedGard, Custom 9240, CrackBuster Pro orSpiderWeb Mat), setting mortar (ProLite or MegaLite ) and grout (Prism SureColor or CEGLite Commercial Epoxy Grout) makes single sourcing from one manufacturer asimple process.Execution and Cost Comparisons of Self-Leveling vs. StandardMortar Bed InstallationsPerhaps the biggest benefit of a cementitious self-leveling floor prep assembly is theinherent cost and labor savings it provides, particularly when compared to traditional

Technical White PaperSELF-LEVELING UNDERLAYMENTScement mortar bed assemblies (ref. TCNA methods F111 & F112). In researching costcomparison information for this paper, flooring contractors who specialize in bothtraditional mortar bed and self-leveling applications indicate that self-leveling installationscost an average of 25% to 35% less than a traditional mortar bed installation, includingmaterials and labor costs. A two-man crew can manually pour a self-leveling applicationin a fraction of the time required to gauge, screed and tamp a traditional 4:1 mortar bed,as described in TCNA details F111 and F112, and ANSI A108.1. Furthermore, comparedto mortar bed assembles, the efficiency of a self-leveling application insures that thefinished product will meet much higher tolerances in regards to floor flatness, with farless labor and tooling of the material required. The cost savings noted above areindicative of this enhanced efficiency.In consulting with floor / surface prep sub contractors, many indicate that projects involvingfloors in excess of 10,000 sq. ft., self-leveling is normally broadcast with automatedpumping equipment, operated by a two- or four-man crew. As the self-leveling material canbe applied to specific areas of the floor using a mechanical pumping method, far lesstooling of the SLU is required. Floor floats are used to broadcast the material over the floorspan and required to achieve the intended floor flatness. Some manufacturers providematerials with extended set/cure times, allowing for a larger timeframe in which to healand smooth the material. This extended set is most beneficial when applying self-levelingover large floor spans in one pour. Consult with the manufacturer prior to selecting a jobspecific self-leveling product. Pumping of flowable self-leveling material can be executedon high-rise projects, including buildings in excess of 20 floors.For surfaces of less than 10,000 sq. ft., self-leveling is often manually mixed on site and“bucket poured” onto the properly prepared floor finish.Estimated per square foot weights of self-leveling installations are approximately 11 lbs.for ceramic tile, and 13 lbs. for stone installations (9 and 11 lbs. per sq. ft. forCUSTOM’s LevelLite), with a self-leveling underlayment at ½” in thickness, in standardapplications over plywood or concrete. Mortar bed installations are typically between 19and 21 lbs. per square foot. With today’s lightweight building construction, this weightdifferential can accommodate designer-preferred ceramic and stone tile flooring.Self-Leveling Underlayment is ready for flooring in as few as 4 hours. This provides amuch faster cure rate compared to a mortar bed application, which requires a minimumof 20 hours, and can be as much as 10 days, depending upon jobsite conditions (ref.ANSI A108.02 – many cases a concrete floor specification (section 03450) will not provide the flatnessrequired for the concrete substrate to be finished with a tile or stone installation. Thisbeing the case, and given the efficiencies of the SLU method, the concrete contractor andgeneral contractor can pay less attention to subsurface tolerances when a self-levelingunderlayment is included in the tiling spec section, as the SLU method provides the mostefficient method for remedying concrete that is out of flatness tolerances for floor finishes.If you want to be assured of a flat surface for installation of all floor coverings, aself-leveling underlayment and cementitious patching materials provide: A cost effective floor finish compared to traditional floor prep methods such astraditional mortar beds Finished floors that provide flatness and levelness characteristics far greater thanthe requirements of TCNA and ACI 117 Reduction in potential lippage conditions in the tile assembly The availability of self-leveling products formulated with post consumer recycledcontent, which provide a floor with a lighter per square foot weight and contributeto LEED certification for the project A subsurface finish that provides for a faster, more efficient, and higher quality tileinstallation

Technical White PaperSELF-LEVELING UNDERLAYMENTSCustom Building Products Answers the Challenges of theEnhanced Floor Flatness Standards with LevelQuik AND CustomTech LevelQuik and CustomTech products are engineered to meet a widerange of job requirements and address a variety of existing floorconditions.Formulated with Controlled Cure Technology (CCT ), LevelQuik RS Rapid Setting SelfLeveling Underlayment seeks its own level within minutes, and provides a high earlycompressive strength that can accept thin-set bonded tile applications in 4 hours or lessafter application. LevelQuik RS will maintain a compressive value of 4400 psi after acomplete 28-day cure, and can be applied up to 1" in thickness in a single pour.LevelQuik can also be feather-edged for smooth transitions to adjacent floor conditionsand finishes.With a 30-minute working time, LevelQuik ES Extended Set Self-Leveling Underlaymentis ideal for large applications that require longer cure rates to allow for additional toolingand working after pour. As a result, LevelQuik ES is ideal for large single or multi floorprojects that require the self-leveler to be pumped with mechanical pumping equipment.LevelQuik ES is formulated for application in conditions that require as much as a 2"thick leveling agent and that can be tooled down to a feather edge. This provides forsmooth transitions to other floor finishes and project conditions.LevelQuik Latex Primer is recommended as a preparation for all surfaces prior totreatment with any LevelQuik cementitious self-leveling material. LevelQuik Latex Primerdries within 30 to 60 minutes, depending upon the project conditions (includingtemperature and humidity), and it dramatically improves the adhesion of the SLU to thesubstrate while controlling subsurface porosity.Contributions of SLUs to LEED and Green BuildingOne recent trend in the formulation of self-leveling underlayments is the addition of postconsumer recycled aggregates to enhance the materials’ contribution to LEEDcertification and green building. CUSTOM has also identified the benefits of using postconsumer recycled aggregates to achieve a lighter weight formula. In some cases, theselection of a so-called “lightweight” SLU can reduce the per square foot (psf) weight ofthe floor by as much as two pounds per square foot. Exactly how much an SLU cancontribute to minimizing floor psf weights will depend on the thickness requirements ofthe self-leveling agent as a floor leveler. The thickness of the SLU will vary based on theexisting conditions and thickness of the substrate, as well as transitions to other floorfinishes.Custom Building Products Responds to LEED and Green BuildingRequirements with LevelLite Lightweight SLU.Engineered with over 20% Post-Consumer recycled content, LevelLite from CustomBuilding Products provides the highest level of Green contribution under LEED 4.1compared to any other material in the cementitious self-leveling product category.Formulated with a unique blend of high quality cements and aggregates, LevelLiteprovides a subsurface that is up to 2 lbs. per square foot lighter than standard mortarbed installations.L evelLite can accept a thin-set / tile application in as few as 4 hours after pour, and canbe applied up to 2" in thickness in a single pour, down to a feather-edge for smoothtransitions to other floor surfaces. In addition, Calcium aluminate-based patching andself-leveling materials provide high compressive value and performance, resulting in aversatile surface preparation solution for a host of selected floor finishes.

Technical White PaperSELF-LEVELING UNDERLAYMENTSCustom Building Products Launches CustomTech To address the needs of all floor coverings, CUSTOM recently introducedthree new products designed for leveling the floor prior to theinstallation of wood and vinyl flooring as well as ceramic and stone tile.These products incorporate state-of-the-art aluminate cements toachieve the performance the industry expects. They have beendesigned for easy application and allow immediate installation of thefloor covering.A High Compressive Strength SLUCustomTech TechLevel XP-1Premium Calcium Aluminum Based Self-Leveling Underlayment For challenging floor leveling installations, Custom Building Products has developedTechLevel XP-1, a premium high-performance calcium aluminate based self-levelingunderlayment. With a compressive value in excess of 5,000 psi, TechLevel XP-1 isideal for floors that are subject to heavy foot traffic and large equipment, such as scissorlifts and pallet jacks. TechLevel XP-1 is an abrasion-resistant formula that requires lesssurface preparation. TechLevel XP-1 can level floors from featheredge up to 2" inthickness. It is the preferred choice for preparing concrete floors to receive alternativefinishes, such as resilient flooring. (Refer to ASTM section F710 for concrete floor prepand flatness requirements for resilient floor finish.)New Generation General Purpose Patching CompoundCustomTech GenPatch General Purpose Calcium Aluminate Based PatchFor general purpose trowel-applied patching of interior or exterior concrete substrates,specify CUSTOM’s GenPatch Calcium Aluminate Cement Based Patching Compound.GenPatch can accept floor finish and adhesive bond coat in 60-90 minutes, and can befeather-edged, or applied up to 1" thick.Provides an Easy-to-Apply High-StrengthCustomTech Silk Patching and Finishing CompoundAs a calcium aluminate-based cementitious compound, CustomTech Silk provides thebest solution for challenging applications, such as ramping between floor finishes whichmaintain a variation in plane, in a smooth, easy to apply, high-strength formula.CustomTech Silk has a rapid cure compound that can accept a host of different floorfinishes, including tile, stone, and resilient flooring.References:Tile Council of North America (TCNA) –Handbook for Ceramic Tile Installation 2011 48th EditionAmerican National Standards Institute (ANSI)Specification for the Installation of Ceramic Tile – 2011American Concrete Institute (ACI) 117American Concrete Institute (ACI)“Guide for Concrete Floor and Slab Construction”TTL News Volume 10 – Issue 1 – February 2009“The Floor Flatness Report” – Concrete International– January 2011ABW Construction – Woodinville, WACustom Building Products – www.custombuildingproducts.comLEED is a Registered Trademark of U.S.G.B.C.About the authorJohn Gallup is an Architectural Consultant for Custom Building Products, based inthe Seattle area, and is responsible for the Northwest Region. In his 20 years inthe ceramic tile and flooring industry, John has been responsible for specificationconsultation and development , project pre-construction meetings, and job installationinspections. John is an 8 year member of the Puget Sound Chapter of the ConstructionSpecifications Institute.Seal Beach, CATechnical Services 800-282-8786custombuildingproducts.comWP122 6/13R

the installation of wood flooring also requires that the floor be dry. because of the rapid curing of cementitious SLu, it is possible to achieve a dry floor that meets the industry requirements in less than 24 hours. Many of the adhesives used to bond wood and resilient flooring are sensi