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Top Five 5 Tips for Crack Isolation in Tile Assemblies

Video Transcript

More than ever before, tile assemblies need effective crack isolation to protect the tile, stone and grout.  In today’s construction, most buildings are designed with lighter and thinner material components, while tile formats are growing larger or heavier. The use of crack isolation membranes will protect your installation and increase the life expectancy of your tile project.  

Tip #1 – Address substrate issues before tiling Pre-existing, in-plane cracks that measure less than 1/8” should be patched prior to leveling or membrane application.  Use rapid-setting, calcium aluminate-based patching products to stay on schedule. When cracks are larger, frequent, actively moving or differential, they should be assessed by a structural engineer to determine why they occurred so treatment will be effective.  Floor settlement or excessive deflection causes should also be identified and corrected.

Tip #2 – Plan your movement joint treatment  All structures are expected to move over time because building materials deflect, shrink, expand and settle. Therefore, using compressible sealants or pre-manufactured profiles are required to accommodate planned movement.  The Tile Council of North America recognizes several types of movement joints. 

Construction joints or cold joints are included between adjoining slab pours.  These pre-planned joints must be carried all the way through the tile assembly at the same width of the joint. Engineered joints, also called control joints, are placed after the slab has been poured.  They are designed to induce cracking in a planned pattern during the concrete curing cycle but could become active, moving joints.  Static engineered joints, and small, in-plane cracks can be relocated to line up with the tile edges. Use an appropriate crack isolation membrane based on TCNA Detail F125 for partial coverage. Full coverage treatment per detail F125 can also be specified to protect against future in-plane cracking.  For criteria on installing movement joints in the field and at the perimeters of the assembly, consult TCNA Detail EJ171.

Tip #3 – Choose the right membrane for the job  All of CUSTOM’s crack isolation membranes meet or exceed ANSI A118.12 and protect tile from in-plane substrate movement for at least 1/8”.  These membranes protect against future cracking and most can also be used to relocate existing in-plane joints.  Sheet-applied crack isolation membranes are installed using primers, adhesives or mortar so they offer a lot of versatility. Plan your installation accordingly, as substrate and environmental conditions can determine which product to use, or affect the drying and cure times.  For concrete with high moisture content or single-layer wood-framed plywood floors, an uncoupling mat membrane provides the best solution. RedGard Uncoupling Mat is adhered with polymer-modified mortar for a strong bond to the tile and substrate.  When exposed to substrate movement, the mat absorbs stresses to keep the assembly intact. 

Commercial projects with heavy traffic and point loading require a membrane with an Extra Heavy Duty rating.  For these applications, use Crack Buster Pro Crack Prevention Mat Underlayment, a self-bonding, fabric-reinforced mat that elongates to handle up to 3/8” in-plane movement. In multi-story residential construction, impact sound reduction may be necessary in addition to crack isolation.  EasyMat Tile & Stone Underlayment with SoundGard Technology will reduce the sound of impacts like footsteps on tile, and also protects against in-plane movement up to ¼”. When sound reduction is required along with a heavy duty rating, use CrackBuster Pro. 

Tip # 4 – Know when to use liquid-applied membranes Liquid crack isolation membranes provide simple, monolithic coverage.  They are typically faster to apply compared to other membranes, but drying time is dependent on jobsite conditions. RedGard Waterproofing and Crack Prevention Membrane is an extremely versatile liquid-applied solution.  RedGard isolates cracks up to 1/8”.  It can be installed over concrete slabs with 85% relative humidity and offers an extra heavy service rating. When applied in two coats, RedGard liquid membrane also meets ANSI A118.10 to waterproof the tile assembly. For an option that combines fabric and liquid components, use 9240 Waterproofing and Anti-Fracture Membrane.

Tip #5 – Use a deformable mortar  To enhance the longevity of any project, install tile with an S1 deformable mortar.  These mortars are highly polymer-modified and stay flexible in the assembly even after curing.  This is especially important in above ground installations, which are subject to increased movement.   Choose an ANSI A118.15 high performance mortar such as FlexBond Premium Crack Prevention Mortar.  There are many demanding installations with large heavy tile, natural stone, exterior or submerged applications.  For these projects, select MegaLite Ultimate Crack Prevention Large Format Tile Mortar.   

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