#MAPEITechTip: ‘Floor & Wall Installation Systems’— Designing for Compatibility

Compatible flooring systems make great sense for building owners as they significantly prolong the life cycle of an installation. One of today’s best role models of compatible construction systems involves increasingly popular sustainable building projects. While typically unseen by the building owner, flooring adhesives and surface preparation products installed beneath tile, stone, floor covering, carpeting or wood can make or break an installation. And with the increasing cost, liability and time constraints associated with today’s construction projects – selecting, specifying and installing the right combination of flooring installation materials are crucial issues.  It is key that ALL the layering components within a floor or wall installation system first of all serve a purpose and secondly perform to design parameters during the lifecycle of the installation—from the substrate to the finished covering.

In the case of an installation system, the ‘whole is really equal to the sum of it’s parts’. One of the best ways to ensure compatibility is during the ‘design phase’ LEED has really championed this intense collaborative process, known as charette.  This term is really a fancy name for a team of designers whose focus is to discuss all the various aspects (product performance & aesthetics) that can impact the project—promoting a single design objective among the various disciplines. These intense ‘design sessions’ are vital to ensuring system component compatibility for the life-cycle of the building, quantifying the degree and type of environmental exposure before project is started. When ALL of the layers work together as a compatible unit, points of failure are minimized and only the products required to meet system performance are specified into the design.

The converse is true also, ignoring ‘layering compatibility’—resulting in a damaged reputation, customer dissatisfaction and loss of confidence in the entire system.  All factors of which can be an expensive lesson for all key players involved in the project, from the design professional to the product manufacturer to the installer.

A good example of a system that can quickly become incompatible with subsequent layers, is gypsum based underlayments or patching compounds.  Gypsum within in the construction industry, particularly in the residential sector has become very popular due to:
-Ultra versatility, used to manufacture gypsum board, spray wall finishes, underlayments, screeds, and patching compounds
-Good fire rating per ASTM E119 for walls, ceilings and partitions
-Lightweight –about ¾ the weight of similar cementitious products for both walls and floors
-Highly resistant to cracking and shrinking
-Superior thermal mass for radiant-heating systems = good heat transfer
-Excellent Impact Insulation Class (IIC) and Sound Transmission Class (STC) sound reduction properties
-Compressive strengths can reach 8,000 psi (55,2 MPa)
-Sustainable –the life cycle lasts for decades by providing environmentally ‘landfill’.  Recycled wallboard improves soil’s workability and holds moisture in the ground to sustain food crops. 

However it is important to note, when setting tile, stone or glass using a cement-based mortar directly over a gypsum underlayment or patch—due to 'chemical incompatibility', it will cause a chemical reaction between the cement-based product and the gypsum known as “ettringite”.   Ettringite (gypsum + water + tricalcium aluminate = ettringite) is formed when gypsum comes in contact with a cement-based product.  These crystallized ettringite salts increase in volume filling the voids of the reactants in the latex-portland cement, as they expand and grow they can adversely effect the integrity of the mortar at the chemical bond line—destroying it.

Does this preclude gypsum as a suitable substrate for flooring installations?  No, the flooring system design just needs to take into account the ‘possibility of incompatibility’ and addressed within the design—typically separating the layers between the cement-based product and the gypsum with a primer and or liquid-rubber waterproofing.

So what are some key factors to keep in mind to ensure a compatible system:
-Select a “system solution” that considers all layers, from substrate to finish floor:
1.) Installation environment: Interior/exterior? exposure to chemical attack? freeze/thaw resistance? thermal growth, movement and deflection? submerged applications?
2.) Type of substrate: Concrete? Gypsum? Plywood? Drywall? Render coat? Cement Backer Unit (CBU)?
3.) Surface preparation requirements: Plumb and flat requirements?  Moisture Vapor Emission Rate in Concrete (MVER)?  Acceptable moisture content in gypsum before installing finished covering? Proper preparation of walls and floors—.imperfections? ‘birdbaths’?
4.) Type of finished covering: Tile, stone, glass? Resilient, VCT, or carpet?  Wood, solid or engineered, bamboo or cork? Cement-based decorative topping?  Epoxy coating?
 -Identify incompatible layers during the design phase, not the installation phase.
 -Keep it simple. Fewer layers mean fewer points of failure.
 -Choose products based on acceptable industry performance requirements versus cutting corners with inferior materials.
 -Maximize installation warranty by using a single manufacturer’s products for a true “system solution.”