The strength of a flooring system is one of the most important factors of a building’s structural integrity. The purpose of the substrate or subfloor is to evenly distribute the weight of everything in a room across the floor joists to maintain balance and provide support. It’s the flooring system that is responsible for carrying the weight of the walls, roof, furniture and people inside.

The consequences of a poorly structured flooring system can not only affect how floor coverings perform, but also the soundness of the building. Cracks may develop from substrate movement, the subfloor can sag and become squeaky, and the structure may no longer be level. This can lead to millions of dollars in damage for commercial properties and extensive repairs that could have been avoided with proper substrate and subfloor preparation.

Ensure a Successful Flooring Installation with Proper Preparation

The quality of the substrate determines the quality of the finished flooring. If the substrate is in poor condition, whether that be not flat enough, dry enough or properly cleaned, the finished flooring performance will be compromised and a complete reinstallation or costly repairs may have to take place.

It is important for installers to consult the manufacturers of products they wish to use prior to installation as surface preparation requirements and methods vary depending on the type of substrate, subfloor, underlayment and floor covering specified. For example, if applying floor finishes over concrete substrates, some floor coverings require a light grind or shot blast to a specific concrete surface profile, while others require a more aggressive mechanical surface preparation in order to achieve a tenacious bond. In addition, slab moisture conditions such as relative humidity (RH), moisture vapor emission rates (MVER) and the level of alkalinity (pH), must be taken into consideration and measured in order to properly prepare a concrete substrate for further treatment and ensure a successful flooring installation.

When using self-leveling products for substrate preparation, installers should also address moving joints and cracks present in the substrate. If not addressed and repaired, moving joints and cracks can transfer up and cause cracks in the finish. To allow for natural building movement against restraining surfaces, it’s also recommended that installers evaluate and isolate the area around walls, columns, penetrations and other building elements where movement may be anticipated.

Commonly Used Substrates

Although there are many types of substrates, plywood and concrete slabs are the most commonly used.

Plywood is made by layering fabricated sheets of wood veneer that are bonded together with special adhesives under heat and pressure. Because these layers are cross-laminated and layered, plywood is incredibly strong and not susceptible to the expansion and contraction that hardwood is. If plywood is chosen for use, installers are recommended to apply subfloor adhesive to the top of the floor joists to prevent the plywood from moving around and squeaking. Depending on the specified flooring finish, the appropriate type and thickness of the required underlayment then follows.

Concrete slabs are typically 4” to 6” (101mm to 152mm) thick. Because these slabs can take a few months to fully dry out, installers will need to test the slabs to ensure the condition of the floor is acceptable to receive the finished flooring. One of the most appealing aspects of a concrete substrate is that the existing floor surface can often be removed without complete damage to the concrete when building owners are interested in remodeling.

Added Protection

Although the benefits often remain underappreciated and undervalued, many individuals in the flooring industry consider the use of membranes and other flooring underlayments types, such as self-leveling underlayments and waterproofing membranes, to be key components of lasting flooring installations. Choosing the right membrane or underlayment provides protection from water intrusion, damages, cracking and provides sound reduction properties. Additionally, these products help to present a better overall surface to adhere the finished flooring.

The addition of an appropriate underlayment may mean the difference between a three to five-year installation and a permanent, durable lifetime installation.