levelers are typically used to create a flat, smooth
surface on an existing substrate. The name can be deceiving
since self-levelers do not level a surface by default.
While it is possible to achieve true level with a self-leveling
product, it requires pouring with the use of pins set
as a benchmark to achieve a predetermined finish floor
height. The normal intent of a self-leveler is to raise
the height of the surface and provide a smooth and
uniform surface finish.
There are various leveling products available, but they generally fall into
two basic categories. Underlayments are levelers utilized underneath a finished
floor and serve to create the proper height, flatness, and/or bonding conditions
for subsequent floor coverings. Overlayments are levelers utilized as finished
floor surfaces. Most overlayments can be integrally colored, stained, coated,
or clear sealed depending on the end-user’s preference and are applied
with a squeegee.
The type of product used will be determined by the unique requirements of the
individual project. Factors such as dry time, compressive or flexural strength,
and minimum/maximum application thickness will all be contributing factors
in the decision making process.
Most finished floor coverings have specific requirements for underlayments
that will be installed underneath their products. If used as a wear surface,
most overlayments require a sealer or coating of some type. This would normally
be a Urethane Topcoat. As with most floor attached floor systems, self-levelers
have moisture and surface preparation requirements that must be met prior to
installation. Additionally, substrates with excessive moisture vapor transmission
levels may require the application of a moisture control sealer underneath
the self-leveler. There are no moisture control systems on the market that
can be installed over self-levelers.
Once testing and compliance with product and floor covering manufacturer requirements
have been met, the installation can begin. Most self-levelers require some
type of surface preparation to insure that the surface is clean, sound, and
free of bond breakers (consult individual product manufacturers for specific
guidelines). Different products have benefits and disadvantages that will make
them the appropriate selection in specific situations.
Self-leveling underlayments are a quick an effective method for adjusting the
height of an existing floor surface. Since the product is designed to flow
and seek its own level, only minimal labor is required to achieve a smooth
and flat surface.
Depending on the type of cement technology the product utilizes, subsequent
floor coverings can be installed within 24 hours of application. High hydrating
cements (also called self-drying) provide the most rapid turnaround while gypsum
based products take the longest (7-10 days typically) to dry.
With either product, moisture (water used to mix) must be completely absent
from the underlayment prior to floor covering installation. The high hydrating
products incorporate technology that rapidly consumes the mix water into the
accelerated hydration process. This yields quicker early strength properties
and shortened dry (cure) times. Gypsum concrete technology has made substantial
improvements recently and has been approved for use with most finished floor
goods. Although the products do not dry or gain strength as rapidly as high
hydrating products, they are less costly. When quick turnaround is not a priority,
newer generation gypsum based levelers can provide value engineering opportunities.
Self-leveling overlayments are similar to underlayments in application and
form. The main difference is that overlayments are designed for use as a wear
surface when sealed. Increased compressive strengths allow overlayments to
serve as finished floor surfaces. Typically, overlayments are of 100% solids
in formulation and are available in grey or white. Color can be added while
in the plastic state or stains or dyes can be applied topically on the cured
surface. Pigmented or clear sealers can be employed to protect the surface
from abrasion or contaminant penetration.
Self-leveling cements are susceptible to moisture and require a film forming
sealer to provide top-side protection. Substrates with excessive moisture vapor
transmission levels may require the application of a moisture control sealer
underneath the self-leveler. Overlayments provide designers with multiple finish
options which include; monolithic, stained, integrally colored, saw-cut, multi-color,
or dyed finishes which are smooth and flat. Generally 30 – 45 mills is
the minimum thickness required for an overlayment to be utilized as a finished
Benefits and Limitations
All floor systems have specific requirements for successful installation. It
is important to verify that the product manufacturer’s written guidelines
govern the installation process. Adherence to instructions is critical for
maintaining the manufacturers’ warranty; neglecting them will almost
certainly void the warranty. Proper product selection based on end use, appropriate
scheduling with other trades, testing and compliance to product moisture requirements,
and installation per industry Best Practice methods are the keys to a quality
Self-levelers are excellent for creating a uniform flooring surface. The design
of the product facilitates the consistent uniformity of surface height and
finish. However, the self-healing and flow properties of the material preclude
self-levelers from being used on sloped surfaces. Additionally, almost all
self-levelers are rated for interior use only.
Regular maintenance is vital to the long term welfare of all floors. There
is no surface available that remains in optimum condition without regular cleaning
and maintenance. The floor is subjected to the most abuse in any normal business.
Keeping the floor in good condition takes a little forethought and consistent
effort. The first key to floor maintenance is preventing as much soil, debris,
and potential damaging agents from being introduced to the environment in the
Interior and exterior walk-off mats can minimize the amount of sand, water,
and foreign matter that are tracked onto the floor. Limiting contaminants will
simplify the maintenance process. Since the self-leveler is beneath the floor
system, the maintenance program for underlayments is determined by the finished
floor covering installed. Overlayment maintenance is determined by the requirements
of the coating or sealer that is applied as the final finish.