Can You Install Rubber Gym Flooring Over Concrete, Wood or Carpet?
Like most flooring products, the best installations come together when the subfloor – the foundation for a floor – is flat, dry and solid. If any of these three are compromised, it will affect how you install your rubber flooring and require some extra steps to get the best results.
The vast majority of rubber flooring installations occur over concrete, wood and carpet. In this article, each of these subfloor options will be reviewed as a foundation for your rubber flooring installation.
Concrete Subfloor
The most ideal subfloor for installing rubber flooring is a flat, smooth concrete surface. The solid construction of concrete offers a permanent, long-lasting foundation for rubber rolls or rubber tiles to be secured to. Concrete also provides the most durability of all subfloors, which is important for protection against damage from heavy equipment or dropped weights in your gym. The thickness of your rubber flooring is another important consideration for protecting concrete. See Choosing Your Rubber Flooring Thickness for more information.
Pitfalls of Concrete Subfloors
Despite concrete being the preferred subfloor for rubber gym flooring, there are several pitfalls that need to be addressed before you invest in your gym floor.
Moisture Problems – When concrete is poured and cured, the water in the concrete mix evaporates and creates microscopic pores throughout the material. These capillary pores allow water, vapor and gases to move through the concrete, which can lead to high humidity, mold and mildew growth.
Moisture in concrete is typically found in subfloors that are located at grade (level with the ground) or below grade (under ground level). Basements and ground-level floors will see the most moisture migration through concrete from the soil. Humidity from the air can also condense on a cooler ground-level floor, creating a damp environment.
Floor levels that are above ground are not in direct contact with the soil and will not absorb this moisture.
However, high humidity environments (not controlled through air conditioning) or condensation from temperature differences between floors can lead to moisture absorption.
Testing concrete for moisture.
Plastic Sheet Test: The easiest, low-tech method is to use a piece of 6mil plastic (24” x 24”) taped to the concrete. The sheet should be sealed on all four edges with a waterproof seam tape. Check the underside of the sheet after 24 hours and 48 hours or longer. If condensation is present (beading) or the concrete appears dark/damp, there is excessive surface moisture. The absence of moisture doesn’t guarantee the entire slab is dry. Moisture can be trapped lower in the concrete.
Calcium Chloride Test: This method is a more accurate test for measuring the rate of moisture vapor emission from the concrete. The concrete surface is prepared by grinding a section to open the pores in the concrete. A pre-weighed dish with calcium chloride tablets under a sealed dome is placed on the concrete. After 72 hours, the dish is re-weighed. The difference in weight indicates the amount of moisture released.
Both tests will confirm the presence (or lack) of moisture in concrete. It is important that the space is acclimated when the tests are performed. If air conditioning will be used routinely in the space or a consistent temperature will be maintained, then the test conditions should be similar to normal use.
Protecting your floor against moisture.
Moisture (Vapor) Barrier: The most economical method for protecting your floor against moisture is the use of a moisture barrier. It is a large polyethylene (plastic) sheet that is spread across the entire concrete surface. Waterproof seam tape is used to join multiple sheets together to create a continuous barrier. Rubber flooring is then installed over the moisture barrier. New home construction may also contain a vapor barrier under the concrete slab to help prevent moisture absorption from the ground.
Moisture Shield Primers and Concrete Sealers: There are multiple concrete sealer products that interact with concrete to help prevent moisture from reaching the surface. Penetrating sealers fill in the pores in concrete to waterproof it from the inside out. Epoxy sealers create an impermeable layer over the concrete to block out moisture. Silicate sealers chemically react with the concrete to create a less porous surface. Moisture primers help reduce vapor emissions and create a strong bond for a topcoat of a sealer.
Without mitigating the effects of moisture in concrete, your rubber gym floor installation can result in some unwanted results.
Mold and mildew growth: Recycled rubber flooring does not absorb moisture and because it is made from synthetic materials, it does not naturally promote mold/mildew growth. Trapped moisture between the concrete and rubber can still develop mold or mildew from other sources of organic matter on the concrete surface (dust, oils, skin cells, etc.). The lack of airflow creates a perfect environment for mold and can lead to musty odors or potential health concerns.
Adhesive failure: Moisture can break down the bonding properties of adhesives and cause rubber gym flooring to lift or become loose. RFS offers Eagle Grip polyurethane adhesive that is waterproof and specifically formulated for rubber flooring installations.
Surface damage: Water vapor can cause the rubber gym flooring to buckle or warp as it pushes against the surface.
Uneven or Damaged Concrete – Concrete subfloors can become uneven and cracked from settling, temperature fluctuations, moisture changes over time, freeze-thaw cycles and heavy loads to name a few. Damaged and uneven concrete does not provide a uniform surface for proper installation of rubber gym flooring. These conditions are typically found in older concrete slabs that have cured over a duration of time and been through multiple cycles of seasonal temperature fluctuations and periods of use. Newer concrete slabs will take more time to naturally acclimate and settle. Let’s look at some options for fixing your damaged concrete in preparation for installing rubber gym flooring.
Self-leveling concrete: One of the most economical DIY solutions for fixing uneven concrete is to use a mix and pour self-leveling compound. Products from Henry, Mapei or Quickrete are easy to use and widely available. These self-levelers are spread across uneven concrete to create a smooth, flat surface.
Self-leveling concrete requires the use of a primer to improve adhesion and to help seal porous concrete. This barrier is necessary to prevent the concrete floor from absorbing the moisture in the self-leveling concrete. A primer also ensures that the self-leveling concrete will dry to a consistent, level surface.
Concrete patch, caulk or fillers: Cracks and chipping in concrete should be filled and cured before using a self-leveling product. Use a patching compound for wide or deep cracks, such as Henry Premixed Patch n’Level Floor Patch & Smoothing Compound. Smaller cracks can be filled with a flexible sealant or a concrete crack filler.
Grinding or Mudjacking: A concrete grinder can be used to smooth down high spots to create a more level surface. For significantly uneven slabs, a slurry can be pumped into holes in the slab to lift it back into place. Major structural issues that involve more complex methods of repair may require a concrete professional to diagnose and fix your concrete.
Uneven concrete with dips, slopes or high spots can create problems with rubber gym floor installations, such as visible seams, ridges, gaps or hollow spots. Although rubber flooring is flexible and will conform to minor imperfections, larger imperfections in the subfloor can lead to lifted edges, poor adhesion and premature wear patterns.
Bulges and ridges: Rubber flooring will follow the contours of the subfloor and create bulges over low spots and ridges over high spots.
Gaps and uneven seams: Uneven concrete can prevent tiles or rolls from lying flush, resulting in gaps that are difficult to clean and tripping hazards.
Lifting and poor adhesion: In areas where the rubber is not in full contact with the concrete, adhesives can fail and cause edges or corners to lift over time.
Premature wear patterns: Stresses from an uneven or damaged floor can cause the rubber flooring to wear out more quickly in high traffic areas or where heavy equipment is placed.
Wood Subfloor
After concrete, a sturdy wooden subfloor can provide an even platform for your rubber gym floor. Whether you are installing over a base-level subfloor like OSB (Oriented Strand Board), plywood, or a floating floor over OSB like engineered hardwood, installing rubber gym flooring can encounter some challenges.
Pitfalls of Wooden Subfloors
The best wooden subfloors are smooth, flat, rigid and dry. OSB/plywood subfloors are common in residential homes and most are above ground level. Similarly, floating wood floors are usually installed over the top of OSB subfloors. Plywood or a finished wood floor can also serve as the “subfloor” for your rubber gym flooring. In either scenario, there are a few pitfalls that could make your rubber flooring installation problematic.
Moisture trapping – Recycled rubber flooring is moisture resistant but can still trap moisture underneath it. The rubber will prevent proper evaporation and potentially lead to mold and subfloor damage.
Subfloor instability – A new floor is only as stable as the layer beneath it. Installing rubber flooring over a floating floor can lead to movement and squeaking as the layers independently expand and contract.
Staining and discoloration – Over time, recycled rubber can leach oils that may stain or discolor the subfloor below. If you are installing rubber tiles or laying rubber rolls with the intent of preserving your floating wooden floor, you will want to use an underlayment barrier between the rubber and your wooden floor.
Adhesive incompatibility – Some adhesives may not be compatible with recycled rubber or the finish on a floating floor. This can lead to poor adhesion and damage to your rubber flooring.
Uneven installation – Imperfections in the wooden subfloor will telegraph through the rubber flooring, creating a poor-looking and unsafe exercise surface.
How to avoid wooden subfloor pitfalls.
Prepare the subfloor: Clean the subfloor completely to remove dust, dirt, or debris. Repair any cracks, gaps or unevenness to ensure a solid, flat base.
Address moisture issues: Mitigate existing moisture issues properly. Use dehumidifiers or air conditioning to acclimate the space. Test for moisture in your wooden subfloor. If moisture persists in the wood over time, a vapor barrier or waterproof coating may be necessary to keep moisture away from your rubber gym floor. Proper ventilation and consistent humidity control will be crucial long-term solutions to prevent mold and mildew growth.
Remove floating floor: If your existing floating floor (hardwood, laminate, etc.) is unstable as a foundation for your rubber gym flooring, then removing the floating floor may be your only solution for a stable base.
Use compatible underlayment: To protect your existing floating floor from potential staining and discoloration, a suitable underlayment should be used over the wooden floating floor. A felt moisture resistant flooring underlayment such as QuietWalk Plus can be used to protect your wood floor from interacting with the rubber gym floor.
Choose the correct adhesive: If you choose to permanently adhere your rubber flooring to an existing floating floor, RFS recommends using Eagle Grip polyurethane adhesive. The adhesive formula is made for rubber flooring installations and compatible with a number of subfloors. Use a loose laid or double-sided adhesive tape method of installation if you look to preserve your floating floor for future use.
Use a self-leveling compound: Uneven wooden subfloors can be sanded down for minor high spots or a fiber reinforced self-leveling underlayment for wood subfloors, like LevelQuick Advance can be used. A primer should be used on the OSB before using the self-leveler.
Wooden subfloors can create similar headaches as concrete subfloors when it comes to installing rubber gym flooring. Attacking each issue head-on will ensure your rubber floor provides maximum durability, longevity and safety in your exercise environment.
Moisture build-up: Rubber gym flooring can trap moisture between itself and the wooden subfloor. This build-up of moisture can saturate the wood and cause mold and mildew growth which will feed off of the organic wood and eventually rot. Likewise, humidity and condensation can create moisture problems if the space is not climate controlled.
Discoloration: Your hardwood flooring can potentially be discolored or stained from direct contact with recycled rubber flooring. If you want to protect the surface appeal of your hardwood floor, a temporary barrier can be used under the gym flooring.
Uneven subfloor: An uneven subfloor can cause pressure points on the gym flooring, which can lead to premature wear and adhesive failure. Gaps between tiles or rolls can form to create tripping hazards.
Adhesive issues: Inadequate or uneven adhesive application can cause parts of the flooring to lift or fail.
Improper preparation: The wooden subfloor should be smooth, flat and clean before installing your rubber flooring. Failure to properly prepare the surface is a common mistake that can lead to high spots, raised seams, instability and visible wear patterns in the rubber.
Carpet Subfloor
Perhaps you’re looking to turn an unused room into a home gym but it has carpeting on the floor and you’re unsure if rubber flooring can be used over the top of the carpet. The type of carpet you have and the type of rubber gym flooring you want to install will help determine the best installation method for your space. Let’s dive in to carpet as a subfloor.
Pitfalls of Carpet as a Subfloor
Carpeting is the least solid subfloor option when comparing it to concrete or wood. In addition, carpet is made in three primary thicknesses. Low-pile (1/4” or less), medium-pile (1/4” to 1/2”) and high-pile or “plush” (over 1/2”). Each thickness is tailored to specific rooms in a residence or business.
Low-pile Carpet: Used in high-traffic areas like hallways, commercial spaces and pet or active rooms with high-wear or utility needs. Berber carpet has a tight, looped construction with short fibers that makes it durable and resistant to wear and tear.
Medium-pile Carpet: Commonly used in living rooms and family rooms, which require a mix of comfort and durability for everyday use.
High-pile Carpet: Used in bedrooms and other areas where a thick, plush feel is desired.
Instability – This is the biggest problem with carpet as a subfloor. Carpet is compressible and uneven, which makes it an unstable base for rubber flooring. Rubber tiles can separate or rolls can lift and ripple during exercise.
Safety risks – An unstable subfloor increases the risk of injury when working out on a wobbly surface or when lifting weights. Uneven seams between rubber flooring can also create tripping hazards.
Uneven compression – Heavy equipment and repeated movements will flatten the carpet and pad unevenly under the rubber and lead to a dips and bumps in appearance.
Damage to flooring and equipment – The constant shifting and unevenness of the rubber flooring over carpet can increase wear and tear on the flooring and your equipment. The carpet can also become damaged beyond repair.
Poor aesthetic – The shifting and unevenness of the rubber flooring can create an unappealing floor.
Solutions for installing rubber flooring over carpet.
The best practice would be to remove the carpeting and install the rubber flooring directly over the rigid subfloor (concrete or wood). If you do not want to remove the carpet or cannot (e.g., rental property), there are a few options to consider for installing rubber flooring.
Plywood over carpet: If your carpet is a medium- or high-pile variety, then the only option is to create a stable “subfloor” over the top of the carpet using plywood. The plywood should be thick enough to provide an even surface for supporting your equipment and your level of exercise intensity. 3/4” thick plywood has the rigidity to span 4’ x 8’ sections and is the most durable.
In addition to the plywood, a 6 mil plastic moisture barrier should be used over the plywood. This is needed to keep any residual moisture absorbed by the plywood, or carpet, contained under the plastic so it can naturally evaporate. If moisture is trapped between the plywood and the rubber flooring, mold and mildew will grow on the plywood and potentially lead to rotting wood and odors.
Keep in mind that by creating a new platform over your carpet and adding rubber flooring, it will raise the overall height of your finished floor. This will affect doors from properly opening without modifying the door height at the threshold. The molding used around the perimeter of your room may also need to be removed and re-installed.
Install rubber directly over carpet: This option is only recommended if your carpet is a low-pile variety like Berber or high wear commercial carpet tiles. Low-pile carpet should feel solid and sturdy when you walk on it.
If you want to keep your carpet looking its best, a plastic moisture barrier should be installed directly over the top of the carpet before you add rubber flooring. Overlap the seams of the plastic by 6 to 8” and use a waterproof seam tape to create one large plastic barrier. The plastic will help protect the carpet from rubber marks and any liquid that may run through the seams when mopping the rubber surface.
If you are not concerned about keeping the existing low-pile carpet in its current condition, you can install rubber flooring directly over the carpet. Depending on the subfloor under the carpet and the location of the room, the original carpet may already have a moisture-resistant pad or vapor barrier under it. Recycled rubber flooring is made from synthetic tire rubber and it could lead to discoloration of the carpet over time and leave rubber marks from continual use and contact wear.
For most small to medium-size rooms, RFS recommends 24” x 24” 9mm rubber tiles. These tiles will provide the stability over carpet and have enough depth for the tiles to stay locked together. Thinner tiles will lead to more movement and have less mass to stay interlocked.
Rubber tiles can be loose laid or a double-sided adhesive tape can be used to hold the tile edges in place.
For larger spaces, it would be more cost effective to remove the carpet entirely and use RFS 5-foot wide 6mm rubber rolls. Rubber rolls will install the best on a solid subfloor and are more durable when permanently installed using a polyurethane adhesive.
Versatility of Recycled Rubber for Your Gym Flooring
Recycled rubber flooring is among the most versatile floor coverings available for your gym. It offers excellent durability and flexibility for many different installation challenges. In addition to top-notch performance and safety as a floor covering, recycled rubber rolls, rubber tiles and rubber mats are economical and relatively simple to install yourself.
RFS is committed to supplying the highest-quality, American-made rubber flooring at affordable prices.
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