When you think of cork, you probably picture the soft stopper that comes in wine bottles. Many people assume that cork flooring isn’t a good match for water because of its flexibility. But that cork protects and preserves liquids in wine bottles, and it also has water-resistant properties when it’s used on floors.

Understanding Cork

Cork is a type of wood that comes from cork oak trees. These plants are native to the Mediterranean region and have special adaptations for using water efficiently. In areas where this tree grows naturally, winters are wet and summers are dry. The plant’s outermost layer of bark grows as a grayish, nubbly surface. It develops over time and keeps the tree hydrated during the dry season.

This is the portion of the tree that is harvested for cork flooring. Its sponge-like structure contains air pockets that create a bouncy, pliable feel. But although cork has a spongy texture, it doesn’t soak up water. This flooring material contains suberin, a waxy substance that resists moisture.

Water Absorption of Cork vs Hardwood

Hardwoods seem like they would be relatively impenetrable by water. Those that fall at the high end of the Janka hardness scale are more water resistant than softer woods. However, wood is largely porous. The open cells in hardwood soak up moisture. You can prevent this by sealing the wood appropriately. But in its natural form, hardwood is not the best flooring option for extremely damp areas, such as basements and bathrooms.

Although more than 50% of cork is air, the material doesn’t absorb water like hardwood does. The suberin that coats the honeycomb-like walls prevents liquids from entering the open areas. This substance makes the cork hydrophobic, which means that it repels water.

In contrast, hardwood is hygroscopic, which means that it absorbs moisture from the air. The more humidity that there is in the environment, the more the hardwood soaks it in.

If you soaked a cork block in water for 48 hours, its mass would increase by 3%. That’s because it’s not completely waterproof. It does have hygroscopic properties, but those are moderated by the hydrophobic qualities.

If you soaked a block of hardwood in water for 48 hours, its mass and weight would increase by much more than that. Some types of wood can absorb more than their weight in water.

Is Cork Flooring Good for Bathrooms and Kitchens?

Cork is an excellent material for kitchen and bathroom floors. It can be used as a surface layer or as an underlayment.

Cork’s limited water absorbency makes it a deterrent to mold and mildew. It isn’t susceptible to rot, making it ideal for areas that are prone to pest infestations and flooding. Another reason that cork flooring is practical in kitchens and bathrooms is that it has a naturally non-slip surface. It’s an ideal option for indoor/outdoor rooms and sunrooms.

You should avoid using flooring in rooms that are always damp, such as saunas and pool rooms. Prolonged contact with moisture will eventually cause the cork to swell.

The type of cork flooring that you use influences its susceptibility to moisture damage, though. Cork tiles, planks, rolls and sheets are made by grinding the wood into small particles. Then, the manufacturer binds those granules together with an adhesive. Some manufacturers create pure agglomerated cork, which involves pressing pieces of the material into a mold and activating the natural resins under high heat.

Many cork tiles and planks have several layers. Although the top layer may be made of agglomerated cork, the other layers often contain medium or high-density fiberboard. This material is similar to the substrate on laminate flooring. It’s more absorbent than cork and may be susceptible to water damage.

The process that the cork undergoes affects its water resistance. Check with the manufacturer to determine if a particular product is appropriate for use in a damp environment. The most waterproof kinds of cork flooring are made with non-absorbent materials and techniques.

Can You Waterproof a Cork Floor by Sealing It?

Cork flooring is usually factory finished with a water-resistant coating. Some manufacturers recommend re-sealing the material every so often.

If your floors have a polyurethane sealant, you should reapply it every five to seven years. Cork floors with natural wax sealant should be refinished every 6 to 12 months. Acrylic and oil-based urethane sealants are much more popular than wax nowadays. They last longer and require less upkeep. Therefore, some homeowners strip the wax from existing cork floors and apply a polyurethane top coat.

Applying the top coat over seams in the flooring prevents moisture from seeping into the gaps. It also protects the floor from wear and tear by preventing dirt particles from settling into the spaces. Your flooring will stay waterproof much longer if you avoid grinding abrasive grains, such as sand, into the material.

Protecting the Surface

Even though cork is naturally water resistant, it gets some support from the top coat. Enhance the waterproof nature of your cork floors by treating them gently.

Some tips for reducing wear and tear on cork flooring include the following:

  • Replace casters on furniture with wide, rubber ones.
  • Place breathable rugs or mats at sinks and entryways.
  • Avoid using rubber-based rug pads.
  • Sweep abrasive particles off of the flooring regularly.
  • Inspect the floor for gouges that penetrate the finish or top layer.
  • Clean up liquids immediately.
  • Avoid dragging heavy items, including chairs, across the floor.
  • Wear soft-soled shoes.
  • Keep indoor temperatures and humidity levels steady.

Factoring in the Installation Method

The installation method also makes a difference in the water resistance of a cork floor. If you use adhesive tiles, make sure that you use the right type of adhesives. Solvent-based glues will dissolve water-based binders. Add a moisture barrier beneath cork flooring in moisture-prone areas, such as basements and sunrooms.

In some cases, you can lay down a subfloor that includes adequate moisture protection. Glue cork tiles directly to this material. You can also install a floating floor with a moisture barrier over concrete slabs.

A reputable professional will install your cork flooring using the most effective methods. Let them know if the flooring will be exposed to high humidity. They will help you select the best products and techniques to prioritize the waterproof qualities of your new floors.

Look for a licensed and insured installer, and learn about their guarantees. The manufacturer will also offer guidelines for proper installation and maintenance of cork flooring.