Hardwood is often used in flooring because it’s durable and looks great. But it’s a porous, organic material, which means that it can develop discoloration and stains that detract from its appearance. In this article, we go over some of the causes of hardwood flooring discoloration and what to do about it.

UV Exposure

Wood is photosensitive. When it’s exposed to UV light, it can develop discoloration. In fact, about 40% of the fading that occurs on surfaces inside your home is due to UV exposure. Light damage darkens some types of wood and fades others.

If you have rugs or furniture on your floors, the sun will discolor the visible wood, leaving behind silhouettes in the shape of your decor. 

What You Can Do About It

If the glass on your windows doesn’t contain UV protection, it only blocks about 25% of harmful rays. However, installing UV-blocking window film allows the glass to block 99.9% of the sun’s light. 

Another option is to add window treatments, such as blinds and drapes. Keep these closed when the sun is streaming into the room to prevent floor damage. Exterior awnings, pergolas or porch roofs also create shade, protecting your flooring and furniture.

You might be tempted to place an area rug on spots where the sun beats down. That will protect the wood beneath it, but the area around it can become discolored. The best way to manage this is to move around your furniture and rugs regularly. By doing this, you’ll expose the floor to sunlight in a more consistent fashion. This might be the best option if you use hardwood flooring in a sunroom, for example.


We already mentioned how rugs can block UV rays, creating discoloration around them. However, rugs that are made from certain materials can chemically alter the color of hardwood flooring.

If you don’t use a rug pad, the dye on the fibers can transfer to the flooring beneath it. Pigments that aren’t colorfast can quickly stain the hardwood if you spill something on the rug.

But using the wrong rug pad can also cause hardwood discoloration. Pads that contain phthalates, which are found in some plastics, can dissolve the finish on wood flooring over time. Those that use adhesive to prevent them from sliding can stick to your floors, creating dull spots or removing the finish.

What You Can Do About It

Always use a high-quality rug pad. Felt and rubber are natural materials that don’t interact with hardwood flooring’s color or finish. They won’t stick to the floors, either.

Type of Wood

Different species of wood have qualities that make them more or less susceptible to hardwood flooring discolorations.

Soft wood, such as pine and poplar, are more absorbent than hardwood. These soak up spills and moisture more quickly than oak, maple or hickory if they’re not finished properly. 

Many tropical woods, such as American cherry, Brazilian cherry and tigerwood, darken when they’re exposed to light. This reaction happens fairly quickly. Oak, hickory and maple, on the other hand, fade in the presence of UV rays. However, this takes place rather slowly.

Some types of wood have natural deposits of minerals, such as limestone, gypsum and potassium. These can cause gray, purple, greenish or blue streaks in the grain. These are natural variations that cannot be removed. However, they will be evident in the planks when you purchase them. 

Tannic acid is a compound found in darker woods, such as walnut, oak and mahogany. Because it’s water-soluble, tannin can get lifted to the surface when you coat the flooring with a water-based sealer.

Finally, some types of wood develop sap stains. These hardwood flooring discolorations come from a fungus that grows on the wood before it is dried. If you’re using kiln-treated wood, you shouldn’t see the sap stain grow. It isn’t mold, and it doesn’t interfere with the structure and strength of the wood. Pine can also begin to emit sap over time. This is often yellow or brown and sticky. 

What You Can Do About It

If you’re installing hardwood floors in a particularly sunny room, consider using a material that reacts slowly to UV light. You can also use UV-protective finishes to prevent the wood from darkening, fading or absorbing stains. 

Natural sap stains are nothing to worry about. However, you can avoid using planks with these stains if you don’t like them. To prevent pine flooring from leaching sap or dark flooring from leaching tannin, use an appropriate sealer

Finishes and Colorants

Speaking of hardwood flooring finishes, have you ever noticed that polyurethane yellows over time? Water-based varnishes and sealants are less likely to darken or yellow than oil-based products. The dyes in pigmented stains are also vulnerable to fading from light exposure.

What You Can Do About It

Choose the right stain for your indoor environment. You might not want to use a bold, dramatic color in a room that gets a great deal of sunlight. You can also use a UV-blocking sealant over the stain to protect it.

Water Damage

Water damage is a common reason for hardwood flooring discolorations. Lingering moisture creates the perfect environment for mold and mildew growth. If these fungi develop on the wood, they can create dark black, brown, gray or green spots or streaks. 

Moisture can also affect the finish. It may dull the sheen or lighten the color of the wood. If the spilled liquid has a color, such as wine, it may seep into cracks and pores, creating a more permanent stain.

What You Can Do About It

Wipe spills on hardwood floors immediately to reduce the risk of water damage. In areas where moisture or spills are likely, protect the flooring. Avoid placing flower pots directly on hardwood floors. Don’t let damp towels sit on the surface. 

If you notice moisture stains but haven’t spilled anything in the area, look for signs of a water leak. Hidden moisture beneath hardwood floors can create shadows between the planks, which are visible from above. 

How to Get Rid of Hardwood Flooring Discolorations

The tips above will help you prevent hardwood flooring discolorations. But if your floor is already stained or faded, you might wonder if there is anything you can do about it now.

Addressing the source of the stain is important. It tells you how deep the discoloration goes and gives you clues about how to eliminate it. For example, surface stains can often be faded with an appropriate cleaning solution. 

You might want to avoid bleach, which can create a dramatic contrast between the affected and surrounding areas. However, you can try cleaning the stain with a vinegar-and-water solution or a paste of baking soda and water. Hydrogen peroxide may also be effective on common stains.

Oxalic acid is often used to remove chemical and water stains from wood. However, this is a harsh product and should be used with caution. Any time you use new cleaning products on hardwood floors, test the chemical in an inconspicuous area first.

If the stains are too deep to clean off, you’ll need to sand and refinish the floors. You may be able to limit the refinishing to the area with the stain. However, for excessively stained flooring, a complete refinishing job is usually necessary. If the boards are damaged, replace them entirely.