How to Clean and Seal Grout: A Two-Step Guide to Lasting Results

Grout starts out looking fresh and uniform, but over time it absorbs dirt, mold, mildew, and stains that make even beautiful tile look neglected. Cleaning alone helps temporarily, but without sealing, the grout will absorb new contaminants just as quickly. The correct approach is a two-step process: deep clean the grout first, then seal it to protect against future staining.

This guide covers both steps in detail, including the best cleaning methods, the right type of sealer, application techniques, and a maintenance schedule to keep your grout looking great for years.

Step 1: Cleaning the Grout

Before you can seal grout, it must be thoroughly clean. Sealing over dirty grout simply locks in the discoloration. Take the time to clean it properly, even if it takes more than one pass.

Start with the Gentlest Method

Always start with the mildest cleaning approach and escalate only if needed. Aggressive chemicals can damage grout, etch tile surfaces, and create more problems than they solve.

Method 1: Warm Water and a Stiff Brush

For lightly soiled grout, warm water and a stiff nylon brush may be all you need. Spray warm water onto the grout lines, let it sit for a minute, then scrub with the brush in a circular motion. Wipe away the loosened dirt with a damp cloth. This works for routine maintenance but will not remove deep stains or mold.

Method 2: Oxygen Bleach (Recommended for Most Situations)

Oxygen bleach (sodium percarbonate, sold as OxiClean, Zep Oxy Cleaner, or similar products) is the best all-around grout cleaner for most homeowners. It is non-toxic, color-safe, and effective against dirt, grease, mold, and mildew without the harshness of chlorine bleach.

To use oxygen bleach on grout:

1. Mix the powder with warm water according to the product label, typically one scoop per gallon.
2. Pour or spray the solution generously onto the grout lines.
3. Let it sit for 15 to 30 minutes. The oxygen bubbles penetrate the porous grout and lift embedded dirt and stains to the surface.
4. Scrub with a stiff nylon brush. For large areas, a grout brush attachment on a drill saves enormous time and effort.
5. Rinse thoroughly with clean water and wipe dry.
6. Repeat if necessary for heavily stained areas.

Oxygen bleach is safe for colored grout and will not discolor natural stone tiles. However, always test on a small area first if you are working with sensitive materials.

Method 3: Steam Cleaning

A steam cleaner with a narrow nozzle attachment is highly effective for grout cleaning. The superheated steam (usually 200 to 300 degrees Fahrenheit) kills mold and bacteria, dissolves grease and dirt, and penetrates deep into the grout pores without any chemicals at all.

Steam cleaning is the preferred method for people who want to avoid chemicals entirely. It works exceptionally well on shower and bathroom grout where soap scum and mildew are the primary contaminants. The main drawback is the cost of a quality steam cleaner ($100 to $300 for a unit with the right attachments), though rental options are available.

When using steam on grout, hold the nozzle close to the grout line and move slowly, allowing the steam to penetrate. Follow immediately with a microfiber cloth to wipe away the loosened dirt before it resettles.

Method 4: Enzymatic Cleaners

Enzymatic cleaners use biological enzymes to break down organic stains, mold, and mildew at a molecular level. They are particularly effective for grout in kitchens (food grease and spills) and bathrooms (body oils, soap scum, and mold). Products like Zymot or Biokleen contain specific enzymes that target different types of organic matter.

Enzymatic cleaners work more slowly than chemical cleaners. Apply generously, let them sit for 30 to 60 minutes (some products recommend several hours), then scrub and rinse. The advantage is that they continue working over time and are completely safe for grout, tile, natural stone, and the environment.

What to Avoid When Cleaning Grout

• Chlorine bleach – While it whitens grout temporarily, chlorine bleach can break down the grout matrix over time, especially with repeated use. It also produces harmful fumes in enclosed spaces like bathrooms.
• Acidic cleaners on cement grout – Vinegar, lemon juice, and acid-based cleaners dissolve cement-based grout. Small amounts occasionally may not cause visible damage, but regular use erodes the grout surface.
• Wire brushes or metal scrapers – These scratch tile glazes and can gouge grout lines, creating channels where water and dirt accumulate.
• Mixing cleaning products – Never combine bleach with ammonia, vinegar with bleach, or hydrogen peroxide with vinegar. These combinations produce toxic gases.

Step 2: Sealing the Grout

Once the grout is thoroughly clean and completely dry (wait at least 48 hours after cleaning), it is time to seal. Sealing fills the microscopic pores in the grout, creating a barrier against water, oil, and stains.

Choosing the Right Sealer

Penetrating (Impregnating) Sealers

Penetrating sealers soak into the grout and form a protective barrier below the surface. They do not change the appearance or color of the grout, which makes them the preferred choice for most applications. Penetrating sealers allow the grout to breathe (water vapor can still escape), which is important in wet areas like showers where moisture needs to evaporate from behind the tile.

These sealers come in two main formulations:

• Water-based – Lower VOCs, easier cleanup, slightly shorter lifespan. Good for indoor use.
• Solvent-based – Deeper penetration, longer protection, stronger smell during application. Better for high-traffic or exterior applications.

Topical (Membrane-Forming) Sealers

Topical sealers sit on top of the grout surface, forming a visible film. They can add a slight sheen or color enhancement. However, they can peel, wear unevenly, and trap moisture beneath the surface. Topical sealers are generally not recommended for showers or wet areas.

For most homeowners, a penetrating sealer is the right choice. It provides excellent protection without changing the grout’s appearance or creating maintenance issues down the road.

Tools You Will Need

• Grout sealer (penetrating type recommended)
• Sealer applicator bottle with a wheel tip, or a small foam brush
• Clean, dry microfiber cloths
• Painter’s tape (optional, for protecting adjacent surfaces)
• Knee pads (you will be on the floor for a while)

Sealer Application: Step by Step

1. Ensure the grout is completely dry. Wait at least 48 hours after cleaning, or longer in humid conditions. Any moisture in the grout will prevent the sealer from penetrating properly.
2. Work in small sections. Apply sealer to a 3 to 4 square foot area at a time. This prevents the sealer from drying on the tile surface before you can wipe it off.
3. Apply sealer directly to the grout lines. Use an applicator bottle with a roller wheel tip for precision. Roll the applicator along each grout line, depositing a thin, even layer of sealer. If using a foam brush, apply carefully to minimize getting sealer on the tile surface.
4. Let the sealer penetrate. Allow the sealer to soak into the grout for 5 to 10 minutes (follow the specific product instructions). You should see the sealer absorb into the grout. If it puddles on top, the grout may already be sealed or the sealer needs more time.
5. Wipe off excess. Use a dry microfiber cloth to wipe off any sealer that remains on the tile surface or pooled on top of the grout. Sealer left on the tile can leave a hazy residue that is difficult to remove once cured.
6. Apply a second coat. Most manufacturers recommend two coats for optimal protection. Wait the recommended time between coats (usually 30 minutes to 2 hours) before applying the second coat using the same technique.
7. Allow full cure. Most penetrating sealers reach full cure in 24 to 48 hours. During this time, keep the area dry. No mopping, no shower use, no wet feet on the floor.

Special Considerations for Showers

Shower grout requires extra attention because it is constantly exposed to water, soap, and humidity. Use a penetrating sealer specifically rated for wet areas. Apply three coats instead of two for additional protection. Pay special attention to the grout around the shower floor, corners, and any horizontal surfaces where water pools.

Even with sealing, shower grout benefits from daily maintenance. After each shower, squeegee the walls and leave the bathroom fan running for at least 20 minutes to reduce moisture and prevent mold growth.

Mistakes to Avoid

• Sealing dirty grout – The sealer locks in stains and discoloration permanently. Always clean first.
• Sealing wet grout – Moisture prevents proper sealer penetration. Wait until the grout is bone dry.
• Not wiping excess sealer off tiles – Dried sealer on tile surfaces creates a hazy film that requires special removers to clean.
• Applying too much sealer at once – Multiple thin coats are far more effective than one heavy coat, which may not penetrate properly.
• Forgetting to reseal on schedule – Sealers wear off over time and need periodic reapplication.
• Using sealer on epoxy grout – Epoxy grout is non-porous and does not need sealing. Applying sealer to epoxy grout is a waste and can leave a residue.

Resealing Schedule

Grout sealer does not last forever. Foot traffic, cleaning products, and water exposure gradually wear it away. Here is a general resealing timeline:

• Kitchen floors – Reseal every 1 to 2 years. Heavy foot traffic and frequent mopping wear the sealer faster.
• Bathroom floors – Reseal every 1 to 2 years.
• Shower walls and floors – Reseal every 6 to 12 months. Constant water exposure depletes the sealer quickly.
• Entryways and mudrooms – Reseal every 1 to 2 years due to heavy traffic and exposure to tracked-in moisture and debris.
• Low-traffic areas – Reseal every 2 to 3 years.

To test whether your grout needs resealing, drop a few drops of water on a grout line. If the water beads up on the surface, the sealer is still working. If the water soaks into the grout and darkens it, it is time to reseal.

Products Worth Considering

The grout care market offers many options. Here are categories and what to look for:

• Cleaning – Oxygen bleach powders (OxiClean Versatile, Zep Oxy Cleaner) are inexpensive and effective. For spray-on convenience, look for grout-specific cleaners from Aqua Mix or Custom Building Products.
• Sealing – Aqua Mix Sealer’s Choice Gold, Miracle Sealants 511 Impregnator, and Tuff Duck Granite Grout and Marble Sealer are all well-reviewed penetrating sealers. For showers, 511 Impregnator is particularly popular due to its proven track record in wet environments.
• Applicators – The Miracle Sealants Applicator Bottle with Roller Wheel Tip is an inexpensive tool that makes precise sealer application much easier.

Final Thoughts

Cleaning and sealing grout is not glamorous work, but it makes a dramatic difference in the appearance and longevity of your tile floors, walls, and showers. The process is straightforward: clean thoroughly with oxygen bleach or steam, let the grout dry completely, then apply two to three coats of a penetrating sealer. Follow the resealing schedule and your grout will resist stains, mold, and discoloration for years.

For more on caring for tile floors, see our comprehensive tile flooring guide.