How to Seal and Protect Grout

sealing grout

By Bill Griffin

Applying a penetrating sealer to grout looks like a simple matter, but the closer you look, the more complex it becomes. There are certain things you need to know before you start the job of sealing grout.

What you are generally dealing with is porcelain or ceramic; however, sealers can also be applied to quarry, terracotta, and Saltillo tile. Penetrating sealer is applied primarily to protect the grout that is between tile—not the tile itself. There are two basic types of grout: Cementitious and epoxy. We primarily seal cementitious grout. Penetrating sealer protects grout against staining and moisture penetration, not abrasive wear.

What is the condition of the clay tile and grout?

If the grout is soft, pitted, powdering, cracked, or missing, or if the tile is broken, cracked, or loose, to avoid further damage and possible claims, repairs should be made before proceeding with cleaning or applying a sealer. Sealer is also beneficial on textured, rough, worn, damaged, cracked, antiqued, and tumbled tile surfaces.

It is standard practice that clay tile and its surrounding grout should be thoroughly cleaned before sealer is applied. Most professional cleaners use an alkaline cleaner or stripper and a 175-rpm rotary floor machine with a brush attachment versus a synthetic pad to loosen soil and stains. Don’t forget to allow 10–15 minutes dwell time before you use the floor machine to scrub or strip the floor. Follow this by vacuum removal of the cleaning solution.

Then, apply a rinse or two, and allow 12–24 hours dry time before applying the sealer. A thoroughly dry floor allows the sealer to sink as deeply as possible into the grout, which gives you the best protection and a longer life for the sealer.

Some cleaners speed up the drying process through the use of air mover fans and heat. The use of an acid etch on clay tile or grout is not recommended by tile or grout manufacturers and may remove color from pigmented grout and damage metal surfaces.

Testing to determine cementitious grout

First, you must make sure you are working on the actual grout itself and not on top of several coats of finish, sealer, and soil. In most cases you can chemically remove all surface soil, finish, and sealer by stripping the floor several times, followed by rinsing. Then, dry the test area with a hair dryer or fan. Once you are sure you are in contact with the actual grout, apply a drop or two of a mild acid (white vinegar) to the bare grout. If the grout is cementitious, it will fizz. If not, then you are not down to the bare grout, or it’s an epoxy grout.

Testing for the presence of sealer

Place a drop of water on the grout. If the water beads up, this indicates that sealer is most likely present. If the water sinks in and, when you wipe it off, the grout appears darker in color than the surrounding grout, this indicates that the grout is not protected by sealer.

You can chemically clean the surface and dry it as outlined previously, or take a small piece of sandpaper (100 grit) and rough up an inch or two of the grout until it starts to powder. All testing should be done in an inconspicuous area and gently so as to not damage the grout.

Applying the sealer

sealing grout

When sealing grout, stay on just the grout. Wipe off any overapplication.

Read the product label and follow the manufacturer’s application instructions. Application options may include the use of a brush, microfiber pad, a roller wheel applicator, or spraying. I would caution against spray application of sealer due to overspray issues and the health risks involved. If spraying is done, proper PPE and other safety precautions must be followed.

Types of sealer

Use a penetrating/impregnating sealer, not a topical seal, finish, or coating. The product you use should be made specifically for the type of material/grout/flooring you are working on. A high-quality sealer will not change the gloss, appearance, or slip resistance of the surface to which it is applied. There are products on the market that contain additives designed to enhance or change the appearance of the surface. Ask the right questions so you get the right product.

Product quality can vary, and most companies sell several quality levels of sealers based on the capabilities, formulation, and price. Most of today’s products are water-based, although some companies offer solvent-based products. Check with the manufacturer as to which product is best for your specific application and surface needs.


Most stains will be removed or lighten during cleaning. If stains remain, test available stain removal products in a small area with longer dwell time, then agitate, remove, rinse, and speed dry to determine results. Some stains may be permanent and won’t come out. I’ve had good luck using products sold for carpet spotting on some grout stains. Don’t mix chemicals or apply more than one chemical at a time to the same area when testing products or attempting stain removal.

Reapplication of sealer

The reapplication of sealer depends on traffic levels, soil type, and the chemicals used for daily/routine cleaning. The best way to determine reapplication frequency is to test the surface for moisture penetration. If the grout is absorbent and water sinks in, the grout needs to have sealer applied.

Safety precautions 

Cleaning and sealing grout will involve processes, equipment, and chemicals that can pose health and safety hazards and risks to the employees doing the work, as well as building occupants and the public. Part of your job as a cleaning professional is to recognize and eliminate risks to everyone who enters the workplace.

William (Bill) Griffin is the president of Cleaning Consultant Services, Inc. He is an industry consultant, author, and trainer with decades of experience. Contact him at [email protected] or visit

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