Sealing Slate Tile Floors Installation Servies – TheFlooringlady

To seal, or not to seal, that is the question. If you are about to install a slate floor, you have probably heard conflicting opinions about sealing your tiles.

The conflicting advice comes from the different experiences contractors and homeowners have had with slate tiles.

Different experiences come from using different types of slate. Sealing slate isn't necessary, especially if you want to keep the natural look and beauty of the slate.

However, if the stone is porous and/or you aren't experienced at grouting, seal the stone first.

 Furthermore, sealing slate is important if you want a shiny or matte finish, and if you want to protect it from staining.

You can buy chemical sealers at retail stone and home improvement stores.

Best Sealer for Your Slate Floor!

To help maintain better air quality, you want to use a water-based polyurethane sealer.

To help give the stone its best protection, a penetrating sealer is a good precaution. 

In addition to being low in VOCs (volatile organic compounds), water-based polyurethane is non-yellowing and non-cracking, giving you years of good looking slate floor tiles.

 The BulletProof Sealer by StoneTech and 511 Impregnator Sealer by Miracle Sealants are popular choices for water-based sealers.

Slate Varieties for Your Home

Slate typically comes from Brazil, Vermont, China and India.

The Brazilian and Vermont slates tend to have a low absorption rate, while Indian and Chinese have variable absorption rates. 

The softer slates need more attention with sealants before and after installation than do the harder slate tiles. Slate is a metamorphic rock, starting as a sedimentary rock and with pressure and temperature over time became slate.

It is made of materials with characteristics like clay, and it has a structure similar to layers of sheets.

Because it has some porosity, you may want to seal it to keep it from staining and soiling.

Brazilian slate

Indian slate

Chinese Slate

A bit more about the origin of your slate will help you determine how you want to treat it. Brazilian slate is typically dense and has variegated colors while Vermont slate is typically dense, smooth and one consistent color (black, blue, green red).

In contrast, Chinese and Indian slates are typically variable in density (soft to hard) and variegated coloring, with a wide range of colors.

 If you get a soft slate, typically Chinese or Indian, pre-seal with a porous stone sealer.

​Step 1: Preparation

The preparation needed before installing your slate floor tiles is to clean the subfloor where the slate is to be installed.

Clean dust and dirt from all slate surfaces, and let them dry thoroughly before applying two coats of the penetrating tile sealer.

Step 2: Application

There are surface, or topical, sealers, but the penetrating sealer gives your stone tile better protection, and looks better longer.

Apply the sealer in a thin coat using a sprayer, roller or brush, following the grain of the slate and let it dry for at least two hours and reapply (your specific product will tell you how long between coats to let it dry).

Step 3: Grouting

After you have laid the tiles, let the mortar dry and cure before grouting the tiles.

To increase the bonding strength of your mortar and grout, mix penetrating sealant with grout instead of water.

This recipe increases bond and tensile strengths and improves the water resistance of the installation.

The increased water resistance is especially important if you are installing your slate tile floor on a concrete slab that can wick ground moisture into the room.

Step 4: Finishing

What look do you want your slate floor to have -- natural, wet, or glossy? You can get the wet-look without going to glossy by choosing the right finish.

There are finishes that will look natural after application, but many people love the wet-look for their slate floor. Black Diamond Stone Works offers such a sealer with a high gloss finish.

 If you want to enhance the color of your slate without making it look too glossy, you could go for the Stone Enhancer by Auqamix.

Step 5: Washing and Cleaning

After you grout the tiles (preferably with latex grout because it increases flex strength, reduces efflorescence, and has great bond strength), let it dry, ideally for a week, before cleaning the tiles.

You want to wash the tiles thoroughly, several times, to remove all remnants of excess grout so that it won't become a permanent part of your slate floor.

Step 6: Recoating

When the tiles are dry from the washing, you can apply two more coats of penetrating sealant.

 This step is to add further protection to the slate, but also to the grout and grout-tile interface.

Step 7: Curing

After you have applied your last coat of penetrating slate tile sealant, let cure for at least 24 hours before walking on the floor.

The longer you can let it cure before walking on it, the better protection you will have, and the longer the finish will last. 

Note that the sealer needs to be re-applied after every 3 to 5 years for interior surfaces, and every 1 to 3 years for exterior surfaces, depending on the brand.

 To have a better idea on how to reseal slate surfaces, check out this video:

Caring for Slate Floors

Compared to ceramic tiles, maintaining your slate floor requires extra care. Like any object, slate tiles will age faster if neglected.

  • For a start, you need to clean it regularly if you want it to look good after many years. Wash it with mild soap and water, and dry mop or vacuum in between washings. This will remove dust and dirt, which is the main cause of scratches on most surfaces. When mopping, move in one direction instead of back and forth. Let the dust accumulate in one spit and them collect them using a dustpan.
  • When the mop is not in use, store it properly with the head off the floor.
  • It is recommended that you mop your slate floor with a damp mop at least once a week.
  • As an added protection, place a welcome mat or rug at the door. Or better yet, have room slippers ready for your household and visitors, so they can leave their shoes at the door.

Regular Cleaning and Maintenance

Highly acidic or alkaline cleaning solutions can reduce the effectivity of your sealer. It’s best to use a cleaner that is neutral, formulated specially for stones, and if possible, matches with the brand of your sealer.

The usual solution is to mix 1 part solution to 4 parts water, but you can also mix 1 part solution to 1 part water when cleaning darker stains. Clean the surface before application.

Use a sprayer, mop, sponge or scrub when applying. Some solutions won’t require rinsing after, while others will.

If you are accustomed to waxing floors, you are in for a treat because wax isn't necessary on slate.

Wax won't hurt the slate, but will obscure it's natural beauty, turn the tiles a darker shade, and may yellow the grout; all good reasons to not wax your floor.

Step 1: Identify original coating

To find out what coating was originally applied, mix one cup of ammonia with one gallon of water.

 Apply it on the floor, scrub it then wipe off. If the coating was removed, most likely wax has been use. If the coating wasn’t removed, then there’s a chance that it is urethane or epoxy based and harder to strip off.

Step 2: Removal of wax or Water based coating

  1. Mix the product in a bucket according to manufacturer instructions.
  2. Apply the mixture in a small area where you can cover scrubbing until it dries.
  3. Let the solution stay for a few minutes and then add more so it stays wet.
  4. Scrub the floor using a buffer or you can do it manually with a scrubbing pad that has just the right hardness.
  5. Rinse the solution thoroughly with water.

Step 3: Removing Urethane or Epoxy Based Coatings

When removing urethane or epoxy-based coatings, you need a strong solvent-based stripping solution. Practice safety measures by wearing mask and goggles when applying.

Also ensure that there’s proper ventilation and that you won’t disturb the neighbors. If you don’t feel confident about handling a dangerous chemical, you can always contact a professional to do it for you.

  1. Apply the solution with a brush or roller and let it sit for a few hours.
  2. Then try stripping off the coating with a putty knife.
  3. If it comes off easily, it means that the solution has taken effect and you can already strip off the coating.
  4. After this, you would need to apply the alkaline stripper.


Slate makes a beautiful flooring. Proper preparation and care of it will keep it looking great for years to come.

If you can't decide if you should seal your new slate tiles before installing them, error on the side of caution. 

Sealing them may not be necessary, but after you have installed them it will be a headache to seal them properly. 

And you may not be able to protect them soon enough, if they are porous and absorb stains.

To seal or not to seal?

Go for it with a penetrating, water-based slate tile sealer and enjoy your natural stone floor for years.

420 thoughts on “Sealing Slate Tile Floors Installation Servies – TheFlooringlady”

  1. I just put a slate floor on my outside patio and the slate is from India. I purchased at Home Depot and they gave me some sealer to apply before I grout. I have applied the sealer and now all the tile has a white cloudy look to it. I’m not sure where to go from here, do I need to remove this sealer and if so, how? How do I prevent this from happening again?

  2. Randy,
    Moisture trapped in the sealant would cause the white cloudy appearance. If the moisture is temporary and is the cause of the white cloudy appearance you would need to strip the sealer off to allow it to dry. Not knowing the manufacturer of the sealant contact the manufacturer of the sealant for the proper method of removal.
    If the white streaks in the sealer is caused by moisture, you can try to remove them by taking the same sealer and apply it over the tile and let it dry for several minutes. Then immediately get a dry lint free cloth and buff the tile dry. You can see if that will take the white streaks away.

  3. Just had a beautiful natural slate patio installed. 24 hrs after grouting, SGM clear penetrating sealer (Southcrete 901 waterbased) was sprayed over the patio. It has left a horrible white film in a spray pattern. The tile store says the sealer was applied too soon and incorrectly. What product can we use to remove the sealer?

  4. I installed indian slate tile around my bathtub walls. It turned out beautiful, however even after sealing it with two different sealers, the color from the tile is running down the wall and staining the tub. What can I do to fix this problem? Thanks in advance.

  5. We recently had California Gold slate installed on both bathroom and shower floors. The slate on the shower floor is ‘bleeding’ a rust color and, in turn, staining the grout. The manufacturer and installer are going back and forth to rememdy the problem; however, without success. They say they’ve NEVER seen this before. I’m concerned they may make it worse. They have suggested dyeing the grout versus tearing it out and putting in a different tile altogether. What do you think about dyeing the grout a darker color? Will this solve the problem? Will this discolor the slate? And, what is causing the slate to rust?
    What product/sealant would you suggest for a low-sheen finish on the slate? Thank you for all your help.

  6. I have an original blue slate floor (Vermont?)in the hallway of my 1968 house. The floor was covered with with 40 years of wax buildup and had cloudy stains. I stripped the wax off with AquaMix stripper and I now have the original unshiny slate color which I kind of like.
    What is the difference between sealers? I see there are color enhancers which I am afraid to use since the floor already has reds, blues, greys and green and the enhancer may make it too colorful for the small space. Are there non-color sealers that would not make the floor too glossy? Thanks.

  7. Nick,
    I am not sure if this could’ve been caused by using the two different sealers. I would not apply more of either until it is thoroughly dried. I would then check with the manufacturers of the sealers to find out what they would suggest before doing anything else with the tile.

  8. Julie,
    Hi. Iron oxide (irons and metals in slate) is common with slate. When installing, the tiles
    need to be washed with water and agitated with a brush. Then left to dry well. This cuts down on the color bleeding into your grout.
    Dying the grout may cover up the stains, and if it is done by a professional, I would think they would know how to protect the tile from being stained as well. Then being resealed according to the manufacturers instructions and recommendations on the sealer should be safe. I personallly recommend Diamond Coat Varathane Polyurethane water-based poly.
    However, if you are working with the manufacturer and the installer, they should be able to advise you of the best options in your specific situation.

  9. I have a slate tile floor over which had been placed a seagrass rug with it’s own rubbery type backing. When it came time for the rug to be replaced I was horrified to find that the backing had somehow fused in many, many areas with the slate–it’s almost as if it melted into the slate and left these awful hard-as-rock scaly deposits. I’ve tried different things to remove them but short of using a hammer and chisel (which I’ve done), that seems to be the only remedy. Do you have a recommendation and if so, if I seal the slate in the future, will that help prevent a rug pad from doing this again?

  10. Karin,
    I would encourage you to call the manufacturer and ask them the best way to scrub those clean. Harsh chemicals would be unhealthy and possibly damage the floor.
    After the slate is sealed, in the future, this should not happen again. The backing may stick a little, but shouldn’t be as hard to remove.

  11. I am currently installing indian slate 12 x 12 tile thoughout my entire home. I am interested in a low sheen sealant that will enhance the colors. What brand of sealer do you recommend. I tried the links offered on this page, but have not been successful in locating Diamond Coan Varathane Polyurethane, if that is what you would recommend for this application. thanks.

  12. A year ago we bought a house with slate flooring. I do not believe it has been sealed. We clean it every few months with some type of floor cleaner. It never really gets clean. Lately we have experienced a black gummy hard scumb on the tile and it seems to be making the file break up in fine pieces leaving a large whole in the tile. Any experience with this and any suggestions on what to do? Thanks, David

  13. Hello,
    First I must say that your article is very interesting and I got some valuable information from reading it.
    The concern that I have is about slate roofing tiles, that came from China. I was wondering if you could help me, because the problem that we have is that the slate roof has been installed about 3 years ago. Over that time the a lot ( and I really mean A LOT) of slates have pealed off and some are just falling apart. To me it seems that the weather conditions (Chicago) are damaging the slates. Do you think that if we applied penetrating sealants it would stop the slates from falling apart. I would really appreciate if you could recommend a product that we could use on the roof slate.
    Thank you

  14. David,
    I have not had this experience, but it does sound as though the tile needs to be sealed.
    I would try to clean it with a mild soap and water. And, maybe check with the manufacturers of your current floor cleaner, and see if they have a solution to the black scum that you getting.

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