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.
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.
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
- Mix the product in a bucket according to manufacturer instructions.
- Apply the mixture in a small area where you can cover scrubbing until it dries.
- Let the solution stay for a few minutes and then add more so it stays wet.
- Scrub the floor using a buffer or you can do it manually with a scrubbing pad that has just the right hardness.
- 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.
- Apply the solution with a brush or roller and let it sit for a few hours.
- Then try stripping off the coating with a putty knife.
- If it comes off easily, it means that the solution has taken effect and you can already strip off the coating.
- 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.