What Is the Best Way to Seal a Slate Floor?

Written by g.d. palmer
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What Is the Best Way to Seal a Slate Floor?
Natural slate provides an interesting texture and attractive rustic surface. (Jupiterimages/Photos.com/Getty Images)

Slate flooring is a durable, natural material that has been used for hundreds of years. This material resists abrasion and cleans up with just soap and water. However, it can also be highly absorbent, making spills and staining a risk. Applying a sealant to your slate floor can reduce its absorbency and add another layer of durability. However, sealing slate floors isn't appropriate for all situations. Consider your flooring material, home conditions and available sealing methods before you make a decision.

Slate Types

Not all slate needs to be sealed. According to The Flooring Lady, a flooring information site, slate from Brazil and Vermont are relatively low-absorption. They tend to repel water rather than absorb it right away, though liquids that are allowed to sit on the floor surface can still cause stains. Chinese and Indian slate may be low- or high-absorption. Generally, soft slates are more likely to scuff, etch or stain, and require sealants for long life.

Sealant Types

Traditionally, slate floors went unsealed, or required periodic applications of wax. Wax is an inexpensive sealant, but requires regular maintenance and can make the surface very slippery. Over time, old wax can yellow, discolouring the slate underneath. Synthetic sealers, such as water-based polyurethane, are low in volatile organic compounds and protect the slate without cracking or yellowing. Some slate sealers leave the stone with a natural finish. Others look glossy or even wet.


Before sealing slate, clean the surface thoroughly, removing all hair, dust, grit or old wax. De-waxing old slate may require an alkaline wax remover, followed by a neutral pH cleaner meant just for slate. Applying sealant before cleaning can trap debris in the floor permanently, damaging its appearance. If you have recently installed your slate floor, wash thoroughly to remove all grout remnants.


Wait until the slate is completely dry before applying sealant, then apply at least two coats, allowing the sealant time to set up between coats. Once you have applied the last coat of synthetic sealant, allow it to cure for 24 hours or more before you walk on the floor. According to The Flooring Lady, longer curing time means a more durable floor.


While sealants protect the surface of the floor from damage, they can still develop scratches and discolourations. Polyurethane sealants, for instance, scratch easily and may develop dull spots. Avoiding wearing shoes when walking on the floor and moving furniture carefully can increase the lifespan of your sealant.


According to This Old House, penetrating sealant finishes, including most modern synthetic sealants, sink into the slate and can never be removed. Wax sealants sit on top of the stone and may be removed using an appropriate solvent.

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