Should I Coat My Marble and Natural Stone?

Sealing marble and natural stone are an important step in prolonging the life and beauty of the surface. Sealing travertine and other natural stone properly help to reduce the porosity of the material and make it water, stain, or oil repellant.

As a stone care professional, we are often asked about coatings, acrylic sealers, or topical sealers by our clients. Although there are certainly times to utilize a sacrificial coating, many stone professionals will recommend using a penetrating or impregnating sealer instead of a topical.

Topical coatings put a layer on the surface. Penetrating impregnators work from within the stone.

The largest concerns that stone care experts have with coating sealers are:

1. Slip. We often get called for slip issues when stone is coated. The COF (coefficient of friction) or slip factor is often a problem if there is water near the flooring. Things to consider would be weather, irrigation and water features. This is an important consideration in exterior flooring, pool decks and bathrooms.

2. Removal. Coatings are easy to go on, but challenging to remove. All coating type sealers must be periodically removed and replaced. If you choose to change the type of sealer at any point in the life of the flooring, stripping must be thorough or the next sealer may not stick, or uneven wear and flaking might occur. Getting a topical coating or acrylic sealer out of grout lines often is the most challenging part of the process. It often takes 2-4 times as long to remove a coating as it does to apply one. Also, some of the parts and equipment being used in removal must be replaced because of the stripping agent and the gumming of the sealers. All of this results in additional costs to the consumer who opts to use a coating type sealer.

3. Localized damage. If an area of the coating is damaged or starts to wear thin or flake, you may be faced with stripping and replacing the sealer on the entire floor, a costly and time consuming endeavor. Partial or localized replacement may be possible in some cases but not others.

4. Breathability. Even if a sealer or coating says it is manufactured for natural stone, always call the manufacturer or ask a stone professional if the sealer that is being used is breathable (gas permeable.) One of the largest stone care suppliers distributes a topical sealer (stone coating) that is made for natural stone. When I had a client that used the product, and was having issues, I called their technical specs line and asked about gas permeability. This (unnamed) stone coating was not breathable. Stone Care 101 says that natural stone must breathe.

Stone without the ability to release moisture may be a candidate for future spalling, weakening and damage. I do not wish to represent which sealers and stone care lines meet this breathability criteria. A consumer should always ask a knowledgeable source (manufacturer, supplier, or stone care professional) about the gas permeability of the sealer you choose.

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