How to Seal Limestone

Written by larry simmons
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Though it may be a natural stone, limestone used as flooring needs protection from the elements in order to retain its durability over years of use. Because it's a porous stone, limestone can absorb moisture that will cause the limestone to discolour, appearing dirty in some areas regardless of actual cleanliness. To avoid this, a seal is necessary over the stone surface. The seal forms a protective coating over the stone, preventing the absorption of moisture while at the same time providing a wear layer for the stone against normal use.

Skill level:
Moderately Easy

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Things you need

  • Alkaline stone cleaner
  • Sponge
  • Nylon scrub brush
  • Limestone sealant
  • Bucket
  • Foam applicator
  • Lint-free cloth

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  1. 1

    Clean the limestone surface to remove any dirt or debris that can interfere with the application of the sealant. Wash the limestone with an alkaline stone cleaner using a sponge or nylon scrub brush to remove the dirt. Rinse away any cleanser residue with water and then pat the limestone dry to remove any remaining moisture. Wait two days for the stone to dry completely before continuing.

  2. 2

    Select the correct sealer for use with your particular limestone surface. Use a penetrating sealer to deal with the pores in the stone, sealing them deeply enough to prevent infiltration of moisture into the stone. Choose a sealer containing silicone for softer limestone tiles, as the silicone will add strength to the sealed surface, creating a wear layer to protect the softer stone beneath the seal. Locate the sealer you need at a home improvement or hardware store.

  3. 3

    Pour the sealer into a small bucket. Dip a foam applicator into the bucket containing the sealer to gather the sealer onto the foam. Shake the foam slightly to remove excess sealant that could drop onto your floor, marring the smooth sealed surface that you're creating.

  4. 4

    Apply the sealer to the limestone using broad strokes of the applicator across the surface. Overlap rows about 50 per cent to ensure complete coverage without gaps between sealed rows. Apply a moderate layering of sealer, creating a wet look on the limestone without leaving pools of sealer on the surface. Wait five minutes after application for the sealant to penetrate into the stone.

  5. 5

    Remove any excess sealer from the limestone with a lint-free cloth. Polish the stone surface with a clean cloth, working in small circles to buff the sealer to a shine. Wait three hours for the sealer to dry, and then apply a second layer of the sealer using the same application process you used with the first. Allow the second layer 48 hours drying time after polishing before using the sealed limestone as normal.

Tips and warnings

  • Wear a dust mask while sealing to protect your lungs from sealant fumes.
  • Apply the sealant when installing the limestone, followed by reapplications every two years.
  • Open all doors and windows to the room where you're applying the sealant to provide adequate ventilation during the sealing process.

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