Aquatic Technology Pool & Spa, "Creating Water as Art."™

Aquatic Technology Pool & Spa, "Creating Water as Art."™
Pools as an art form - the way it should be!

Tuesday, November 18, 2014

Stone Tiles Discoloration - Swimming Pool Expert Witness

It has been well documented that improper installation practices and setting materials can contribute to discoloration of natural stone and stone tile pool decks and patios.

Research Setting Materials

The installer or specifier should always check with the vendor as to the recommended setting materials and mortar and grout colors.  

If the vendor cannot or refuses to provide specifications, then the specifier should turn to the Marble Institute of America (MIA) or the Ceramic Tile Institute of America (CTIOA).

Both of these organizations have published field reports and technical papers regarding the proper setting materials and colors for various types of stone and tiles.

Correct Setting Materials

Some dark setting materials may bleed through lighter porous stones or tiles, creating a clouding, mottling or darkening effect.  Dark grouts can absorb into the sides of the tiles, causing a darkening of the edges.

Conversely, light setting materials can also bleed through darker materials, causing a lightening or ghosting effect.  Lighter grouts can also bleed into the materials, causing a halo effect around the tile edges.

Some epoxy adhesives have been known to cause stones and tiles to curl or twist.

So, it is important to research the proper setting materials for your type of stone or tile.

Improper Installation Practices

Using the incorrect technique when setting some tiles can also contribute to discoloration.  If the setting trowel's gauge marks (aka "comb marks") are not knocked down, then water may accumulate in the resulting voids.  Water saturating the stone, sill cause discoloration and an irregular clouding.

The best method, is to back butter the tiles after a thorough cleaning.  The comb marks are knocked down and the tiles set into the fresh thinset or mortar.  This will ensure an almost 100% contact and few, if any, voids.

Protect the Stone

It is also a good idea to protect the surface of the stones or tiles with a quality sealer or grout release prior to setting the tiles.  This will prevent the edges of the tiles from becoming discolored if grout or mortar gets onto the surface during installation.

A little knowledge will prevent having to tear out large areas of stone or tile.
Paolo Benedetti - Aquatic Artist "Creating water as art."™ 
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You may contact Paolo Benedetti at: or at 408-776-8220