Limestone
Use in Wet Areas
By Frederick M. Hueston
In a nutshell I would not recommend
using limestone in wet areas. The following is why I would not recommend it
1.
Limestone
is a sedimentary stone. It naturally contains minerals such as iron. When iron
is exposed to continued wetting the iron will begin to oxidize causing a large
stain. At first the stain may appear light brown but over time it will darken
and continue to oxidize to a deep brown to reddish stain. Removing the iron from the stone is nearly
impossible since it is part of the mineral makeup of the stone.
2.
Limestone,
even when sealed is typically very porous.
Water will enter the pores of the stone and react with the setting bed.
The setting bed contains salts which become dissolved in the water. The water
carries the salts into the pores of the stone. When the stone dries, the salts
recrystallize causing pressure in the pores resulting in the stone blowing
out(spalling).
3.
Limestone
is an organic sedimentary rock
that forms from the accumulation of shell, coral, algal, and fecal
debris. It is formed by sediment settling to the bottom of a water basin.
The main mineral is calcium carbonate.
Calcium carbonate can be soluble in water. This is yet another reason to
avoid using limestone in a wet environment. Since it often contains organic
matter, this too is soluble in water.
4.
Steam
showers are even a bigger concern with limestone installation due to the fact
the vapors produced by the steam can enter very tiny pores that liquid water cannot.
The steam than condense in the pores causing the stone to deteriorate.
5.
The
Natural Stone Institute, who is the leading trade association in the industry,
recommends that only class A & B stones be used in interior wet areas.
Limestone fall into a C class at best, Many fall into the D classification. For
more info on this classification system go to The Natural Stone Institutes
website at https://www.naturalstoneinstitute.org/
One may question the fact that
limestone is used on building exteriors with no issues. This is true but there
is a big difference. The average shower produces on average of over 8000 inches
of water per year. To put this in perspective the rainiest area of earth is in
China which has 321 inches of rain a year.. The average shower has over 26
times that amount. That’s a lot of water.
I have been in the stone business
for over 35 years and have numerous colleges who agree that using limestone in
a shower is not recommended.
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