Why do I now have Problems with my Limestone After it was Cleaned and Re-Sealed?

QUESTION

Hi there,

I am looking for help with my German fossil stone (limestone) tiles. We have a large quantity through our house. It is in all our bathrooms and living areas.

In 2015 we had a company come in and reseal the tiles. Very quickly we started having issues with the tiles. Within a couple of weeks we started getting pitting and the tiles in areas started to look like they had no sealer on them. We also have rooms where what looks like brush marks showed up months later. These problems were particularly bad in the bathrooms.

We got another company in for their opinion and a expert. Both concluded that it was poor workmanship.

The company that carried out the work got the supplier of the product in as the product was suppose to have a 15 year warranty and he concluded that the stone was of such poor quality that any moisture was marking the stone behave as it was. This assessment included rooms that were living areas or bathrooms that only had the toilet and wash basin, so had very little exposure to water. He provided no independent evidence to back his conclusions. We had not had issues like this before the work was carried out. The sealer was an impregnating sealer.

I am trying to find research or documentation where it details these kind of problems due to poor quality stone and what I can do to sort it out or weather we just have to rip it all out and start again. I am struggling to find any independent help in my home country of New Zealand. Every person who looks at it gives a different opinion. Even from the company that carried out the work I got 3 different opinions from 3 different people.

I would appreciate any help you could give or suggestions on who to contact.

Kind regards

ANSWER

ANSWER - Refinishing or restoration of stone floors is a common maintenance process.  There are many levels and degrees of what that might involve.

Typically the stone floor will be cleaned with cleaning solutions and rinsed with water.  After the stone is clean and dry they would then seal the stone with a penetrating type of sealer.  If done correctly it should give the stone floor a clean fresh look where water beads up off of the stone surface like water on a wax surface.

In some cases, it will involve the cleaning process and then they bring in a grinding machine to refinish the surface to a hone or polish finish.  Then they seal the stone.  This can make a stone floor look like new.  That is one of the benefits of natural stone, is that you can restore it; assuming there are no deficiencies or problems with the stone installation.

Sometimes when certain types of stones are ground, like with travertines, it can open up pores in the stone surface that were not there prior to the refinishing.  A professional stone restoration company will fill those pits or holes during the refinishing process.

Another condition that can cause pitting, which we call spalling, is when the stone is subjected to excessive moisture from one source or another.  As the moisture under the stone comes into contact with minerals (a form of salts) they dissolve in the moisture.  As the moisture migrates to the stone surface as the moisture evaporates it precipitates the minerals causing an expansion at the stone surface that can cause pitting or spalling.

Perhaps with the cleaned the limestone floor they used a lot of water. If the underlying conditions below the stone doesn't allow the moisture to be absorb into the substrate to migrate away from the stone, it might cause the moisture to in effect become a reservoir of water subjecting the stone to prolong moisture that could then cause the spalling.

Every type of stone has a geological classification.  Limestone has 3 sub-classifications that are low density, medium density, and high density limestones.  The high density limestone is less absorbing, more durable, and more resistant to various types of conditions. A low density limestone is more absorbing, less durable, and less resistant to various types of conditions.  In each case they meet the requirements for a stone used in buildings, but will be more or less suitable for various types of applications.

You can test your limestone for its physical properties.  If your limestone has the low density physical properties it will be less resistant to moisture issues and it could be a contributing factor to your problem.  Although the problem may have nothing to do with your stone.

It may not be practical to hire a forensic company such as www.CTaSC.com to investigate the problem to determine the cause and how best to remediate it.  If you can find an experienced quality professional stone restoration company, they might be able to restore the stone to the way it was.  On the other hand you might be only treating the symptoms of the problem, and not remediating the problem itself.

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