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


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 - 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.

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

  1. Glenn Grey says:

    Thanks you for your time. I am experiencing spalling on my front steps made of limestone. Likely combo of water, and salt. It started within the last year although is 16 years old. Is there anything that I can do to stop the spalling from continuing, or am I forced to have the limestone replaced at some point in the future.

    • Donato Pompo says:

      The spalling might actually be wear on the stone treads. Often with weaker limestones they will wear and degrade along the edge from pedestrian traffic. The only thing you can do about that is grind it down smooth. There isn’t any treatment to make it wear better. You could run textured strips along the front edge of the tread to project the stone.

      If it is truly spalling then that is caused by the stone being subjected to excessive moisture. Minerals in the underlying material dissolve in the water like salt and when the water migrates and evaporates at the surface the minerals precipitate and expand causing the spalling.

      If it is spalling, I have heard of a sealer product called PROSOCO Conservare® H100 that consolidates deteriorated stone to block the moisture from migrating through the stone. Here is a link to their website: https://prosoco.com/product/h100-consolidation-treatment/. It may or may not remediate your problem.

  2. Robin says:

    I’m experiencing pitting in a brand new installation of Marbella Shellstone LF pavers that were honed and filled when delivered. The paver installer set some of the pavers in cement to ensure stability, and I’m wondering if this pitting is caused by the moisture in the Portland cement? At first I thought it had something to do with polymeric sand causing corrosion burning can’t find anything to support that. Anyone have any thoughts?

    • Donato Pompo says:

      There are many different types of Shellstones and even with the same category of a Shellstone the physical properties of the stone can vary substantially from one shipment to the next.

      Shellstones normally have weaker physical properties than some other types of stone. The pitting could be from the foot traffic or other types of traffic it is being subjected to. Normally a new installation would not have spalling from moisture and the migration of minerals. It normally takes awhile for that to occur. If it is the fill in the stone that is pitting it maybe because the fill is weak for some reason? Polymeric sand is just stand with a polymer and it should not cause any damage to the stone. It does help keep water out of those grout joints. If it were practical to do, a stone could be removed and we can evaluate it in a testing laboratory, but it may not be worth spending the money on.

  3. Ms. Troy Arrandale says:

    Thank you for your time. This is a research question about 1950s graffiti on a Missouri town’s inactive ( no longer mined as it once was in the early 1900s) quarry bluffs- predominantly natural sandstone/shale –for a novel I’m writing, so this may not be the appropriate place for the question, so I apologize if it isn’t. If left alone by the town, what might the graffiti look like after 20 to 30 years on the bluff face (i know trees and vegetation would be growing but let’s pretend the bluff face is clear of vegetation in large spaces.) The graffiti was variously drawn with carvings, (i have pictures of examples of old ones on sandstone (or denser stone) bluffs and they still show after 100 years so I don’t need that one addressed), lumps of coal, chalk, and emulsion paint (house paint?). If no one can venture a realistic guess, maybe someone can point me where to find such info, perhaps a geologist? lol I’m also wondering, if in the 1950s or 60s the town tried to clean the graffiti off , would they use emulsion paint (like yellow, tan or white, or the sealers or stains mentioned here by our learned expert Mr. Pompo? Thanks for reading! I’ve learned a lot just from reading your posts, Mr. Pompo and everyone. (I place acknowledgments in my novels so if you have info I use, I may want to list your name in acknowledgments.) Have a wonderful day!

    • Donato Pompo says:

      Natural stone can be subjected to many types of stains. Some are organic stains and some are inorganic stains. Some stains are caused by what the stone surface is subjected to. Some stains originate below the stone or within the stone itself as all natural stones have minerals and some minerals contain iron that can rust and cause stains.

      To determine how to remove a stain, you first need to know what caused the stain. Then you need to determine what will act as a solvent to break the stain down, and you have to determine how to reach the stain if it has penetrated deeper into the stone. There are poultices that are produced with different components or chemicals that are made to migrate into the stone, break down the stain and bring it to the top to remove.

      A lot of this work is done by trial and error. There are some stone restoration companies who may have the experience to know how best to remove various types of stains.

  4. Troy Arrandale says:

    thanks Mr. Pompo. Perhaps I’ll reach out to a stone restoration company and ask. In speaking with my husband who knows a little science about natural stones and sedimentary stone from a construction point of view, he mentioned that limestone is harder than natural sandstone like in these quarry bluffs. That the sandstone would crumble and be looser and may wear away naturally over the years. I may ask a stone restoration company what a town might try to remove this graffiti. Or perhaps I’ll just skip that part as it seems like from what you say, especially if they’re limestone bluffs, if the town had tried without experts to remove those human markings in the 1950s they might have failed, and that this (i’m now thinking I may make it a limestone ) quarry would still have worn vestiges of the old graffiti. That’s perfect for my story, if that seems realistic. Is it feasible to you that the limestone is harder and more likely to retain human art (not natural stains) drawn on it over the years?

    • Donato Pompo says:

      Natural stone is not only categorized as sedimentary materials, they can also be in the categories of metaphoric and igneous rock.

      Then often each geological classification within each of those categories can have different classifications. Not only are the physical properties of the different categories of stone different, but the even the stones within a single geological classification can have substantially different physical properties as stated in the respective ASTM standards.

      For instance, ASTM C568 limestone comes in 3 classifications of either Low Density Limestone, Medium Density Limestone and High Density Limestone. So respectively their physical properties are substantially different.

      Actually Sandstone, which has the lowest physical properties within the geological classification of ASTM C616 Quartz-Based stone has a higher density than a low density limestone, and is a much more durable material than limestone.

      I think it is unlikely that limestone exposed to the exterior environment would retain the graffiti, and more likely that the Quartz-based stones and granite would not degrade under those conditions.

  5. Troy Arrandale says:

    Thankyou kindly Mr. Pompo. This was so incredibly helpful! I plan to axknowledge and thank you (with your credentials) inside the book for your information should I publish the book.

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