Stone FAQ - Stone

First of all you need to make sure you are aware that some stones are water sensitive and are not recommended for wet areas. Some common problems could be that the stones can stain and have some degree of deterioration. You can assume that all stones will tend to lose its shine from the polish caused by the constant exposure to the water and cleaning agents. Granites are much more resistant than marbles. Also Polish stones are not recommended for the wet area floors due to the chances of slipping.

People do install stone over green board (water resistant wall board), but it is not considered a good method of installation. It will deteriorate if exposed to moisture which can reach it from the front, side or back. Also it isn’t considered as structurally sound for a long lasting installation. Considering all the mold litigation, it is further not recommended. If you get a moisture problem and the green board gets wet then you are likely to get mold. It is worst with wall boards because it is an ideal source of food for the mold that then further perpetuates the problem. It is always recommended first to do a cement mortar installation and second best would be to install over cement backerboard.

If you choose to go ahead and install over green board, then several manufactures of installation products make products for this type of application. Most important is to have a vapor barrier over the studs, make sure all transitional joints are sealed with a caulking, and apply a liquid or troweled applied waterproof membrane that you can use to paint over the surface of the green board and then thinset the marble to it. You can go to the resource section of my web page for some of those manufacturers at www.ctasc.com/.docs/pg/307.

Good Luck!

Updated: October 8th 2008

Granite Exterior Use: We are planning on using a black & tan granite on an outside installation of an outdoor kitchen in southern Mississippi. The granite will be in an area that is direct/indirect sun nearly during peak sun times. How can we expect this to affect the granite surface? We realize the surface will get hot but will the weather & temp damage the granite over a reasonable amount of time (say 5 to 10 years).

Granite is normally one of most durable natural stone and normally very resistant to climatic conditions. Although today stone comes from all over the world in various degrees of quality and is processed differently.

Dark stone does get very hot, so you need adequate movement joints throughout. Stone must be protected from underlying moisture to minimize potential staining and spalling. Much of the stone today is being treated with resins during the manufacturing process to help stone be more durable through the manufacturing process. There is no standard for these resins so some have been known to be sensitive to some of the climatic elements.

Your particular stone would have to be researched and evaluated to determine if there is any known history of problems with that type, plus it would have to be tested to determine how its performance characteristics compare to industry standards.

It is a natural stone so there are no performance guarantees, but you can evaluate it to make a better decision.

We do evaluate ceramic tile and stone for product suitability relative to the application for an hourly fee plus the cost of any testing.

Updated: September 23rd 2008

Suitability of Stone for Steamroom - We are interested to use light colored marble or limestone for floor and wall coverings in a TURKISH BATH (steam bath) where we will have high temperature and humidity. We would appreciate if you could inform us what specifications of the candidate materials we have to consider as most critical for the material to have the best possible behavior in the above conditions. What must the values of the suggested specifications be according ASTM standards? May we consider of using marble or limestone with resin treatment? or the specified materials must be resin free?"

Regarding your question on what to specifically take into consider for use of a marble or limestone in a Turkish Steam Room, it is difficult to be specific without extensive testing of the particular stone in question.

I will make some generalities and specific statements.

For Limestone to be considered standard grade it must meet ASTM C568-99 specification for Limestone Dimension Stone. Marble has one too.

Polished marbles and limestones will end up becoming unpolished over time and use. The softer the stone, the less lasting the polish. It is best to go with a honed surface, so the change won't be as noticeable.

Stone comes from different sources and has different minerals within the stone. Some stones will have voids filled with a resin or cementitious material. When exposed to constant moisture and varying temperature cycles these areas could possible expand and cause spalling. Also inorganic metal elements can cause staining and other minerals can combine and cause a crystallization that travels to the surface. Having the stone treated with resin is supposed to help it be more moisture resistant. Sealers can help minimize these potential problems. There is no practical way to determine if you will have these problems or not. I would check with the source of the stone to see if they have any history of problems with the type use you propose.

I do offer the services of evaluating the suitability of specific stones for specific applications for a fee. I would have to do research and testing of the specific stone to determine how likely there would be a problem, but the results would still be inconclusive.

Updated: September 23rd 2008

Granite too dark - We have recently had granite installed in our kitchen and it has turned into a nightmare. We chose Verde Florence at the tile supplier. They sent over 3 slabs to the fabricator. We have a kitchen countertop (with sink) that is not quite 13' long, an L shape counter that is about five feet, and another freestanding counter that is 5 feet. We were told when the template was drawn that there would be one seam in the 13' countertop. When we arrived home the day of install there were two, one almost directly down the center. We rejected this install as we had not approved of the very visible seam and had been told when the template was drawn up that there would be only one. We were then told that it was "impossible" to complete the counter with one seam -- but the impossible became possible when, out of frustration and a desire to have the remodeling done, we agreed to pay the installer $750 for another piece of granite. We went to his shop on three occasions, bringing with us a small piece of the existing countertop for a color/pattern match. The first time, not only did the color not match but the template for the smaller section would not fit on the remnant of the slab from the first install. We were told to come back and view the granite outdoors to get a better perspective of the color. My husband went back the other two times. He was reassured on both occasions that the reason the color did not match was because the slab was wet and that once it dried there would not be a problem. On the day of install we returned home again to find that there were two distinct color variations at the seam. We were told, again, that it was because the granite was wet from fabrication and that once it dried it would lighten up and there would be a better match. One month passed, the colors had not changed and we were told, again, that the granite was still wet and that it can take months -- depending on the humidity in your home -- for the granite to dry. Were we given "expert", honest advice and treatment?

Generally speaking granite is very dense and low absorbing, and does not darken from moisture. There are some cases when some granites can be more absorbing and will darken when exposed to moisture. It is not reasonable or realistic to say that a granite slab that has darken from absorbing moisture would stay dark for a month, let a lone a week, unless it was being continuous exposed to moisture.

I'm not familiar with Verde Florence, so you would have to hire someone like CTaSC to do an investigation for you. Good Luck, and let me know if I can be of service.

Updated: September 23rd 2008

Cleaning Tumbled Stone - I recently had some of tumbled stone installed in my home, and the decorated border was completely unsuitable after grouting than the original border that looked great before grouted. None of the displays in the store show this result...which is cracks and dullness from grout inside of all of it...totally changed appearance to an old chipping look;; installer used sanded grout. How is this supposed to be installed for the original look before grouting and is their anything to remove grout to restore the look?

Tumbled stone comes in many different types of stone. Some stone is more porous and are unfilled types of stones such as travertine. People have different preferences on how they treat the stone. Some will intentionally grout it to give it an antique look that will vary depending on the color of grout selected. Others will seal the stone prior to grouting and go through the extra labor to keep it unfilled from the grout because they prefer that look.

Sounds like the later case is what you wanted. It would be very difficult to remove the Cement grout that is in the pores of the stone. The best way would be to sandblast, but that may not be practical in a furnished home. Acid will attach the cement to some degree, but may cause more harm to the stone and the surrounding material and may be prohibitive. I would test varies methods in out of the way corners and make sure you get the results you desire. Good Luck!

Updated: September 23rd 2008

Granite Countertop Quality - I'm hoping someone can answer my concerns. I am having a home built and had granite slab counters put in kitchen at some point during construction of the counters the cabinet company moved the cabinets which caused the granite counter to be off 1/4 inch and had to be replaced. the section they replaced looks horrible. I realize that like wood not all slabs of granite will match, but the seam is so blatantly obvious and the seam on the back splash is about an inch and a half from the seam on the counter which looks even more obvious. It is an (L) shaped section of a counter with a sink cut out. They cut a seam about 3 inches from the sink to replace the problem section . Should they have used a new slab for the entire (L) shaped section or do I not have a leg to stand on? Our walk through is in a couple days and I just don't know where I stand? PLEASE HELP!!!
Industry standards don't say that the slab stone for a countertop needs to be made from the same piece because usually one slab isn't enough. Normally they will use slabs that come from the same crate because they were likely processed at the same time and more likely to match.

Industry standards does say that color shades shall blend from one stone to another in a pleasing manner. This can be subjective, but it would be based on what is considered the standard of care for the industry.

In your case, you may be expecting too much, or perhaps as you suspect it isn't reasonable?

The seam of two abutting slabs are to be clean smooth, and consistent, gauged to uniform thickness within +/- 1/32", and lightly raised.

I'm not aware of any standards regarding joint in deck to match joint in backsplash. I would expect them to match where possible.

Hopefully you can resolve this concern. If you need to have it arbitrated or if litigation arises, you can contact CTaSC to arrange an unbiased inspection with a report.

Good Luck!

Updated: September 23rd 2008

Finishing Edge of Stone - I am remodeling my house. I purchased marble for the bathroom. How could I end the edge with a nice and shine looking?

There are several ways to treat the exposed edge of a marble. Most commonly the edge can be ground to a rounded bullnose edge and polished. Or at a lower expense you can polish the square edge of the marble. Or some people will take a stone or ceramic tile trim piece and set it next to the edge of the stone, which can give it a very decorative and custom look. Please refer to the resources and links section of the CTaSC website. Under "Sealers and Cleaners, there are some companies who provide polishing compounds for stone and tile.

Updated: September 23rd 2008

Granite Quality - I'm trying to find out how to differentiate granite by grade/quality Thank you...
It is very difficult to differentiate granites let alone any other stone. People in the trade through experience may be able to notice key characteristics by looking, but even then it is very subjective depending on the person's experience. It is one thing to determine quality in terms of performance criteria and another to determine quality of stone in terms of color. There are not standards for color.

There are some national ASTM standards and tests for certain types of stone that quantify several performance minimums to be considered standard grade material of that type. It does not address degree or consistency of color. Granite's category has an ASTM C615 standard that specify minimums for density, absorption, modulus of rupture, flexural strength, water absorption, compressive strength, and abrasive resistance. It costs about $1200 to perform these tests, plus shipping costs, which I can provide those services.

Best thing to do is work with an importer/distributor/fabricator that has been in business for awhile and has good references. Good luck!

Updated: September 23rd 2008

Removing Stone - Is there any way to get stone up without damaging it? We would love to save some very expensive stone from a sunroom and move it

The only time this is normally possible and practical is if the stone had been installed poorly. Particularly if the adhesive used did not bond well to the stone, then it may be possible and practical to reuse. You can simply clean the back and re-install.

To try to reuse a stone that was installed well is probably not practical. When you tried to chisel or cut it out it is like to chip or break up into pieces. For historic stone where there is more value and more money available, it is possible to saw deeply around sections of the floor and remove the substrate with the tile. Then it would be very costly to reinstall it assuming you have room to raise the floor several inches to accommodate the thickness of the section you removed.

Best bet is to find another stone; there is a great selection of stone available today.

Good Luck!

Updated: September 23rd 2008

Quality Standards for Slab Countertops- What are the industry standards cocerning granite seams, and the splitting of these seams?

ANSWER - Countertops are to be flat within 1/8" in 10 feet.

Transition joints from counter to wall or other material is to be 1/8" with a tolerance of +/- 1/64".

Joint seams widths are to be 1/16" with a tolerance of +/- 1/64".

The seams should not split.

Lippage at seams can not be more than 1/32"

The Marble Institute of America has a Dimension Stone Design manual that you can buy at http://www.marble-institute.com/industryresources/manual.cfm.

Good Luck!

Updated: November 2nd 2007

Mildew on Travertine - I am considering having Travertine Tile installed in my master bath. The tile I purchased was a Durango tile from Mexico and is beautiful except that it has some mildew growing on the boxes ot was in and also on the backs of some of the tiles. It was pre-sealed. Should I be concerned about the mildew?

ANSWER - You can put some detergent in water and wash the stones with an appropriate bristle brush to remove the mildew. The stones can be installed damp, but not wet.

As long as you don't have a moisture problem in the substrate to which the travertine will be attached you shouldn't have a problem.

Good Luck!

Updated: August 28th 2007

Stone Quality - Can you please tell me what grade COAST GREEN granite is? I have a one person telling me it's grade 3 and another that it's grade 6!! I would really appreciate your help.

ANSWER - There is no such industry standard that grades granite with numbers like that. Marble has a class A, B, C, D and that has nothing to do with granite.

Without checking, Coast Green doesn’t sound familiar, so it may be a marketing name. A certain geological type of stone doesn’t automatically have a certain classification because its physical properties can vary from source to source and from time to time. The stone supplied from a particular quarry in a particular area of the quarry needs to be tested to determine how its physical properties compare to minimum ASTM requirements.

It’s not easy getting this type of information, but the importer of the stone or the stone quarry should provide this to the consumer in order to substantiate it meets the minimum requirements and to determine its usage suitability and limitations. Good Luck!

Updated: May 23rd 2007

Is Travertine Porous? - Is Travertine considered impervious? My contractor told me it was when he installed the product, but my zoning officer has informed me that I am now over my impervious coverage for my property.

ANSWER - I'm not sure what you mean by "my zoning officer has informed me that I am now over my impervious coverage for my property."

Travertine is not an impervious stone rather it is considered a very porous sedimentary stone and is known to have void spaces that are distinctive features of travertine.

The solid portion of the stone is considered vitreous and can be impervious in spots, but can range up to 2.5% absorption and be acceptable for the industry standards.

Not all travertine stones have the same physical properties. They will vary from quarry to quarry and location within the quarry. There are low grade travertine that have a lot of voids and other travertine that have few and are more like a marble. This is true for other types of stone as well.

I hope that answers your question.

Good Luck!

Updated: February 8th 2007

Quality of Granite - We just purchased a new home, but not directly from the builder. We closed on the same day as the original sale from the builder, though. Our problem is that the kitchen granite is very visibly porous and has millions of mini cracks on the surface. It is not smooth and no matter how much we clean it always looks dirty. The builder sent the granite installer to "re-seal" it, but whatever they did made no difference. We have had granite before and this had never been an issue. The granite contractor says it is the nature of this granite and there is nothing they can do about it. To me, it is unsanitary as food gets stuck on the "unfinished" portions and it is very hard to clean. Could it be that this is substandard granite? Could the quality of the granite be tested? If so, how much would it costs?

ANSWER - There is a lot of natural stone sold as granite that is not true granite. Due to the large demand for stone today, stone that would not have been sold or used before is now.

You might have what is called an over-burden stone, which is quarried at the top of the mountain and it tends to be more unstable and have more voids in it.

Some of these stones that are over-burden or not true granites are very unique looking and can be very beautiful. So some people may choose to select this material knowing that it may not meet the minimum standards for that category of stone.

Every category of stone has various levels of performance depending on what type of stone it may be, which quarry it was mined from, and which part of the quarry it was mined from. Stone is a natural product and will vary in looks and performance.

Generally the same stone from the same part of quarry will vary, but relatively consistently.

There are ASTM standards for each category of stone in terms of what the minimum physical properties should be. The Marble Institute of America publishes what those minimums should be if the stone is tested per the respective ASTM standard. This series of the 5 basic tests cost approximately $1,500.

Many of the slab stone imported today is impregnated with a resin to make them more durable. There is a chance what you are seeing are cracks in the resin coating. If it is porous then it isn’t likely true granite, and it may be over-burden granite if you have voids and pits. Good Luck!

Updated: November 8th 2006

Selecting Onyx - I am an architectural designer who currently has a client who is looking for an onyx slab (color: honey/pale orange/pink/some white). The slab must be able to accommodate a finished 9' x 2' rectangle. Your prompt attention would be appreciated.

Color and look is very subjective. Then you need to consider performance based on physical properties. Unlike other materials that you specify for a project, stone is natural so you have to select it for the project and application to ensure it is suitable.

The best way to find what you want is to visit a stone importer who has a large selection of onyx. Go through the inventory and pick the slab that is of the right size and looks. Then substantiate with the supplier that it has the right physical properties to perform for its intended use. Good Luck!

Updated: May 8th 2006

Stone Banker - What is a Stone Banker?

According to Matthew Merrett of Israel, a banker mason is the mason who recieves the stone in a square or rectangular shape, then with drawings, sections top bed moulds and bottom bed moulds etc the banker mason will begin to carve out the shape of the stone to be. Whether this is a piece of cornice, a pediment springer or a piece to a tracery window from a cathedral or a window cill, mullions etc, some work is extremely intricate and can take months to carve out e.g. lettering and plaques and fountains. Probably the name is synonymous with a stone carver in the modern world; a banker is the name for the stone table on which the mason works. This may be old English. I was trained in Bath, UK where there was a very old tradition with regard to stonework.

A fixer mason will be the type of mason who takes the carved stone from the banker mason and much like a bricklayer fixes it into the building, however stone buildings require a different fixing and building technique from brick and fixer masons normally oversee all the type of modern restoration work, basic face cleaning, ie, taking off pollution from stone facades.

Mostly I have found the term stonemason to cover anyone who works with and builds with stone, however here in modern Israel which is were I am now, they have a old tradition of building with stone but in a very basic manner; as in Jerusalem, its very plain . I was hoping to pass on my banker masonry skills here in israel and commence some training or teaching base in this old skill.

Updated: February 28th 2006

Stone Restoration - I have a travertine floor instlled for several years, is there a way to restore it? Grout joint lines are visible and dirty, holes on the surface. Can it be honed smooth? Can you direct me to someone who does this service?

Yes, travertine and other natural stones can be restored by cleaning, filling voids, re-honing the surface, and sealing. If the grout joints are cleaned, then maybe they won’t stand out so much, but otherwise they are suppose to be noticeable.

There are companies who sell the products for stone restoration and they can give you names of the companies who perform the restoration by going to their websites. Go to our www.CTaSC.com website Resources and Links section at Resources and Links for their website addresses.

Good Luck!

Updated: December 10th 2005

Dull Polished Stone - Is there an industry standard for gloss level on medium honed travertine tile? The tile has a dull blotchy appearance after sealing. What are possible corrective actions polish, re-hone...?

If your question is relative to a new stone tile being installed, then it isn't acceptable to have an inconsistent polish/finish. There is no standard in terms of rating the intensity of the gloss. It is subjective in suggesting it needs to be consistent.

Whether new or an older installation that has traffic patterns, which is expected, then look for a stone restoration company who can re-polish it in place. Good Luck!

Updated: August 5th 2005

Is Slate Suitable for a Driveway? I am in the process of designing a new driveway and walkway to the front of a home. We've used slate and the rear yard patio using irregular shapes of slate with grass in between. It looks beautiful, and the homeowner would like to use the same idea on the drive. I'm worried that the slate is too soft and will break under the pressure of the car. Can you advise as to whether my concerns are valid?

Most slates are considered hard and dense, but it varies depending on the type and source. Slate is a layered material so it can flake but is normally sturdy.

A good quality slate will work on a driveway if it is installed correctly and attached well over a concrete substrate with no voids under the stone.

All stone can be sensitive to prolong exposure to moisture and should be protected from the moisture with moisture barriers under the concrete slab and at their edges adjacent to landscape. Normally slates are low absorption so you must verify it is freeze thaw stable. Make sure there are problem expansion joints placed every 8 feet in each direct. Good Luck!

Updated: June 7th 2005

Clean off Finger Prints - How do you keep Finger Prints off Honed Black Granite?

Suggestions from Fred Hueston:

1. Clean the granite with acetone and apply a color enhancer. This will darken the stone but should keep the finger prints away.

2. Seal the stone with mineral oil...Mineral oil is a good option and is also used on soapstone..If not applied properly, it could get sticky.

3. Again, clean with acetone and seal with a good stone impregnator that contains a fluro alphatic.

4. Apply a good paste wax. I have used carnuba wax which works very well.

5. Tear it out and replace it with another type of granite.

Updated: February 18th 2004