StoneSpeak: Fixing on Fiberglass
Q: The grout in the limestone floor we installed recently is cracking. What could be the reason?
A: The probable reason is that the limestone absorbed some of the moisture in the grout before it could cure completely.
Q: The bluestone installed in my steam shower is changing color. What can I do to bring the color back to its original appearance?
A: Steam will react with the elements in dimension stone and cause a chemical reaction. Color change is a normal reaction of the stone to heat. There is no cure, as the elements in the stone have changed.
Q: How is dimension-stone quality determined?
A: Normally, each stone has background, veining and markings that are inherent to that stone. When these conditions are not in the usual range of proportions, or there is introduction of another mark or color that stands out from the rest, the stone is considered to be inferior to the species. The more variation from the norm, the lower the quality.
Q: Where is waterproof underlayment required in a kitchen countertop installation?
A: When installing thin (2 cm) stone kitchen countertops, use a waterproof plywood in the wet areas as a substrate.
Q: Is it possible to construct a thin stone bench for exterior use? What are the concerns and considerations?
A: The stone should be at least 3cm thick. The length of the bench should be kept under 4’. Cut and finish the top and posts as you normally would; place the two posts approximately 10” in from each end of the top.
Use a drill-and pin-assembly, with two threaded pins per post. The trick is to make a very good bond with the epoxy or polyester resin. Lay the posts on the bottom of the top and mark off their location. Make sure that the stones member together perfectly.
Thoroughly sand with 40 grit or rougher – and this is the most-important part – both surfaces to be jointed. The stones must be very clean, moisture-free, and slightly warm. Epoxy together upside down, and allow to sit for 24 hours.
I constructed a similar bench more than 30 years ago of White Danby, and another 3 years ago of Absolute Black. They both sit outside in the snow and sun, and I have not had a problem. You should not, either.
Q: Is it good maintenance practice to pressure-wash stone paving?
A: No. Don’t pressure-wash more than two or three times a year. The pressure will push water through a grout joint, and it will weaken a caulk joint. If you must use a pressure washer, keep away from the stone joints.
Q: We are planning to use marble to face a 300’-high office building. The building code requires a minimum stone thickness of 1 5/8". We have not decided as to whether the 5 – 0 dimension will be the width or the height, and we are considering using a hand-set method or panel system, either bonded or with a bond break. Please advise us how thick the stone should be for this size panel, and the size and location of the required anchors?
A: The thickness of the stone, and the quantity and location of the anchors are related matters. The anchor requirement cannot be determined until the thickness of the stone is established, and the panel system selected. The thickness of the stone cannot be determined until the relevant ASTM test results are performed.
Q: We use a local method in installing stone floors. We use 15# felt paper as a bond break, and then nail diamond wire to the plywood. We recently had a problem with a portion of the floor cracking. Is our installation method wrong?
A: This is an old method of installing stone floors. There is some question in these days about the benefit of nailing diamond wire to wood substrates affecting the ability of the felt-paper slip sheet to perform properly. However, there are many experienced stone setters that use this method, and we would doubt that the method itself would cause the described failure. Look for another reason.
Q: I want to install some small stone tiles about 4” square and 3/8” thick as a border on a large mirror. How can I adhere them?
A: Before you start, you must understand that the bond to the mirror will be by suction only, and that the bond should be checked periodically. There are two methods that can be used: tape or caulk. 3M VHB™ Double Coated Acrylic Foam Tape #4930 must occupy 25 percent of the 3/8” stone tile’s back-face area. Dow Corning795 Silicone Building Sealant can be used as an adhesive, and must cover 100 percent of the stone tile’s back face. Both of these materials require the back face of the stone and the face of the mirror to be absolutely clean. I would recommend further washing the contact area on the mirror with acetone prior to placement.
Q: I have a project where I have to drill some very small holes, about 1mm in diameter. Any suggestions on how to do the project nicely?
A: I would suggest that you look into using a water jet to make the holes.
Q: My new Absolute Black granite honed countertop has ring marks all over it. They are visible only when the top is wet. What is causing the marks and how can I remove them?
A: After viewing a photo of the stone, we determined that the "rings" were marks left by the suction cups used to move the stone in the fabricator's shop. Repeated washings with stone soap will remove the marks.
Vincent Migliore served as technical director for the Marble Institute of America, and wrote “Technical Q&A” for the MIA’s Through The Ages newsletter. Mr. Migliore passed away in late 2003.
The opinions and advice of Vincent M. Migliore are being provided as general information only. The Marble Institute of America ("MIA") assumes no responsibility and shall not be liable for any damages resulting from your use of this general information. The opinions and advice provided by Mr. Migliore are the exclusive property of MIA and shall not be disseminated, republished, or reproduced in any manner without the prior written consent of MIA.
For more information, contact the Marble Institute of America at (440) 250-9222.
This article first appeared in the September 2004 print edition of Stone Business.