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1. Are tiles flat with no lippage? 1/32 in.
2. Size of grout joints. <1/8 in.
3. Are joints intact? Are joints showing any signs of cracking? Where?
4. If tile, are they set straight?
5. Pay attention to adjacent surfaces such as carpets, walls and other materials.
6. What is the overall condition of the stone?
7. What are traffic patterns like?
8. Does the floor vibrate or move when walked on?
9. Are there any visible patterns?
10. Are the edges of the tile chipped?
11. What type of installation is it? Mud, thin set, five point, etc?
12. Note expansion joints.
13. What is the color of the setting mortar? Gray or white?
14. If spalled or cracked, note patterns.
15. Is the stone discolored?
16. Is the stone wet? Take moisture readings.
17. Is the installation sound? Tapping is useful here.
18. Are there any visual clues of improper maintenance or unusual events?
19. Is there anywhere the subfloor can be examined? Heat registers, carpet transistions,etc.?
20. Is laboratory or destructive testing necessary?

Destructive Testing

During, after or prior to the visit you may determine that stone has to be removed to further investigate. If this is the case, you need to decide if you will perform the removal or have someone else do it. This can be an insurance issue, and you need to check with insurance company to see if you are covered for this type of work.

Destructive Test Types

The type of destructive test you may need will vary on the project. The following is a description of some of the tests and what you will need to look for:

Stone Removal —The stone is removed with a hammer and chisel, which will destroy the stone but give you an opportunity to view the setting bed. When the stone is removed, look for the following:

1. What color is the setting bed?
2. Is the setting bed soft and crumbling?
3. Is there any setting material on the back of the stone and on the substrate?
4. How much coverage is there?
5. Can you see trowel marks in the setting bed?
6. Note anything unusual about the setting bed.
7. Take photographs of the setting bed, the substrate and the back of the tile.
8. Collect samples of the stone and setting bed.
9. Note any slip or fracture membranes.
10. Is the setting bed wet? Take a moisture reading on the setting bed and the substrate.
11. Is there any foreign manner on the substrate?

Core Sample — In some cases you may want to take a core sample. A core sample needs to be taken of the stone, setting material and substrate. Core samples are useful for moisture problems. A good laboratory can perform several tests on the core to tell how the concrete was mixed, the ingredients in the mix, if too much or too little water was added, the strength of the bond, etc.

Pull Test — The pull test uses a suction cup placed on the stone, which is then pulled with a hoist to see how well it is bonded.

The second part of this article will cover petrographic and design analysis, field and laboratory investigation and photo documentation, and will appear in the May issue of SF.

About the author:
Frederick M. Hueston runs the National Training Center for Stone & Masonry Trades, Asheville, NC 28806, www.ntc-stone.com, and can be reached at Fhueston@aol.com.