How slippery a tile is can be very subjective. People walking on the same surface, with the same footwear, can experience very different levels of grip. If someone claims a tile is non-slip or non-skid there is no way to back up that claim. There is a testing method done in the lab that will determine the Dynamic Coefficient of Friction (DCOF), but it's more of a general ranking among other tested tiles than real world cause and effect.
SHOWER TILE INSTALLATION BUILT TO LAST
So how can you tell if a tile is more or less slippery than any other?
The answer is DCOF. This stands for Dynamic Coefficient of Friction. The American National Standards Institute has developed this standard (A326.3) for testing slip resistance. When a tile manufacturer wants to have their tile certified that it meets ANSI 137.1, the tile will also undergo a DCOF test at a lab such as the Tile Council of North America. The TCNA will wet the tile surface with water and run a small mechanical monitor over the tile. The monitor produces a number. This number indicates a floors relative slipperiness. For example, numbers less than 0.42 are often used in areas such as shopping malls(outside the food court), hotel lobbies, office buildings etc. where appearance and ease of cleaning are highly desired and measures are in place to keep the floor dry when walked upon. It is not to say floors with this number are, or are not slippery. It is showing the floors perceived slipperiness in relation to other tile surfaces tested. Slipperiness is a relative thing. You can slip on most any surface. A number close to 0.42 may indicate to a business owner that as long as I keep the floor dry, it should provide solid footing for their customers, look nice, and be easy enough to clean. A high texture or pitted tile design can trap contaminants creating a slip hazard as well as the need for an increased cleaning regimen.
A DCOF >0.42 is considered the standard for which a wet tile can be walked upon safely by some tile manufacturers and architects. So a tile for an outdoor deck that receives rain would require this number at a minimum. The number should be stamped on the box. If your box of tile does not have this stamp, it may not meet ANSI 137.1 It would be advised to assume the tile has a DCOF less than 0.42 if it is not on the box.
A tile's DCOF can change. For instance in a shower a tile may have a number of >0.42 when it is wet with water. However when soap or shampoo is on top of the tile the DCOF may be reduced. Care must be used on any wet tile, especially after a potential contaminant has been introduced. People that frequent the beach and bring sand up to their condo from their shoes can create a slip hazard that did not exist until they brought the sand in.
A tile installer nor a salesperson can determine what tile is appropriate for your area to receive tile. That determination must be made by the consumer and end user. Some tiles are easier to make a determination on than others by sight and touch alone, but knowing the DCOF number can be a helpful starting point. Truly that is all it is at best. A reference. The DCOF does not tell you how safe or slippery a tile is. It only tells you how slippery one tile may be over another. All tile can be slippery!
Tile is everywhere. It's so durable that we use it outside, we drive on it, and we walk on it with or without shoes so often we might not even realize we're on top of it. Rain, snow, or multiple shower heads, the show must go on. Customers are often concerned with how slippery a tile might be prior to their tile purchase. I will show you how to avoid a slippery tile, but first consider the following.
Did you know that a tile can have too much grip. Customers sometimes purchase a tile with a rougher texture in hopes of it being non-slip. Typically that is a good thing but not everyone has the same stride or gate . A person that shuffles their feet or fails to lift them high enough between strides can actually get hung up, which may cause them to trip. I don't mean trip over a small obstacle, I mean just the unintended action of dragging a foot over the walking surface. Too much grip can sometimes be just as bad as too slippery. A trip and a slip are two different actions, but both possibilities should be taken into consideration.
We installed a tile floor in a garage for an elderly couple some time ago. The tile was extremely textured. It was almost gritty and had a sandpaper type of feel on it. Of course they purchased this tile for the garage because water could potentially drip off of the car after a rain making the garage floor wet. Well you couldn't slip on this floor no matter what, but it could take rubber off of the tires of the car. They often have to get the floor pressure cleaned because hot tires and an abrasive floor will leave tire tracks. Now you can see, you must temper your choice to it's intended use, as well as it's intended user.