Does the word flat have the same meaning as the word level? If we look in various dictionaries it can have almost the same definition, which can be confusing. However, in tile work these two words are drastically different and as you will see, the difference in their meanings can be very expensive.
In the tile world, the word “flat” means that the surface does not have any significant high or low spots and will yield a smooth tile installation with no lippage between tile edges. If the surface is less than required, it must be either ground down, built up with the proper patch material or a combination of the two.
On the other hand, the word “level” has a much different meaning in relation to tile work. If the tile installation is required to be level by the architect or owner, the bubble of spirit level must rest between the lines as shown in the above photo, otherwise the surface is “out of level.”
Here is a true story of a tile contractor who didn’t know the difference between flat and level. The job he was doing had a large concrete floor which was in terrible shape. He told the architect that he would “level” the floor for a specified amount of money. The change order was approved and the work was completed with a cementitious floor patch which made it suitable to receive tile (it was flat).
When completed, the architect came to the job with a four-foot level in hand, promptly placed it on the floor and you guessed it, the floor was not level. The tile installer said, “I meant flat.” But the architect reminded him that he had signed the change order for LEVEL. The installer was forced to have a specialized floor preparation company come in and pump enough self-leveling cement over the recently flattened floor at a cost of over $50,000. This was an extremely expensive mistake, but this contractor now knows the difference between the words flat and level.
The next time you are called on to fix a bad floor, be absolutely certain you know whether you are providing a flat surface or a level surface. Level can be much more expensive than flat. Make sure you know the difference.