When you’re taking a walk, flat ground is the same as level terrain, right? Yes – and easier on the knees than all those hills and bumps! In many contexts, these words are virtually synonymous. Are flat and level the same thing? In the world of flooring, they do not have the same meaning. Flat means that the surface being discussed has no significant low or high spots. Level means that the surface is parallel to the horizon (horizontal plane).  What is acceptable floor levelness?  You will need a professional to determine that.

CAUTIONARY TALE

Are flat and level the same thing? Here’s a little cautionary tale to illustrate our point that “flat” and “level” are two different beasts in the flooring world. A contractor was hired to tackle a concrete floor that was in disrepair. He promised he would level it and gave a quote. He then applied a cement floor patch and flattened the surface so tile could be installed.

Great, the flooring contractor saved the day! Not so much, as it turns out. The architect turned up with a level, and the floor failed the test. The contractor meant that he would make the floor flat. However, his work order and quote were built around making the floor level. It was a $50,000 mistake. 

HOW TO CALCULATE FLOOR FLATNESS 

Flat means that there are areas on the surface that are either raised high or sunken low – flat means really, exactly, specifically … flat. Basically, there are no bumps or lumps. This way, when a tile is installed, there is no slippage between the edges. To determine if a floor is flat, contractors use a ten-foot straight edge (either an L shape or rectangular). 

Contractors use “F numbers” to determine a floor slab’s flatness and levelness, which are calculated using ASTM E1155 standards. FL numbers relate to the floor flatness and architect specifications that indicate the acceptable limits. For example, in general office or light industrial spaces, the American Concrete Institute states that the flatness of FF is acceptable. For warehouse floors and labs, it is FF 30-35.  This can be confusing for lay people but essential for contractors. Making a mistake can be very costly. In any case, your floor needs to have the right FF for your application. An experienced flooring installer will understand this terminology and ensure it is done right.

If a floor is not flat according to industry requirements, the flooring contractor can grind the floor down to achieve the proper specs, use a patch material, or do a combination of both.  If the surface requirement is not as level as necessary, it must be made to be so using the appropriate tools. The Occupational Safety and Health Administration (OSHA) has stringent methods to accomplish this task, and those practices must be adhered to. If the floor needs to be built up, the appropriate method must be utilized to adhere to the proper patch material. On occasion, a combination of the two methods may be required. Additionally, what is known as an SLU (an underlayment that is self-leveling) can be placed over the surface that has been prepared according to standards and then coated with a primer that has been approved by the manufacturer.

ACCEPTABLE FLOOR LEVELNESS 

On the other hand, unlike the flat, the word “level” has a much different meaning in relation to tile work – rather than something just being “level.” The word level means that the floor is parallel to the horizontal plane. Contractors use F numbers here, too, and there are standards for acceptable floor levelness (FL). For example, in general office or light industrial spaces, this is FL 20, and for warehouse floors and labs, it is FL 20-25. Professionals use a 10-foot straight edge with a spirit level to determine if they’re hitting the mark.

The calculations can seem complex, but experienced commercial flooring contractors and installers know the standards and the methods to achieve acceptable F numbers, and they have the tools by which to measure and ensure accuracy.

LET’S RECAP

Are flat and level the same thing? Knowing the difference between flat and level is important: flat means there are no significant high or low spots. Level means it is parallel to the horizon (horizontal plane). There are acceptable levels for both flatness and levelness, and these depend on the application. It will be a little different for offices, labs, hospitals, non-critical areas (e.g., back of houses), heavy industrial, etc.  For contractors, it is important to know the difference between flat and level. In general, fixing a level floor is much more expensive than making a floor flat.

East Coast Flooring & Interiors has extensive experience in understanding acceptable floor levelness, and we will ensure your project specs are met to the letter – well… to the F-number! Give us a call at 1-954-626-8053; we are here to help your project move along smoothly and deliver the results you need.