All Commercial Slabs Not Created Equal

Those in the business of concrete know the importance of a flat and level slab. Especially in industrial warehouse settings, where unmanned forklifts rule the floor and goods may be stacked on shelves 20 feet or higher, flatness and level specifications are a key indicator of project success.

But other businesses are catching on. Flatter and more level floors have been shown to be lower maintenance and provide an improved operational surface for many types of businesses. As a result, the demand for flatter floors is being seen in many different types of projects, from warehouses to retail store operations.

The degree of a slab’s flatness is expressed by two numbers, the FF (which describes the concrete slab’s flatness) and the FL (which refers to the slab’s levelness). Flatness is how close to geometric planarity a slab approaches. Flatness numbers run on a scale from 10 to 150, and most slabs fall into the range of 15 to 100. The higher the FF number, the flatter the slab.

Levelness is the amount of slope (or pitch or tilt) in a slab.  This is the degree to which the surface of the slab approaches true horizontal perfection.

These numbers aren’t only telling of the flatness and levelness; they are also indicative of the quality of work. Floor flatness and levelness are determined by the skill of the concrete forming, placement and finishing crews, as well as the quality of their equipment. The floor levelness is most affected by form quality and the method of strike-off. Forms should be straight and sturdy to resist bowing and warping. Placement is affected by the manner of screeding (leveling) selected. Wet screeding without rails, is typically capable of producing FL values no higher than 18. Screed rails and vibratory screeds can achieve FL ‘s in the mid to high 20s. Laser screeds – as used by Custom Concrete — can reach as high as 100.

Commercial projects specify the desired FF and FL values within the project contract. The average retail floor is FF 25 and FL 15; a general purpose industrial warehouse is typically from FF 50 / FL 35 to FF 60 / FL 40. Custom Concrete’s commercial division consistently exceeds expectations and delivers well beyond the required FF and FL values. Some notable projects include:

  • Subaru warehouse in Lebanon, required FF 50 / FL 35 and Custom Concrete achieved FF 80 / FL 54
  • Project Steel in Greenwood required FF 50 / FL 35  and Custom Concrete achieved FF 91 / FL 49
  • Fastenal in Indianapolis required FF 50 / FL 35 and Custom Concrete achieved FF 69 / FL 45.

We are proud to utilize our nearly 50 years of concrete experience to deliver these high-quality projects.

For more information about our commercial division, contact us here.

Awards from the Indiana Ready Mixed Concrete Association

Suburu Project Description:

Subaru Award

Award-winning Subaru project team

The project is located in Lebanon Indiana about 25 miles north of Indianapolis Indiana on I-65. The project scope requirements were 3,500 lf of building footing, 280 structural column pads, 715,000 sf of 7” and 8” slab on grade, 135,000 sf concrete dock aprons, 1,000 lf of dolly pads, and 8,000 sf of sidewalks. This project schedule was to pour 23,000 cubic yards in 5 months with 50% to be completed during the winter.

Project Summary:

Primarily, Custom Concrete is known in the Indianapolis market as a residential foundation and wall contractor. Custom Concrete was awarded the 715,000 square foot warehouse on the basis of professional referrals, team experience, and budget. The highest slab on grade tolerance specification was to be an FF 60 / FL 40. The tolerance was exceeded and reported as an overall value of FF 80 / FL 54. The largest single pour was over 60,000 sf and more than 1,400 cubic yards. This project was the first large scale commercial project for Custom Concrete in over 40 years of business. On time and on budget! 

Fastenal Project (166,500 sf)


This project was started on 12/19/2014 and went through a record winter with regards to temperatures and snowfall.

Fastenal Award

The award-winning Fastenal team

During construction is was found that the precast supplier was unable to deliver the wall panels on schedule so Custom Concrete was asked if they could cast in place the exterior 18’ tall wall.  Custom Concrete accepted the challenge and poured 500 lf of 18’ tall exterior building wall when temperatures ranged from 10 degrees to 35 degrees.  We used self consolidating concrete to achieve the exceeded strengths.

The floor slab was poured from Jan 20th to April 15th all in open air conditions.  Ground heaters and blankets were used to defrost the sub grade during this time frame.  We had over 38” of snowfall that was removed from the building pad during this timeframe to keep the project on schedule.  We achieved an overall FF 69 / FL 45 from the required FF 50 / FL 35.

The exterior was poured in concrete paving for a total of 98,000 sf.


  1. CIP wall pour when originally was to be precast
  2. 38”+/- of snow removal by Custom Concrete during construction
  3. FF 69 / FL 45 achieved (open air pours in record winter)
  4. Temperatures from
    1. Working temps from -13 degrees to 65 degrees
    2. Pouring concrete from 18 degrees to 65 degrees
  5. Weather days lost of 22 days
    1. Made all but 6 days up from overall schedule
  6. Numerous design changes throughout the project with no loss of production/schedule days
  7. 7,175 cyds poured in winter

This project was very challenging for everyone involved do to the record low temps and snowfall amounts during construction.  Custom Concrete worked through some of the most challenging worksite conditions and was still able to bring the project in on only 6 days after the original schedules end date.

Project Steel (100,000 sf)


This project was Custom Concrete’s first project with The Peterson Company.

The floor slab was poured in (3) pours averaging 33,000 sf at 7” thick  We achieved an overall FF 91 / FL 49 from the required FF 50 / FL 35.


  1. FF 91 / FL 49 achieved
  2. 2,960 cyds poured