ASTM E1155 is the American Society for Testing and Materials standard test method for determining FF floor flatness numbers and FL floor levelness numbers on concrete slabs. Developed as the industry’s primary quantitative framework for evaluating slab surface quality, ASTM E1155 uses the F-number system — a statistical method that translates elevation readings collected by a floor profilometer or Dipstick device into two distinct metrics: FF, which measures short-interval surface waviness, and FL, which measures longer-interval tilt relative to design plane. The standard defines the measurement protocol only — required FF/FL targets are set by the project specification, not by ASTM E1155 itself. For warehouse floors with defined-traffic (DT) aisles and narrow-aisle forklifts, FF numbers of 50–100+ are commonly specified; general commercial slabs may require only FF 25–35. IFTI (International Floor Testing and Inspection) performs ASTM E1155 testing on concrete slabs nationwide, issuing reports that include section-by-section F-numbers, test location maps, and non-compliance callouts.
ASTM E1155 measures FF floor flatness and FL floor levelness numbers on concrete slabs using the F-number system. FF quantifies short-interval surface waviness — how smooth the slab is underfoot — while FL measures longer-interval tilt relative to the slab’s intended plane. The standard defines the measurement method; required F-number targets are set by the project specification.
FF (Floor Flatness) measures short-interval surface bumps and waves — relevant for flooring installation, equipment travel, and polished concrete. FL (Floor Levelness) measures how closely the slab follows its intended slope or plane over longer distances — critical for racking plumb, drainage, and elevated slab design. A slab can have a high FF (very smooth) while having a low FL (significantly out of level).
ASTM E1155 testing is performed by qualified floor testing specialists using calibrated floor profilometers or Dipstick devices. IFTI (International Floor Testing and Inspection) is a national provider of ASTM E1155 testing services, delivering section-by-section F-number reports, test location maps, and non-compliance documentation for concrete slab projects.
What ASTM E1155 measures (and what it does not)
ASTM E1155 is the “Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers.” FF measures surface bumpiness over short intervals — essentially how smooth the floor feels underfoot and how well it accommodates resilient flooring, polished concrete, and equipment travel. FL measures tilt and slope over longer intervals — relevant for racking plumb, drainage design, and elevated slab deflection.
What the standard does not do: it does not set required FF/FL targets. The standard defines the measurement method; the project specification and use-case determine what numbers are required. A warehouse with defined-traffic aisles and narrow-aisle forklifts will require very different FF/FL targets than a general-purpose retail space.
FF vs. FL in plain English
FF is how smooth the slab feels — the measure of short-interval floor waviness that affects how flooring materials lie, how carts and pallet jacks ride, and whether large-format tile telegraphs substrate conditions. A higher FF number means a flatter, smoother surface.
FL is how close the slab is to its intended plane across longer distances — whether it tilts, slopes away from design intent, or creates drainage problems. A high-bay racking system’s plumb condition is sensitive to levelness; a floor can be very smooth (high FF) while still sloping significantly (low FL). Both numbers matter, and a specification should address both.
How measurements are collected on site
Technicians lay out test lines across the slab per the ASTM E1155 protocol, collecting elevation readings at regular intervals along each line. The test captures slab areas by defined test sections, and construction joints are handled separately from overall FF/FL statistics — you do not measure across a joint and include those readings in the overall calculation. The equipment walks or rolls the profiler along planned lines, and the resulting elevation differences feed into the FF/FL statistical formulas.
Deliverables should include a test location map, the raw readings, calculated FF/FL values by section, and any non-compliance callouts with localized defect identification. A well-prepared report supports go/no-go decisions and mitigation planning. Learn more about floor flatness testing procedures and how to plan a complete floor flatness and levelness standards program.
Equipment used for ASTM E1155 testing
ASTM E1155 testing is performed with a floor profiler — commonly called an F-meter or dipstick profiler — that records elevation changes at defined intervals. The instrument must be calibrated, and operator discipline matters: consistent line placement, correct handling at starting positions, and proper documentation of test section boundaries all affect the validity of results. Output is a tested and documented FF/FL report, not just a single number.
What FF/FL numbers mean for project risk
Higher FF/FL means lower risk of flooring installation issues and less remedial grinding or self-leveling before finishes. A slab that falls short of specified tolerance can require significant corrective work: grinding high spots, filling low spots, or applying self-leveling underlayment — all of which add cost and extend the schedule if discovered late.
The concept of “specified overall” versus “minimum local” is important in practice: a slab’s overall statistics can pass while localized defects create real installation problems. A thorough acceptance plan defines both overall and minimum local criteria to catch these cases. For context on how floor flatness requirements vary by industry, review IFTI’s industry-specific guidance.
When to test (timing) and who should order it
The best time to test is before flooring, racking, or TI work begins — when corrections are cheapest and schedule impact is minimal. Testing after materials are delivered or installed dramatically reduces options. Key triggers for ordering ASTM E1155 testing include: before tenant improvement buildout; before resilient or polished flooring installation; before racking or robotics deployment; at slab turnover from GC to owner; and as part of due diligence for existing buildings being repositioned or re-tenanted.
What a good ASTM E1155 report should include
A useful FF/FL report contains: slab identification and test area descriptions, methodology statement (ASTM E1155), test section maps, FF/FL results by section, pass/fail assessment against the specified tolerance, localized defect callouts with location and magnitude, and recommended corrective actions before installation. A report that only presents aggregate numbers without a location map and defect callouts provides limited value for project decision-making. IFTI’s standardized reporting format delivers all of these elements, documented and signed for independent third-party value.
Frequently Asked Questions
Is ASTM E1155 the same as FF/FL testing?
Yes. ASTM E1155 is the test method used to generate FF (flatness) and FL (levelness) numbers for concrete floors.
What’s a good FF/FL number?
It depends on use. General commercial floors may use lower tolerances; defined-traffic aisles, robotics, or high-bay racking typically require higher tolerances. Your spec and intended use determine the right target.
Can you test across construction joints?
Typically no. Joints create discontinuities and are handled separately from overall FF/FL statistics per the standard.
Does elevated slab testing work the same way?
The profiling method is similar, but levelness requirements on elevated slabs may be treated differently because they deflect under load. Consult your structural engineer’s acceptance criteria for elevated-slab projects.
What happens if a slab fails FF/FL?
Common corrective options include grinding high spots, filling low spots, and applying self-leveling underlayment, followed by re-testing to verify compliance before proceeding with installation.
