ASTM E1155: The Measurement Method, Not the Requirement

ASTM E1155 defines how to measure and calculate floor flatness (FF) and floor levelness (FL) numbers. It does not set the numbers a project must achieve. A spec that cites E1155 and stops there has described a measurement procedure, not a performance requirement.

The full title tells you everything: ASTM E1155/E1155M-23, Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers (ASTM International, 2023). FF describes surface bumpiness, the small-wavelength deviations a straightedge would catch. FL describes levelness, the larger deviation from a true horizontal plane across a slab. The method walks a profiler down defined sample lines, captures elevation data at fixed intervals, and runs that data through a statistical calculation that produces the F-numbers everyone references on a punch list.

That’s the entire job of E1155. It tells a testing agency where to walk, how often to sample, and what math converts raw elevation readings into FF and FL values. ASTM is explicit that the method also supports evaluating how construction technique, placement sequence, strike-off method, or finishing approach affects the resulting profile. That’s a legitimate and common use, but it’s a diagnostic use, not a contractual one. E1155 quantifies what a floor is. It never says what a floor has to be.

That distinction matters because specs sometimes get written as if citing the standard is enough. It isn’t. Without a target number, a reference to E1155 only confirms how a dispute would eventually get measured, not who wins it.

ACI 117: Where Standard Tolerance Values Come From

ACI 117, Specification for Tolerances for Concrete Construction and Materials, is a reference document that specification writers use to select appropriate tolerance values, including flatness and levelness along with dimensional and location tolerances for concrete construction generally. It is a source of standard values, not an automatically enforceable requirement unless the contract adopts it.

ACI 117 is broader than FF/FL. It covers plumbness, squareness, dimensional tolerances for formed concrete, placement tolerances for reinforcement, and a long list of other construction tolerances that have nothing to do with floor flatness at all. Flatness and levelness are one section inside a much larger tolerance reference, which is part of why people conflate it with a floor spec when it’s really a toolkit architects and engineers draw from (American Concrete Institute, ACI SPEC-117-10, 2010, reapproved 2015).

ACI’s companion guidance describes tolerances in general as “permissible variations that establish limits within which the designer and contractor are expected to perform the work” (American Concrete Institute, ACI 117.1R-14, Guide for Tolerance Compatibility in Concrete Construction, 2014). That phrasing matters: tolerances in ACI 117 are defaults meant to be selected and incorporated by a specifier, not blanket rules that apply automatically to every slab regardless of what the contract says.

The U.S. Access Board, in its technical discussion of dimensional tolerances in construction, notes that ACI 117’s traditional straightedge-based approach was built around randomly trafficked floors, and that ramps and other specialized surface conditions need separate criteria (U.S. Access Board, Dimensional Tolerances in Construction and for Surface Accessibility). That’s an early signal of a theme that becomes critical later in this article: standard tolerance values assume standard conditions. Fixed-path and automated floors are not standard conditions.

The Practical Distinction: Test Method vs. Tolerance Source vs. Contract Requirement

ASTM E1155, ACI 117, and a project’s contract documents answer three different questions. E1155 answers “how is this measured?” ACI 117 answers “what values are typically used?” Only the contract documents answer “what does this project require?” Confusing any of the three for the others is the root of most flatness disputes.

Read the table from right to left when a disagreement comes up on site. The contract documents are the only entry with enforcement authority. ACI 117 and E1155 are both upstream of that document, supplying the values and the method a good spec should reference by name.

Specified Overall (SO) vs. Minimum Local (ML): Why Both Numbers Matter

A complete FF/FL requirement needs two numbers for each measure: a Specified Overall (SO) value, which is the average standard required across the whole floor area, and a Minimum Local (ML) value, which is the lowest value permitted in any individual measured section. A spec with only one of the two is incomplete.

A technical bulletin from LATICRETE on the correlation between Division 3 floor flatness and flooring requirements makes this point directly: SO and ML together are needed to fully describe a flatness and levelness requirement, and ASTM E1155 is the method used to calculate both from measured floor profiles (LATICRETE, Correlation Between Division 3 Floor Flatness (FF) and Flooring Requirements, technical bulletin). SO tells you whether the floor is flat on average. ML tells you whether any single section is bad enough to cause a problem even if the overall average looks fine.

That gap between average and worst-case is exactly where disputes happen. A floor can post an excellent SO number while still having one localized low spot deep enough to catch a pallet jack wheel or create a trip hazard near a doorway. Without an ML threshold in the contract, there’s no basis to flag that spot as noncompliant, no matter how obvious the problem looks in the field.

One clarifying point worth stating plainly: there is no universal rule of thumb for how ML should relate to SO as a percentage or ratio. Numbers sometimes informally associated with minimum local values get repeated around job sites as if they were standard, and they are not. Only the contract documents set the acceptance threshold for a given project. If your spec references SO without ML, or vice versa, that’s a gap to close before the floor is poured, not after a dispute starts.

Why Random-Traffic F-Numbers Aren’t Enough for Fixed-Path and Automated Floors

For narrow-aisle, very-narrow-aisle (VNA), wire-guided, AS/RS, and robotics floors, a standard random-traffic FF/FL number is not sufficient to enforce contract tolerances. ASTM states plainly that E1155 results must not be used to enforce tolerances for floors primarily intended for fixed-path vehicle systems; those floors need criteria based on actual vehicle wheel paths and operating tolerances instead.

This is the single most expensive misunderstanding in high-bay and automated warehouse construction, and it deserves direct attention. Random-traffic F-numbers are statistical averages describing a floor that forklifts and foot traffic will cross at varying angles and locations. A fixed-path system doesn’t do that. A VNA truck, a wire-guided reach truck, or an AS/RS shuttle runs the same wheel path, inches wide, thousands of times a day. The relevant question isn’t “how flat is this floor overall,” it’s “how flat is this floor along these specific six-inch-wide tracks, at this mast height, at this travel speed.”

ASTM International’s own standard identifies this limitation directly (ASTM E1155/E1155M-23, 2023): a floor can pass a strong overall FF/FL score and still be unsuitable for the automated system installed on top of it, because deviations within the actual wheel path affect mast movement, vehicle stability, operating speed, rack clearance, guidance-system performance, and elevation differences between adjacent rack bays. None of those failure modes show up in a random-traffic F-number because that number was never built to describe a six-inch-wide travel path in the first place.

The fix is to build the floor criteria backward from the operating system, not forward from a generic default. That means defining tolerances around the actual vehicle type, wheel configuration, aisle geometry, guidance system, and rack layout before the slab is poured, then measuring against that project-specific criteria rather than a textbook FF/FL target. The U.S. Access Board’s discussion of dimensional tolerances for specialized surface conditions makes a parallel point about ramps and non-standard surfaces: standard straightedge-based tolerances were developed for randomly trafficked conditions, and specialized use cases need their own criteria (U.S. Access Board, Dimensional Tolerances in Construction and for Surface Accessibility). Fixed-path warehouse floors belong in that same category. If your project includes narrow-aisle racking, wire guidance, or any automated material handling, confirm with your engineer that the spec addresses wheel-path tolerances specifically, not just a slab-wide SO/ML number.

Who’s Responsible for What: Owner, Architect/Engineer, Contractor, Testing Agency

Four parties typically share responsibility on a flatness-critical project: the owner, the architect or engineer of record, the contractor, and the independent testing agency. Each has a distinct role, and confusion about who owns which decision is a frequent source of disputes once a floor is poured and measured.

The owner or facility operator defines the operational need: what equipment will run on the floor, what performance that equipment requires, and what risk tolerance the business can accept. The architect or engineer of record translates that need into enforceable contract language, selecting SO and ML values (often informed by ACI 117 defaults, sometimes modified or replaced with project-specific operational criteria) and specifying ASTM E1155 as the test method. The contractor builds to that contract, and is responsible for workmanship, placement method, and finishing technique that produce a compliant slab. The independent testing agency measures the finished floor per ASTM E1155 and reports the resulting FF/FL data accurately, without authority to change what the contract requires or to declare engineering compliance on its own.

That last point is worth underlining. A testing agency’s report is data, not a verdict. Whether a reported FF/FL number satisfies the project is a question the contract documents answer, administered by the architect or engineer who wrote them. An independent testing provider can tell you, accurately and without bias, what the floor measured. Confirming whether that result satisfies your specific contract language is a conversation worth having before testing starts, not after a number comes back that someone on the project didn’t expect.

Specification Checklist: What the Contract Documents Should Actually Say

A complete flatness and levelness specification should state, in enforceable language, the performance category, governing tolerance source, measurement method, required SO/ML values, testing timeline, sampling plan, and responsible parties. A spec missing several of these items is incomplete regardless of which standards it cites.

1. Performance category: random-traffic, or fixed-path/automated with project-specific operational criteria
2. Governing tolerance source: ACI 117 default values, or modified/custom values stated explicitly
3. Measurement method: ASTM E1155/E1155M, cited by current edition year
4. Required SO value for FF and FL
5. Required ML value for FF and FL
6. Testing deadline relative to placement (how many hours or days after pour)
7. Test boundaries: which areas of the slab are included or excluded (loading docks, column lines, construction joints)
8. Sampling plan: number and location of test sections per measured area
9. Parties responsible for scheduling and paying for testing
10. Acceptance authority: who reviews results and makes the pass/fail call
11. Remedies: what happens if ML or SO values aren’t met (grinding, re-test, re-pour thresholds)
12. Operational criteria for fixed-path or automated systems, defined by vehicle type, wheel configuration, and guidance system where applicable

Run your own specification against this list before the first pour, not after the first failing test report. The two IFTI resources on writing and specifying FF/FL requirements, How to Write FF/FL Floor Flatness Specifications and How to Specify FF/FL Floor Flatness and Levelness Correctly, go deeper into drafting language for each of these items.

Bottom Line: The Contract Documents Control

Neither ASTM E1155 nor ACI 117 is, by itself, an enforceable floor requirement. E1155 defines how FF/FL gets measured. ACI 117 is a source of standard tolerance values. The contract documents are the only document on a project with the authority to say what a specific floor must achieve, whether they adopt ACI 117 values directly, modify them, or set custom targets for a fixed-path or automated floor.

That hierarchy resolves most of the confusion this article opened with. A spec that cites E1155 is telling you how a dispute would eventually be measured. A spec that cites ACI 117 is telling you where typical values come from. Only a spec with explicit SO/ML numbers, a defined test method, a testing timeline, and named responsible parties is telling you what your floor actually has to do. If any of those pieces are missing from your project’s contract documents, that’s the gap to close, and it’s far cheaper to close before the slab is poured than after a testing agency reports a number nobody agreed on in advance. For readers evaluating floor flatness calculations in more detail, IFTI’s guide FF/FL Floor Flatness Explained: How the Numbers Are Calculated walks through the math behind the numbers referenced throughout this article.