How to Read an ASTM F1869 Calcium Chloride Report Before Signing a Columbia Epoxy Quote

September 26, 2026

The calcium chloride result is the one number on a coating proposal that predicts whether the floor stays stuck. Here is how to read it line by line.

What a Calcium Chloride Test Actually Measures

ASTM F1869 is the test most proposals mean when they say calcium chloride. A dish of anhydrous calcium chloride sits under a sealed dome on bare concrete for 60 to 72 hours, and the weight the salt gains converts to a moisture vapor emission rate, reported as pounds of water per 1,000 square feet per 24 hours. That single figure is what a coating system has to live with for its service life.

The method's limit is depth. The dome reads vapor leaving roughly the top quarter to half inch of the slab, not the moisture sitting deeper in it, so a floor can test comfortably during a dry stretch and behave differently later. That matters in a climate with no dry month: the 1991-2020 normals at BWI put annual precipitation at 45.00 inches, with July the wettest at 4.48 inches and February the driest at 2.90 inches.

The Lines on the Report, One by One

A usable report is more than one number on letterhead. Before that number decides anything, check that the paperwork accounts for each of these:

• The result for every test location, in pounds per 1,000 square feet per 24 hours, not averaged into one site-wide figure.
• How many locations were tested. The method calls for at least three in the first 1,000 square feet of slab, plus one more for each additional 1,000.
• Start and end timestamps showing the dome sat for 60 to 72 hours, not overnight.
• Confirmation the space was held at service conditions for at least 48 hours first, near 65 to 85 degrees F, with the HVAC running as it will once the floor is in use.
• Whether the slab is on grade, below grade, or suspended, since a below-grade floor is fed moisture from underneath year round.
• That the test areas were bare concrete, with sealers, curing compounds, old coatings and patching material removed. Testing through any of those returns a number about the coating, not the slab.

Why the Report Has No Pass or Fail Line

F1869 measures; it does not judge. The standard sets no acceptance criteria, so a report stamping a slab as passing is quoting somebody else's limit. That limit belongs to the product going down, and the figure most often cited across coating data sheets sits near 3 pounds per 1,000 square feet per 24 hours. Plenty of products are tighter, and a few moisture-tolerant systems are looser.

ASTM F2170 is the other method worth knowing, and many specifications now ask for both. Probes go into holes drilled at 40 percent of slab thickness for a floor drying from one side, equilibrate for at least 24 hours, and report internal relative humidity rather than a surface emission rate, with common limits in the 75 to 80 percent range. Because those probes read into the body of the slab instead of its skin, F2170 is the more predictive of the two.

What a Columbia Slab Adds to the Picture

Columbia's villages were platted by the Rouse Company in the late 1960s, and a slab of that vintage arrives with a history nobody wrote down. What sits beneath it, how it was cured, and what has been sealed on it are usually unknown, which argues for testing rather than assuming. Soils reinforce the point: a garage over Glenelg clay loam behaves differently from a floor cut into Baile-series low ground, where water sits.

Below-grade floors deserve the extra scrutiny. A basement slab under continuous vapor drive can feel bone dry and still read high under a dome, and white crusting at the perimeter is a signal to test before anyone talks about color chips. More of the local figures behind these calls are collected on the Columbia epoxy by the numbers page.

Questions Worth Asking Before You Sign

A few questions separate a proposal built around the slab from one built around a calendar. Anyone quoting resin floor coatings for Howard County homes and businesses should be able to answer all five without hedging:

• Which product's published limit is this result compared to, and where is that limit written down?
• Were the wettest-looking areas included in the test locations, or only the convenient ones?
• Was the space conditioned for 48 hours before the dome went down, and was the slab bare?
• If the number comes back high, what changes: a moisture-mitigating primer, a different system, or a delay?
• Who pays for the retest if prep exposes a wetter layer than the original test saw?

How the Result Changes the Install

A comfortable number does not shorten prep. Mechanical profile still governs adhesion, and ICRI Technical Guideline 310.2R describes the target as a concrete surface profile from CSP 1 to 10, with diamond grinding typically landing at CSP 1 to 3 and shot blasting at CSP 3 to 7. That step anchors any concrete grinding and surface prep scope, and no primer compensates for skipping it.

A high number changes the system rather than the schedule: a moisture-mitigating primer or vapor-barrier coat under the build, a chemistry chosen for tolerance, or more drying time on new concrete. Ambient conditions apply on top of that, since most epoxies want roughly 50 to 85 degrees F with the slab above the dew point, and polyaspartics widen the cold end. Those choices, not square footage alone, shape what a garage floor coating or commercial epoxy flooring scope contains, and the cost page covers which variables move the total.

Treat the moisture report as a design input rather than a formality, and be wary of any proposal that skips it on a below-grade or unknown slab.

More from the blog

• Coating a Columbia Basement Floor: Efflorescence, Vapor Drive, and When a Coating Is the Wrong Answer
• Getting a Columbia Garage Floor Ready Before the First Brine of the Season
• When Is the Best Time of Year to Epoxy a Garage Floor in Columbia, MD?