Why epoxy fails in South Florida
SFL Epoxy is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Epoxy fails when its bond to the slab breaks, and the epoxy data sheet we read sets the limits that protect that bond: 85% humidity at most; slab at least 5 F above dew point1, and slab moisture of 4% by weight at most (Tramex meter)1 1. NOAA normals put South Florida air near those limits on many days, though airport air is not your slab. We found no Florida failure rate, so we do not rank the causes.
SFL Epoxy is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Last reviewed October 18, 2026 against the cited sources.
Updated . Sources
The limits on one epoxy data sheet
A data sheet is the maker's own rulebook for a product. This one is for a smooth-finish epoxy, and the figures are the maker's (vendor data), not independent tests 1.
| Condition | What the sheet says |
|---|---|
| Air and slab | 85% humidity at most; slab at least 5 F above dew point1 |
| Temperature | 50 F to 86 F1 |
| Slab moisture | 4% by weight at most (Tramex meter)1 |
| Readings | at least every 3 hours1 |
If slab moisture is over the limit, the sheet says not to apply the coat 1. It also says the product is for indoor use 1.
The polyaspartic topcoat sheet we read is tighter on air and slab: 75% humidity at most; slab at least 5 F above dew point2.
Heat: how often South Florida air passes the sheet's ceiling
NOAA's 1991-2020 normals count 91.5 days per year3 with a high of 90 F or more at Miami's airport and 74.1 days per year4 at West Palm Beach's airport. These counts are our arithmetic, summed from the monthly normals.
The sheet's top temperature is 86 F for air and slab 1. The normal daily high is above 86 F for 5 months per year3 at Miami's airport and 4 months per year4 at West Palm Beach's airport.
A shaded garage slab can run cooler than airport air, and a closed garage in the sun can run hotter. Only a reading on your slab settles it.
Humid mornings and the dew point
Dew point is the temperature at which air starts to leave water on a surface. If the slab is close to it, a wet coat can trap moisture. That is why the sheet asks for a margin and for readings during the work 1.
We computed how often the 6 a.m. normal humidity is above the sheet's 85% cap 1, using the Magnus formula on NOAA's hourly normals. It is 41 days per year5 at Miami's airport and 130 days per year6 at West Palm Beach's airport (our arithmetic). This is a derived estimate, not a measured humidity count.
| Airport | Days at 90 F or more | Months above 86 F | Mornings above 85% humidity |
|---|---|---|---|
| Miami Intl | 91.5 days per year3 | 5 months per year3 | 41 days per year5 |
| West Palm Beach Intl | 74.1 days per year4 | 4 months per year4 | 130 days per year6 |
A damp patch on a floor is not proof of a wet slab. Condensation and slab moisture can look alike, and only a test tells them apart (our reading).
Which months give a coat the most room
The sheet limits and NOAA's hourly normals can show which months leave the most room for a coat. Treat this as guidance, not a schedule. It describes airport air, not your slab.
How we counted: a day passes when every hour from 8 a.m. to 5 p.m. stays inside the limits 7. Epoxy months use the Sikafloor-264 limits 7. Those are 50 to 85 F, humidity of 85 percent or less and a slab at least 5 F above the dew point 7. Polyaspartic months use the Sikafloor-511 limits 8. Those are 50 to 85 F, humidity of 30 to 75 percent and the same dew point margin 8.
Our arithmetic: a month counts when at least 90 percent of its days pass. Under that rule Miami's epoxy count is 6 months per year5.
| City (NOAA station) | Epoxy months | Polyaspartic months | July hours above 85 F |
|---|---|---|---|
| Miami (Miami Intl Airport) | Nov to Apr: 6 months per year5 | Mar to Apr: 2 months per year5 | 89 percent5 |
| West Palm Beach (WPB Intl Airport) | Nov to May: 7 months per year6 | Apr to May: 2 months per year6 | 77 percent6 |
Months just outside a window came close. These are the days that passed in them (our arithmetic):
- Miami. Epoxy: May 20 of 31 days; Oct 21 of 31 days5. Polyaspartic: May 20 of 31 days5.
- West Palm Beach. Epoxy: Oct 24 of 31 days6. Polyaspartic: Mar 16 of 31 days6.
No June through September day passes in either city 5 6. July is the hardest month. The share of its 8 a.m. to 5 p.m. hours above 85 F, the top of the substrate range on two Sika sheets, is 89 percent5 at Miami's airport and 77 percent6 at West Palm Beach's airport.
Most polyaspartic misses come from morning humidity above the sheet's cap, which is lower than the epoxy cap (our arithmetic). The caps are 75 percent for the Sikafloor-511 sheet 8 and 85 percent for the Sikafloor-264 sheet 7. These are 30-year airport averages, not a forecast 5 6. Air temperature stands in for slab temperature, and a coat also has to cure overnight, when humidity runs higher.
Use the table to see which months give the sheet limits the most room. A start in a listed month is not a promise, and a start outside one is not barred. Ask the installer for air, slab and dew point readings on the day, and put the go or no-go numbers in the scope. The guide on when to book covers early starts.
Moisture from below
Ground moisture can move up through a slab on the ground. Building Science Corporation names a plastic sheet directly under the slab as the barrier, and argues that Florida slabs do better than California's because of that practice 9.
The barrier may be there, and you still cannot see it under the slab. Ask for a moisture reading on your own slab, with the method, the meter and the number written in the scope.
Common tests
- Calcium chloride test, ASTM F1869: a federal guide specification for resinous flooring lists it as "Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride" (2023 edition) 10. Sika describes a dish of calcium chloride under a plastic dome stuck to the slab for 60 to 72 hours 11. The result is in pounds per 1,000 sq ft 11.
- Probe test, ASTM F2170: the same specification lists it as "Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes" (2019a edition) 10. Sika describes holes drilled in the cured concrete that stabilize for at least 72 hours before probes are placed and read with a hygrometer 11.
A moisture meter is another option. The Sikafloor-264 epoxy sheet reads percent by mass on a Tramex meter 7.
The limits on the sheets
| Source | Limit |
|---|---|
| Sikafloor-264 epoxy (Sept 2026) | 4 percent by mass or less on a Tramex meter, or 85 percent RH or less by ASTM F2170 7 |
| Sikafloor-511 polyaspartic (2023) | 4 percent or less on a Tramex meter 8 |
| Sikafloor-1620 primer, US (2025) | Considered at 6 percent by weight or less on a Tramex meter, or 96 percent RH or less by ASTM F2170 12 |
| Sikafloor-1620 Canada (2026) | Cured resin resists moisture vapor emission up to 25 pounds by ASTM F1869 and 100 percent RH by ASTM F2170 13 |
| ARMPOLY85-CM topcoat (ArmorPoxy) | Substrate humidity under 4 percent 14 |
| Federal guide specification | The specifier picks 3 or 4.5 pounds by F1869, or 75 percent RH by F2170 10 |
On the Sikafloor-264 sheet, a probe reading from 85 to under 96 percent points to the Sikafloor-1620 primer 7. A reading of 96 percent or more points to a different system 7. The Sikafloor-1620 sheets say a probe test does not replace a moisture-meter reading 12 13.
Each limit belongs to one product, so do not compare rows as if they were one rule. We found no garage-market epoxy sheet that states a calcium chloride pound limit. The pound figures above come from a federal guide specification and a Canadian primer sheet. You may hear that a certain pound reading is common. We could not source that, so we do not repeat it.
Ask which test the installer will run, which sheet's limit applies, and what happens at a failing reading. The epoxy sheet we read says not to apply the coat if slab moisture is over its limit 1.
Surface prep: grinding, blasting and acid etching
The sheet measures slab moisture on a surface that has been mechanically prepared 1. It expects a prepared surface, not one that has only been swept. The prep guide lists what to ask for in the scope.
Makers name the roughness they want with the ICRI concrete surface profile scale, called CSP. KTA-Tator, a coatings inspection firm, says the scale runs from CSP 1, very smooth and typical of acid etching, to CSP 10, very rough and typical of jackhammering 15.
| Product or method | What it asks for |
|---|---|
| Sikafloor-264 epoxy | Mechanical prep to a profile equal to CSP 3 to 4, after removing efflorescence, laitance and contaminants 7 |
| Sikafloor-511 polyaspartic | CSP 3 to 4 8 |
| Sikafloor-1620 Canada | At least CSP 3 13 |
| ArmorPoly 80 (garage) | Grinding or acid etch on new concrete cured at least 30 days 16. No CSP number named. |
| Acid etching, typically | CSP 1 15 |
Sika's surface prep guide calls shot blasting the industry standard. It says diamond grinding creates a profile, and that grinding pads of hard aggregates such as aluminum oxide only polish the surface and do not create the required profile 17.
So the sheets do not agree on the minimum. Our reading is that acid etching alone sits at CSP 1, below the CSP 3 to 4 the Sika sheets ask for 15 7. No sheet we read says so in those words. We did not read the ICRI guideline's own table that pairs each method with a CSP number, so the CSP 1 figure rests on KTA-Tator's page alone 15.
Ask the installer which method they use, which CSP they aim for, and which product sheet that number comes from. On new concrete, ask how long it cured first. One garage polyaspartic sheet asks for at least 30 days 16.
White powder or a damp patch: efflorescence or condensation
A white powder or a damp patch is not proof of a wet slab on its own. They look alike but have different causes.
- Efflorescence is a white crystalline salt deposit left when water seeping through concrete, brick or stone evaporates 18. K-State Research and Extension says it is not a fungus, and that if a little water and a rag remove it, it is not mold 18.
- Condensation can form when the slab is close to the dew point. The Sikafloor-264 sheet asks for a slab at least 5 F above the dew point, because condensation may lead to adhesion failure or blushing 7. It adds that the slab can be cooler than the air 7.
- A plastic-sheet check. The same sheet says a plastic sheet test (ASTM D4263) may give a visual indication of vapor drive 7.
The same sheet tells the installer to remove efflorescence, laitance and contaminants before coating 7. K-State's page is about basements. We found no single source that explains both for garage slabs, so use this to ask better questions, not to diagnose your floor. Ask for a moisture test and a dew point reading before anyone names the cause.
What a coating will not fix
A coating is a finish, not a repair. It does not stop moisture that keeps rising, and it does not hold a crack that keeps moving (our reading).
If the slab fails its moisture limit, the sheet says not to apply the coat 1. Ask what the installer will do instead, and who pays for that step.
Sellers blame hot tires and sun for many failures. We found no independent test of either, so the peel guide treats them as claims.
Salt air: advice only
We found no data sheet or independent source on salt and garage slabs, so we state no effect and give no number.
If you live near the water, ask the installer for the product's chloride limit from its data sheet. Ask what they test on your slab before the work, and put the answer in writing.
Questions to ask before you pay
- Which product sheet will you follow, and what are its humidity, dew point and temperature limits?
- Which moisture test will you run, which sheet's limit applies, and what number stops the job?
- Which surface profile (CSP number) will you prepare to, by which method, and from which sheet?
- Who records the air, slab and dew point readings during the work, and where do I see them?
- What happens to the start date if a reading misses the sheet?
- The guide on when to book covers early starts and dry-season windows.
What we could not confirm
- A Florida failure rate for epoxy garage floors.
- Any effect of salt air on a garage coating.
- How the airport counts above relate to the slab in a garage.
- The ICRI table that pairs each prep method with a CSP number.
- A garage-market epoxy sheet that states a calcium chloride pound limit.
- Whether the sheets' limits match every epoxy product. The Sikafloor-261 sheet is a Canadian edition read in French 1, so check the sheet for your product.
This is research, not a quote or a diagnosis of your floor.
Facts used in this guide
| Fact | Value | Source |
|---|---|---|
| Average days per year with a high of 90 F or more at Miami Intl Airport (USW00012839) (sum of the 12 monthly NOAA 1991-2020 normals), the climate an epoxy garage floor is installed and lives in near Miami | 91.5 days per year | [3] 1991-2020 |
| Number of months in which the normal daily high temperature at Miami Intl Airport (USW00012839) is above 86 F, the upper substrate limit on one epoxy data sheet (vendor); NOAA 1991-2020 normals for Miami | 5 months per year | [3] 1991-2020 |
| Days per year when the computed normal relative humidity at 6 a.m. is above 85%, the cap on one epoxy data sheet (vendor), at Miami Intl Airport (USW00012839) | 41 days per year | [5] 1991-2020 |
| Average days per year with a high of 90 F or more at West Palm Beach Intl Airport (USW00012844) (sum of the 12 monthly NOAA 1991-2020 normals), the climate an epoxy garage floor is installed and lives in near West Palm Beach | 74.1 days per year | [4] 1991-2020 |
| Number of months in which the normal daily high temperature at West Palm Beach Intl Airport (USW00012844) is above 86 F, the upper substrate limit on one epoxy data sheet (vendor); NOAA 1991-2020 normals for West Palm Beach | 4 months per year | [4] 1991-2020 |
| Days per year when the computed normal relative humidity at 6 a.m. is above 85%, the cap on one epoxy data sheet (vendor), at West Palm Beach Intl Airport (USW00012844) | 130 days per year | [6] 1991-2020 |
| Months in which at least 90 percent of days have every hour from 8 a.m. to 5 p.m. inside the Sikafloor-264 limits (50-85 F, relative humidity 85% or less, 5 F above dew point) (vendor), using NOAA normals at Miami Intl Airport (USW00012839): Nov to Apr | 6 months per year | [5] 1991-2020 |
| Months in which at least 90 percent of days have every hour from 8 a.m. to 5 p.m. inside the Sikafloor-511 limits (50-85 F, relative humidity 30-75%, 5 F above dew point) (vendor), using NOAA normals at Miami Intl Airport (USW00012839): Mar to Apr | 2 months per year | [5] 1991-2020 |
| Share of July hours between 8 a.m. and 5 p.m. whose normal air temperature is above 85 F, the top of the substrate range on two Sika data sheets (vendor), at Miami Intl Airport (USW00012839) | 89 percent | [5] 1991-2020 |
| Months in which at least 90 percent of days have every hour from 8 a.m. to 5 p.m. inside the Sikafloor-264 limits (50-85 F, relative humidity 85% or less, 5 F above dew point) (vendor), using NOAA normals at West Palm Beach Intl Airport (USW00012844): Nov to May | 7 months per year | [6] 1991-2020 |
| Months in which at least 90 percent of days have every hour from 8 a.m. to 5 p.m. inside the Sikafloor-511 limits (50-85 F, relative humidity 30-75%, 5 F above dew point) (vendor), using NOAA normals at West Palm Beach Intl Airport (USW00012844): Apr to May | 2 months per year | [6] 1991-2020 |
| Share of July hours between 8 a.m. and 5 p.m. whose normal air temperature is above 85 F, the top of the substrate range on two Sika data sheets (vendor), at West Palm Beach Intl Airport (USW00012844) | 77 percent | [6] 1991-2020 |
| Near-miss months, Miami Intl Airport (USW00012839), the two months just outside the epoxy window: days with every hour from 8 a.m. to 5 p.m. inside the Sikafloor-264 limits (50-85 F, relative humidity 85% or less, 5 F above dew point) (vendor limits, NOAA normals) | May 20 of 31 days; Oct 21 of 31 days | [5] 1991-2020 |
| Near-miss months, Miami Intl Airport (USW00012839), the month just outside the polyaspartic window: days with every hour from 8 a.m. to 5 p.m. inside the Sikafloor-511 limits (50-85 F, relative humidity 30-75%, 5 F above dew point) (vendor limits, NOAA normals) | May 20 of 31 days | [5] 1991-2020 |
| Near-miss months, West Palm Beach Intl Airport (USW00012844), the month just outside the epoxy window: days with every hour from 8 a.m. to 5 p.m. inside the Sikafloor-264 limits (50-85 F, relative humidity 85% or less, 5 F above dew point) (vendor limits, NOAA normals) | Oct 24 of 31 days | [6] 1991-2020 |
| Near-miss months, West Palm Beach Intl Airport (USW00012844), the month just outside the polyaspartic window: days with every hour from 8 a.m. to 5 p.m. inside the Sikafloor-511 limits (50-85 F, relative humidity 30-75%, 5 F above dew point) (vendor limits, NOAA normals) | Mar 16 of 31 days | [6] 1991-2020 |
Garage Floor Readiness Score
Answer each question. The score shows how much needs sorting out before a coating, and which answers added the most. It is a starting point, not a price or a promise.
Start the Garage Floor Readiness ScoreSFL Epoxy is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Questions people ask
Why does epoxy fail in a Florida garage?
It fails when the bond between the coat and the slab breaks. The sheets we read point to slab moisture, a weak surface and a start outside the humidity, dew point and temperature limits 1. We found no Florida failure rate, so we cannot say which cause is most common.
Does humidity ruin epoxy?
One epoxy sheet we read caps air humidity at 85% during the work and the cure 1. NOAA normals put Miami's 6 a.m. humidity above that cap on 41 days per year5 (our arithmetic). Airport air is not your slab, so ask for readings in your garage on the day.
Does salt air damage epoxy?
We found no data sheet or independent source on that, so we make no claim. Ask the installer for the product's chloride limit and for what they test on your slab.
How is slab moisture tested before epoxy?
Common tests are a calcium chloride dish under a dome (ASTM F1869) and probes in drilled holes (ASTM F2170) 11. Some sheets also read a moisture meter 7. Ask which test, which sheet's limit and the result in writing.
Is acid etching enough before epoxy?
The Sika sheets we read ask for a profile of CSP 3 to 4 7. Acid etching is typically CSP 1 15. One garage polyaspartic sheet accepts grinding or acid etch on new concrete 16. Ask which method and profile are in your scope.
Is the white powder on my garage slab mold?
It may be efflorescence, a salt deposit left when water moving through concrete evaporates. If a little water and a rag remove it, it is not mold 18. That page is about basements, so ask for a moisture test either way.
Sources
- Sikafloor-261 CA Product Data Sheet (fiche technique), 2026-06
- Sikafloor-515 Product Data Sheet, June 10, 2021
- NOAA NCEI U.S. Climate Normals 1991-2020, monthly: Miami Intl Airport, FL, 1991-2020
- NOAA NCEI U.S. Climate Normals 1991-2020, monthly: West Palm Beach Intl Airport, FL, 1991-2020
- NOAA NCEI U.S. Climate Normals 1991-2020, hourly: Miami Intl Airport, FL, 1991-2020
- NOAA NCEI U.S. Climate Normals 1991-2020, hourly: West Palm Beach Intl Airport, FL, 1991-2020
- Sikafloor-264 product data sheet (Sika USA, September 2026, vendor), 2026-09
- Sikafloor-511 product data sheet (Sika USA, June 2023, vendor), 2023-06
- Building Science Corporation, BSI-003 Concrete Floor Problems (Lstiburek), May 26, 2008
- UFGS 09 67 23.13 Standard Resinous Flooring (USACE/NAVFAC/AFCEC, references per UMRL July 2026), 2019-11
- Test Methods in Concrete (Sika USA), August 23, 2019
- Sikafloor-1620 product data sheet (Sika USA, March 2025, vendor), 2025-03
- Sikafloor-1620 product data sheet (Sika Canada, June 2026, vendor), 2026-06
- ARMPOLY85-CM technical data sheet (ArmorPoxy, vendor), 2024-04
- Measuring the Surface Profile of Prepared Concrete (KTA-Tator), July 18, 2019
- ARMPOLY80-RM technical data sheet and instructions (ArmorPoxy, vendor), May 30, 2025
- Surface Preparation Guide (Sika USA, vendor; page undated, read 2026-10-18), October 18, 2026
- Basement Moisture Problems Continue (K-State Research and Extension, Cottonwood District), November 8, 2019