C04.05
Epoxies, basecoats, and the moisture ladder
The epoxy family shares a rhythm — 2:1, bead on the floor, 24-hour recoat — but every sheet has its own temperatures, windows, and moisture tolerance. Know the ladder before anyone opens a kit.
- Run the epoxy numbers: ratios, windows, temperatures, coverage
- Read the moisture ladder — which product survives which slab
- Broadcast correctly: to rejection, never into the wet edge, never piled
Epoxy coatings and basecoats — critical numbers per sheet
| Product | Ratio | Working time | Recoat window | Temps (air/surface · material) | Coverage |
|---|---|---|---|---|---|
| MavCoat PC | 2:1 | 25 min pot | Within 24 hr @70°F | 50–90°F ambient · ≥5°F over dew | 100 sq ft/gal @16 mils (prime 175–250) |
| MavCoat HPE | 2A:1B by volume | 25 min pot @77°F | 24 hr max — miss it and the surface must be sanded before recoating | Air 50–90°F · surface at least 5°F above dew point · store 65–80°F | 16 wet mils = 100 sq ft/gal per coat · as primer 175–250 sq ft/gal (thinnable up to 5% xylene) |
| MavCoat CRE | 2:1 | 25 min pot | 24 hr | Substrate 55–90°F | 8–16 mils · 100–200 sq ft/gal |
| MavCoat OPE (orange peel) | 2:1 | 25 min pot | 24 hr | Substrate 55–90°F | 8–16 mils; texture from consistent back-roll — never thin or re-ratio it |
| MavCoat SLE (self-leveling) | 2:1 | Slow 35–40 / Std 20–25 / Fast 12–17 min | Min 14/8/5 hr · max 24 hr | 35–85°F (below 60° use Fast) · 60–85°F | 10–30 mils · 53–160 sq ft/gal |
| MavCoat FC (fast-cure) | 2:1 | 10–15 min | Min 4 hr · max 24 hr | 35–85°F · 60–85°F | 16 mils = 100 sq ft/gal (16 mils required for its moisture rating) |
| MavCoat Metallic | 2:1 + 16 oz acetone + 32 oz additive | 30–35 min | Min 16 hr · max 48 hr | 60–85°F all three | 32–80 mils · 20–50 sq ft/gal; indoor only — UV is its enemy |
| MavCoat Flex | 1:1 | 20–25 min | Min 10 hr · max 24 hr | 60–85°F all three | 20–30 mils; never stand-alone — must be overcoated |
| MavCoat WBE (water-based) | 4:1 | ~1 hr pot after 15-min induction | 12–24 hr | 50–90°F; RH under 85%; never within 5°F of dew | 4–6 mils · 250–350 sq ft/gal · two coats; freezing destroys it |
| MavCoat CES (epoxy siloxane) | 2:1 | 25 min | Within the base epoxy's window or sand | Air/surface 45–95°F · material 60–85°F | 320–535 sq ft/gal; NEVER over 8 mils; hand-mix only |
| MavPrime EP (primer) | 2:1 | 30–35 min | Min 6 hr · max 24 hr | 60–85°F all three | 3–8 mils · 200–533 sq ft/gal; tight thin coat, inspect for pinholes |
| MavCoat HB / MavCoat SLE | 2:1 | 10–15 min to place | Next coat within 24 hr or degloss | 60–85°F all three | Primer 3–8 mils · SLE 8–30 mils per system |
| MavClad EM (trowel topping) | 2:1 binder | 25 min pot | Grout/topcoat within 24 hr | Ambient 50–95°F | 1/4 inch · 120 sq ft per 3-gal + 200 lb aggregate mix |
| MavCoat Polyurea (chip basecoat) | 2:1 | 10–60 min by speed | Chip immediately, seal after scrape (~1.5 hr) | Air/surface 35–85°F (below 50° use Medium/Fast) | 6–8 mils ONLY · 200–267 sq ft/gal — thicker foams in joints and holes |
The moisture ladder — MVER (ASTM F1869) and slab RH (ASTM F2170) limits per sheet
| Slab tests at | What can go down |
|---|---|
| ≤3 lbs / ≤75% RH | Standard family — PC, HPE, CRE, OPE, SLE, WBE, CES, Polyurea, UPA, HWU, UHD, EM, MavPrime EP |
| ≤12 lbs / ≤85% RH | MavCoat FC at a full 16 mils (the UFB 1-Day system) · MavCrete UQ-HD |
| ≤20 lbs / ≤99% RH | MavCrete UF-HD, UM-SL, and MavTop UQB urethane cement systems |
| ≤25 lbs / ≤95% RH | MavCoat MVB moisture vapor barrier at 16 mils — then the system goes over it |
| Over the product's limit | STOP. Nothing goes down. The office picks the mitigation — that is never a field call. |
Broadcast rules — chip, quartz, and sand
- 01To rejection means to rejection
Keep throwing until no wet spot shows. Chip covers about 6 sq ft/lb; quartz on urethane cement runs about 0.75 lb/sq ft; 20/40 silica on the PC system runs 0.4–0.5 lb/sq ft.
- 02Toss it into the air
Broadcast falls like rain, it is never dumped. Piles telegraph through every coat that follows.
- 03Stay out of the wet
Do not walk in broadcast resin, and never broadcast into a wet edge that has not been settled and back-rolled.
- 04Polyurea moves fast
Chip goes into MavCoat Polyurea before the surface skins — on Fast that is minutes. Scrape and recover loose flake after ~1.5 hours, then seal.
- 05Scrape before the next coat
Vacuum and gently scrape loose broadcast after cure. Loose chip under a topcoat is a defect you installed on purpose.
- Not this
The slab tested 5 lbs — the epoxy label says moisture 'resistant,' send it.
ThisStandard epoxies stop at 3 lbs / 75%. Over that, the office chooses FC at 16 mils, MVB, or urethane cement. Coating over a wet slab buys a delamination.
- Not this
We missed the recoat window by a few hours — it looks fine, keep going.
ThisThe sheets are unanimous: outside the window, sand until the gloss is gone, vacuum, then coat.
Takeaways
- Standard epoxies tolerate 3 lbs MVER / 75% RH. Higher than that and the slab needs FC at 16 mils, MavCoat MVB, or a urethane cement system — that is an office decision, not a field improvisation.
- Miss a 24-hour recoat window and the sheet says sand the surface before the next coat. Every time.
- Outgassing is managed, not hoped away: falling slab temperature, a tight thin prime coat, double prime on porous slabs.