Garage Floor Coating Standard

Purpose

A failed garage floor does not fade, it lifts in sheets the customer can pick up with a fingernail, and it takes the whole ticket with it. Two causes account for most of them. Water vapour was moving up through the slab faster than the coating could tolerate, which no amount of surface prep fixes, or the slab was never actually opened up, so a hard troweled or previously sealed surface got a film that had nothing to key into. A third, hot tire pickup, is a cure-schedule failure rather than a product one. This standard puts a measured slab moisture number, a measured surface profile and a mock-up adhesion test in front of the first mixed kit.

Scope

Thin-film epoxy and urethane coatings on residential attached-garage and small shop slabs on grade, from slab assessment through return to service.

Not covered: polished concrete, self-leveling overlays and decorative resurfacing; structural slab and crack repair; isocyanate-containing polyurea and polyaspartic systems, which need respiratory protection this SOP does not cover; and industrial floors carrying forklift traffic or chemical service.

Roles and responsibilities

Procedure

1. Assess the slab and the garage before quoting a system. Note slab age, any existing coating or sealer, cracks, spalling, pitting, oil staining, floor drains and pitch, and whether the customer knows if a vapour retarder was placed under the slab. Acceptance: a written condition list with photographs, and any existing coating stated present or absent, never assumed. Wrong, and the stop rule: an existing coating of unknown chemistry is not overcoated on a guess; either it comes off or a mock-up in step 5 decides it. Spalling and structural cracking are concrete repair, quoted separately or declined. Hazard: none at this step, it is a walk with a camera and a flashlight.

2. Test slab moisture at the sampling density the standards set, on a separate earlier visit. Run calcium chloride tests per ASTM F1869 or in-situ relative humidity probes per ASTM F2170, in the editions your specification references, both of which set the sampling density at three tests for the first 1,000 square feet and one more for each additional 1,000. Hold the space at service temperature and humidity for the conditioning period the standard states, 48 hours in the editions in common use, before the test starts. Acceptance: every test at or below the maximum the coating manufacturer's data sheet states, worst test governing rather than the average. Commonly cited limits are 3 pounds per 1,000 square feet per 24 hours by F1869 and 75 percent relative humidity by F2170, but the sheet's number governs, and moisture-tolerant systems state higher ones. Wrong, and the stop rule: a single test over the sheet's limit stops the standard system, and the answer is a moisture-tolerant primer rated for the reading, a source fix, or declining the job. It is never a heavier coat of the same product. Hazard: none beyond kneeling.

3. Open the surface mechanically to the profile the data sheet names. Grind the full floor to the concrete surface profile the sheet specifies, referenced to the ICRI Guideline No. 310.2 CSP chips, which for thin films is typically in the CSP 1 to 3 range; verify by feel against the chip, not by appearance. Acceptance: uniform profile matching the specified CSP chip across the whole floor including corners and the door threshold, with no polished or glossy areas left. Wrong, and the stop rule: a missed strip along a wall is where the coating lifts first, so the floor is re-walked with the chip before any vacuuming is called done. Hazard: grinding concrete releases respirable crystalline silica, an inhalation carcinogen that a glove does nothing for: run the tool with the shroud and dust collector its matching entry in 29 CFR 1926.1153 Table 1 specifies, with a respirator under a written program per 29 CFR 1910.134, and if the shroud or the collector is missing the grinding does not happen.

4. Decontaminate the oil, then prove it with a water absorption check. Degrease every stained area with a concrete degreaser at the label rate and dwell, rinse, dry, then drop clean water at six points including each former oil stain and the two heaviest tyre tracks. Acceptance: the water darkens and soaks in within 30 seconds at all six points, oil stains included. Wrong, and the stop rule: beading over an old oil stain means oil is still in the pore structure, and a coating over it fisheyes and releases in exactly that outline, so the spot is degreased again or ground deeper and re-tested. Hazard: degreasers are commonly alkaline and a contact and eye hazard, so gloves and eye protection per the safety data sheet, with a 15 minute flush and medical attention on any contact; rinse water carrying degreaser and oil does not go to a storm drain, it goes where your local requirements say.

5. Coat a mock-up and test its adhesion before the floor is committed. Coat a small area in a corner at the specified film, let it reach the sheet's cure for testing, then run an X-cut tape test per ASTM D3359 Method A in the edition your specification references, the method that standard assigns to thicker films. Acceptance: classification 4A or better, meaning no more than trace peeling along the incisions. Wrong, and the stop rule: 3A or worse means the profile, the contamination or the moisture is still wrong, so the floor goes back to step 3 or step 4 and nothing else is coated. Hazard: the knife making the X-cut is the sharpest thing on site, so the cut runs away from the hand and never toward a knee on the floor.

6. Mix full kits to the stated ratio and spread inside pot life, never in the bucket. Combine the full A and B components in the ratio and for the mixing time the sheet states, pour the mixed material onto the floor immediately, and spread and back-roll to the wet film the sheet requires. Acceptance: wet film readings inside the specified range on each kit, the kit emptied onto the floor inside the sheet's pot life, and any flake broadcast to refusal before the film sets. Wrong, and the stop rule: material thickening in the pail is past pot life, and spreading it anyway produces a soft patch that never hardens, so that kit is discarded per the sheet and the next one is mixed. Hazard: epoxy amine hardeners are skin and respiratory sensitizers, so gloves chosen off the maker's chemical resistance chart, sealed eye protection, and no skin contact at all, because sensitization is permanent and it ends careers. A mixed kit left standing in its pail exotherms, can smoke and can reach a temperature that burns, which is why it goes onto the floor immediately; a pail already hot goes outside away from the structure, carried at arm's length. Ventilate the garage; if a gas appliance with a standing pilot is in it, its shutdown and relight belong to the customer's gas contractor, not the crew.

7. Cure to the sheet, restore what was shut down, and hand over two different dates. Keep all traffic off for the sheet's foot-traffic time and all vehicles off for its vehicle time, which is always the longer of the two, then confirm any appliance the gas contractor shut down has been relit by them and is firing and venting correctly before handover. Acceptance: written handover naming the foot-traffic date and the vehicle date separately, contents and garage door restored, and any shut-down appliance confirmed back in service by the contractor who shut it down. Wrong, and the stop rule: a car parked on an under-cured floor lifts the coating off in the shape of the tyre, so if the customer needs the garage sooner, the honest answer is that the vehicle date does not move. If an appliance has not been relit, do not attempt it and do not leave, tell the customer and the office before you go. Hazard: an unlit or badly vented gas appliance is a carbon monoxide hazard to the family, which is exactly why the relight sits with the gas contractor and gets confirmed rather than assumed.

The record this produces

The floor file carries the slab condition list with photographs, the moisture test method with every result, its date and the manufacturer limit beside it, the specified CSP and the chip used to verify it, the six water absorption results, the ASTM D3359 classification from the mock-up including any failure, product and batch with mix times and wet film readings per kit, and the two handover dates.

The office reads the moisture record when a floor lifts: one that tested at or under the sheet's limit and lifted anyway is a product conversation with the manufacturer, and one coated over an out-of-limit reading is not.

One filled-in run: 440 square foot two-car attached garage

Step 1: slab about twelve years old, no existing coating, two oil stains under the left bay, light pitting at the door threshold, no hairline cracking beyond shrinkage, customer does not know whether a vapour retarder was placed.

Step 2 fails. At 440 square feet the density rule gives three tests, so three relative humidity probes go in per ASTM F2170 after the garage is held at service conditions for the conditioning period. Readings at 72 hours: 71, 74 and 82 percent. The coating's data sheet states a maximum of 80 percent, and the gate is worst test governing, so the 82 percent probe fails it. The average of the three is 75.7 percent, which a mean-based rule would have passed, and that is why the rule is written per test. The office prices a moisture-tolerant primer rated by its own sheet to 90 percent relative humidity, the customer approves the change in writing, and the job continues on the revised system.

Step 3: floor ground to the CSP the revised system's sheet specifies, verified against the chip in six locations including both wall edges and the threshold. Step 4: both oil stains degreased twice; water dropped at six points darkens within about fifteen seconds at all six, inside the 30 second acceptance. Step 5: mock-up coated in the right rear corner, cured to the sheet, X-cut tape tested at 5A, no peeling, which clears the 4A gate. Step 6: four kits mixed, each emptied onto the floor inside pot life, wet film readings inside range on all four. Step 7: handover names the foot-traffic date and the vehicle date separately, and no gas appliance was in this garage, so nothing needed relighting.

Self-check against the criteria as written: step 2 wants every test at or below the sheet's maximum, worst governing, and 82 against 80 is a FAIL, so the stop rule was taken and the system changed rather than the coat thickened; the revised sheet's 90 percent limit clears that same 82 percent, PASS. Step 4 wants absorption within 30 seconds at six points, six of six at about fifteen, PASS. Step 5 wants 4A or better, 5A, PASS.

The exception this run hit is the useful one: a stop rule does not always mean wait, it sometimes means change the product and re-price it in writing. The one it did not hit is a customer who declines the upgrade, where the job is declined rather than coated on a system its own sheet says will fail.

References

• ASTM F1869 and ASTM F2170, in the editions your specification references, for slab moisture test method, conditioning and sampling density.
• ASTM D3359 Method A, for the X-cut tape test used on the mock-up in step 5.
• ICRI Guideline No. 310.2, for the concrete surface profile chips the coating data sheet references.
• Coating manufacturer technical data sheet, for moisture limits, required CSP, pot life, film build and both cure times. Label directions govern where they differ from anything here.
• 29 CFR 1926.1153 Table 1 with respirators under 29 CFR 1910.134, for silica control while grinding concrete.