Rain is the most common reason an outdoor coating job goes wrong, and it is also the most avoidable. The damage happens in the window between the last coat going down and the surface being water-safe, and that window is where somebody has to make a decision.
While a polyaspartic or polyurea top coat is curing it is reacting, and water in the wrong place during that reaction causes real problems:
And on a slab that is still damp when the base coat goes down, you get the worse version: adhesion loss, which is not cosmetic at all.
This is the part people do not expect. If two feet of a patio gets rained on and has to be redone, that section is now a different batch, applied on a different day, at a different temperature, over a slightly different surface. It will almost never match the rest. The gloss will read differently and the flake density will read differently. A homeowner ends up with a permanent seam across their patio or an apron that does not match the garage.
That is the real cost of coating into a bad forecast, and it is a complaint you can find attached to most coating companies in this market.
Roughly: the surface needs several hours before it can shed light moisture, and a full day before weather is genuinely a non-issue. Cold slows that down. Humidity slows that down. Those are the numbers we work from and we will give you the real ones for your floor on the day, not a generic figure.
Covering a curing coating with plastic sounds reasonable and usually makes it worse. Plastic traps solvent vapor and moisture against the surface, which causes its own blushing, and it moves in wind. A sheet that blows off halfway through a storm has protected nothing and has probably left a crease pattern in the finish. It is an emergency measure, not a way to beat a forecast.
For exterior work we watch the forecast through the morning of the job, not the week before. If the window is not clean we call you and move the date, and we tell you why. Interior garage and basement work is largely unaffected by rain, though a soaking wet slab from a leak or a drain still has to be dried and tested before anything goes down.
Moving a date costs you a week. Coating into weather costs you the look of the floor for as long as you own the house.
Not necessarily. If it was more than a day after the top coat and the floor had cured, it is almost certainly fine. If it rained within hours, look for haze, dull patches or small craters, and get the installer out to look at it while the job is new.
Usually yes. The inside of a closed garage is protected. What we check is whether the slab itself is damp, because humidity and a cold slab together can put moisture on the surface you are bonding to.
Tenting traps solvent vapor and humidity over the curing film, which causes the same hazing you were trying to avoid. For a small area in a light drizzle it can work. For a real forecast it does not.
Tell us the room, the rough size and your town. You get a written price, not a two-hour pitch. Fastest way is to text a photo of the floor to (815) 585-1750.
