The Solution

When applying any paint, including both waterborne (so-called "latex") and solvent borne, including alkyd (oil-based), rubber-based, epoxy-based, urethane-based, etc., always make sure the surface to which you are applying the paint or coating is NOT TOO HOT – i.e. the surface should NEVER be 90° F (32.2° C) or hotter.  Note:  The surface is frequently hotter than the ambient (air) temperature.

  The Reason Why?

In order to get good adhesion of any paint or coating to any surface, the surface MUST be (A) rough (like rough, 80-grit, sandpaper) and/or (B) porous (have pores in the surface, like the pores in a piece of wood or lumber).  This requires that surfaces be properly prepared, e.g. concrete must be made porous by being etched with acid, and sheet metal, such as steel, aluminum, copper, etc., must be scarified or roughened until it has a profile (peaks and valleys) measuring 2 to 3 mils (50.8 to 76.2 microns) from highs to lows; even smooth enamel paint must be roughened with sandpaper.

The reason for the rough and/or porous surface is so the paint or coating has something to grab onto to hold itself onto the surface, or to penetrate into and anchor itself to.  The bond between a paint/coating and the surface to which it is applied is a mechanical bond – not a chemical bond.

When the surface is too hot, i.e. hotter than 90° F, then the paint will dry too fast on the back side of the paint film – the side next to the wall, roof, patio or floor – BEFORE the paint has had a chance to penetrate into the pores of the surface, e.g. the pores in the concrete or macadam surface of a driveway, patio, walkway, tennis court, wall of a swimming pool, or stucco walls on the exterior of a building or the tiles on a roof.  This is like pancake batter be ing put onto a hot griddle, and the bottom side of the pancake that touches the hot griddle cooks much faster than the top side of the pancake.  It cooks so fast that in a few seconds you have to flip the pancake so it doesn't burn the bottom side of the pancake.

If a paint or coating is put on a hot wall, roof, patio or floor surface, you get the same rapid drying on the back side before the paint has the opportunity to penetrate into the pores, cracks, crevices, or the roughened or abraded surface to which it is applied.  The result will be a lack of adhesion to the surface, which will eventually result in bubbling, peeling, flaking and chipping of the paint from the surface.

  HELP!

 Here's a TIP – If you are applying a "latex" (waterborne) paint, you can cool a hot wall, patio or roof  by spraying it with a cool mist of cold water from a garden hose, which generally can lower the  surface temperature enough so you can apply the waterborne paint.  But be sure there is no liquid  water left on the surface when you start applying the paint.

 Of course, you cannot cool a hot surface with cold water if you are applying a solvent borne (oil- based, rubber-based, epoxy-based, urethane-based) paint or coating.