3 / 11
Never spray a wet surface
Never spray foam on a surface with a moisture level of more than 20 percent—the foam won’t stick. If the surface you’re spraying hasn’t been exposed to water for a few weeks, it should be OK to spray. But if you’re patching a wall that recently sustained water damage, or was just assembled with new, wet lumber, you may want to test the moisture level before you spray. You can get a moisture meter here.
4 / 11
Make a plan before you pull the trigger
Before installing the first tip/mixing nozzle, point the gun into a garbage bag or empty box, and pull the trigger until both chemicals are flowing evenly. But long before you do that, plan your work.
You’ll have to install a new tip every time you stop spraying for more than 30 seconds because the foam will set inside the nozzle and clog it. Spray foam kits come with extra tips, but it’s still important to (1) clear the room of everything that could get in the way, (2) decide which areas you’ll spray first, (3) put ladders wherever you need them, and (4) set up a fan or two to vent the fumes outdoors.
Before you start, shake the cans to mix the contents, and then shake every few minutes after that.
5 / 11
Cover windows with plastic
Staple plastic to the framing around the windows (and doors). Don’t worry about covering the gap between the window and the framing because you’ll want to fill those with low-expanding canned foam specifically designed for windows. Cover all the switch and outlet boxes with masking tape so you don’t fill them with foam. You don’t need to use gasketed electrical boxes when you insulate exterior walls like you would if you were using fiberglass—the foam will air-seal around the box.
ncG1vNJzZmivp6x7p63MoqOyoJGjsbq5wKdlnKedZLmqv9Noqqmqka56p7vApmSipqOquaLAyKilZqyZpcBw