When installing an air barrier, nail heads and screw heads need to be treated to keep air and water from leaking into the building envelope. The same is true for any deficiencies, wood knots, or any surface imperfections that may be subject to air/water leakage.
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Gun It
You gun a bead of FastFlash gun grade onto the nail or screw head.
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Tool it
Tool out the FastFlash with a bondo spreader, caulking tool, or chip brush.
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Let it cure
So let's talk cure times. FastFlash uses STP technology which is a moisture cure technology. It likes heat and it likes humidity. The higher the humidity the quicker it'll cure. Most of the time in a high heat, high humidity area you can move on within about a half an hour. It will stay tacky to the touch but as long as it doesn't transfer onto your hand, you're ready to move.
Now that you know how to use Fast Flash and you've completed all of your detail work you're ready to move on to the air barrier.