HELP! There is a Water Stain on My Ceiling

Air Vent StainingWhy Is There A Water Stain On My Ceiling Next To An A/C Vent?

Now that summer is in full swing, the temperature inside your attic can be well over 100 degrees.  The temperature inside your air conditioned house is probably between 72 and 80 degrees.

Construction Details Count

If there is an air gap between the register “can” and the ceiling drywall, condensation (water) will form on the warm side because of the extreme temperature differential and drip onto the drywall leaving a stain when the drywall dries out.  Do not fear.  There is a solution for this problem.

How To Solve The Problem

First, remove the grill from the ceiling.  Then, carefully spray expandable foam between the register “can” and the drywall that surrounds it.  I say carefully because the foam can drip, or if too much is applied, it can get over everything and it’s difficult to clean up.

Once the foam is completely dry, tear off any excess foam and spray the water-stained ceiling drywall with oil-based Kilz (white pigmented shellac).  Once the Kilz dries, touch up the ceiling with matching paint and reinstall the grill.

Problem solved!


If you have questions about about any home improvement or remodeling project, please call me at 561-795-2551 or email me at: and I’ll be happy to share my knowledge with you.
Leading Edge Homes, Inc. is a Florida certified building contractor specializing in improving your lifestyle through room additions, bathroom renovations, kitchen updates, hurricane-resistant screen enclosures, and more!  In business since 1991, they demolish your stress by building your trust. Contact them at 561-795-2551 or visit their website to discover how they can help you with your next home remodeling project in Palm Beach County.