Things You'll Need
4-to-8-inch wide 24-gauge sheet metal, 1-inch deep
High temperature spray paint
Heat resistant adhesive caulk
A flue that is too small for the fireplace opening can sometimes cause smoke to leak out through the top of the fireplace. When this happens, you can end up with soot stains on your ceiling, walls and fireplace surround. Smoke guards keep the errant smoke from slipping out of the fireplace. You can build your own fireplace smoke guard with a simple piece of sheet metal and heat resistant adhesive found at your local home improvement store. A coat of heat resistant paint to complement the fireplace surround and mantle provides the finishing touch.
Measure the length and height of the fireplace opening to determine the size of the sheet metal needed. The average height of a fireplace opening ranges from 24 to 32 inches; smoke guards typically range between 4 and 8 inches in width. Use 24-gauge sheet metal with at least a 1-inch depth that won't interfere with the flue block-off plate inside the fireplace. Take the measurements to your local home improvement store to have the sheet metal cut to your specifications.
Paint the piece of sheet metal with high temperature spray paint. You can find this type of paint at fireplace shops or in the grill section of the home improvement store. Let the paint dry overnight.
Apply a bead of heat resistant adhesive caulk along the length of the underside of the top of the fireplace opening.
Press the piece of sheet metal, lengthwise, to the caulk. Tap the metal securely in place with a mallet.
Place several strips of masking tape on the metal and fireplace surround overnight to help hold the smoke guard in place while the adhesive dries.
Remove the masking tape before you use the fireplace. Place a piece of aluminum foil across the top of the fireplace for one or two uses as a guide for the width of the smoke guard needed.