How to Build a Mantel for a Gas Fireplace

Use the circular saw to trim the boards to fit around your gas fireplace; you should have two boards for each side of the fireplace and one for the top. Trim a fourth board the width of the fireplace plus the width of the two sideboards. This will be the shelf for your mantel. Take the sandpaper and smooth out any rough edges on the boards.

Run the stud finder across the wall the fireplace is on to locate the wall stud behind the wall. Pencil a mark to designate the location of the studs.

Use the caulking gun to lay a bead of adhesive in an "S" shape on the back of the boards that will surround the fireplace. Place the boards on the wall around the fireplace and use a level to ensure they are straight and even.

Drive nails in each of the boards with the nail gun; drive them into the wall studs designated by the pencil marks.

Spread adhesive along the on the top edge of the board over the gas fireplace with the caulking gun, and apply adhesive on the back edge of the fourth board that will make the shelf for the mantel. Set it on the top board, pressing it against the wall so it adheres. Set a level against it to make sure it is sitting evenly. Insert nails into it from the top down into the board underneath.

Miter the ends of the trim pieces at 45-degree angles using the miter saw; trim them to the lengths requires to face the sides and front of the shelf for the mantel. Spread adhesive on the back of the trim pieces with the caulking gun and affix them to the shelf. Drive finishing nails through the trim with the hammer.

Sink and exposed nail head with the nail punch by placing the tip of the punch on the nail and hitting the punch with a hammer. This will sink the nail head below the surface. Use a putty knife to spread wood putty over the holes and sand the putty when it dries to conceal the nail holes. At this point, you can stain or paint the mantel to finish it.