Q. I want to add ceiling lighting and a ceiling fan to my living room, but there is no wiring up there. I would like to add decorative box beams and run the wiring through them. How can I do this?

This is an excellent idea for adding lighting and a fan to a room without access to existing wiring. Even if you did not need access to electrical wiring, box beams can be an excellent addition.

You need at least standard height ceilings when installing box beams. The beams do not have to be extremely deep to hide the wiring, but if they are too shallow they will not look right. A depth of 4 to 5 inches is about the minimum for functionality.

Measure the dimensions of your room to determine the spacing for the box beams. Check for protrusions from the walls, such as window frames, fireplace mantels and doors. These will interfere with the box beams reaching the walls.

If this will be a problem, it is best to build dropped soffits along those walls. Frame and finish the soffits with drywall to the same depth as the box beams for a professional look. These soffits may be excellent locations for recessed lighting.

Before building and finishing the soffits, determine the layout and spacing of the box beams on the ceiling. The ideal spacing is forming perfect squares, which may not be possible with all room shapes.

You may be able to extend the size of the soffits slightly more than needed to allow for square beam spacing.

A general rule of thumb is rectangular spacing at a 1-to-1.62 ratio. This is pleasing to the eye and is definitely a rectangle by design. If you space the beams just slightly off true square so they fit the existing ceiling, it will look as though you did not measure properly.

An easy-to-build size for the box beam is about 6 inches wide and 4 inches deep, using standard lumber. The first step is to make the backer support, which will be attached to the ceiling. It will be hidden inside the beam when it is complete. Start out with a 2-by-6 and rip it down to 4.5 inches on a table saw. Attach the boards securely to the ceiling.

The vertical sides of the box beam can be made from 1-by-4 lumber, and the horizontal bottom from 1-by-6. Determine the type of finishing lumber to use depending on the decor you desire and whether you are going to paint or stain the lumber.

You have several options for fitting the sides and bottom together. One attractive joint design requires a half-inch rabbet cut along the edges of the sidepieces. This allows the bottom 1-by-6 to be slightly recessed. This is also a strong joint.

Another option is just attaching the 1-by-6 to the flat bottoms of the sides. Finish the sides against the ceiling with cove molding to hide gaps.