How to Build a Soffit Box With a Wall

Measure the dimensions of the wall space, so you can design wall framework first. Use graph paper to draw the top plate, bottom plate and wall studs on 16-inch centers. Figure out where electrical outlet boxes will fit along the wall, attached directly to studs, so you can route wiring through the open studs to the outlets.

Cut the wall framing from 2-by-4-inch boards using a circular saw. Nail the sole plate into position first. Drive 4-inch screws through the sole plate into floor joists. Cut and install the top plate into ceiling joists next. Use a pencil to mark stud positions on both top and bottom plates on 16-inch centers. Install wall studs individually and drive nails through the studs on an angle into the plates.

Design and build the soffit box framework separately. Allow room to house the installed duct work or build the box big enough to hide other obstacles, such as pipes. Draw the soffit framing with a top plate, bottom plate and short studs along the front side on 16-inch centers, forming a small-framed cage open against the back wall. Keep the framed box open on the back so it will slide over pipes or ductwork.

Use a circular saw to cut the soffit framework using 2-by-4-inch boards. Miter joints when connecting pieces of boards to form the top and bottom plates. Be sure to miter all corners of the framework as well. Use 4-inch screws to assemble every section of the soffit framing. Check all angles and corners with a carpenter's level. Strive to create sharp corners and 90-degree angles, so the drywall covering will fit properly.

Install ductwork or run any plumbing or electrical materials in the soffit space before lifting the framed box into place on the upper wall. Get a couple of friends to help you position the soffit framework over the ductwork. Use 4-inch screws to secure it to wall studs and ceiling joists.

Cut drywall to fit the soffit. Use 1/2-inch drywall, cutting each section so seams meet in the middle of each short stud along the front. Use metal capping sleeves, called corner bead, over the drywall corners. Use aircraft shears to snip corner bead. Set the bead, working in a single direction, with nails.

Slide a corner crimper over the metal bead stripping. Drive hard blows with a mallet to fasten the metal tightly to drywall.

Cut 1/2-inch drywall for wall sections with a utility scoring knife and a carpenter's T-square. Use a drywall hammer to set the nails. Hit with the hammer, which has a rounded head, to set the nails just below the surface -- leaving a shallow dimple in the drywall. Use 1 1/4-inch ring shank nails that will prevent the drywall from popping loose. Cut any openings for wall light covers (sconces) with a keyhole saw.

Place drywall tape over seams on the soffit box and the wall. Add joint compound, smooth it out and allow it to dry. Sand the seams and apply joint compound a couple of more times.

Paint the wall and soffit box with satin enamel paint. Hook up electrical outlets in the wall space and add outlet covers. Cut baseboard material to fit the bottom of the wall space and nail baseboards in place.