DIY Network

How to Install a Soffit

A vertical soffit is installed to encase a hood vent, which will make the hood appear to be one built-in unit.

More in Kitchen

vertical soffit installed to encase hood vent
  • Time


  • Price Range

    $500 - $1,000

  • Difficulty



Step 1: Break through the Wall

When you purchase a vent hood for a professional cooktop, it has to be sized correctly to meet the air-flow requirements of the particular cooktop you have in your kitchen. The size of the vent is determined by the number of cubic feet of air that has to be moved per minute (CFM); the higher the CFM, the larger the vent needs to be. The one for this project (Image 1) moves more than 600 cubic feet of air per minute.

Consult the dealer where you purchase your hood or a talk to an HVAC contractor to make sure the hood and the vent you purchase meet or exceed requirements.

With the hood vent in hand, measure where the vent stems out of the house, and draw a circle on the interior wall. In this project the exterior wall is brick, so a drill hole through the brick wall structure is the best way to mark the outside wall (see below in this step).

It’s wise to remove any trim, cornice or other molding within the area so it doesn't get damaged when you break into the wall. Use a pry bar and hammer to carefully remove the trim, marking it so you remember where it goes.

Use a hammer to break through the drywall and pull out the drywall and insulation (Image 2).

Note that you will probably have to remove drywall for the entire hood and above stove area, depending on the type of vent and hood you have purchased. Once the vent is placed through the wall, you will cover the wall again with drywall.

Mark the inside surface of the outside brick wall where you are going to break through. Use a hammer drill and carbide bit to drill four pilot holes. Then drill a series of holes around the rest of the circle (Image 3) and, finally, use a chisel bit to connect the holes. This will lessen the risk of loosening the surrounding brick.

Drill through to the outside, then make the same circular drill hole on the exterior wall to get a clean cut. Remove the center of the vent hole using a hammer and a chisel bit.

Step 2: Install the Vent

After the holes have been drilled and the vent hole is through both interior and exterior walls, it's time to place the vent in the hole (Image 1).

After placing the vent in the hole, remove the rest of the drywall and insulation from the area around the vent.

To move or remove any existing wiring or to run lines for the new vent, you may need to have a professional electrician do the electrical work. You’ll want to do that prior to the installation of the 2” x 6” backer boards that will support the hood.

Using an impulse nailer or a hammer and 16 penny nails, position two 2” x 6” backer boards between the 2” x 4” studs in the wall (Image 2).

Add minimally expanding insulation to plug the air holes and replace the missing insulation around vent.

Place a layer of polyurethane sheeting over the exposed area to act as a vapor barrier on the outside wall.

Cut drywall to size and secure it back in place with 1-5/8" drywall screws.

Step 3: Build the Soffit

The soffit (Image 1) encases the new vent, and the hood attaches to the bottom of the soffit. The vent extends from the mounted hood through the soffit to the outside vent.

Using a stud finder, first mark the location of ceiling joists and walls studs on the back wall. The soffit attaches to both surfaces.

To build the soffit, cut supports to size and lay out the soffit on the floor. Secure 2”x4”s together with an impulse nailer or a hammer and 16 penny nails. The top piece has two flat 2”x4”s that will be screwed into the ceiling joists. The back of the soffit frame is nailed to the wall studs.

Before securing the soffit to the wall, check to make sure it's level and plumb. Tack it in with an impulse nailer and screw or nail the frame in place. Then attach the bottom portion of the framework (Image 2).

Once the vent and hood are in place, cover the soffit frame with 1/2" plywood.




  • Vent hood (model: PMLSS-42-SS w 600CFM) from Independent Inc.