Soffit Installation


Soffit is used to enclose the underside of an eave. The installation of soffit will determine the positioning of the inside and outside corner posts. It also is necessary to complete the soffit before the final course of siding is installed on the wall.

Vinyl soffit is designed to be easily installed lengthwise from wall to fascia. Soffit panels are similar to vertical siding. Manufacturers produce both solid and vented panels, as well as combinations of the two.

NOTE: Ventilation Requirements: Proper attic ventilation is important for any home. Consult local building codes for the appropriate requirements for a specific geographic area, and use vented soffit or other vented products as required.


Inspect and plan the job in advance. For re-siding applications, nail down any loose panels, boards, or shingles. Check surfaces for straightness and fur when necessary. Surfaces should be uniform and straight from various viewing angles.

The procedure used to install soffit depends on the construction of the eave. There are two different types of eaves:

  • Open eaves—eaves with exposed rafters or trusses—are typical of new construction. Open eave installation procedures are also used when removing damaged soffit during a re-siding project.
  • Enclosed eaves—eaves with soffit in place are typical of re-siding projects.

When transitioning soffit at the peak of a gable (Fig. 63), secure two J-channels back to back to receive an individual piece of soffit on each accessory. Alternatively, bend a section of soffit, using a field brake, to match the angle of the peak of the gable.

Figure 63.

Installation Over Open Eaves

Follow this five-step procedure:

  1. Install receiving channels (soffit receiver or J-channel).
    • There are several ways to install receiving channels for soffit. You can use accessories such as J-channel or F-channel. The best approach is to select a method that works most effectively with the construction techniques used to create the eave.
    • Examine figures 64 through 67 and find one that most closely resembles the construction methods used on this particular project.
    • Install the receiving channels following the details shown in figures 64 through 67. Nail channels every 8” to 12” (203mm to 305mm), positioning the nail in the center of the slot. Do not nail tightly.
    • NOTE: Nailing strips must be installed as shown in Fig. 67 if the eave span is greater than 16” (406mm), unless otherwise specified in the soffit manufacturer’s instructions. In areas with high wind restrictions, nailing should not exceed 12” (305mm) on center, unless otherwise specified by the manufacturer.
    • If no soffit receiver is available for a situation best suited for the product, the J-channel can be modified to create an F-receiver (Fig. 68).
    • Simply cut slots in the nail flange area where it would be nailed to the wall (Fig. 68). After cutting the nail flange, bend the flange back and nail it to the wall.
    • If the soffit will turn a corner, cut and install the channel so there is 1/4” (6.4mm) for expansion at each of the adjoining walls.

    Figure 64.

    Figure 65.

    Figure 66.

    Figure 67.

    Figure 68.

    NOTE: These illustrations are based on common installation practices used in most areas of North America. Local environmental conditions (particularly high wind zones) and building codes may call for different installation techniques. Always consult the manufacturer’s installation instructions and local building codes to determine the correct installation methods to use on any job.
  2. Measure from the wall to the fascia board. Then subtract 1/2” (12.7mm) to allow for expansion. Mark and cut this dimension on a soffit panel.
  3. In situations with two channels, (Fig. 67), flex the panel between the two channels installed. It is critical in this application that the installed nailing strips are wide enough (4” [102mm]) to allow a fastener to attach to the soffit. Make sure the panel is perpendicular to the wall when fastening.
    In situations where the soffit panel will be attached at the wood fascia board and then covered with an aluminum fascia cover (Fig. 66), each soffit panel should be fastened through the nail hem and either into the wood fascia or into a wood shim using nails, screws, or staples.
  4. To turn a corner, measure from the channel at the wall corner to the channel at the corner of the fascia board (Fig. 70). Subtract 1/4” (6.4mm) for expansion. Cut and install soffit double channel lineal or back-to-back J-channel. If necessary, install nailing strips to provide backing for the lineal. Miter cut the corner soffit panels and install as described in Step 3.
  5. NOTE: According to the 2012 and later International Residential Codes, “Soffit panels shall be individually fastened to a supporting component such as a nailing strip, fascia, or subfascia component or as specified by the manufacturer’s instructions.”
  6. Once the soffit has been installed, apply the field or factory-formed covers.
    • The fascia covers can be installed into utility trim (either factory-formed or field-fabricated) (Fig. 69) or behind the existing drip edge. The fascia has to be fastened with aluminum or stainless steel painted trim nails into the bottom leg, no more than 24” (610mm) on center.
    • When overlapping aluminum/vinyl fascia covers, make sure to overlap 3/4” (19mm).
    • Drive these nails through the fascia and only into the “V” groove of the soffit.
    • You may also need to face-nail the fascia. Always pre-drill holes into fascia and do not nail tight.

    Figure 69.

    Figure 70.

Installation Over Enclosed Eaves

The procedure used to install soffit over an enclosed eave in a remodeling project is almost identical to that used for an open eave in new construction. The major difference is the installation of the J-channel (Fig. 71 and 72).

NOTE: If the existing soffit is rotted or damaged, remove it completely before installing vinyl soffit, then use the instructions for open eaves.
  • Determine the preferred method of installing soffit at the fascia board.
  • When installing J-channel at either wall of fascia board, nail every 8” to 12” (203mm to 305mm).
  • If the soffit is to turn a corner, cut and install J-channel to allow 1/4” (6.4mm) for expansion at each of the adjoining walls and fascia boards.
  • When installing vented soffit panels, if the existing soffit doesn’t have openings for ventilation, cut an adequate number of openings.
  • To complete the installation, follow Installation Over Open Eaves, Steps 3 through 5 of Installation Over Open Eaves.

Figure 71.

Figure 72.

Porch Ceilings

The procedures used to install a porch ceiling are in many ways similar to those used to install soffit. These procedures vary slightly, depending on whether the installation is a new construction or a re-siding project.

New Construction Projects

  1. Begin by installing receiving channels on all four sides of the porch (Fig. 73). If F-channels are being used, nail them to the existing walls. If J-channels are being used, a nailing base will have to be installed.
  2. When using light blocks to attach external light fixtures, install them to adequate backing.
  3. Figure 73.

  4. Plan the layout of the ceiling panels to achieve an even balance or to align with adjacent work. If the ceiling panels will run parallel to the ceiling joists, additional 1” x 3” (25.4mm x 76.2mm) wood furring nailing strips will have to be installed. Install these nailing strips perpendicular to the ceiling joists, placing a strip every 8” to 12” (203mm to 305mm).
  5. Invert the J-channels and nail them to the underside of the wood strips along the perimeter of the ceiling area.
  6. Install the first panel into the channels at one end of the porch. Be sure to leave room for expansion. Nail every 8” to 12” (203mm to 305mm), positioning nails in the centers of slots. Do not nail tightly. Install the remaining panels. When cutting the last panel of the first course, be sure to allow room for expansion.
  7. For areas where more than one panel length is needed, use a double channel lineal or back-to- back J-channel.
  8. If it is necessary to cut the nailing hem off the final panel, use a snap lock punch to create tabs every 6” (152mm) along the cut edge. Attach utility trim and insert the panel into the receiving channel.

Re-siding Projects

  1. Check to be sure the existing ceiling can serve as a solid nailing base.
  2. If the existing ceiling is solid, remove all existing moldings and fixtures from the ceiling and begin by nailing inverted J-channels along the perimeter of the ceiling area. Then follow Steps 2 through 6 in the instructions under “New Construction Projects.” With a solid ceiling, however, additional nailing strips are not necessary. Use the existing ceiling as the nailing base for the panels.
  3. If the existing ceiling is not solid, install nailing strips to provide a secure nailing base, then install the J-channels. Additional nailing strips should be installed if the ceiling panels are to run parallel to the ceiling joists. Follow the instructions in Steps 2 through 6 for new construction.

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