Soffit Solutions

How to fix airflow problems from damaged soffits to create a healthier home

Just as it’s difficult for someone with a broken nose to breathe, it’s hard for your house to breathe when its soffits are damaged or the vents are blocked. And your house needs to breathe: Proper attic ventilation is vital to maintain a healthy indoor environment and to ensure the longest life for the materials that make up your home.

Houses are designed so that air flows into the attic through ventilation openings in the soffits. As the air cycles around the attic space, it carries heat and moisture up through the roof vents and out of the house. This cycle of air being drawn in through the soffits and pushed out through the roof vents prevents rot in the sheathing and roof-framing members, and it minimizes temperature differences between the attic and the air outside, lowering your home’s energy costs, preventing ice dams from forming and reducing humidity in the attic space.

Over the years a variety of materials have been used for soffits. Wood and wood products such as tempered hardboard were early choices, and in some parts of the country they are still widely used today. But now one of the most popular soffit materials is aluminum. Available in a variety of colors (although white, tan, green and brown are the most common), aluminum soffits and their fascia coverings and moldings are low-maintenance, DIY-friendly products that provide exceptional ventilation and are easily cut and installed using standard tools, so even first-timers can achieve professional looking results in a soffit repair or replacement project.

Typical Aluminum Soffit Construction

What you'll need to buy
For most soffit projects, the materials are fairly simple and easy to work with. Soffit panels come in vented or unvented 12-ft. lengths and are typically 16 in. wide. Vented panels have thousands of small perforations that allow air to flow into a home’s attic space, but the holes are small enough to keep out all but the tiniest of insects.

Vented aluminum soffit panels are sold in 12-ft. lengths and have thousands of tiny holes that allow air to flow up into the home’s attic

To calculate how many 12-ft. soffit panels you’ll need, multiply the width by the length (in feet) of each complete soffit surface, add them all up to get the total square footage and divide by 16 (the square footage of one 16-in.-wide panel). Add 5 percent extra for waste and overlaps.

Aluminum fascia covering can be installed directly over existing wood fascia boards. It has a lip at the bottom that laps over the outer edge of the aluminum soffit, and it comes in 6- and 8-in. widths. Measure the width of your fascia boards to determine which width to buy; then measure the length of your home’s fascia (in feet) and divide by 12 to find the number of 12-ft. strips you’ll need.

In addition to soffit panels and fascia covering, you’ll need aluminum J-channel or F-channel to hold the soffit panels in place against the house walls. J-channel has one longer side that’s intended for use as a nailing fin and is typically fastened to the underside of an existing wood or hardboard soffit. F-channel is similar to J-channel but has an additional nailing fin and can be nailed directly to the house wall when there is no overhead nailing surface (photo, below). Purchase the same length of J- or F-channel as fascia covering.

Both J-channel and F-channel securely hold the soffit panels in place against the walls of the house. Fasten J-channel to existing overhead soffit boards; fasten F-channel directly to the wall.

When working with aluminum, it’s important to use fasteners that will not react through galvanic action when touching the metal surface – plain steel nails and staples are not acceptable. Use 1-1/2-in. aluminum or stainless steel ring-shank nails, or if you plan to use a pneumatic crown stapler (which will greatly speed installation), use Monel staples, which will not suffer from galvanic corrosion.

Preparing the surfaces
If you’re repairing existing aluminum soffits and fascia, remove any torn or otherwise damaged sections (photo 1). Check for loose nails along the J-channel, and make sure that any existing aluminum you’re leaving in place is sound.

If your house has existing aluminum soffits, remove any worn or damaged sections. Don’t be tempted to reuse old components, as they’re like to have weak spots that will tear in windy conditions.

If you’ll be installing new aluminum panels over a wood or hardboard soffit system that has small vents, remove the old vent covers to allow for free air movement once the new aluminum panels are installed. Measure the existing vent holes to determine whether there is adequate ventilation, and enlarge them if necessary. As a rule of thumb, there should be approximately 1 sq. ft. of vent opening for every 300 sq. ft. of ceiling area, but because of regional differences in temperature and humidity, ventilation requirements vary. Check with your local code authority to see what’s required in your area.

Examine existing fascia boards to make sure they are sound enough to hold the new fascia and soffit nails. If you encounter any soft or rotted sections, replace them with straight pine boards of the same width and thickness.

Installing soffit panels
If you are installing aluminum over existing wood or hardboard soffit panels, use a pneumatic crown stapler to attach aluminum J-channel to the underside of the existing soffit panels where they meet the house walls (photo 2). Otherwise, fasten F-channel directly to the walls by firing crown staples through the nailing fin.

Attach J-channel to the old overhead soffit boards. If there are no existing soffit panels, use F-channel instead and fasten it directly to the house walls.

When it comes to cutting the 12-ft. aluminum soffit runs to length, there are two ways you can achieve professional results. If you have access to a portable panel saw or can rent one, you’ll save a lot of cutting time. Install a 40-tooth carbide-tip blade in the saw, lay the soffit panel across the cutting tracks and pull the saw backward across the aluminum (photo 3).

When it comes to cutting the soffit runs to length, a sliding panel saw will greatly speed the cutting process – just remember to pull the saw backward along the cut line.

If you don’t have a panel saw, use a circular saw outfitted with a 40-tooth carbide-tip blade installed so that it rotates backward. Lay the aluminum soffit material across a pair of sawhorses and push the saw forward along the cut line.

Insert the end of the first soffit panel into the J-channel, with the grooved side facing the direction in which you’ll be working. Use a square to make sure that the soffit panel is properly aligned; then fasten the opposite end of the panel to the underside of the fascia board (photos 4). I used staples and a pneumatic staple gun to speed the installation process, but you could use a hammer and nails if you don’t have an air compressor.

Insert the first soffit panel into the J-channel. Make sure that it’s square to the house and the fascia board; then fasten it to the underside edge of the fascia board (inset).

Install additional soffit panels in a similar fashion by sliding them into the groove of the previously installed panel, inserting the end into the J-channel and fastening it to the underside of the fascia board.

Installing fascia covering
One you’ve installed the soffit panels, you’re ready to cover the fascia boards with aluminum, starting at the end of one of the eaves. Attaching the aluminum covering to existing fascia boards is easy: Simply slide the fascia covering up under the roof’s drip edge so that the aluminum fascia’s lower lip covers the ends of the soffit panels; then drive nails through the aluminum into the bottom edge of the fascia board (photo 5).

To clad the fascia boards in aluminum, simply slide the cladding up under the roof’s drip edge and nail it to the underside edge of the fascia board (inset).

Where the eaves meet the rake edges of the roof, you’ll need to form a 90-degree angle in the aluminum fascia covering. One of the easiest ways to do this is by using a locking sheet-metal tool to fold the metal and form the angle (photo 6).

Use a locking sheet-metal tool to cleanly create bends in the fascia covering.

You’ll need to cleanly cut the fascia covering not only to length but also to the proper angle for covering the rake edge of the roof. First use a utility knife to score the aluminum along the cut line; then use the locking sheet metal tool to snap away the excess material (photo 7).

When cutting the fascia covering, first score it with a utility knife; then use the locking sheet-metal tool to cleanly snap it along the score line.

When you’re ready to cover the rake ends, start at an end where the rake meets the eave. Work up toward the peak of the roof, allowing the fascia covering to overlap the vertical line of the roof peak; then work from the other side of the roof’s rake edge, nailing the fascia covering in place as you go. Cut the last fascia covering to the appropriate angle so that it overlaps the other section of fascia covering at the peak and forms a clean, vertical line (photo 8).

To create a clean line at the roof peak, allow one section of fascia to extend past the peak’s vertical line; cut the opposite fascia covering to the proper angle and install it so that it overlaps.

When your project is complete, recycle any old aluminum you’ve removed as well as any scraps or cutoffs from the new aluminum. Then sit back and breathe easy – your house certainly will, and you’ll have a healthier home thanks to your hard work.