How Much Soffit Do I Need? Vinyl Panels and Channel
Soffit closes the underside of the roof overhang. 120 ft of eaves with a 16 inch overhang is 160 sq ft (1.6 squares), which takes 22 vinyl panels of 12 ft by 12 in, with 10% waste. The soffit calculator gives the panels and the channel for your eaves.
Panels by overhang depth
For 120 ft of eaves, with 12 ft panels and 10% waste. Panels run parallel to the wall and the last row is cut to fit.
| Overhang | 8 in panels | 12 in panels | 16 in panels | Area |
|---|---|---|---|---|
| 12 in | 22 | 11 | 11 | 120 ft² |
| 16 in | 22 | 22 | 11 | 160 ft² |
| 18 in | 33 | 22 | 22 | 180 ft² |
| 24 in | 33 | 22 | 22 | 240 ft² |
Area by length of eaves
For a 16 in overhang with 12 in panels:
| Eaves | Area | Panels | J- or F-channel pieces |
|---|---|---|---|
| 60 ft | 80 ft² | 11 | 11 |
| 100 ft | 133 ft² | 19 | 19 |
| 120 ft | 160 ft² | 22 | 22 |
| 160 ft | 213 ft² | 30 | 30 |
| 200 ft | 267 ft² | 37 | 37 |
Panel width
A wider panel means fewer rows and fewer joints, but a row must still end at the wall and the fascia. For a 16 inch overhang the 16 in panel gives one row, which needs 11 panels against 22 for two rows of 12 in, though it must be cut to fit exactly. Check the real overhang at several points, because it can change where the roof was extended.
Channel and trim
The panels slide into J-channel or F-channel on the wall side and the fascia side, so you need about twice the length of the eaves in channel: 22 pieces of 12 ft here. Corners need their own pieces, and the fascia needs trim if it is bare.
Venting the attic
Soffit is where the attic takes in air. Vented panels have slots, and the attic ventilation calculator shows how much vent area the attic needs. Keep the vents clear of insulation with baffles, and do not paint over them.
Fitting tips
- Check the lookouts and the fascia for rot while the old soffit is off.
- Fit the wall channel first and the fascia channel second, then slide the panels in.
- Do not nail panels tight: vinyl expands and contracts with temperature.
- Cut panels about 1/4 inch short at each end for the same reason.
See also the gutter calculator. Panel sizes are typical: follow the instructions for your product.
Frequently asked questions
How much soffit do I need?
Multiply the length of the eaves by the depth of the overhang. 120 ft with a 16 in overhang is 160 ft², which is 22 panels of 12 ft with 10% waste.
How wide and long are soffit panels?
Usually 12 ft long (12 ft 6 in for some makers) and 8, 12 or 16 inches wide.
How many squares of soffit is that?
A square is 100 ft², so 160 ft² is 1.6 squares.
Do I need J-channel or F-channel?
Yes: one run at the wall and one at the fascia, about 22 pieces of 12 ft for this job.
Should the soffit be vented?
Yes, normally. The attic needs intake air at the eaves, and a vented panel supplies it.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.
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