Siding, Soffit & Trim Takeoff
Panel count from wall area, plus soffit panels, J-channel, corner posts, starter strip, rain barrier, and nail boxes, in the units siding ships in.
A 6 in exposure lap panel that is 12 ft long covers 6 sq ft; 8 in exposure covers 8. Enter the coverage of the product you are buying, not the box label.
How the math works
- Panels: wall area × (1 + waste) ÷ coverage per panel. Coverage = exposure × length: a 12 ft panel at 6 in exposure covers 6 sq ft, at 8 in exposure 8 sq ft.
- Soffit: 6 in wide 12 ft vinyl soffit panels cover 6 sq ft, with 10% waste. Vented strip is per the vent area the local code requires (typically 1 sq ft of vent per 150 sq ft of attic).
- Trim: J-channel and start trim ship in 10 ft lengths; corners are 10 ft corner posts; window and door casing runs in 9 ft utility trim. Add one length per run for splice loss.
- Rain barrier: a 75 sq ft roll per 75 sq ft of wall with 10% lap overlap, plus a drainage mat at kickout and wainscot zones. Siding nails: 5 lb box per 500 sq ft at 8 in fastener spacing.
- Cost: 2026 DIY vinyl siding averages $1.60 to $3.20 per sq ft installed by the panel, so the panel price you enter drives the total. Trim and barrier typically add 20 to 30% to the panel cost.
How many squares of siding for a 1,800 sq ft house?
18 squares: 1,800 sq ft of wall is 1,980 sq ft bought with 10% waste. With 8 sq ft panels, that is 248 panels.
How much J-channel do I need?
Measure every straight edge the siding terminates into: start trim at the bottom, J at soffits and inside corners, and utility trim at every window and door. Most 1,800 sq ft homes need 14 to 18 ten-foot lengths.
Do I need a weather barrier under siding?
Yes, and in most jurisdictions it is code: a drained rainscreen over the sheathing, 75 sq ft rolls lapped 4 in at horizontal seams and 6 in at vertical, plus flashing at every opening head.