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Calculate underlayment rolls, ice & water shield, staples, and accessories for your roofing project. Supports felt, synthetic, and peel & stick options.
Premium option, 1000 sq ft per roll
Enter roof dimensions to calculate area.
Enter dimensions to calculate underlayment.
Enter dimensions to calculate ice & water shield.
Enter dimensions to calculate fasteners.
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| Type | Coverage | Typical Cost | Best For |
|---|---|---|---|
| 15 lb Felt | 400 sf/roll | $15-25 | Budget projects, low-slope roofs |
| 30 lb Felt | 200 sf/roll | $20-35 | Standard roofing, general use |
| Synthetic | 1000 sf/roll | $80-150 | Premium roofs, faster install |
| Peel & Stick | 75 sf/roll | $60-100 | Valleys, eaves, low-slope areas |
| Rubber (EPDM) | 200 sf/roll | $50-80 | Flat roofs, extreme weather |
Yes, underlayment is required by building codes in most areas. It provides a secondary water barrier protecting the roof deck from moisture that may penetrate the shingles. It also provides temporary weather protection during installation.
The numbers refer to the weight of the material per 100 square feet. 30 lb felt is thicker, more durable, and provides better protection but covers less area per roll (200 sf vs 400 sf). Most professional roofers prefer 30 lb felt or synthetic underlayment for better performance.
Ice and water shield is required in cold climates (where average January temperature is 25°F or below). Install it along eaves (first 24" to 36" from edge), in valleys, around penetrations (vents, chimneys), and at any low-slope areas. Some codes require it at all critical areas regardless of climate.
Standard horizontal overlap is 4 inches (6 inches in high-wind areas). Vertical end laps should be at least 6 inches. For low-slope roofs (2:12 to 4:12), increase horizontal overlap to 19 inches or use self-adhering underlayment.
Synthetic underlayment offers several advantages: lighter weight, larger rolls (faster installation), better tear resistance, slip-resistant walking surface, and longer exposure time before shingles are installed. However, it costs more than felt. For premium roof installations, synthetic is generally recommended.
Plan for approximately 4 staples or cap nails per linear foot of underlayment. For a typical 1000 sf roll of synthetic underlayment (333 linear feet), you'll need about 1,300 fasteners. Use cap nails for felt underlayment and staples for synthetic.