Enter your pitch to see which roof coverings the code allows. Asphalt shingles need 2:12 minimum with a double underlayment and 4:12 for a single layer. Metal shingles need 3:12. Standing seam can go to 0.25:12. Every figure below cites its IRC section.
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| Roof covering | Minimum slope | Angle | Code |
|---|---|---|---|
| Asphalt shingles (double underlayment) | 2:12 | 9.46° | IRC R905.2.2 |
| Asphalt shingles (single underlayment) | 4:12 | 18.43° | IRC R905.2.2 |
| Metal roof shingles | 3:12 | 14.04° | IRC R905.4.1 |
| Lapped metal panels, no sealant | 3:12 | 14.04° | IRC R905.10.1 |
| Lapped metal panels with lap sealant | 0.5:12 | 2.39° | IRC R905.10.1 |
| Standing seam metal | 0.25:12 | 1.19° | IRC R905.10.1 |
| Clay and concrete tile | 2.5:12 | 11.77° | IRC R905.3.1 |
| Slate | 4:12 | 18.43° | IRC R905.6.1 |
| Wood shingles | 3:12 | 14.04° | IRC R905.7.1 |
| Wood shakes | 4:12 | 18.43° | IRC R905.8.1 |
| Mineral-surfaced roll roofing | 1:12 | 4.76° | IRC R905.5.1 |
| Built-up roof | 0.25:12 | 1.19° | IRC R905.9.1 |
| Modified bitumen | 0.25:12 | 1.19° | IRC R905.11.1 |
| Thermoset single-ply (EPDM) | 0.25:12 | 1.19° | IRC R905.12.1 |
| Thermoplastic single-ply (TPO, PVC) | 0.25:12 | 1.19° | IRC R905.13.1 |
| Sprayed polyurethane foam | 0.25:12 | 1.19° | IRC R905.14.1 |
| Liquid-applied coating | 0.25:12 | 1.19° | IRC R905.15.1 |
| Photovoltaic shingles and modules | 2:12 | 9.46° | IRC R905.16.1 |
Can I put shingles on a 2/12 roof?
Only with a double layer of underlayment across the whole deck, per IRC R905.2.2. Most manufacturers will honour the warranty at 2:12 if a full ice and water shield is installed. Without it, the minimum is 4:12.
What happens if I install below the minimum slope?
The installation violates the building code and voids the product warranty. It can also cause a failed inspection, a denied insurance claim, and water getting through the laps into the deck.
Do these minimums apply everywhere?
These are the IRC figures, which most US jurisdictions adopt with amendments. Your local code and the manufacturer instructions always take precedence. Snow regions often push the practical minimum higher than the code allows.
What is the lowest pitch that can be roofed at all?
A quarter inch in twelve, using a fully adhered membrane, built-up roof, or a mechanically seamed standing seam system. Below that you cannot drain the roof reliably.
