Your roll
How the picker decides
- Slope sets the family. Mineral surface roll roofing is not allowed below 1 in 12 (IRC R905.5), and the GAF and TAMKO instructions we read ask for 2 in 12 (GAF, TAMKO). Between 1 and 2 in 12, a 19 inch selvage roll (TAMKO) or peel-and-stick works. Below 1 in 12, the picker points to self-adhered modified bitumen or EPDM.
- The building adds rules. RVs need a membrane that matches what is on the roof now (Camping World). On a house at 4 in 12 or steeper, shingles usually make more sense.
- Climate adds the ice barrier. On heated buildings in snow country, the picker reminds you about ice and water shield at the eaves (Fine Homebuilding).
- The roll count is plain math. Area divided by 100 gives squares. Rolls add 10 percent for laps and waste, using about 100 sq ft per standard roll (GAF) and about 50 per selvage roll.
Roll roofing types compared
| Roll | Slope it suits | Life (estimates) | How it goes down | DIY? |
|---|---|---|---|---|
| Mineral surface roll | Code minimum 1 in per foot (IRC R905.5); GAF and TAMKO wrappers say 2 in or more | About 5 to 15 years (Hunker) | Nails plus lap cement, in lapped courses | Yes |
| 19 in selvage roll | Down to 1 in per foot on TAMKO’s data sheet (TAMKO) | Not published; two layers everywhere | Half lapped and cemented, half a square per roll | Yes |
| Peel-and-stick SBS | Low slope; GAF lists Liberty for low slope areas up to 3 in 12 (GAF) | Modified bitumen up to about 30 years (Hunker) | Self-adhered base and cap sheets, rolled in | Yes, with care |
| EPDM rubber | Flat and low slope roofs that drain | More than 20 years (Hunker) | Glued sheet, taped seams | Small roofs |
| TPO | Flat and low slope roofs that drain | 10 to 20 years (Hunker) | Fastened or glued, hot air welded seams | Mostly pros |
When the picker is not enough
- Ponding water. If water sits on the roof after rain, the slope or the framing needs fixing before any roll goes on.
- Rot or soft spots. Replace damaged decking first. Roll roofing will not bridge it.
- High, steep or big roofs. Get quotes from licensed roofers. The cost guide shows what to compare.
Questions people ask
How do I measure roof slope?
Hold a level horizontal against the roof (or the underside of a rafter), mark 12 inches along it, and measure straight up from that mark to the roof. That number is the rise per foot: 2 inches means a 2 in 12 slope. Phone level apps can read the angle too.
How many rolls of roofing do I need?
Work out the roof area in square feet (length times width of each plane, measured along the slope), divide by 100 to get squares, and add about 10 percent for laps, starter strips and waste. A standard mineral surface roll covers about one square; a 19 inch selvage roll covers about half.
Are the picks tested?
No. We have not tested these products. The picker applies slope limits and installation rules from maker instructions and the model code, then searches current listings for that type.
Sources
- City of Hopkins, MN, Mineral surface roll roofing (IRC R905.5) handout
- GAF, Mineral Guard residential roll roofing application instructions (maker, archived copy)
- TAMKO, Fiberglass slate surface roll roofing application instructions (maker)
- TAMKO, 19 inch selvedge edge roll roofing data sheet (maker)
- Camping World, Which RV roof type do you have?
- Fine Homebuilding, Ice barriers explained: how far up the roof slope?
- Hunker, A homeowner’s guide to roll roofing
- GAF, Liberty SBS self-adhering cap sheet (maker)
Last reviewed October 12, 2026. Products and listings change; check the data sheet and wrapper before you buy, follow the maker’s instructions, and check your local building code.