Roll Roofing vs. Tiles

Roll Roofing Basics

• Roll roofing is commonly marketed in rolls that are 36 inches wide and 50 feet long. Although it is sometimes applied vertically beginning at the eaves, it is best to apply it in overlaying laps beginning at the bottom of the roof. The two basic types of roll roofing are single-layer, suitable for roofs with steep slopes, and selvage edge, applied to roofs that are nearly flat.

Roll Roof Application

• Overlap the top over the bottom layer of standard roll roofing by 2 to 4 inches. Roll roofing is applied by a method that exposes the nails to the weather and a method that conceals them. Use exposed nails to apply on roofing slopes with a ratio of 4:12 or greater. The ratio means the roof extends 4 feet vertically for every 12 feet horizontally. Use exposed nails to apply roll roofing parallel to the edges or eaves of a roof with a ratio of 6:12 or greater. Use concealed nails to apply roll roofing laid parallel to the eaves of roofs at 2:12 or greater.

Selvage Edge Roll

• Seventeen inches of selvage edge roll roofing, the mineral edge, comes saturated with petroleum. You apply a sticky petroleum-based coating to the other 19 inches, the selvage edge, and lap the mineral edge over the selvage edge. This seals the overlap, providing double thickness. Use selvage edge roll roofing on roofs with ratios less than 2:12, provided the nails are not exposed and there is enough slope for water to drain off naturally.

Tile Basics

• Tiles are far more attractive than roll roofing. They are also more expensive and difficult to apply. The two main types of roofing tiles are ceramic tiles, either glazed or non-glazed, and terra cotta and cement tiles. Both ceramic and concrete tiles are marketed in a wide variety of sizes, weights and shapes. They are generally applied in an overlapping manner similar to that of shingles, but secured in a variety of ways.

Tile Application

• The National Roofing Contractors Association, or NRCA, does not recommend laying tiles on roofs with a slope less than 4:12. The NRCA recommends two layers of No. 30 asphalt-saturated underlay for roofs with slopes of 4:12 to 10:12. A No. 30 underlay can bear the weight of 30 pounds. Lay the underlay in overlapping strips. Lay tiles on one layer of No. 30 underlay on roofs with a slope of 10:12 or greater.