Steep Slope Roofing: Asphalt Shingles and Tile

Inspection scope

A home inspection includes the visible and accessible roof components: roof coverings such as shingles; gutters, downspouts, and other roof drainage systems; vent flashing and other roof flashing components; and skylights.

Steep slope roof coverings

A steep slope roof covering is installed on a roof with a slope of 2:12 or greater, meaning 2 inches of vertical rise in 12 inches of horizontal run. A low slope roof covering may be installed on slopes from 1/4:12 to 2:12.

Most steep slope coverings are water shedding. A water shedding covering relies in part on the underlayment, the layer beneath it, as a water-resistive barrier system. Under asphalt (fiberglass) shingles, the underlayment is a secondary water-resistive barrier. Under concrete and clay tile, it is the primary one.

Asbestos cement shingles

Description

Asbestos cement shingles are most commonly square or rectangular, and may also be polygons. They came in a variety of colors. Less expensive shingles are about 1/8 inch thick, and better quality shingles about 1/4 inch. Reported service life is around 50 years for the thinner shingles; the thicker ones last around 75 years.

They were fastened, preferably over underlayment, to solid-sheathed roofs. First made in the early 1900s, they were most popular from the 1910s to the 1950s. Asbestos was banned from most building products in 1973. Manufacture of these shingles continued until the early 1990s. They are no longer available, and matching replacements can be hard to find and expensive.

Typical defects

Home inspectors should report these typical defects:

1. Absent shingles
2. Cracked and damaged shingles, which could allow friable asbestos
3. Roof penetration located in a valley

Safety issues

During cutting and removal of these shingles, abatement and containment protocols for asbestos must be followed. These procedures can be costly.

Asphalt (fiberglass, composition) shingles

Description

Asphalt shingles are also called fiberglass shingles and composition shingles. Two types are commonly available. The base of an organic shingle is felt impregnated with asphalt. Today most available shingles are fiberglass shingles, built on fiberglass impregnated with asphalt.

Three styles are commonly available, and style names and warranty lengths vary by manufacturer. The least expensive style, found on many homes, is the three-tab strip shingle. Its profile is flat, and its warranty is usually 20 years. Next up is the dimensional shingle, with a raised profile and a warranty that usually runs 25 to 30 years. The most expensive style is the laminated shingle: two shingles bonded together for a more pronounced raised profile, usually warranted for 35+ years.

One square equals 100 square feet of roof. Laminated shingles weigh over 400 pounds per square, and less expensive three-tab shingles about 200 pounds. Shingles count as a light roof covering. Heavier shingles can still cause problems on inadequately framed roofs and where more than one layer is installed. Where laminated shingles are present, home inspectors should look for framing issues, especially on older homes and where multiple layers exist.

Installation

Shingles should be installed over solid sheathing. Unless the shingle manufacturer specifies otherwise, the minimum slope should be 2:12, and a 4:12 minimum is recommended by industry guidelines. A valley has a lower slope than the roof planes that intersect to form it. On a roof near the minimum slope, the valleys may be too low in slope for shingles.

Underlayment is specified beneath shingles. It should run horizontally, parallel to the eaves, with lapped seams. The traditional material is #15 asphalt-impregnated felt. New installations often use a synthetic of polypropylene or similar material. Double underlayment is usually specified on slopes between 2:12 and 4:12, and single underlayment at 4:12. In cold climates, ice barrier underlayment is specified where local authorities require it. IRC 2012 requires drip edge flashing along the eaves. Underlayment should lie over the drip edge flashing at eaves and under it at rakes.

Roofing nails for shingles should be galvanized steel or aluminum, and should reach 3/4 inch or more into the sheathing. The usual manufacturer specification is four nails per strip. On very steep slope roofs and in high wind zones, six are specified. A nail above the seal strip usually voids the manufacturer warranty, and high wind may then blow the shingle off. The IRC does not currently permit staples, a problematic shingle fastener. Some manufacturers may allow them but do not recommend them.

Shingle valleys are commonly open, closed-cut, or woven. Closed-cut and open valleys usually suit every shingle style. For laminated shingles, some manufacturers specify an open valley.

• For closed-cut and woven valleys, the flashing should be smooth roll roofing 36 inches wide, or any material used to flash open valleys.
• Flashing for an open valley should be aluminum or galvanized steel at least 24 inches wide, or roll roofing in two layers.

Other materials may also be acceptable. No penetration, including a plumbing or appliance vent, should pass through valley flashing.

Typical repairs

The common material for repairing and sealing shingles, and for bedding before flashing is installed, is asphalt-based roofing cement. Flashing cement, usually the thicker, is meant for vertical surfaces. Lap cement, the thinner, is meant for bonding shingles together. Home inspectors find the two difficult to tell apart during an inspection.

Lap cement is acceptable as a seal for the starter strip and for sealing other shingle tabs. On a small hole such as a nail hole, lap cement should go under the shingle tab, and the repair is then usually considered acceptable.

Roofing cement is not meant to replace shingles or flashing. It degrades rapidly in the elements, especially sunlight, and needs regular maintenance. Similar material may replace damaged and absent tabs and strips if it is properly integrated with the existing shingles.

Algae and moss are organic growth that sometimes concerns clients. Warm wet climates and north-facing roofs, which get less sunlight, see more of it. Algae is usually considered cosmetic and not a reportable defect. Moss is a reportable defect, because it can loosen granules and damage shingles. Cleaning shingles risks granule loss, and many manufacturers do not recommend it.

Typical defects

Home inspectors should report these typical defects:

1. Shingle deterioration: granule loss, fibers visible at edges, curling, and a stiff or dry feel (a cold shingle often feels stiff).
2. Damaged and absent shingle tabs: causes include tree limbs scraping, foot traffic, wind, and hail.
3. Absent sealant strip at first course
4. Improper nail quantity and location
5. Exposed or withdrawing fasteners
6. Roof penetration in a valley
7. Dimensional or laminated shingles used as cap shingles
8. Three or more shingle layers: a second layer is allowed but not recommended.
9. Improper offset between a course and the course above: especially with laminated and dimensional shingles.

Safety issues

Defects in shingle roof coverings rarely create safety issues. Loose granules, which are often present on older shingles, can make walking the roof more difficult and dangerous.

Standards: IRC 2018 R905.2 (asphalt shingles), manufacturer's instructions, National Roofing Contractors Association guidelines.

Concrete and clay tiles

Description

Tiles are classified two ways: by material and by shape. Concrete tiles combine Portland cement and water with sand or another aggregate. Their color comes from pigment mixed with the concrete or sprayed on during production. Clay tiles combine clay and water with other materials that color the tile and alter its hardness and durability.

Three shapes are most common: the Spanish tile (S shaped), the Mission tile or pan and cover tile (C shaped), and the flat tile, also called shingle tile. A flat tile's sides may be flat, or grooved to lock the tiles together. Ridges and rakes use accessory tiles made for each shape.

Depending on tile quality and the environment, tiles can last 100 years or more. In climates that are very hot or very cold, underlayment service life can drop to 20 years. Mineral surfaced roll roofing or another durable underlayment is preferred in those climates, because #30 felt, which is the minimum, will probably wear out before the tile.

Tile counts as a heavy roof covering. Some clay tiles weigh about 600 pounds per 100 square feet, and some concrete tiles about 1,100 pounds. The roof framing should be designed for that weight. Before tiles are installed on a roof meant for a light covering, an engineer should evaluate the structure.

Some tiles absorb more water than others. The manufacturing process or a sealer applied to the tile can adjust this tendency. Too much absorbed water may cause a tile to deteriorate prematurely in freeze-thaw cycles. Tile failure may show as widespread cracking and spalling.

Clay tiles are usually brittle and break readily under loads and impacts. Where hail is likely, clay tile use should be carefully considered. Walking on clay tile roofs is something most home inspectors should not do. Concrete tiles are usually sturdier, and they can usually take loads and impacts better. A home inspector trained in proper safety procedures may choose to walk on a concrete tile roof.

Installation

Tiles may go on spaced structural sheathing boards or on solid sheathing. Unless the tile manufacturer specifies otherwise, the minimum slope should be 2-1/2:12. Industry guidelines recommend 4:12. On a roof near minimum slope, the valleys may be too low for tile.

Tiles mainly shed water and shield the underlayment from the elements and solar radiation. In a tile roof covering, the waterproof material that keeps water from entering the roof is the underlayment.

At least #30 felt underlayment is specified under tiles. It should run horizontally, parallel to the eaves, with lapped seams. On slopes from 2-1/2:12 to 4:12, double underlayment is usually specified. In cold climates, ice barrier underlayment is specified where local authorities require it. At the eaves, drip edge flashing is recommended, but it may not be required. Underlayment should go over it there. Underlayment should lap over the rakes by at least 1 inch, which protects the rake edge against water damage.

Tiles may be attached with nails, screws, clips, wire-ties, and wood battens, which are usually 1x2 inch boards. Methods are sometimes combined. The appropriate method depends on local weather, the roof slope, and the tile. Local regulations and the manufacturer's instructions determine the proper method.

Every perimeter tile should be fastened. The perimeter usually means the eaves, the gable rakes, and at least 36 inches on both sides of ridges. Field tiles, those not at the perimeter, may not need fasteners when battens support them. Any nails used should be galvanized steel or aluminum and reach 3/4 inch or more into the sheathing.

Tile valleys are commonly open or closed. An open valley leaves the metal valley flashing exposed. A closed valley (mitered) has the metal valley flashing covered by tiles. Where debris is expected to accumulate, or where freeze-thaw cycles are common, open valleys are preferred.

Flashing for both tile valley types should start with a base layer of at least #30 felt, 36 inches wide. Above it should go galvanized steel at least 22 inches wide, carrying a splash diverter 1 inch tall at its center. Vents and other penetrations should not pass through it.

A nailer under hip and ridge tiles, usually a 2x4 with its long side vertical, gives the tile a fastening point. No water-resistive covering is required over the nailer. A mud ball is the common name for the mortar that secures the first and last tiles on each hip or ridge.

Head lap, the overlap of a tile onto the course below, should be sufficient for the tiles to shed water better. Head lap is typically 3 inches, varying with tile style and the manufacturer's instructions.

Typical repairs

1. Loose tiles may be secured and repositioned.
2. Cracked tiles should be replaced; adhesive is not a recommended repair.
3. Tiles with minor corner chips may stay in place if the underlayment is not exposed.
4. Underlayment that is damaged or deteriorated should be replaced; the eaves and gable rakes are common locations.
5. When the tiles a cracked mud ball secures are loose, the mud ball should be replaced.

Typical defects

Home inspectors should report these typical defects:

1. Tiles loose or not in installed position
2. Damaged or absent tiles: includes cracked tiles and tiles whose edges are significantly chipped.
3. Inadequate head lap: at least 3 inches is usually recommended.
4. Absent fasteners at perimeter tiles
5. Damaged or deteriorated underlayment
6. Roof penetrations located in a valley
7. Cracked or damaged mud balls
8. Over-cut tiles exposing the underlayment: usually at hips.

Safety issues

Defects in tile roof coverings rarely create safety issues. Wet tiles can be very slippery, especially those with a glazed surface.

Standards: IRC 2018 R905.3 (clay and concrete tile), manufacturer's instructions, National Roofing Contractors Association guidelines.

Numbers and Rules to Memorize