Asphalt Roof Shingles

Asphalt shingle roofing is one of the most common roof types for residential and light commercial sloped roofs. Asphalt shingle systems are relatively easy to install, economical compared to more premium products, and are very effective. Composite (or fiberglass) shingles are a type of asphalt shingle most commonly produced and utilized today. A fiberglass shingle has an outer layer made of an inorganic asphalt composition, and the underneath part of the shingle is made of a fiberglass matting.

(An asphalt shingle has the same outer layer, but the underneath matting is of an asphalt organic material.)

Fiberglass shingles typically have colored or mineral ceramic granules on the weathering side.

The standard composition shingle possesses ‘tabs’ with self-sealing adhesive or locking characteristics which help make them wind-resistant.

Two Tab Square Butt

Three Tab Square Butt

Randon Edge Cut

Laminated Overlay Shingles

Wind resistance becomes increasingly important in high wind areas and low sloped roofs.

When installing an asphalt shingle roofing system, roofing felt or underlayment (asphalt-impregnated), typically either 15lb or 30lb, is placed first directly on the sheathing or substrate.

Underlayment protects the sheathing from moisture until the shingles are installed and also afterwards as additional sheathing protection from wind driven rain. 15lb felt is commonly sufficient for most fiberglass/asphalt shingle roofs, with 30lb felts being reserved for those desiring a heavier duty system or for other roofing material types (wood shakes, metal roofs, etc). 15lb roofing felt commonly covers 400 square feet and 30lb will cover about 200 square feet. Roofing felt is held down with roofing nails or staples with just enough fastening to stay in place until shingle installation.

Eave flashing is commonly installed along the eave for ice dam resistance which typically consists of two layers of 15lb roofing felt. Roofing felt is commonly side-lapped 4″ and top lapped 2″. Like eave flashing, felt at hips and ridges are also doubled and should extend out on either side at least 6″.

For additional ice-dam resistance, on some occasions (particularly low sloped roofs; 3:12 to 4:12) an extra course of felt is asphalt-cemented in place from the rake to at least 36″ past the inside wall.

Once roofing felt is placed, drip edges (sheet metal) are installed on perimeter of roof (rakes and eaves) to resist moisture exposure of the roof edges. Drip edge is typically purchased pre-bent, installed with roofing nails, and is commonly a corrosion-resistant material like aluminum or zinc coated sheet steel.

Ultimately the shingles should overhang from the drip edge about 1/2″. Prior to starting shingle placement, snapping a chalk line for each shingle row will be a time saver and also ensure nice neat, straight lines.

Before laying shingles, a starter strip is installed which is essentially an added shingle course (but often about half the width) at the eaves and protects the shingles from wind at the bottom of the roof. The starter strip can be a specialized size/product but some roofers fashion starter strips from common shingle stock (often by trimming tabs away) and assuring the shingle’s sealant line is placed right along the eave.

Shingles can very in weight anywhere from 205lb – 380lbs per square. Composite shingles typically are not recommended for roof slopes less than 4:12. The standard shingle piece size is 12″ x 36″, and ‘bundles’ commonly house 20, 25, or 33.3SF of shingles each (with this coverage being calculated by exposure not total shingle area). Heavier, three-tabbed shingles, typically only have 20 or 25SF of shingles in a bundle, with the lighter two tab shingles commonly housing 33.3SF/each.

The shingle ‘exposure’ is the portion of the shingle actually exposed to vision and weather after lapping has taken place, most typically 5″. The ‘top-lap’ is the amount of lap from one shingle to the next, most typically 7″. The ‘head-lap’ is the lap distance where 3 shingles overlap, most typically 2″.

There are 3 primary ways to install courses of shingles:

Half-Break Points – aims to terminate successive shingle courses at the midway points of the tabs (first course full strip, second course remove 1/2 tab, third course full strip, etc).

Third-Break Points – aims to further break up the simple lap look (first course full shingle, second course cut 4″, 3rd course cut 8″, 4th course full strip, etc).

Randomly Spaced – provides for an irregular look where break points are at the random discretion of the installer.

Asphalt shingle waste on most project typically averages in anywhere from 3-8%.

As valleys are areas which handle alot of water, they must be flashed properly to help eliminate leaks. There are three ways to flash an asphalt shingle roof valley:

Open metal – utilizes exposed sheet flashing valley joint.

CLosed Cut – utilizes a one side lapped and other side cut valley joint

Woven (Closed Valley) – overlapped courses in alternate directions.

The option used is often determined by local building code, architect’s specification, or roofer’s preference. No matter the flashing style, additional layer/s of roofing felt and/or a waterproof bituminous material with adhesive backing (or similar) is installed on top of the roofing felt along the valley prior to laying shingles.

This flashing procedure is also commonly required at the eaves for ice dam resistance and is referred to as ‘ice and water guard’.

Hips and Ridges will receive capping shingles which often yield a 5″ exposure.

Hip Shingles are used for a weather barrier on the hips between sections of the roof. When installing Hip shingles, snapping a chalk line approximately 6″ from the peak is typically the easiest way to assure a straight, visually appealing shingle line. Shingle manufacturers will typically require hip shingles to have a starter shingle.

Ridge caps are the shingles and vents installed across the peaks of a roof to weatherproof and ventilate the roof. Ridge shingle laps should occur opposite the prevailing wind direction, to reduce wind-driven shingle pulling and damage.

When installing over a ridge vent, 3″ roofing nails should be used to assure fastener penetration is achieved all the way down to the sheathing.

The final shingle on a ridge cap will have exposed nail heads which should be covered with roofing cement.

Roofing Nails for typical asphalt/composite shingle installation should be corrosion-resistant (typically galvanized steel), have a minimum nominal shank diameter of 12 gauge (0.105″), and have a minimium head diameter of 3/8″. No nails should be left exposed.

Roof deck or sheathing penetration should be at least 3/4″ (or 1/8″ past underside of deck). What will drive nail length is number of shingle layers, total single/flashing system section thickness where being driven. Nails can be driven by hand or with a pneumatic nailers.

Improper pneumatic air adjustment or nail placement accuracy can lead to defects like sealing failures, raised tabs, and buckling. The typical minimum number of nails required for each shingle is 4, but may vary based on manufacturer/product type. No nail head should be closer than 1″ from the edge of the shingle. Nails should not be driven into knot holes or cracks in the deck. Nails should be driven tight against the shingle but not overdriven or underdriven. If a heat-activated sealant strip exists on the shingles, nails should be driven through them so the sealer may later melt around the penetration and seal hole/nail joint.

Typically anywhere from 1-1/2 to 3 pounds of nails are required for each square (100SF).

*ADVANCED INFORMATION*

MAJOR INDUSTRY PLAYERS

Manufacturing

Top 2 Manufacturers in the US – GAF and Owens Corning.

Other Manufacturers – Tamko, Certainteed, Malarakey, Atlas, IKO

FOREMAN AND FIELD NOTES

Scheduling

In new construction, shingles are commonly installed prior to interior finishes, siding, gutters, exterior trim, etc. Asphalt shingles are commonly installed right after: Rough electrical, rough plumbing, rough HVAC.

Means and Methods

Starter strip often placed upside down with self seal strip near bottom, flush with sheathing edge, nails at the top with 3 per shingle.

Snap chalk line for top of starter shingle, and also for every course or every other course, double checking ‘squareness’ measuring from both eave and ridge if possible.

Butt shingles and install nails approximately ½” above shingle tab cutouts

Both starter shingle and ridge caps are often fashioned by cutting standard shingles to appropriate size

4 nails in each shingle is common though 5 or 6 may be a requirement of some local codes

For a clean ‘rake’ edge, snap a chalk line along rake and cut shingles with a utility knife

Interaction with Other Trades

Flush sheathing is required for smooth, bump and depression free shingle surface

A square roof framing system is required to assure proper/even exposure is maintained and that rows are parallel to ridge

Installation Tips & Tricks

Expedited installation by ‘Racking’ of shingles is used by some installers which is vertical ‘column’ oriented installation versus horizontal ‘row’ orientation. However some manufacturers do not recommend this as it causes ‘pattern curling’ and ‘shadowing’.

Shingle bundles are more easily accessed when ‘scattered’ on roof. If equipped with boom, have delivery truck place shingles directly on roof, slope permitting. If too steep roof jacks may be utilized for material placement.

EQUIPMENT AND TOOLBOX TALK

Essential Tools

Tape measure, ladders, hammer, square, pry bar, tin snips, caulking gun, utility knife (or shingle cutter), chalk snap line

Recommended Tools

Pneumatic gun, roof jack, roof harness

CAVEATS

What can go wrong

Shingle cracking, cupping, curling, blistering, extractive bleeding

Blow ups or blow offs

Leaking and faulty flashing installations

Incorrect nail installation

ESTIMATING ASSISTANT

Productivity Conditions and Factors

Long, wide open runs are more conducive to better productivity

Lots of valleys, ridges, caps, can slow overall productivity

‘Racking’ can increase production rates

Steep slopes can slow productivity as movement will be slowed and access will be more difficult

Heavier shingles can decrease productivity for handling times

Productivity Range

0.75 to 1.5 man hour per square can be expected

Manpower

2 laborers needed minimum, with 3-4 recommended for small to medium sized roof 15-25 squares

Actual number of laborers needed dependent on size of roof and intended schedule

Larger companies with busy schedules will often employ anywhere from 4-10 or more workers to tackle a larger sized shingle project to assure it’s done in 1-2 days

Manpower Task Breakdown

Laborers will perform tasks like: relaying shingle bundles, spreading bundles among roof, preparing materials, throwing away waste, layout assistance, picking up nails, site restoration, moving and securing ladders, installing/removing roof jacks, etc

Skilled installers will perform tasks like: layout/snap chalk lines, nail shingles, install hips/valleys/ridges, use experience and good judgement to make subjective project-specific decisions

Material Considerations

+/- 10% waste is common for average roof, more for lots of irregular features