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’
-‘laminated overlay’ shingles types.
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.
MAJOR INDUSTRY PLAYERS
Top 2 Manufacturers in the US – GAF and Owens Corning.
Other Manufacturers – Tamko, Certainteed, Malarakey, Atlas, IKO
FOREMAN AND FIELD NOTES
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
Tape measure, ladders, hammer, square, pry bar, tin snips, caulking gun, utility knife (or shingle cutter), chalk snap line
Pneumatic gun, roof jack, roof harness
What can go wrong
Shingle cracking, cupping, curling, blistering, extractive bleeding
Blow ups or blow offs
Leaking and faulty flashing installations
Incorrect nail installation
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
0.75 to 1.5 man hour per square can be expected
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
+/- 10% waste is common for average roof, more for lots of irregular features