AZ Roofing Contractor cheat sheet

One roofing square equals 100 sq ft of finished roof area; asphalt shingles are normally packaged three bundles per square.

Asphalt shingles require a minimum slope of 2:12. Slopes from 2:12 up to 4:12 require a double layer of underlayment.

Below 2:12 slope, a low-slope membrane system must be used (modified bitumen, EPDM, TPO, PVC, or spray foam); shingles are not permitted.

Approximate dead loads: 3-tab asphalt about 2.5 psf, architectural asphalt about 3.5 psf, standing-seam metal about 1.5 psf, concrete or clay tile 9 to 12 psf, slate 7 to 10 psf.

Wind ratings: ASTM D7158 classifies shingles as Class D, G, or H; ASTM D3161 uses Classes A through F from wind-tunnel testing.

Typical minimum slopes by covering: slate 4:12, wood shakes 4:12, clay or concrete tile 2.5:12 to 3:12, standing-seam metal 3:12, asphalt shingle 2:12.

Class A fire rating is assigned to a tested assembly, not to a single product; fiberglass asphalt shingles over a listed underlayment commonly achieve it.

An ice-dam protection membrane is required where the January mean temperature is 25 degrees F or lower.

A panel span rating such as 24/16 means the panel may span 24 in. on center as roof sheathing and 16 in. on center as floor sheathing; the rating must meet or exceed the rafter spacing.

Sheathing fastening: 8d common or 6d ring-shank nails at 6 in. on center along panel edges and 12 in. on center in the field.

A 1/8-in. gap is left between panel edges for expansion, and every panel end joint must bear on framing.

Minimum underlayment on slopes 4:12 and steeper is No. 15 asphalt-saturated felt (ASTM D226 Type I) or an equivalent synthetic; slopes of 2:12 to 4:12 take two layers.

Felt is lapped 2 in. on side laps and 4 in. on end laps, laid shingle-fashion so upper strips overlap lower strips.

Ice-dam membrane runs at least 36 in. measured from the eave edge and extends at least 24 in. inside the exterior wall line.

Valley underlayment is a minimum 36-in.-wide strip centered on the valley, or two 18-in. strips.

The deflection limit for roof decks under most coverings is L/240 under total load.

Asphalt shingles take 4 fasteners placed in the manufacturer's nail line, 1/4 in. to 1 in. above the exposure line and about 3/4 in. from each end; 6 fasteners are used in high-wind zones.

Fasteners must penetrate at least 3/4 in. into solid decking or completely through the underside of the panel.

A starter course is installed at the eave, and each succeeding shingle course is offset 6 in. from the one below it.

Standard 3-tab shingles are 12 in. by 36 in.; a 5-in. exposure produces 80 shingles per square.

Slate headlap is 3 in. for slopes from 4:12 to 8:12 and 2 in. on slopes steeper than 8:12.

Wood shakes: 24-in. shakes are exposed a maximum of 10 in. with a minimum 1-in. headlap; 18-in. shakes are exposed a maximum of 7.5 in.

Standing-seam metal uses concealed clips and must accommodate thermal movement of roughly 1/8 in. per 10 ft per 10 degrees F of temperature change.

Fasteners for tile and slate must be corrosion resistant (copper, stainless steel, or hot-dip galvanized) and long enough to reach the framing.

Low-slope roofing is defined as a slope at or below 3:12; the minimum practical drainage slope is 1/4:12, about 2 percent.

EPDM is a thermoset single ply, typically 45 or 60 mil, seamed with splice adhesive or butyl tape using a 3-in. to 6-in. lap.

TPO and PVC are thermoplastics joined by heat or solvent welding; TPO seams are hot-air welded at roughly 500 to 1,000 degrees F.

SBS-modified bitumen is elastomeric and may be torch-applied, hot-mopped, or cold-adhered; APP-modified bitumen is plastomeric and is normally torch-applied.

A conventional built-up roof consists of alternating plies of felt and asphalt, usually three or four plies, finished with a flood coat and gravel or a cap sheet.

Spray polyurethane foam is applied in passes limited to about 1.5 in. per pass and must receive a protective coating or granule surfacing.

Single-ply attachment methods are fully adhered, mechanically attached, and ballasted; uplift resistance comes from the rated assembly, such as UL 1897 or FM approval.

Roof insulation in a low-slope assembly must be listed for the assembly's fire classification and protected by a thermal barrier or an approved assembly.

Base flashing on shingle roofs must extend at least 4 in. above the roof surface; 8 in. is common practice at low-slope walls and curbs.

Step flashing pieces are at least 4 in. by 4 in. per shingle course and lap the piece below by 2 in.

Counterflashing laps the base flashing by at least 1 in. and is set in a reglet at least 1 in. deep.

A cricket is required on the uphill side of any chimney or curb wider than 30 in.

A pipe penetration uses a listed boot with a collar sized to the pipe and a flange lapped at least 2 in. onto the field membrane.

Open valley metal is at least 16 oz copper or equivalent, with a minimum 4-in. exposure between the shingle edges.

Roof drains are set in a sump with the membrane flange clamped to the drain ring, and strainers are installed before the roof is accepted.

Kick-out flashing at the base of a roof-to-wall intersection directs water away from the wall and into the gutter.

Slope is rise over run; a 1/4:12 slope equals about 2 percent, or 1/4 in. of fall per foot.

Net free attic vent area is at least 1/150 of the attic floor area, or 1/300 where a Class I or II vapor retarder is installed.

In a balanced ventilation system, 40 to 50 percent of the vent area is located at or near the ridge and the remainder at the eaves.

A 1-in. air space is maintained between the roof deck and the insulation at the eaves with rigid baffles to keep the intake path open.

Downspout sizing rule of thumb: 1 sq in. of leader area for each 100 sq ft of roof area served.

Gutters are pitched about 1/16 in. per foot toward the outlet.

Cold-climate ceilings are typically insulated to R-49; warm climates allow R-30 to R-38, as set by the adopted energy code.

Roof drains and scuppers are sized from the 100-year, 1-hour rainfall rate for the project site.

Granule loss that exposes the asphalt mat, along with curling and clawing, indicates the covering is at the end of its service life.

Blisters are raised, circular, and unadhered beneath the shingle; hail bruises are soft, randomly scattered, and show a fractured mat.

Infrared thermography and nuclear moisture meters locate wet insulation in low-slope roofs without destructive testing.

A core sample through a low-slope roof reveals ply count, insulation type and thickness, and the presence of moisture in the assembly.

Repairs extend at least 6 in. beyond the damaged area and are lapped shingle-fashion with the existing plies.

Routine maintenance inspection occurs at least twice a year and after any windstorm or hail event; drains and scuppers are cleared of debris.

An open single-ply seam wider than about 1/2 in. is cleaned, primed, and re-welded or covered with a splice rather than sealed with caulk.

Roof area equals plan area multiplied by the pitch factor: 1.054 at 4:12, 1.083 at 5:12, 1.118 at 6:12, 1.202 at 8:12, 1.250 at 9:12, 1.414 at 12:12.

Waste allowance is about 10 percent for simple gable roofs and 15 percent or more for hip roofs with many cuts and valleys.

Accessories are taken off in linear feet: eave and rake edge metal, ridge and hip caps, valley metal, and step flashing.

At a scale of 1/4 in. = 1 ft 0 in., 1 in. on the drawing equals 4 ft in the field.

Labor is estimated in squares per crew-day, and productivity drops with pitch, height, and the number of penetrations and valleys.

A contingency of 5 to 10 percent covers concealed deck repair, flashing replacement, and code-required upgrades.

Scale is verified against two or more printed dimensions on the drawings before any dimension is scaled from the plan.

OSHA 29 CFR 1926 Subpart M requires fall protection whenever a worker is exposed to a fall of 6 ft or more.

Personal fall-arrest anchors are rated for 5,000 lb per worker or are part of an engineered, certified system.

Guardrails are 42 in. plus or minus 3 in. high with a midrail at about 21 in. and a toe board.

On low-slope roofs a warning line is set at least 6 ft from the edge, and mechanical equipment stays at least 10 ft back.

Extension ladders extend at least 3 ft above the landing and are set at a 4:1 base-to-height ratio.

Torch work and kettle operations require a hot-work permit, a dedicated fire watch during the work, and a watch period of at least 30 minutes afterward.

A charged extinguisher is kept immediately available at kettle and torch locations, and kettles are located away from combustible construction.