Roofing Foreman flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Minimum slope for asphalt shingles

Standard asphalt shingles require a minimum slope of 2:12 (2 units rise per 12 units run). Below that, shingles need a special low-slope installation method and doubled underlayment.

Ice barrier membrane placement

A self-adhering ice-dam membrane is installed along the eaves, starting at the eave edge and extending at least 24 inches inside the exterior wall line, or as required by local code (often 36 inches).

Shingle fastener count

Use 6 fasteners per shingle on slopes up to 60 degrees and 8 fasteners above 60 degrees or in high-wind zones. Fasteners must penetrate at least 3/4 inch into the deck.

Minimum roof deck thickness

Plywood or OSB roof decking must be at least 15/32 inch (1/2 inch nominal) for shingle roofs. Some tile and heavy systems require 19/32 inch or thicker.

Deck panel expansion gaps

Leave a 1/8-inch gap between deck panels and at end joints to allow for expansion. Fasten 6 inches on center at panel edges and 12 inches in the field.

Attic ventilation ratio

Net free ventilating area should be 1/150 of the insulated ceiling area. It may be reduced to 1/300 when a vapor retarder is present or when most venting is at the ridge.

Balanced intake and exhaust

Intake vent area at the soffit and exhaust vent area at the ridge should be roughly equal, about 50/50, so air flows evenly through the attic without pressurizing or depressurizing it.

Step flashing at sidewalls

Step flashing is installed in layers, one piece per shingle course, where a roof meets a vertical sidewall. Each piece overlaps the one below and is covered by the shingle above.

Counterflashing reglet depth

Counterflashing is set into a reglet cut into masonry or wall material. The reglet must be at least 1 inch deep to hold the flashing securely against water entry.

Valley lining width

Valley lining, either metal or membrane, must extend at least 12 inches on each side of the valley centerline. This protects the most water-concentrated part of the roof.

Chimney cricket threshold

A cricket is required on the upslope side of chimneys wider than 30 inches. The cricket diverts water around the chimney instead of letting it pool against the masonry.

Shingle wind rating standards

Shingle wind resistance is rated under ASTM D7158 (Class D, G, H) and ASTM D3161 (Class A through F). The rating must meet or exceed the site design wind speed.

Metal panel uplift testing

Metal roof panels are rated for wind uplift by ASTM E1592 or UL 580 pressure testing. Slope alone does not determine wind performance; the tested assembly and attachment do.

Standing seam minimum slope

Mechanically seamed standing-seam metal panels require a minimum slope of 3:12. Snap-lock and some hydrostatic panels can go lower only with manufacturer approval and sealed seams.

Built-up roof minimum slope

Built-up roofing (BUR) requires a minimum slope of 1/4:12. Ponding water is a defect, so the designer must also provide positive drainage to drains or scuppers.

Single-ply membrane slope

EPDM, TPO, and PVC membranes may be installed on slopes as low as 1/4:12 or on dead-flat decks, but only where the design provides a positive drainage path.

Modified bitumen minimum slope

Modified bitumen membrane systems require a minimum slope of 1/4:12. Lower slopes need manufacturer approval and a drainage design that prevents standing water.

Tile roof minimum slope

Most tile profiles require a minimum slope of 3:12. Some flat tile may be installed at 2.5:12 with doubled underlayment and manufacturer approval.

Tile dead load range

Clay and concrete tile dead loads range from about 6 lb/sf for lightweight concrete to 10-12 lb/sf for clay. The structural engineer must verify the roof can carry this load.

Ballast weight for membrane roofs

Gravel ballast is typically 1,000-1,200 lb per 100 square feet; paver ballast is about 10-12 lb/sf. Ballast weight must match the wind-uplift calculation for the site.

Fully adhered vs mechanically fastened

Fully adhered membranes are bonded with adhesive over the whole sheet; mechanically fastened systems use plates and screws at intervals. The choice depends on wind uplift and deck type.

Underlayment under metal roofs

Metal roof panels require a minimum No. 30 felt or synthetic underlayment over the entire deck. Ice barrier membrane is also required at eaves in ice-dam regions.

High-wind shingle fastening

In high-wind zones, shingles need 8 fasteners each and often a starter course cemented with asphalt plastic cement. Fasteners must be placed in the manufacturer's nailing zone.

Ridge vent NFVA

Ridge vents provide exhaust net free area, usually 18-20 square inches per linear foot. The ridge vent area must be balanced by soffit intake of similar total area.

Drip edge requirement

A drip edge is required at eaves and gables to direct water away from the fascia and deck. It is installed under the underlayment at eaves and over it at gables.

Roofing square definition

One roofing square equals 100 square feet of roof area. Material quantities, fastener counts, and labor estimates are all calculated in squares.

Slope to angle conversion

Roof slope in rise:run converts to angle by arctangent of rise divided by run. A 4:12 slope is about 18.4 degrees; a 6:12 slope is about 26.6 degrees.

Roof area slope factor

Multiply the plan area by the slope factor to get actual roof area. The factor is the square root of (rise squared plus 144) divided by 12 for a rise:12 slope.

Flashing at wall base

Base flashing at a wall extends at least 4 inches up the wall and 4 inches onto the roof. It laps under the counterflashing and over the roof membrane or shingles.

Drainage for low-slope roofs

Low-slope roofs need positive drainage, typically 1/4 inch per foot toward drains or scuppers. Ponding water deeper than 1/2 inch after 48 hours indicates a drainage defect.

Fastener corrosion for treated wood

Fasteners in preservative-treated wood must be hot-dip galvanized, stainless steel, or otherwise rated for the treatment chemistry. Electroplated or plain steel fasteners corrode rapidly.

Roof system wind design basis

Wind uplift design uses ASCE 7 pressure coefficients based on building height, exposure category, and roof zone. Corner and edge zones see higher uplift than the field.