​

• Waste Pipe = ¼ inch per foot (0.25) minimum & 3 inches per foot maximum or vertical

• Gas Vent = ¼ inch per foot (0.25) with minimum rise of 1 foot above draft hood before an elbow

• Roof with shingles:

  • 4inches per foot (4/12)

  • With Double Ice Shield (2 – 4 per 12)

  • Maximum Slope:

    • Asphalt shingles should not be installed on vertical walls.

    • > 12/12 to 18/12

      • 6 nails per shingle

      • Hand sealing or "tabbing" roof shingles on a steep slope means applying a dab of sealant (roof cement) under each shingle. For architectural-style laminated shingles use four equally-spaced dabs of sealant under the shingle's leading (lower) edge.

        • NRCA recommends 3 sealant dabs for 3-tab (cutout type) asphalt shingles, with each spot centered at the bottom of each shingle tab.

        • ARMA recommends 6 sealant dabs for 3-tab (cutout type) asphalt roof shingles, with a dab at both corners of each shingle tab.

•  Gutter = ½ inch per 10 feet (0.05) with runs no greater than 40 feet

• Grade = 6 inches per 10 feet (0.6)

Loading

​

• Downspout (2x3 typical….3x4 & 3x4 diverter multiple by 2) = 1200 sq ft (1 inch rain/hr)

  • It is based on the assumption that during a rainfall with an intensity of 1 inch per hour, each square inch of downspout can drain 1200 square feet of roof. If the intensity is doubled the downspout capacity is halved, or 600 sq. ft.; if it is tripled the capacity is one third, and so on.

Venting

​

• • Crawl

    • Poly = 1 sq foot per 1500 sq ft

    • No Poly = 1 sq ft per 150 sq ft

      • One square foot of net free vent area is recommended for every 1500 square feet of floor area covered by a polyethylene vapor retarder. Ratio is 1:150 if vapor retarder is not used.
        *Net free vent area is that area unobstructed by screens, louvers, or other materials.
        *Heated crawlspaces and basements do not need vents.
        Earth floors should be covered with a 4 - 6 mil. polyethylene vapor retarder.
        *Providing at least two crawlspace vents will allow for a flow of air in and out of the crawlspace

  • Roof = 1 sq ft per 150 sq ft divided evenly between soffit and roof peak

Pipe Hangers

​

Most plumbing codes have the following hanger spacing requirements: ABS and PVC pipe have a maximum horizontal hanger spacing of every four feet for all sizes. CPVC pipe or tubing has a maximum horizontal hanger spacing of every three feet for one inch and under and every four feet for sizes 11⁄4 inch and larger.

​

​

Slopes​