• 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)



  • 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.



    • 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.