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Building Code

Building Code:

Deck slope and International Code Council:

 

http://publicecodes.cyberregs.com/icod/ispsc/2012/icod_ispsc_2012_3_sec006.htm

 

SECTION 306 DECKS 
306.1 General. 


Decks shall be designed and installed in accordance with the International Residential Code or the International Building Code, as applicable in accordance with Section 102.7, except as provided in this section. 

306.2 Slip resistant. 

Decks, ramps, coping, and similar step surfaces shall be slip-resistant and cleanable. Special features in or on decks such as markers, brand insignias, and similar materials shall be slip-resistant

306.3 Stair treads and risers. 

Stair riser heights shall be in accordance with the International Residential Code or the International Building Code, as applicable in accordance with Section 102.7.1. 

306.4 Slope. 

The minimum slope of decks shall be in accordance with Table 306.4 except where an alternative drainage method is provided that prevents the accumulation or pooling of water. The slope for decks, other than wood decks, shall be not greater than 1/2 inch per foot (1 mm per 24 mm) except for ramps. The slope for wood and wood/plastic composite decks shall be not greater than 1/4 inch per 1 foot (1 mm per 48 mm). Decks shall be sloped so that standing water will not be deeper than 1/8 inch (3.2 mm), 20 minutes after the cessation of the addition of water to the deck. 

TABLE 306.4 MINIMUM DRAINAGE SLOPES 

SURFACE

TYPICAL MINIMUM DRAINAGE SLOPE
(INCH PER FOOT)

Brick and heavy textured finish

3/8 inch

Carpet

1/2 inch

Exposed aggregate

1/4 inch

Textured, hand-finished concrete

1/inch

Wood

1/8 inch

Wood/plastic composite

1/8 inch

 

For SI: 1 inch per foot = 83.3 mm per m.

 

Deck slope and Industry professionals:

See http://housecraft.ca/the-essentials-of-deck-planning-and-construction/

‘’You also want to have your deck sloped very slightly as well – again, this will help direct water away from the foundation of the house. The grade for Chris’ deck is approximately a 1 % slope (as the deck gets further away from the house), which is about ½ inch over 4 feet: enough to carry the water away, but not enough to be noticeable. You can get away with less – this is a Mike Holmes-esque overbuild that allows for a considerable safety margin. The slope of the deck should not exceed 2%, or it may be noticeable.’’