What is the recommended slope for a deck so that water will not pool on the wood?

It differes by state, this if for California: The Uniform Building Code requirements for plaza decks (waterproofed surfaces designed for pedestrian-type occupancy) has always been somewhat ambiguous in the past, inviting experts in construction litigation to testify both in defense of and in criticism of architects who have designed decks without slope. One part of that argument has been whether or not a deck is a "roof." As far as the surface of decks (roof or no roof) are concerned, the California Building Standards Code is now clear. Section 1506.1 states, "Unless designed for water accumulation in accordance with Section 1605.6 and approved by the building official, roof systems shall be sloped a minimum of 1/4 unit vertical in 12 units horizontal (2% slope) for drainage." Section 1402.3, Waterproofing Weather-exposed Areas, states, "Balconies, landings, exterior stairways, occupied roofs and similar surfaces exposed to the weather and sealed underneath shall be waterproofed and sloped a minimum of 1/4 unit vertical in 12 units horizontal (2% slope) for drainage."

"1/4" per foot fall (one inch drop in slope per four feet of travel)is the standard, however, gaps in wood decking may mitigate this requirement as water is thus shed more rapidly. Consult your local building code for strict compliance."

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I agree with the above statement with this additional information:

General engineering practices will accept that water will SHEET (flow from a horizontal surface) at not less than 1% slope or 1/8 unit vertical in 12 units horizontal.

The standards setforth in the 2003 ANSI 117.1, the International Residential Code and the International Building Code do not allow landings to slope or cross slope (The slope in other than the direction of travel) greater than 2%.

With this in mind anything between 1% and 2% would generally be acceptable. Warping and cupping of wood products will occur and the closer to the 2% the better, IMHO. Where i live ice buildup is also a concideration.

As mentioned earlier you should always check with your local building official or building department for clarification.

Good Luck

Terry

First answer by KaraRae278. Last edit by Maintain. Contributor trust: 131 [recommend contributor]. Question popularity: 99 [recommend question]