Decks California - builder - contractor - design - constructionDecks California - builder - contractor - design - construction
Deck Footings and Piers
Deck Footings and Piers
Designing decks for our location We live in the beautiful wine country of Northern California. When we design decks for our area these are the building practices we follow. Always refer to your local building codes or a structural engineer.
Alter Eagle is a professional licensed and insured deck building contractor
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Footings recommended by the 2010 deck prescriptive The above table for footings is from the deck prescriptive based on the 2009 IRC being adopted by most building depts. but they can vary so check your jurisdiction. The loading conditions
The deck 40 psf live and 10 psf dead. The soil bearing 1,500 psf. The concrete 2,500 psi compressive. The footing bottoms are located a minimum of 12 inches below undisturbed ground at native soil or below the frostline whichever is the deepest. The ground slope not greater than 2 horizontal for every 1 vertical. Example: If the deck has a beam span of 6 ft. or less and a joist span less or equal to 10 ft they recommend a footing either 15" in diameter x 6" thick or a square footing 13"x13"x 6" thick Footings closer than 5'-0 Footings closer than 5'-0" to the existing exterior house wall must bear at the same elevation as the existing wall footing. Most jurisdictions in California change this to within 3'-0" Decks building codes - Footings - IRC & IBC
IRC R403 & IBC 1805 Footings
Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 IRC R403.1.1 & IBC 1805.4.1 Minimum size The size of footings supporting piers and columns shall be based on the tributary load and allowable soil pressure in accordance with Table R401.4.1 (above) The minimum width of footings shall be 12 inches, spread footings shall be at least 6 inches in thickness IRC R403.1.4 & IBC 1805.4.1 Minimum depth All exterior footings shall be placed at least 12 inches below the undisturbed ground surface. IRC R403.1.5 Slope The top surface of footings shall be level. The bottom surface of footings shall not have a slope exceeding one unit vertical in 10 units horizontal (10% slope). IRC R404.1.2.3.1 Compressive strength The minimum specified compressive strength of concrete, shall be not less than 2,500 psi
Decks - How we design our footings Decks - Footings - Soil bearing Decks over 30": We would calculate the tributary loads (including the spa load if any from the manufacturer) and size the footing for the soil type. We prefer to use a footing to stabilize the deck from settlement and use a pier with rebar to get the post connection above grade. Decks under 30": We typically use a 8" dia x 8" thick footing with 4x4 P.T. uncut end embed in concrete to the footing at 24" deep due to the height restriction for the framing. Spas would be set on a concrete pad with the same specifications as a garage slab. Sandy gravel, gravel: Gravel and sand will settle in water almost immediately. It's usually pretty easy to recognize. Moistened it can't be rolled into a ball. 3000 LB/sq.ft. It’s hard to identify soils precisely in the field, sometimes an engineering soil report will be required, here are some quick on-site tests we use. Sand, silty sand: Finer silt particles will take fifteen minutes to an hour to settle. Granular, gritty texture. Moistened it can't be rolled into a ball or readily fragments. 2000 LB/sq.ft. Clay, silty clay, silt: Clay particles will remain suspended in water for a day or longer. When moistened it has a sticky texture and if it can be rolled as thin as 1 in. without breaking apart, it probably has a substantial percentage of clay. 1500 LB/sq.ft. When in doubt: Common sense just tells you to use 1500 LB/sq.ft. but most building dept. officials know their territories so give them a call or check on-line. Especially when building on a slope here in California some areas are known for their slides. Decks building tutorials and design tables
The frequently asked questions on how to build decks for Northern California Deck footing & pier sizing for California Deck connections for California's #4 earthquake zone California decks built up and solid beam size tables and post size table. Tables for the minimum joist spans in California's moderate climate regions How we build a closed in riser stair for decks with a skirt for solid railings Deck stair total rise table with calculations for riser heights and number of treads
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