residential deck design and construction - lawrence, kansas · 2015-08-25 · construction details...
TRANSCRIPT
March 2015
Residential Deck Design and Construction
March 2015
General Notes The purpose of this document is to provide contractors and homeowners with guidelines and construction details for the construction a typical residential deck. These guidelines and details are limited to deck designs using a uniform floor load of 40 pounds per square foot live load and 10 pounds per square foot dead load over the entire floor of the deck and should be considered safe for normal residential use. Deck supporting loads in excess of normal loads such as hot tubs, sunrooms or decks with roofs are not covered and will require a more detailed review and approval from the City of Lawrence Building Safety Division prior to construction. A building permit is required to construct, alter or replace freestanding or attached decks, porches deck covers or attached ornamental shade structures. Decks where any part of the surface is not more than 30” above grade are exempt from permit requirements
Site plan The site plan should include an overhead view of the property showing an outline of the proposed deck, the location and distances from the deck to the property lines and any buildings or structures located on the property. The plan should also show any utility or drainage easements. Deck plans Deck plans should include the following;
Area of the deck.
Size and spacing of built up beams
Size and depth and spacing of footings or piers
Deck ledger attachment details.
Size and spacing of floor joist, and rafters
Size and spacing of support post
Lateral bracing details
Design Criteria
Frost depth 30”
Floor Live load 40 lbs/ ft2
Floor dead load 10 lbs/ ft2
Roof snow load 20 lbs/ ft2
Roof dead load Actual weight of the materials. This is typically 10 lbs/ ft2
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Sample Site Plan
Double 2”X 12” Treated posts
8’
8’
5’ to side property line
30’ to rear property line
Rear Yard
Front Yard Driveway
New 16’X 16 Rear Deck
6”X6” posts and 2”X10” floor joist treated
Deck Height is 4’ above grade
Cedar decking and handrails
18” diameter X 30” depth footings
5’ Utility Easement
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Post and Beam Sizing
To properly size a beam or post it will is first necessary to determine the area of the deck which is being supported by the beam. A beam at the end of deck does not support the entire length of the deck. Half of the weight of the deck is supported by the structure and half of the weight is supported by the beam. That area which is supported by the beam is referred to as the tributary load. As an example a deck which has 14 feet floor joists, the tributary load on the rim beam is 7 feet. This also applies to the area supported by deck post. The tributary area of a post is the distance from the post to ½ the distance to the next supporting structure.
40 lb/ft2
live load – 10 lb/ft2 dead load
Beam
Size
Tributary load width (ft.)
4’ 5’ 6’ 7’ 8’ 9’ 10’ 11’ 12’
2x6 5-7 4-9 4-2 3-8 3-4 3-1 2-10 2-8 2-6
2x8 7-2 6-2 5-5 4-10 4-3 4-0 3-9 3-6 3-4
2x10 8-7 7-8 7-0 6-2 5-7 5-1 4-9 4-5 4-3
(2)2x6 7-10 7-0 6-5 5-11 5-7 5-2 4-9 4-5 4-1
(2)2x8 10-1 9-1 8-3 7-8 7-2 6-9 6-3 5-10 5-5
(2)2x10 12-0 10-9 9-10 9-2 8-5 8-1 7-8 7-4 7-0
(2)2x12 14-0 12-7 11-6 10-8 10-0 9-5 9-0 8-7 8-2
(3)2x8 12-10 11-10 10-10 10-0 9-5 8-10 8-5 8-0 7-6
(3)2x10 15-7 14-1 12-10 11-11 11-2 10-7 10-0 9-7 9-2
(3)2x12 18-3 15-5 15-0 13-11 13-1 12-4 11-9 11-2 10-9
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Maximum Post Height
Species
Post Size
40 lb/ft2 live load – 10lb/ft
2 dead load
Tributary load area to post(ft2)
36 48 60 72 84 96 108 120 132 144 156 168 180 192
Southern Pine
4x4 10’ 10’ 10’ 9’ 9’ 8’ 8’ 7’ 7’ 6’ 6’ 6’ 6’ 5’
4x6 14’ 14’ 13’ 12’ 11’ 10’ 10’ 9’ 9’ 8’ 8’ 8’ 7’ 7’
6x6 (No. 1)
17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 16’ 16’
6x6 (No.2)
17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 16’ 16’ 15’ 14’ 13’ 13’
Redwood
Western Red Cedar
4x4 10’ 10’ 9’ 8’ 7’ 7’ 6’ 5’ 5’ 4’
4x6 14’ 13’ 12’ 11’ 10’ 9’ 8’ 8’ 7’ 7’ 7’ 6’ 6’ 5’
6x6 (No.1)
17’ 17’ 17’ 17’ 17’ 17’ 17’ 17’ 16’ 15’ 15’ 14’ 14’ 13’
6x6 (No.2)
17’ 17’ 17’ 17’ 17’ 16’ 13’ 7’
Lateral Bracing Detail
Larger decks with greater mass and decks supported on longer posts can produce substantially higher lateral loads and may require additional Bracing
March 2015
Joist Spans
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Beam Sizing
Built up Beam
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Ledger Details
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Post Decking and Handrail Details
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March 2015