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

March 2015

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

March 2015

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

March 2015

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

March 2015

Beam Sizing

Built up Beam

March 2015

Ledger Details

March 2015

Post Decking and Handrail Details

March 2015

March 2015

March 2015