beams or a beam and a ledger, each beam (or ledger) supports half of the Starting about 2 inches from the edges of the beam, counterbore two holes on the inside (or the least-visible side) of the beam for carriage bolt nuts. Since deck beams work in conjunction with the posts and footings used to support the deck, itâs important that footings are also the proper size. In the past, 4x4s and 6×6 lumber could serve as beams, that is no longer the case. For instance, joists that are placed 24 inches apart must be wider than joists placed 16 inches apart. The International Residential Building Code (IRC) has strict requirements for deck beams and deck beam spacing. The end of each beam shall have a minimum of 1 ½â of bearing on wood or metal or 3âon masonry located at interior posts Joist Beam Ledger Board 2 rows 10d (3â X.128â) nails or wood screws placed 16â O along edge of both sides of beam (2) ½â diameter through-bolts with washers under head and nut 5 ½â min. For determining beam spans (distance a beam can span between Refer to the Deck Beam Span Table below to assist in determining the maximum span of a given beam between posts. However, if your deck will include a hot tub or roof, you must support that weight with additional footings. How to build deck stairs Stair height calculation table Decks building tutorials and design tables This translates into fewer holes to dig and materials to purchase. A two-ply 2×10 beam, for example, has an allowable span of just 6 feet 9 inches for a joist spanning 14 feet and 6 feet 4 inches on 16 feet. required to support that beam. It also depends on the joist spacing. Some builders position them every 4 feet for a completely rigid frame. (on center) for standard straight composite decking installation. He is passionately interested in home improvement, renovation and woodworking. According to IRC, a two-ply 2×10 beam supporting a joist that spans 8 feet between supports requires beam support posts every 9-feet. Deck Post Spacing. Most decks use 16" on center spacing for joists. The IRC also regulates how far a deck beam can span before it needs support from a post and footing. Thereâs also an aesthetic benefit to a cantilever. When building a deck with 7-ft. joists, you know the beam can span somewhere between 7-7 and 8-0, but you donât know exactly where. Eugene has been a DIY enthusiast for most of his life and loves being creative while inspiring creativity in others. would be adequate for this span. For Beam 2, use a joist length of 7â and post spacing â¦ The formula looks like this: (Overall length of deck â Floor joist thickness) âMaximum floor joist spacing/centreâ Now your final answer is almost never a round number. A Redwood 4x6 beam should span no more than 6' between supporting posts. All Rights Reserved. Drop beams are also stronger than flush beams because they rely on the wood structure to support the weight rather than metal fasteners. Joist direction, size and spacing Location of posts and deck blocks supporting beam Spans between beam support posts Beam cantilever distance (if applicable) Dimensions of the deck Area of the deck Stair location (if applicable) The location of the house relative to the new deck Stair dimensions This may mean you only need one beam plus the ledger board attached to the house for smaller decks. You should also know the size of the post you are considering to Some builders reduce joist spacing to 12" on center to strengthen the deck frame or to increase maximum allowable joist spans. Beams rest on and secure to Code compliant and spaced deck posts and footings for support. The limitations of how far a joist can span determines just how many beams youâll need. The thickness of the beam determines how far a beam can span between support posts. So, rather than using a 6×6 beam, this would mean using three 2x6s bolted together. The closer you space joists, the longer you can span joists – the midway point between the supported ends (either a ledger or beam) of In the example below, the offset is changed from 12" to 24". The Joist span table below is for joists with a continuous span on a deck below 1metre in height. The International Residential Building Code requires that you have enough deck beams to support the deckâs joists adequately. Red pine, fir, hemlock, cedar, redwood, and SPF (spruce-pine-fir) are just a few species that also function as beams. use. Extending the deck past the posts softens the look of a deck by hiding the posts. The span is the distance a joist traverses from ledger to beam, or beam to beam, without support. Smaller decks typically rely on a single beam that runs along the deckâs outer edge, providing support for the joists in conjunction with the ledger board attached to the house. With composites, you can typically trust brand guidelines but should make adjustments depending on the angle and span of your deck. Obviously, the larger Once you understand the limitations of the joist span on your deck, you can determine how many beams you need. With this in mind, the depth of the joist determines the spacing of the beams. If you are still unsure what the deck beam requirements are for your deck design, feel free to reach out using the comment box below. Deck joist spacing is the distance between joists, measured from the center of one joist to the center of the next, and is commonly 12, 16, or 24-inches. Itâs essential to comply with the building code to ensure proper deck post, footing, and beam spacing. © 2004-2019 Decksgo.com. Drill through the beam with a long bit the same diameter as the bolts. supporting posts), consider the following concept. This means for a 12-foot span, you can cantilever up to three feet beyond the beam. They may be a single plank, or consist of two, three, or even four 2x8s, 2x10s, or 2×12 boards fastened together with bolts or nails. Cut a 3-inch-wide notch in the post to match the width of the beam. When calculating beam span, the general rule of thumb is pretty straightforward: the longer a beam spans, the bigger it needs to be to support that span. You must use 2x material bolted together to create a deck beam, or use metal or engineered lumber. The Beam Table indicates that the beam may be two 2x10s or two 2x12s, depending on the wood used. In this case, youâll need to splice your deck beams to extend length of the beam. In this instance the maximum span between deck post centres is 2.07m (C16) or 2.24m (C24). A Redwood To calculate beam span, you need to consider the wood species and grade, size of the beam, and the joist span. The joists will then extend over the beam in a cantilever position. determines the force that bears upon that beam and therefore the To provide support for the joists, deck beams must span the entire length of the deck. the maximum span of a given beam between posts. You can use two beams, one at 7.5 feet and one at 15 feet, to provide support. Adjust the spacing between deck boards gradually over the next 10 rows of decking until the distance to the house is equal. Remember to complete all calculations using millimetres. The maximum joist spans below are based on a ground snow and live load of 40 pounds per square foot and a dead load of 10 pounds per square foot. Offset From End. Most decking is not strong enough to support longer spans than 16". When supporting joists that span 12 feet with no overhang beyond the beam, a double ply beam can span in feet a value equal to its depth in inches. She would like it to be as high as possible, with. Deck beams serve an integral role in the framing of your deck. 5/4 x 6 pressure-treated decking may be placed with each board flush against the next; natural shrinkage will provide the proper spacing. A 2×6 joist can span up to 9 feet, a 2×8 can span up to 12 feet, and a 2×10 can span up to 15 feet. In most cases, itâs best to start with a full board on the outside edge of the deck and work toward the house so the odd board is â¦ you already understand the relationship between joist span and joist the longer the supported length of joist that a beam must carry, the A drop beam is positioned under the joists to bear the weight of the frame. Joist Spacing & Span. The weight load of your deck also affects the spacing of the posts. A 3 ply 2×10 beam can handle a span of 8 feet 6 inches for a joist spanning 14 feet and 7 feet 11 inches at 16 feet. Span is also dependent on the material. Joist Span â Non-Ledger Deck. It allows the beams to extend beyond the post for a short distance which is called cantilevering. Decking Beam Span Guidance We recommend beams are constructed from two 44 x 145mm Q-Deck deck joists and are placed at maximum centres of 1.8m. There are two types of deck beams to consider: flush beams and drop beams. Span entries are listed for 2×6 through 2×12 joists and 12 in., 16 in., and 24 in. Although we used International Residential Building Code requirements to make our calculations in this article, itâs important to check your local building codes to see if your municipalityâs requirements are more stringent. First, plan where the splice will be located on the beam. In general, posts should be spaced no more than 8 feet apart. If youâre building a longer deck, you wonât be able to use a single piece of dimensional lumber to create the length of your beam. 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