Cantilevering the beams allows the posts to be partially concealed beneath the deck, creating a more visually appealing look. Cost estimates and framing layouts are provided for comparison only; actual costs will vary for different markets. Then divide this measurement by the maximum floor joist spacing that is mentioned on your drawings. Obviously, the larger the beam, the greater the distance it can span between posts. Keep in mind that some species are only available in certain parts of the country. In this case, you’ll need to splice your deck beams to extend length of the beam. To calculate beam span, you need to consider the wood species and grade, size of the beam, and the joist span. The International Residential Building Code (IRC) has strict requirements for deck beams and deck beam spacing. Determining proper deck beam spacing can be confusing. Use this to specify the spacing between the posts that support the deck. Deck beams serve an integral role in the framing of your deck. When the deck joists are 8 ft. long, the beam can span 7-7. For determining beam spans (distance a beam can span between Joist Size and Spacing Smaller decks typically rely on a single beam that runs along the deck’s outer edge, providing support for the joists in conjunction with the ledger board attached to the house. Although we used International Residential Building Code requirements to make our calculations in this article, it’s important to check your local building codes to see if your municipality’s requirements are more stringent. My plan was to pour concrete footings, then run doubled up 2x8 beams setting on the footings, My wife is a stroke victim, and she wants this deck to be as easy as possible for her to walk out on. Beam Deck Post Post Cap 2 ½â€ min. For Beam 1, use a joist length of 13’, (6’+7’) and a post spacing of 9’. The tributary area, coupled with the live load or snow load for the locale, and the soil’s load bearing value are used to identify the required dimensions of the footing (Reference Table R507.3.1 of the 2018 IRC).. Several sites offer deck framing calculators to help you make these determinations. Maximum 2x6 Deck Joist Span According to the 2018 International Residential Code, beams can cantilever at each end up to 1/4 of the actual beam span (R507.5). What if your deck is more than 20 feet long? Refer to Table R507.5 of the 2018 IRC for specifics. 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. 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. you already understand the relationship between joist span and joist Drill through the beam with a long bit the same diameter as the bolts. 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. Below are some common beam span values from Table R507.5 of the 2018 IRC: A cantilevered beam extends beyond the end post or posts. A steel beam can hold remarkably more than a wood beam, which reduces the number of support posts needed. It makes sense if you think about it. The Deck Beam Span Table on this page makes it easy to determine how far apart your posts and therefore the span of the beam should be. 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. So, for example, a 16-foot beam span can cantilever a maximum of 4 feet. See the deck joist calculations below and study your local code. For instance, joists that are placed 24 inches apart must be wider than joists placed 16 inches apart. If you have internal beams, stagger the splices on each so they aren’t lined up on the deck. Most decks use 16" on center spacing for joists. This table compares requirements at both minimum (50 psf) and elevated (70 psf) design loads. The International Residential Building Code requires that you have enough deck beams to support the deck’s joists adequately. on-center spacing. The majority of composite deck board brands including Trex, TimberTech, and more require deck joists spacing to be at 16 inches O.C. The required width of a joist depends on its span: how far it must travel between beams or between a beam and a ledger. How to build deck stairs Stair height calculation table Decks building tutorials and design tables Working in concert with the deck posts and footings, a deck beam is responsible for holding up the joists, which holds up the decking. Step 2: Run String Lines to Ensure All Joists Are Level & In Plane. the beam, the greater the distance it can span between posts. Remember to complete all calculations using millimetres. beams or a beam and a ledger, each beam (or ledger) supports half of the Joist Span – Non-Ledger Deck. If the outside edge of your deck is at least 17” above grade, a double 2x8 beam should be installed to support the joists along the outside. He is passionately interested in home improvement, renovation and woodworking. Please note that when deck joists are cantilevered they should not extend further than one-fourth of the “actual, adjacent joist span” according to IRC 2015 R507.5. your planning stage, don’t forget to consider the spacing for your Remember, the IRC allows you to cantilever joists up to one-fourth of the joist’s span from beam to beam (or in this case, from ledger board to beam). Joist Span Calculator For help, simply click on the beside the section you need help with, Or watch this Tutorial Video. Dimensional Lumber Use the Beam and footing sizes table and find the 8' post spacing column. BEAM SIZE & ASSEMBLY REQUIREMENTS Deck beam spans shall be in accordance with Table 3 and can extend past the post face up to L B /4 as shown in Figure 3. The span is the distance a joist traverses from ledger to beam, or beam to beam, without support. There’s also an aesthetic benefit to a cantilever. If the width of the deck exceeds this span, you’ll need more beams. To properly space deck beams, you need to consider the joist span. The weight load of your deck also affects the spacing of the posts. Some builders position them every 4 feet for a completely rigid frame. distance that a given size of beam can span before another post is The closer you space joists, the longer you can span joists – Joists spaced the standard 16 inches apart can span 1.5 times their depth in feet. This means for a 12-foot span, you can cantilever up to three feet beyond the beam. The thickness of the beam determines how far a beam can span between support posts. Most span tables use Southern pine for their calculations, but this isn’t the only material you can use for a beam. the midway point between the supported ends (either a ledger or beam) of A double 2x12 beam can span 12 feet; a (2) 2x10 can span 10 feet and so on. Secure the beams to the post using four carriage bolts. Joist Spacing & Span. Remember, you need enough beams to keep the span of the joists in code. Lumber Species Southern Pine Douglas Fir Douglas Fir-Larch Hemlock-Fir Spruce-Pine-Fir Redwood Western Cedar Ponderosa Pine Red Pine Some builders reduce joist spacing to 12" on center to strengthen the deck frame or to increase maximum allowable joist spans. The Joist span table below is for joists with a continuous span on a deck below 1metre in height. This distance is half the distance to the next beam in either direction. Starting with your perimeter, mark the location of each deck post to locate the fitting position. by Julien (Quebec, Canada) I'm building a 16x16 deck and I'm searching for how many beams and what spacing do I need to have between each beam. 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. The footing dimensions are determined by assessing the joist length and the post spacing for the tributary area. Determine the length of the joist actually supported by the beam. That is a fairly simplistic way of looking at it. First, plan where the splice will be located on the beam. Lumber Species Southern Pine Douglas Fir Douglas Fir-Larch Hemlock-Fir Spruce-Pine-Fir Redwood Western Cedar Ponderosa Pine Red Pine For Beam 2, use a joist length of 7’ and post spacing … At Softwoods we use 450mm spacing as a default as it provides ample support in almost all uses. Example: a = 12'; Post spacing # 8' Use the joist span table to find the acceptable joist sizes for a 12' span, 2x8s at 12" O.C., 2x10s at 16" O.C., or 2x12s at 24" O.C. (on center) for standard straight composite decking installation. If you have seen the Deck Joist Span Table, To provide support for the joists, deck beams must span the entire length of the deck. Once you understand the limitations of the joist span on your deck, you can determine how many beams you need. A drop beam is positioned under the joists to bear the weight of the frame. However, if your deck will include a hot tub or roof, you must support that weight with additional footings. The narrower the spacing between joists, the greater the span can be. Figure 2. Joists may bear on the beam and extend past the beam face up to the lesser of L O You would only need one deck beam for a small deck that is 12 feet wide or less in the above example. The span of the joists the beam is supporting also determines the maximum deck beam span between support posts. Check with your local code official, or simply drop back to the shorter value in the table and assume the allowable span is 7-7. While this can vary depending on the size, species, and grade of the framing lumber, a deck with 2×8 southern pine joists spaced 16 inches apart must be supported by a beam a maximum of every 12 feet. This will ensure a stronger frame. Most decking is not strong enough to support longer spans than 16". Joist Spacing for Composite Decking supporting posts), consider the following concept. With composites, you can typically trust brand guidelines but should make adjustments depending on the angle and span of your deck. The length of joist span actually supported by a beam is what 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. 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 If you're building a simple deck, footings and posts should be placed less than 8 feet apart. 4x6 beam should span no more than 6' between supporting posts. Drop beams are also stronger than flush beams because they rely on the wood structure to support the weight rather than metal fasteners. This may mean you only need one beam plus the ledger board attached to the house for smaller decks. For a deck that is 15 feet wide with 2×10 joists spaced at 16 inches apart, you have two options. Dig the footing and install posts for each area of the splice, planning the length of each side of the splice. 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