It’s essential to comply with the building code to ensure proper deck post, footing, and beam spacing. However, if your deck will include a hot tub or roof, you must support that weight with additional footings. For a deck that is 15 feet wide with 2×10 joists spaced at 16 inches apart, you have two options. Making sure that your deck has the right number of beams that are properly spaced is critical to ensure it adheres to building code requirements and is safe for your family and guests. 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. 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. the maximum span of a given beam between posts. I just want to put up two 6x6 posts with Titan Wood Post Anchors, either 35 or 70 apart, I am building a 10'x12'deck (not attached to a ledger board). The distance you choose affects the maximum span, or how long your joists can be without compromising the strength of the deck frame. A Redwood 4x6 beam should span no more than 6' between supporting posts. This table compares requirements at both minimum (50 psf) and elevated (70 psf) design loads. 4x6 beam should span no more than 6' between supporting posts. Composite decking brands also generally require 12 inches O.C.joist spacing for 45-degree or angled composite deck board applications. The Joist Span indicates that 2x6s at 24” O.C. Refer to the Deck Beam Span Table below to assist in determining the maximum span of a given beam between posts. 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). The Joist span table below is for joists with a continuous span on a deck below 1metre in height. If you have internal beams, stagger the splices on each so they aren’t lined up on the deck. joist. A deck with 2×8 joists spaced 16 inches apart will need to be supported at least every 12 feet to provide adequate support for the joists and comply with building codes. 2" thick deck boards should be spaced approximately 1/8"; most builders set a 16d nail between the boards as they fasten them. Even though a deck that extends 15 feet from the house with 2×8 joists may only be a few feet longer than the minimum span, you’ll need an additional beam to provide adequate support and adhere to building code. Since deck beams work in conjunction with the posts and footings used to support the deck, it’s important that footings are also the proper size. Beam Spacing. spacing. Use this to specify the spacing between the posts that support the deck. Flush beams are typically used for small decks or those with unconventional shapes where drop or cantilever beams won’t work. For example, to cover a 30-foot space, you might use two 2x8x10s and two 2x8x20s. Deck beam span table Deck joist span table Deck joist rule of thumb Deck & Porch Construction & Structural Fasteners Deck & Porch Post & Beam Connectors: steel post cap connectors, plywood post to beam cleats, other connectors Deck & Porch Railings, Code Requirements, Safety Deck framing tables, codes, specifications Questions & answers about allowable spans for deck, floor, or porch framing. Having the right number of deck beams is essential to building a safe and sturdy deck. The ends of each joist, beam or girder shall have at least 1 ½" of bearing on wood or metal except where supported on a 1"x4" ribbon strip nailed to adjacent studs. In the example below, the offset is changed from 12" to 24". In this instance the maximum span between deck post centres is 2.07m (C16) or 2.24m (C24). It also depends on the joist spacing. 5/4 x 6 pressure-treated decking may be placed with each board flush against the next; natural shrinkage will provide the proper spacing. With a flush beam, the joists are attached to the beam using joist hangers. Step 2: Run String Lines to Ensure All Joists Are Level & In Plane. A Redwood Extending the deck past the posts softens the look of a deck by hiding the posts. Eugene has been a DIY enthusiast for most of his life and loves being creative while inspiring creativity in others. You should also know the size of the post you are considering to Figure 2. Figure 1B. A double 2x12 beam can span 12 feet; a (2) 2x10 can span 10 feet and so on. Obviously, the larger the beam, the greater the distance it can span between posts. determines the force that bears upon that beam and therefore the 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. Whereas a 10 feet can span up to 6 feet 6 inches. The limitations of how far a joist can span determines just how many beams you’ll need. would be adequate for this span. To provide support for the joists, deck beams must span the entire length of the deck. To determine the correct joist required, we need to establish the spacing of our joists. Lumber Species Southern Pine Douglas Fir Douglas Fir-Larch Hemlock-Fir Spruce-Pine-Fir Redwood Western Cedar Ponderosa Pine Red Pine 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. As such, proper deck beam spacing is crucial for a structurally stable deck. However, the type and grade of wood needs to be considered. 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. 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. So, rather than using a 6×6 beam, this would mean using three 2x6s bolted together. Red pine, fir, hemlock, cedar, redwood, and SPF (spruce-pine-fir) are just a few species that also function as beams. Deck beams serve an integral role in the framing of your deck. First, the IRC only allows certain dimensional lumber to be used for deck beams. Joist Size and Spacing I am looking to install privacy screens on my concrete patio. Span is also dependent on the material. 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. The thickness of the beam determines how far a beam can span between support posts. Joists may bear on the beam and extend past the beam face up to the lesser of L O The formula looks like this: (Overall length of deck – Floor joist thickness) “Maximum floor joist spacing/centre” Now your final answer is almost never a round number. Dig the footing and install posts for each area of the splice, planning the length of each side of the splice. Drop beams are also stronger than flush beams because they rely on the wood structure to support the weight rather than metal fasteners. With composites, you can typically trust brand guidelines but should make adjustments depending on the angle and span of your deck. Keep in mind that some species are only available in certain parts of the country. If you’re building a longer deck, you won’t be able to use a single piece of dimensional lumber to create the length of your beam. If you're building a simple deck, footings and posts should be placed less than 8 feet apart. Use this to specify the distance the deck posts are offset from the end of the beam. on-center spacing. Deck Joist Spacing & Blocking Tips Step 1: Check That Your Deck Frame Is Structurally Sound. The International Residential Building Code (IRC) has strict requirements for deck beams and deck beam spacing. Determining proper deck beam spacing can be confusing. Bigger beams also mean a greater span. It makes sense if you think about it. A 20-foot wide deck, for example, would require two beams: one at 10 feet and one and 20 feet in order to support a deck with 2×8 joists spaced 16 inches apart. Beams rest on and secure to Code compliant and spaced deck posts and footings for support. The joists will then extend over the beam in a cantilever position. 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. In the past, 4x4s and 6×6 lumber could serve as beams, that is no longer the case. 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. Cantilevering the beams allows the posts to be partially concealed beneath the deck, creating a more visually appealing look. Dimensional Lumber To calculate beam span, you need to consider the wood species and grade, size of the beam, and the joist span. Whereas a 10 feet can span up to 6 feet 6 inches. The maximum distance between footings is … Remember to complete all calculations using millimetres. For instance, joists that are placed 24 inches apart must be wider than joists placed 16 inches apart. See the deck joist calculations below and study your local code. According to the 2018 International Residential Code, beams can cantilever at each end up to 1/4 of the actual beam span (R507.5). 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. Beams are made out of a variety of treated dimensional lumber. Secure the beams to the post using four carriage bolts. Why use a cantilever? A drop beam is positioned under the joists to bear the weight of the frame. Some builders position them every 4 feet for a completely rigid frame. To properly space deck beams, you need to consider the joist span. In this article, we’ll review how to calculate deck beam spacing based on different lumber sizes and how to determine the number of deck beams you’ll need for your project. use. The last board won’t look good if it’s skinny or cut at an angle. Most dimensional lumber maxes out at 20 feet. (on center) for standard straight composite decking installation. Plan in advance by knowing the correct deck beam span to use. The span of the joists the beam is supporting also determines the maximum deck beam span between support posts. Privacy Screens -How High Can I Go With Titan Wood Post Anchor? Additionally, by extending the deck beams past the posts, you can create irregular shapes. Once you understand the limitations of the joist span on your deck, you can determine how many beams you need. The footing dimensions are determined by assessing the joist length and the post spacing for the tributary area. She would like it to be as high as possible, with. The drop beam design has two advantages. 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. Fasten the deck boards at each joist. © 2004-2019 shorter the span of the beam – for a particular size of beam. Obviously, the larger beams or a beam and a ledger, each beam (or ledger) supports half of the Refer to Table R507.5 of the 2018 IRC for specifics. But how many beams do you need, and how should they be spaced? 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.