Joists that cantilever allow for the use of longer joists than those that terminate at the outside face of the beam. Check out the calculator below. Joists distribute the weight of the live and dead loads of the deck to the supports. Medium Strength: Redwood, hemlock, and spruce will span almost as far. The joists are fastened to the beams to maintain spacing and prevent movement. The span of deck joists depends on the selection of dimensional lumber available in your area. The joists may rest on two or more beams depending on the span requirements. Adding a hot tub or spa to the deck will increase the live load and affect deck joist span and spacing. Joists can usually span up to 1.5 times their thickness in feet. That leaves one beam to be supported by two or more posts. The type of decking selected may require special fasteners and tools too. It requires two 3” or 3-1/2” fasteners in every joist and is also spaced 1/8” to 3/8” apart. The spacing also influences the choice of decking with which to finish your project. If you are unable to attach or don’t want to attach, your deck joists to your house with a ledger board, then your design becomes more flexible. With a $35 billion economy, low taxes, a vast multi-modal transportation system, highly skilled workforce and excellent educational institutions, Anne Arundel County is the premier location to do business. 12”o.c. and 16”o.c. for boards laid at an angle to the joists. The pier size is in the intersecting box of the row that corresponds with your joist span and the column that corresponds with your pier spacing. To show how the joist spacing, span, and sizing interact, here are several examples based on a 12×12 deck. The joists are usually not visible, so using expensive premium timbers isn’t necessary as long as the beam structure is properly placed. Tributary Load. Maximum joist span of a 2X8 is 10’ – 6” at 16” o.c. To make it simple, place your posts no further than 8’ apart. The most obvious factor is how your deck is laid out and the type of space it occupies. The more complete the plan, the fewer surprises. For conventional guardrail post installation bolted to the side of the framing, larger framing will provide more strength in the rails. Remember to follow local code for deck posts. Materials Decks must be constructed of long-lasting, moisture-, rot-, decay- and insect-resistant materials. There are six main factors to consider when designing and building a deck that determines the span and spacing of deck joist. Downsizing to 16”o.c. Deck joists, similar to those in any structure, determine the load a floor or deck framing can carry. Deck Brighteners contain oxalic acid, which will also remove tannins. Figure 2. The last factor is also the size of the footing. The narrower the spacing between joists, the greater the span can be. Total height of low level ground level deck. A three-ply 2×12 would allow you to use only two deck support posts for the 10×10 deck. can bridge 18’-6”. The IRC reflects proven construction techniques for wood decks using widely accepted conventional construction materials and practices. Joists commonly are spaced at 12”, 16”, or 24” centers depending on the load the deck frame will carry and the size, type, and orientation of the deck boards. Spacing also impacts the distribution of weight, influencing the structural strength, and deck integrity. The Building Code stipulates acceptable spacing to prevent injury or death due to improper spacing which can cause structural failure. While these online calculators are great for visualizing what your deck might look like in terms of where you place your deck support posts, keep in mind that they are only an estimate. Deck joist spacing affects how well supported the deck boards are; if too far apart, the decking will be springy or soft, and can sag. Another way for 16”o.c. How the decking runs determines the joist pattern, which in turn identifies the number, size, and placement of beams and support posts, and the ledger board. If you look at the deck post spacing chart below, you’ll notice that the higher the post, the shorter the beam span it can support. REMEMBER THESE THINGS. Opting for the 3-ply 2×10, resulting in 3 deck support posts, would result in a seriously strong deck, and you would place the third support post right in the center of the beam. Residential Deck Construction Guide ... All deck support posts shall be a minimum 6”x6” with a maximum unsupported height of 10’-0” ... span decks have more than one beam; spacing between beams is dependent on the allowable span lengths of the supports joist. A beam of that size can span nearly 12’ while supporting 10’ joists. For commercial applications, joist spacing is 12”o.c. 2×6 deck boards can span up to 24”o.c. Pressure-treated lumber is protected from moisture and insect damage, as well as mold and mildew. Having long joists is nice because, in theory, it could mean a shorter beam. It is important to note that not all values in some tables are the same as what is in the IRC, so it is important to check the local Code for accurate current values for your area. Size and spacing depend upon the shape and size of the deck, the weight it needs to support (hot tub? Each factor affects the span, the spacing, or both, as well as the placement of beams and support posts that make up the deck frame. The frost line and snow load tables in Florida are different than Minnesota, so code has to take that into account, for example. joist spacing increases material cost between $70 for 2x8s and $100 for 2x10s. deck guard s05 nts 2 6'-0" max post spacing 36" min [r312.1.2] openings shall not allow the passage of a 4" diameter sphere [r312.1.3] see detail 2/s05 2x6 or 5/4 board rail cap attached to each post with (3) 16d nails or #10x3" wood screws 2x2 balusters attached at top and Most decks have joists that are attached to a ledger board, which is affixed to the house. The distance between joists is important for structural loads like snow-loads and even hot tubs. Decks commonly follow the perimeter of a wall or structure, or the contours of the landscaping, or both. 4. Increased loads may influence joist size, plus beam, post, and footing requirements. It’s best to adhere to the Code or involve a Structural Engineer. They bow too easily to span much distance and won’t support heavy loads. or 16”o.c. Space balusters with a jig. Start at the center of the rail and work toward the … The future is … A deck is an outdoor living area and enhances the look and character of a home. when laid diagonally to joists, and 16”o.c. Beams must sit on top of deck support posts, using code-approved fasteners. It doesn’t affect the strength of the wood and is available in 2-by and 5/4 decking formats for decking and frame construction. Manufacturers of different composite decking products commonly include instructions with their products. On the other hand, you can always fabricate a larger deck beam and put your deck support posts further apart. When I built my deck, one of the biggest questions I had was how far apart should I put my deck posts? You are limited to two-ply beams – that means two pieces of lumber, such as two 2x8s nailed together for use as a deck support beam. For upper-level decks, 2x10 is recommended as the minimum size to use for strong guard post connections. Deck Board Spacing. Joist size determines span and spacing, so select the grade and type of wood best suited for your needs and budget. 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. Why? A Joist Span calculator commonly identifies the maximum span and cantilever for dimensional lumber joists based on wood type, joist size, and spacing between joists. It is available in green or brown tones of preservatives, so the color is reasonably consistent. One of the biggest is knowing what your local building code allows. The maximum spacing for 5/4 wood and most composite decking is 12”o.c. Although 2x4s may be used for low-profile joists near ground-level they aren’t normally included in structural joist tables. The shape and size of the deck influence the layout and number of joists, potential spans, and even the spacing. Knots and defects affect the strength of the timber, making it weaker. The spacing reduces to 12”o.c. Decking may be perpendicular or diagonal to joists, full run or staggered, or something unique. … If your deck is more than 2’ high, your corner support posts will need to be braced parallel and perpendicular to the support beam and deck joists, respectively. Factors that Determine Deck Joist Spacing and Span, How to Determine the Proper Deck Joist Sizing and Spacing, 4. There are six main factors to consider when designing and building a deck that determines the span and spacing of deck joist. Many North American municipalities follow the guidelines set out by the American Wood Council, which offers a comprehensive deck post spacing chart (Table 3A): Understand that the above chart is only a guideline – many municipalities are not as strict as the AWC. Standard rail … ), and the height off the ground. Use calcium chloride or rock salt to melt the snow and ice from the deck surface. It also permits the use of 2x8s at 16”o.c. Local building codes address unique conditions for their specific region, including the load-bearing ability of soil, frost and seismic issues, plus snow and wind load concerns. Whether the deck framing is free-standing or attached to a structure with a ledger board, joists span the distance and help shape a deck. The spacing helps to determine the span. The spacing between joists is 12”o.c. The weight load of your deck also affects the spacing of the posts. It offers greater strength and allows joists to be spaced up to 24”o.c. The shape often determines the direction of the joist grid, which in turn affects the deck board layout and direction. The type of decking and its layout affect the joist spacing. With almost 54,000 businesses, Anne Arundel County is a major hub of commerce and development. Additionally, many municipalities allow 4×4 deck posts for decks up to 5’ in height. The spacing depends on the thickness of decking used. It varies because decks come in so many different sizes and shapes. The wood needs to be cleaned yearly and have a water-proof boost every other year, depending on your climate. The distances deck joists must span and their spacing influence the size and grade of the lumber, and vice versa. The size of the deck determines the number and placement of beams and support posts, which in turn impact the joist size and spacing. Spacing the balusters. Most span and spacing tables present values for common dimensional lumber sizes and species. Incising is the process of infusing preservative deeper into the wood through small 1/4” deep cuts on all surfaces. The distance between deck support posts depends on the type of wood species used and the size of the joist and beam. That affects the joist and beam directions, as well as the live load requirements. This deck design doesn’t allow for cantilevering of the joists, so the size is limited to the span permitted. Your comments and suggestions are always appreciated. Joist Span – Joists Attached at House and to Side of Beam. Smaller beams require more support posts, so any money you gain by purchasing 4x4s instead of 6x6s is more than likely lost because you’ll have to dig more footings to accommodate the weaker 4×4 support posts. Eugene has been a DIY enthusiast for most of his life and loves being creative while inspiring creativity in others. The local Building Code is adapted from the State or National Building Code, which in turn is based on the International Residential Building Code (IRC). By the time you’re finished reading this guide, you’ll have a better understanding of how span and spacing work, and what will structurally work best for your deck. Therefore, a longer deck span means that you’ll have to space your deck support posts closer together. or less if diagonal to prevent sag and bounce. This is confusing because it is not only telling you the beam span but also telling you maximum distances you can space your deck support posts. Never take one municipality code to be the rule – code varies drastically depending on your geography. Adding a deck to a home or yard is a great way to create an outdoor living space. Joist Span – Non-Ledger Deck. This is good if you are looking to save a few dollars; however, code will not allow you to space your deck posts as far apart beneath your beam when using 4x4s. My preference is to use span and spacing values readily available in Code tables or calculators. If you can’t find any of their information online, just call or, even better, go in person. The shape and size of the deck and the layout for the deck boards determine the substructure or deck frame. Another issue is joist spacing. Factors that Determine Deck Joist Spacing and Span. Regardless of the span, 2×6 joists are usually limited to ground-level decks without railings. Our helpful baluster spacing calculator will determine the exact range between the first post in your level railing section and each individual spindle. Most calculators allow for the selection of three or four common wood types or species, standard dimensional lumber from 2×6 to 2×12, and on-center spacing of 12”, 16”, or 24”. One of the most difficult parts when building a deck is planning, especially when trying to determine your deck post spacing. Most codes in North America offer charts that will take into myriad factors that we’ll talk about, plus we’ll go over how to read those charts, as they can be confusing. Like a deck beam, joists that are longer will require deck support posts that are spaced closer together. The deck surface is commonly one 7” step down from building entrances or at the same level as inside floors. Decks may provide access to various rooms of a building and also to the ground which affects the design and height of the deck. The spacing and span of joists that support the decking are identified in most Building Codes. Joist Spans for #2-Grade Dimensional Lumber, Redwood, Western Cedar, Red Pine, Ponderosa Pine. But the 2015 IRC included a new one (Table R507.5) that will make it easy for deck builders to spec a joist size for a given span and joist spacing. We’ll also explore how they influence the strength and safety of a deck. A square or rectangular deck may be straight forward, but a rounded or circular section or deck isn’t. Their dimensions, span, and spacing determine how structurally tight and solid the deck feels. Lumber with no blemishes is rated select, clear, or #1 and is stronger and more expensive. Oil, Grease, and Food Joist installation doesn’t impact the spacing between joists, but it does affect the span. 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