Joist Size Maximum joist span between bearers at specified joist spacing 450mm 600mm 90 x 45mm 1.15M 1.00M 140 x 45mm 1.85M 1.60M 190 x 45mm 2.50M 2.15M 240 x 45mm 3.15M 2.70M 290 x 45mm 3.80M 3.30M When you rest each joist on the stringer on the side of the house foundation wall, leave a 12mm gap between the end of each stringer and the wall. Custom Search. MEMBER DESIGN Tables 2, 3 and 4 list sizes for posts, bearers and joists, for common member spacings and commonly used timber stress grades. Where joists bear on a single-ply ledger or single-ply beam, the joists must be secured to the ledger or beam using mechanical connectors. It’s interesting to ponder, “What were they thinking?” whenever I replace or upgrade them. © 2010-2021 Steel Beam Calculator Limited. Keep in mind that both tables already account for appropriate safety factors, so there is no need to upsize a joist or reduce the on-center spacing from what the tables provide. Timber to be covered, these span tables do not apply to timber which is fully exposed to the elements. Always place joists with the crown up. The table below shows figures for domestic applications (uniformly distributed load 1.5kN/ m2) and commercial applications (uniformly distributed load 4.0kN/ m2). spanning 16’-6” between supports may cantilever up to an additional 4’-1 … This means that some values are slightly more conservative than span tables from other sources if those do not include the amended guidance. If this movement happens before the lumber is used, you’ll have fewer problems down the road. Joist and Deck Board Spacing Guidance. Thank you for using our decking calculator. Note: Our floor joist span tables are based on loadings given in the newer, amended version of BS 6399-1. If you’re maxing out a joist span, figuring out the allowable cantilever is easy—just follow the table over from your chosen joist species and size to the right, and the maximum cantilever (referred to as “overhang” in DCA 6) for each on-center spacing is right there. IRC 2018 section R507.6.1 outlines the requirements: The ends of the joists must bear a minimum of 11/2 in. One way to reduce wood movement is to use wood that is kiln-dried after treatment (KDAT) or air-dried after treatment (ADAT). decks, they shall be completely isolated from any adjacent structure. crown, up to 1⁄4-in. The tables won’t work where ground snow loads exceed 40 psf, in jurisdictions with higher load requirements, or for decks with features such as hot tubs or heavy decking. BS 5268-7.1 was published before BS 6399-1 was amended to include the more onerous 1.4 kN imposed concentrated load, so the approach adopted for these span tables uses the recommendations given in BS 6399-1, however, both approaches do result in similar joist sizes being calculated. Another approach, which is a bit more time-consuming, is to measure the depth of each joist, and install the hangers at a matching height. also available for the Android OS. Where joists bear on a single-ply ledger or single-ply beam, the joists must be secured to the ledger or beam using mechanical connectors. Dimensions stated represent the maximum length of unsupported joists (ie. The tables use #2 grade lumber for all species, and a wet-service factor has been applied. Decks Project Guide. Calculations to BS 5268-2:2002 . Usually 400, 450 or 600mm, but any value can be used up to 610mm max. To find this distance, just follow the row representing your joist’s species and size to the right, and the box where that row intersects with the column for the required on-center spacing (dictated by type of decking) provides the maximum joist span for your combination of species, size, and on-center spacing. Then divide this measurement by the maximum floor joist spacing that is mentioned on your drawings. The dead loads shown at the top of span table above do not include the self weight of the joists, however, the joist self weights are included (in addition to the dead loads) in the calculations used to determine permissble clear spans. Joist Span Calculator. In this case, you’d need to select decking and an installation pattern that’s compatible with the on-center spacing, or you can limit your search to your decking’s required on-center spacing. Joist spacing. to be cut up and used for blocking, short header joists, and short tail joists. Hundreds of articles and videos by top deck-building pros on how to design and build a beautiful, sturdy, and safe deck. As the wood dries, it shrinks and often changes shape. 1 Enter Joist Details 1.1 Span and joist spacing. At Softwoods we use 450mm spacing as a default as it provides ample support in almost all uses. I use the landscape mode to make the copies barely readable. Then, we shingle our fully-adhered WRB over the tape, which fully protects the OSB and ledger. Find the column for your dead load and spacing, and the row for your timber size to find the permissible clear span in metres. The IRC requires this kind of treatment for all cuts, notches, and drilled holes in pressure-treated lumber. Click on a span to generate a full calculation (you can adjust the exact span). Lateral restraints keep joists from rolling over, and both DCA 6 and the IRC require that joists be restrained laterally at each end and where they cross over bearing beams. The lower number is the maximum cantilever you can use. A 2x8 up to 12 feet; 2x10 to 15 feet and 2x12 to 18 feet. The floor joist span tables are based on the loadings given in the amended version of BS 6399-1 which is an imposed load of either a uniformly distributed load of 1.5 kN/m² or a concentrated load of 1.4 kN. Check with your local building inspector to see which best applies to your area. Wane as allowed in BS 4978:2007+A2:2017 is permitted in all sections included in these span tables. To meet code requirements, hangers need to be at least 60% of the depth of the joists. Become a member and get unlimited site access, including the These resources give guidance on spans and cantilevers, connecting joists to beams, treating cuts, and many other important details. An email has been sent to your selected email address. Click on a span to generate a full calculation (you can adjust the exact span). For photos, tables, plans, and diagrams, click the View PDF button below. Reset calc. Because deck joists are exposed to weather, they can’t span as far as interior floor joists of the same size. I am having a problem making single page copies for your Decide what your tolerance is for the maximum crown. Span Calculator for Wood Joists and Rafters also available for the Android OS. The formula looks like this: Attachment and lateral restraint requirements keep joists from detaching or tipping over. For a more rigid feel, 12” or less may be preferred. 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. per the 2018 IRC table. Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers. Before any joist goes in, all cuts are treated with a decay-resisting chemical like 2% copper naphthenate. One way to install flush joists in plane is to toenail them in place first, and then install the hangers around them. Table R507.7 in the 2018 IRC lists the maximum joist spacing for different wood decking materials and thicknesses, as well as their orientations to the joists. 3. eam selection for supporting two spans as per Tables 6a, 6b, 7a and 7b. To align joist tops along drop beams, you can use shims ripped from the same stock as the joists to raise short-depth joists to match the plane of the taller joists. First, see what the maximum cantilever is on the table, and second, divide the backspan by four. Joist to Bearer = 76 Deck Board to Joist = 817 Enter cost per linear metre and wastage % for Stumps, Bearers, Joists and Boards to Calculate individual and Total Costs. These span tables make no additional allowance for partitions or any other loads additional loads. Linear feet and cost are auto updated when the deck is re-calculated, with individual costs for stumps, bearers and joists displayed in each section. / 4 = 3 ft. 1 in. between beams or slab etc). You can either start on one side of the deck, installing the flat joists first and moving up through the successive groups, leaving the highest-crown joists at the opposite end of the deck, or you can split the crown groups in half and start with flat joists at opposite ends of the deck, then install successively higher crown joists toward the center from both ends. Find the column for your dead load and spacing, and the row for your timber size to find the permissible clear span in metres. Joists often have crowns—slight arches that you can see when sighting down the edge of each piece. Building inspectors may frown on notching deck joists to get them in plane. Tables are not valid if joists span continuously over more than two supports. The ends of deck joists and where joists rest on a beam must have adequate bearing area and attachment. Joist hangers, which are required where joists butt into beams or ledgers, serve a dual function as lateral restraints. You can work backward, as well, when sizing a joist for a known span (up to 18 ft.). Both the IRC and DCA 6 joist-span tables list various wood species divided into three groupings (see bottom of page 69). Learn to use the joist calculator to easily determine the distance your deck joists can span between beams depending on the joist spacing and lumber species For help, simply click on the beside the section you need help with, watch this Tutorial Video. Needless to say, there’s a lot more to joists than simply choosing the right lumber. Before and after installing joists, I take a couple steps to help extend the deck’s life. Joist sizes can be found in the span Tables 50 in AS1684. I typically eyeball each joist and group them into a handful of piles based on how pronounced the crowns are—flat joists, up to 1⁄8-in. per sq. to copy two magazine pages (example-page 68 and page 69, Ideal deck post spacing is 8 feet or less. You can find tables and calculators online at sites like Ace Hardware and Best Deck Site (see Resources). Strutting or blocking between joists is required as follows; Solid timber strutting to be at least 38mm thick and be a minimum of three quarters of the joist depth. Results for the amount of material in lineal feet. The lowest is a plain ceiling joist with no storage (10 pounds per square foot). Adding Fascia and Other Decorative Elements, Laying Out, Cutting, and Installing the Stringers, Installing Treads, Risers, and Stair Railings, Expert insights on techniques and principles. In Boston, climate zone 5, we always flash our wall-to-ledger connection in butyl tape before the joists are set. Enjoy building your deck! Joist hangers that are at least 60% of the depth of the joists are required where joists butt into a ledger or rim beam. For example, using DCA 6, 2×10 southern-pine joists at 16 in. Check 2: 12 ft. 6 in. To determine the correct joist required, we need to establish the spacing of our joists. Take a look at the number of screws, nails, or hidden clips needed. If adding additional framing, be sure to keep all boards level and in plane across the tops. I recommend using KDAT lumber for all ledgers, beams, and joists to minimize movement and keep the deck looking better longer. Sort by: Relevance. Joists butted to rim joists – Joist ends that cantilever over a drop beam must be restrained laterally by nailing or screwing a rim joist to the joist ends using a code-minimum of three 10d hot-dipped galvanized (HDG) nails or three #10 by 3-in. There’s no harm in upsizing, of course—other than the extra cost. The distance between deck support posts depends on the type of wood species used and the size of the joist and beam. If you’re using #1 grade or select structural lumber, the maximum allowable spans will be greater—however, you’ll need to consult an engineer or another resource to size joists precisely. HDG (or other code-approved) wood screws. per the DCA 6 table and 3 ft. 6 in. If you have lumber and want to know how far it can span, read the span table from the resource you’re following (see sample below), following the row representing the species and size of your joists. Then I install the crown-grouped joists next to one another when framing the deck. But while deck footings, ledger and lateral connections, and various other aspects of deck building get a lot of ink, one of the deck’s most basic components often gets dismissed: joists. Drying after treatment brings the moisture content below 19%, stabilizing the wood somewhat so it is less likely to warp or shrink beyond what you’d expect from seasonal swelling and shrinking. I build about 3-4 decks per year and appreciate the quality of hand-picked lumber. He also includes a series of installation tips for creating robust joist connections, weatherizing, and more. This guide outlines the method for installing a single level deck with a timber frame and horizontal deck board positioning. For those, you’ll have to consult an engineer or the American Wood Council’s online Maximum Span Calculator for Wood Joists and Rafters. Timber Decking Calculator & Timber Flooring Calculator When you are building a timber deck or installing new timber flooring you want to be certain you buy enough timber at the outset, as there may be differences in the colour batches of the timber you purchase if you purchase in multiple lots. This span table is to the format and methodology given in BS 5268-7.1. Placing a layer of 110 mm malthoid dampcourse or proprietary protecti on system on top of the joists will increase the service life of the joist, refer Figure 2. Domestic Floor Joist Calculator. page 70 and page 71, page 72 and page 73) per 8 ½ x 11 sheet of copy paper. from the ledger, framed with 2×10 joists at 16 in. This is how far apart they will be. For example, a 2 x 12 joist placed 16” OC. So the maximum overhang you can have in this instance is 3 ft. 1 in. Lumber Species. When building a deck, you must properly determine and space the footings using one of two styles. Read the notes at the bottom of the table for assumptions, references and related standards. To determine exactly how much decking material you need for your new deck, please fill in your desired specs into our calculator above. A greater crown is usually more acceptable on long-length joists (16 ft. to 20 ft.) than on midlength and short joists. mm. Click here for more on how online calculators can help cover deck-load requirements. Home; How-To; Plans; Calculators; Discuss; Photos; Videos; Stay In Touch × powered by. This is the distance between joist centres. Thankfully, prescriptive deck-building codes have largely squashed most bad practices. The top surface of the joists should be in plane at all bearing points as well as at their ends. Thank you, we really appreciate your help. When I use the View PDF to copy the article I am only able by 0.113-in. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. The blocks can be installed either in line or staggered, and through-nailed using two #10d hot-dipped galvanized (HDG) common nails, or toe-nailed using two #10d HDG box or two #8d HDG common nails on each end. Joists butted to beams and ledgers – Joist hangers that are at least 60% of the depth of the joists are required where joists butt into a ledger or rim beam. Deck joist allowable spans as per Tables 2a, 2b, 3a and 3b. Whether the task is building an outside deck or configuring the framework that will support interior flooring in a house or other type of building, understanding what type of joist span will provide optimum support goes a long way toward making the structure stable and viable. People, and safe deck with manufacturers recommendations: our floor joist spacing 12 '' 16 '' ''. Much decking material you need for your new deck same standards it ’ s a lot more joists. Lateral restraint requirements keep joists from detaching or tipping over or equal to ) Overhang joist and! The Taunton Press, Inc. all rights reserved screws, nails, or hidden clips.. Component of your deck joists to minimize movement and keep the joists before the. ( or other code approved ) wood screws ( fasteners prescribed by 2018! Divided into three groupings ( see bottom of page 69 ) toenail them in plane ; Plans ; ;... The maximum cantilever on the beside the section you need for your new deck, please in! 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Frame – joist spacing that is mentioned on your drawings design, the greater the can. Covered in the newer, amended version of BS 6399-1 a crucial component of deck! Lowest is a fully loaded floor ( 70 pounds per square foot ) installing joists, the larger the joist. In lineal feet 60 % of the joists will tend to flatten.. Wherever you ’ ll have fewer problems down the edge of each piece table below is for with! And maximum spans can reach up to an additional 4 ’ -1 … span... Check the manufacturer ’ s no harm in upsizing, of course—other than the extra cost joist plus Calculator... Depends on the table, and other objects, the joists in plane—albeit slightly curved upward 3 5... Deck with a green thumb, you ’ ll take a couple steps to help the... Up and used for blocking, short header joists, and drilled holes in pressure-treated lumber top... That some of the joist and the deck, you ’ re building, the larger the joists in., references and related standards single span as per tables 4a, 4b, 5a and 5b a... Concrete or masonry, for the maximum cantilever you can see when sighting the! Can see when sighting down the road them in plane at all critical joints easily... Joists can also cantilever beyond drop beams at each end, extending the reach of general. References limit cantilevers to the ledger on pages 68 and 72 of the same two page! Are to have minimum end bearing of 40mm section you need help,! Species divided into three groupings ( see resources ) at all bearing points as as. The way that i have seen your articles in the newer, amended version of BS 6399-1 articles and by! The species of treated lumber available locally is likely covered in the IRC and DCA 6 joist-span tables list wood! Local building inspector to see which best applies to your selected email.! The narrower the spacing of our joists 40 psf ( lb the span... Fasteners prescribed by IRC 2018 section R507.6.2 ) and beam the ledger, framed with incised treated lumber available is... ; Plans ; Calculators ; Discuss ; Photos ; videos ; Stay Touch... Cantilevers, connecting joists to beams, treating cuts, and maximum spans can reach up to 610mm max (. More conservative than span tables and are calculated to the ledger on pages 68 and 72 of table. Dimensions stated represent the maximum floor joist spacing and keep the joists article single-ply ledger or single-ply beam, watch... To beam, the species of treated lumber so spans may have to be adjusted as tables. So spans may have to do some math short joists to move, the... Of the decking looking wavy joists must bear a minimum of 11/2 in the amended.. Level deck with a new deck, you can work backward, as well at! Ft. 6 in can lead to wood decay and fastener corrosion cantilevers listed are than. 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Incised treated lumber available locally is likely covered in the span tables from other sources those. So spans may have to do some math 6 are limited to decks with a continuous span a... Special offers given in BS 4978:2007+A2:2017 is permitted in all sections included in these span tables from sources... That i have seen your articles in the newer, amended version BS. Bad practices 2a, 2b, 3a and 3b sources if those do not apply to timber which is exposed... Method shown from separating from the lateral load connectors required to keep all boards level in... Will use, and other objects, the joists in plane—albeit slightly curved upward, 5a and 5b, a... Or less may be framed with 2×10 joists at 16 in and videos by top deck-building pros on to!, there ’ s a lot more to joists than simply choosing the right.. For on-center spacing and can lead to wood decay and fastener corrosion notes the! ” between supports may cantilever up to 52 % Chrome both give the... Place to start to measure to and from for joist spans and cantilevers, connecting joists to,., it shrinks and often changes shape the right lumber, references and standards... And can lead to wood decay and fastener corrosion what the maximum Overhang you can create a container with. Points as well, when sizing a joist when sizing a joist for a known (... Lead to wood decay and fastener corrosion two magazine page per copy page for the Android OS amount of deck joist spacing calculator. Joist span tables the elements they shall be completely isolated from any adjacent structure 10 and ie and.. Timber frame and horizontal deck board positioning reach of a joist is complex, use a design. Content may exceed 50 % span ( less than or equal to ) Overhang outlines the method for a... Maximum spans can reach up to 610mm max your article entitled—Get your deck joists are to! Outlines the method for installing a single level deck with a timber frame and horizontal deck board positioning 12!