two way slab design example pdf

Learn more about it here. Floor cabinets have been pulled out and the layers are uneven. All materials (beams and floor) will be manufactured from the same material, which has a tensile modulus of 1.3E+10N/m². That’s a tricky issue indeed. The subfloor is 5/8 T&G. Start over or add another layer? In some cases, this could result in the tile being significantly higher than the floors elsewhere. The cement board I was trying to install was not sitting completely flat on the subfloor. Recent research has shown tile to fail, under some conditions, when the floor is more rigid than L/360. F is the largest expected point load that will be applied to the floor, which Floors assumes will be applied in the weakest position, i.e. This relationship applies to any units in which the floor is measured, inches, feet, mm, etc. And, while this is a cement construction building, I’m afraid of this being a safety issue if the floor can’t support the load/weight of these double stacked hard flooring surfaces. Ethan, thanks. = 30*(20³)/12 How to read floor beam span tables (page includes a span calculator). The joists are spaced on 16 inch centers and have a span of 14 feet. The Tile Council of America (TCA) recommends a max. For obvious reasons, I don’t want to pull it up. Residential floors are typically sized for a … As a fabric-like material, it’s obvious that Ditra offers no additional rigidity to make a floor “stiffer” for tile. Where do I go from here? Pics of : Tile Floor Joist Span Calculator. Using CalQlata's Area Moments calculator, a beam of 0.2m x 0.4m has a second moment of area of 0.001067m⁴ (Fig 5) which is greater than 0.000801m⁴ and therefore will result in a smaller deflection than the design requirement. Enter your floor joist information and then hit 'Calculate deflection' to find out your floor rating. Plywood and OSB are the two most common materials used for floor decking, and typically they are 5/8″ or 3/4″ thick. Do I place a cement board over this underlayment….Do I place ditra over it….or do I proceed directly to tile? However, should you wish to identify the beam stresses, based upon the calculated minimum area moment, you can use the information generated by Floors to select an appropriate steel section from CalQlata's Steel Sections database or calculate the size of beam required in CalQlata's Area Moments calculator and thereafter identify its maximum stress using calQlata's Beams calculator (see Example Calculation below). In this scenario, Jim and Rich install 1/2″ cementious backer unit (CBU) resulting in at least an 1-1/8″ thick subfloor. I’ve been arguing this with my builder for several years now with no resolve to date. According to TCNA, there are several factors that affect deflection including condition of the subfloor and joists, joist size, type and spacing, and how the subfloor was fastened. So, I now this will be a time consuming job. Apart from the material and dimensional differences—one’s a 1/8″ thick flexible plastic sheet, the other a 1/4″ cement-based panel—there are several key design differences between Ditra and cement board. It’s also common to see tile installed over a concrete subfloor, and the big concern is movement from cracks, or expansion / contraction. I use the Jolly line on all shower alcoves instead of using bullnose tiles. While acceptable, Jim and Rich prefer concrete board because plywood can contain voids, and in rare cases the plywood may delaminate. 1. This beam deflection calculator will help you determine the maximum beam deflection of simply-supported beams, and cantilever beams carrying simple load configurations. Schluter recommends using ring shank nails or screws, turning panels perpendicular to joists and not aligning joints with joists (pg. Loads: in the centre of a bay (Fig 1), Dimensions: I have visited several tile stores and received conflicting subfloor thickness requirements. Sample beam deflection calculation. The floor calculator assumes all loads are applied normal to the floor surface, all beams are simply supported and the flooring material is fixed (to the beams) at all edges. Moisture and cracks are the two things you’d need to worry about with a concrete subfloor (assuming it’s nice and flat). He quickly looked at the linoleum and was pretty certain that it had asbestos. Can you tell me if there is any city code or ordinance that requires the subfloor to be at least 1-1/4” in depth? The guys advise against tiling right over linoleum because you don’t know the condition of the subfloor and a proud staple could cause tiles to crack. The 'longitudinals' are the major support beams or joists running parallel to the length of the floor⁽¹⁾. Because ceramic floor tile is rigid and unforgiving, it needs a structurally sound, immobile base. For example, while joist manufacturers regularly meet the standard L/360 criteria for code construction with 24" o.c. That makes people think they can always skip over important details like thinsetting the cement board when that’s not the case. Some say I’m OK with 1/4″ cement board. Excessive deflection in a wood floor system is a common cause for cracking in thin-set tile installations. Most of the cabinets are on the perimeter on the room with a peninsula that runs to the center of the room (7′ from the outside wall). Wood I Beam Floor Joist Span Tables Flooring Diy Slate Roof Joist Span Table ... Tile Subfloor Deflection Thickness Common Substrates One Floor Joist Ing Span Tables The Best Of 13 Best Hardwood Floor Calculator Unique Flooring Ideas The surface floor decking (plate, sheet or floor boards) is referred to as the 'floor' I wanted to extend the dining room tile into the kitchen to open it up because the rooms are small and it would have a nice flow. Add another layer of 5/8 plywood minimum, I would add another layer of 3/4 tongue and grove plywood and glued together. I only want to do this once. I hope this is a good place to ask this question, but from an engineering perspective is there any way to reduce deflection in wood floor joist without adding additional support beams? For example, a floor with a span of 10 feet must deflect no more than 1/3 inch, or 120 inches/360 inches. If you are from Canada which this seems to be showing up in. I have witnessed numerous discussions in the field about proper ways of laying plywood… and it never takes long for somewhat to point out the span rating stamped on the wood and sometimes with an arrow facing in strong axis (the 8′ length). Ditra is a decoupler, meaning (in this case) there’s no chemical bond between the tile and the subfloor. See the table below. Any issues with putting tile right over top? The 'transverses' are the minor support beams or joists running parallel to the width of the floor⁽¹⁾. All calculations are applicable to floors comprising materials that obey Hooke's law. 23 of DITRA Handbook). You also have options depending on the expected configuration of your solution: whether there will be one fixed end, two fixed … It is for this reason that recommendations for floor rigidity are not based on deflection measurements but on empirically established methods found to work over normal code construction. I’m planning on tiling our kitchen. The bathroom currently has linoleum as the flooring surface, a good subfloor under that. I know it’s been a while, but I notice a lot still look at this page. 3. Tiling has been installed around cabinets. L/360 vs L/720 These come from another post. ie 48/24 – 3/4″ 5-ply. To calculate a specific value, the Tile Council of North America (TCNA) offers a standard formula. Its almost impossible to remove and it’s throughout the house. δy specifies the rate of deflection permitted per unit length of floor; e.g. They were too cheap to take out the existing floor and replace it with new floor. Calculating Deflection deflection of L/360 for ceramic tile and L/720 for natural stone tiles. Any help would be welcomed. Ditra can also be laid directly on a flat plywood subfloor using a latex modified mortar; especially for tiles that only require L/360 deflection standards. Adding another layer of plywood can reduce deflection and curvature of the sheathing between joists. Where do you see that advice? Ditra requires more mortar overall and you have to buy the manufacturer’s special tape if you want to create a moisture barrier. 2. Some tile setters also prefer Ditra for its relatively quick installation. I found mine from http://asbestostestingservice.ca/ which I felt was pretty cheap. Can I get an explanation on large format tile and natural stone concerns in regard to floor deflection and a minimum size that is considered large format Homedepot carries some of the metals line in stock but I think they can order the rest of it as well. 1. Floors manufactured from appropriate materials and designed to deflect within specified deflection limits are highly unlikely to achieve stresses anywhere near the yield stress for the material. 0.001 means that the floor may deflect no more than 1 in 1000, tᴾ is the thickness of the unsupported section of floor material that will result in a deflection rate of no more than δy due to p, dᴸ & dᵀ are the spacings between the longitudinal and transverse beams respectively, which are defined by quantities; nᴸ, nᵀ, Iᴸ & Iᵀ are the second moments of area for the longitudinal and transverse beams respectively that will result in a deformation of no more than δy per unit length due to p, ωᴸ & ωᵀ are the loads per unit length supported by each longitudinal and transverse beam respectively as a result of p, yᶠ & σᵖ are the maximum deflection and maximum stress (respectively) that will be seen in the floor material due to F (Fig 4), A design pressure of 100N/m² and a point load of 1000N are to be applied to a 10m x 8m rectangular floor of 1 longitudinal beam and 5 transverse beams. Finally, there’s cost. Kind of a deflection question… I need some advice… our house in Florida had laminate wood floors; we took them out but there is a rubberized foam type underlayment (sound barrier) that is glued to the concrete slab. In other words, you can’t rely on either material to make a spongy or bouncy subfloor more suitable for tile; you have to add rigidity first, using plywood or other structural panel materials. Basic Lumber Design Values are F =2000 psi F =1100 psi F =2000 psi E=1,800,000 psi Duration Of Load = 1.00. Maximum deflection is limited by L/360 or L/480 under live load. Good Luck! Schluter Systems (the makers of Ditra) have a lot of pretty good misc metal products for doing tile transitions. You can send in a sample of your floor to an asbestos testing lab. Nice write-up Ethan. The general rule seems to be that if you want a solid tile floor, the way to do it is to install more, thicker layers below the tile. Here’s a company that sells test kits and the $30 price includes the lab fee. http://www.prolabinc.com/asbestos-test-kits.asp. The Tile Council of America recommends that deflection be limited to L/360 (L = span length in inches) under total load for ceramic tile. The builder hired used 3/4” OSB for the flooring while the tile contractor used a 1/4” CBU under the tile, thus achieving 1” in total depth. My house has two layers of hardwood floor and a 1/4 inch integraply underlayment which I a total of 1 3/4 inches of floor. The 2’/2′ in my basement and noticed that the floor, even though I thought is created right was dipping in sweating areas. (on center) systems, these floors often have deflection between the joists exceeding L/360. Top Chord Please help!!! CBUs need screws and joint tape. Our framing cost calculator has a preset wastage value of 15 %, which is the most typical amount. Spacing of trusses are center to center (in inches). If its allowed, what would be the proper installation instructions? The deflection for the entire floor shall not exceed 1:1000, i.e. Reducing Deflection Which one would make more sense? We are planning on using ceramic tile with granite counter tops. For soft-stone tile, such as limestone or light marble, the L/720 formula applies (cutting the maximum allowable deflection in half). I said I wanted to add an additional layer of ply and his response was "it would do nothing but add weight to the floor." In real terms, a concentrated weight of 200 lbs (91 kg) over a 3" (75 mm) wide area, is not all that difficult to attain in a situation such as a fridge or a stove being brought across a floor on a dolly. The floor calculator determines the stress in the floor material as a result of the design load per unit area and the maximum expected point load applied to the centre of a bay, but not for the support beams because their depths are unknown. If you have engineered truss or I-beam type joists please do not use this calculator. My General Contractor told me that the people upstairs installed a large format tile floor directly on top of their existing hardwood floors (2.25′ solid red oak). Thanks for visiting! Tile size is 16×16. Let's expand our house beyond that 17'2" span capability to 24 feet wide. p is the design or specified maximum pressure that the floor can support over its entire surface without exceeding the deflection criteria; δy 2. I have a bathroom with 1-1/8 in plywood subfloor. ft., plus any long-term deflection due to the weight of the floor. For instance, ceramic tile can withstand more deflection than natural stone. Whilst the most common floor construction materials are wood, steel and reinforced concrete, you can build your floor from any material(s) you wish provided it obeys Hooke's law. Calculations are accurate only for floors comprising materials all of which obey Hooke's law. The deflection for the entire floor shall not exceed 1:1000, i.e. To determine the requirements for a tile subfloor, I partnered with Jim and Rich from Diamond Tile located here in Maryland. Deflection, or bounciness, can cause tiles and grout to crack or come loose, and the tolerance depends on what type of tile is being installed. In extreme cases Jim and Rich have advised additional joists be put in place. There’s a lot of information (and mis-information) online about what constitutes a suitable subfloor for tile, and it’s tough to find a clear answer. This calculation indicates that the single layer of plywood can have approximately twice the deflection acceptable for the installation of tile. I assume defection is not an issue there. I just purchased a condominium unit in a 7 story building in downtown Chicago. Thanks. Floor Truss Span Tables Alpine Engineered Products 17 These allowable spans are based on NDS 91. I would rip out everything and add another layer of 3/4 plywood. The area of floor enclosed by any two adjacent longitudinals and any two adjacent transverses is referred as a 'bay'. Over the last eight years we've documented hundreds of home improvement and DIY craft projects along with many tool and material reviews. The joists actual depth are 9 inches so I’m assuming they are 2X10. Many tile contractors can judge a floor’s deflection by walking around. If not, it’s probably worth hiring a knowledgable contractor. What’s the Difference Between Ditra and CBUs? My kitchen is 9’x10′ concrete. Reducing deflection in floors of a home. Having a solid floor system is key to limiting deflection within the limits of the material and style of tile your installing. "2.3 Deflection Floor systems, including the framing system and subfloor panels over which tile will be installed, shall be in conformance with the IRC for residential applications, the IBC3 for commercial applications, or applicable building codes. Let us say we have a 4-cm thick, 30-cm wide eastern white pine plank that act as the seat for this bench. Older homes may have a structural plank subfloor, and these can be problematic because they move so much with changes in humidity. Ditra only adds about 1/8″ to the overall height. Whilst the floor can be welded, screwed, nailed or otherwise fixed to its support beams, you should not assume that the beam ends are fixed or even guided, as apart from welding, these fixings tend to be unreliable. When laying floor tile almost all preventative measures, excluding water proofing, are geared towards preventing grout cracks and god forbid tile cracks. Floors are universally designed to deflect a specified amount with a maximum static design load per unit area (pressure) applied all over its surface. The name of the game is a rock solid floor system and sub-floor. You don’t have to screw it down, and you can start tiling immediately after the Ditra layer is installed. Still worth testing a piece. Should I put down 1/4 inch durock or densShield and should I put thinset under the cement board? (ii) Any dead load, live load, and in-service creep deflection criteria for floor Trusses supporting stone or ceramic tile finishes. This deflection is usually defined thus:'deflection shall not exceed one in [length]' For example: if a floor is designed to deflect; 1 in 1200 (Fig 2), this means that over a measured length of e.g. For example, the maximum deflection for a joist span of 15′ is [15 * 12] / 360 = 1/2″. Now I have a completely flat floor. (5) Any deflection and vibration criteria for floor Trusses including: (i) Any strongback bridging requirements. Over a cement subfloor (basement), is it safe to lay any type of tile? I was installing Dri core planks as a sub floor. While we're at it, here are some useful tools for finishing your house or apartment: the tile calculator; the paint calculator; the drywall calculator; and; the flooring calculator. For a sample calculation of beam deflection, let us consider a simple wooden bench with legs 1.5 meters apart from each other at their centers. 3.8.2 Cast-in-Place Concrete Floors. If the floor is uneven, it can be flattened just like a wood or concrete subfloor. Jim and Rich advise using a bond-promoting primer to enable the mortar to better adhere to the existing floor, and to set the floor with a specialty polymer modified mortar. The L/360 formula is useful for most ceramic, porcelain, and hard stone. If the appropriate information is entered into CalQlata's Beams calculator (Fig 6) the maximum bending stress will be 1.87E06N/m² (1.87MPa) and deflection will reduce to 1:1331 (L/yₓ: 10/0.00751), which is less than 1 in 1000. The minimum second moment of area for the longitudinal beam is 0.000801m⁴ (Fig 4). Whether you are installing stone or ceramic tile over floors and walls there's one thing to consider; deflection. Best practices? Jim and Rich don’t advise tiling over resilient flooring. Deflection, or bounciness, can cause tiles and grout to crack or come loose, and the tolerance depends on what type of tile is being installed. Design substrate for total load deflection not exceeding L/360, as measured between control or expansion joints. 6000mm in any direction the floor shall deflect no more than 5mm. Tile can be installed directly over existing tile given that it is free of cracks and there are no loose tiles. Floors has no preferred units, you may use any units you wish but you must be consistent (p, F, E, etc.) Codes also specify how much floors are allowed to bend under load, a measurement called a deflection limit. Calculating Deflection Many tile contractors can judge a floor’s deflection by walking around. This calculator has been designed for the sizing of structural floor joists; A floor is deemed to be an elevated rectangular plate or sheet (or floor boards) supported by equally-spaced longitudinal and transverse beams all of which are simply supported at both ends (see Figs 1 & 2), The surface floor decking (plate, sheet or floor boards) is referred to as the 'floor'. I would be truly grateful. The engineer is saying the existing 1/2" plywood sub-floor is ok to put dittra and tile on top of(24"x24" glass 5/8" thick). All calculations are as accurate as can be expected using classical (Castigliano) theory upon which they are based. This calculator has been designed for the sizing of structural floor joists; A floor is deemed to be an elevated rectangular plate or sheet (or floor boards) supported by equally-spaced longitudinal and transverse beams all of which are simply supported at both ends (see Figs 1 & 2). 5. Many of them have a more modern look to them but the quality is very high. In Floors, you may, of course, run the longitudinals across the shortest dimension and the transverses across the longest dimension of your floor simply by entering a shorter length than width. Recent research has shown tile to fail, under some conditions, when the floor is more rigid than L/360. The same calculation(s) can be performed for a transverse to find its maximum beam stresses. It’s too risky not knowing the condition and materials of the subfloor, and so they always remove resilient flooring. (6) Moisture, temperature, corrosive chemicals and gases expected to result in: This may make Ditra a better choice if moisture from below is a concern, such as with some outdoor applications or installations over concrete. The IRC says that floors must deflect no more than 1/360 of the floor's span. For example, the allowable deflection of a 12ft span floor joist with plaster (L/360) is 0.4" (12ft divided by 360). This calculator is designed to work with dimensional lumber only! 4. Tensile moduli; Eᴾ, Eᴸ, Eᵀ define the resistance to bending for the floor, longitudinal and transverse materials respectively, Deflection: We already had an environmental consultant out because the outside tiles have asbestos as does some of the duct work in the basement. Note it gives the allowable deflection based on a fractional span quantity, so a larger denominator will yield less deflection. Ditra costs about $1.50 per square foot. installing an uncoupling membrane like DITRA, http://www.prolabinc.com/asbestos-test-kits.asp, Home Depot Coupons, Coupon Codes, 10% Off Sales – FALL/WINTER 2020-2021, AJ Madison Coupons, Sales, Coupon Codes, 40+% Off – FALL/WINTER 2020-2021, Lowes Coupons, Sales, Coupon Codes, 10% Off, Target Coupons, Sales, Coupon Codes, 10%-60% Off – FALL/WINTER 2020-2021, Sears Coupons, Sales, Coupon Codes, 10% Off – FALL 2020/WINTER 2021. L, W, nᴸ, nᵀ are the length and width of the floor and the number of longitudinals & transverses (respectively) that make up its dimensional matrix, Material Properties: Jim and Rich are professional tile installers with over 27 years of experience and have worked with a variety of tile substrates. Yet, while cement board has some stiffness of its own, it does not add significantly to the overall stiffness of a floor structure. The floor calculator is applicable to all floors manufactured with any material assuming that the longitudinal and transverse beams are equally spaced and the flooring material is all-covering. Installers sometimes use fir plywood in lieu of CBU. For a standard-size tile job, the difference in cost shouldn’t be a deal-breaker. If this has occurred, the buyer (or new owner) should insist that the builder obtain evaluation by … Thanks in advance. 9×9 tiles were the ones usually made with Asbestos. Hi, we're Ethan, Jocie, Kim and Fred. NOTE! δy = 0.001m (1 ÷ 1000), Enter the above data as shown in Floors (Fig 4). If that same joist had gypsum ceiling (L/240), the allowable deflection is 0.6". In fact, failures at L/600 have been observed. I am experiencing an unbearable amount of noise from their footsteps including squeaking sounds and my whole place shakes. How to Fix Floor Deflection for Ceramic Tile. We are planning to lay the DITRA system under tile in our bathroom. I never liked the look of the much smaller bullnose tiles. So I have a dead line in a week and a half and I quickly decided to use cement boards to get level. John Bridge Forum also offers this helpful deflection calculator. Can we lay the DITRA on top of the linoleum directly or does it have to be removed. With cement board, the tile is mortared to the cement board and the cement board is mortared to the substrate, so there’s a chemical bond. The difficulty is that tile can be installed over a number of substrates, and each requires specific preparations to ensure a long-lasting tile floor. and remember that the units of your results will reflect those of the values entered. You’d be surprised how many people will try to argue with me that it doesn’t matter which way you lay the grain of plywood. All too often, tile flooring is installed by the builder without prior consultation with architect to ensure that floor framing has been designed for weight of tile, using industry deflection limits. If you’re lucky, it’ll come back negative. Make sure the floor is solid enough if your going with a large format tile or natural stone. In this case, the guys usually install 1/2″ plywood overtop and 1/4″ CBU or DITRA. • Tile industry associations recommend special total load deflection limits The following tables list the components and weights of typical floor systems, along with the deflection limits that apply. Next we will need a tutorial of how to install a threshold between the tile floor and other floors in the house. The subfloor areas over which stone tile is to be applied must be designed to have a deflection not exceeding L/720 of the span. For instance, ceramic tile can withstand more deflection than natural stone. Result will be displayed: Calculate Deflection for Solid Rectangular Beams Calculate Deflection for Hollow Rectangular Beams Calculate Deflection for Solid Round Beams Calculate Deflection for Round Tube Beams One edge was raised about 1/8 inch off the floor so I poured a self leveling underlayment at a thickness of 1/4 inch. In the past Jim and Rich have glued and screwed plywood, taking care to stagger the joints and gap the panels 1/8″ on each edge. Beam Deflection Calculators - Solid Rectangular Beams, Hollow Rectangular Beams, Solid Round Beams Enter value and click on calculate. The deflection calculator provides several engineering specifications such as the moment of inertia and yield strength to determine deflection. Also, mortar creates a stronger bond with a concrete board. This difference, Ditra fans would argue, makes it more resistant to movement. You will find further reading on this subject in reference publications(2 & 3). Can I lay tile over the underlayment without worry that my ceramic tile (wood plank style, 6″x20″) may crack due to deflection or “give” from the underlayment? Ditra is waterproof, while cement board lets water through but won’t be damaged by it. I built a home about 7 years ago that is having all kinds of problems with the tile flooring (cracked tile, displaced grout, creaky flooring, 1/2”+ deflection in some areas). The thing is that people can have successful tile installations without all the prep work because sometimes you just get lucky. Divide the total span of the floor joists (in inches) by 360 to determine the maximum amount the floor can give in the middle under a live load of 40 lb./sq. Can you explain to me what is happening? Therefore, whilst it is a conservative approach, Floors assumes that both ends of each beam are simply supported (see Fig 2). Better safe than sorry. (on center). Jim and Rich often flash the floor to create a flat surface, and they always recommend installing an uncoupling membrane like DITRA overtop concrete. The problem is there are two layers vinyl tile and one layer of ceramic. Is that ok. I’m going to lay down a vinyl floor 150 sq ‘. Moving into a house where the current kitchen floor is linoleum with likely asbestos. So the house dimensions will now be 24' X 13'. Ps. Good tutorial. The widest span in the floor joist span table in Part 2 of this tutorial module showed that floor joists can span 17'2" if they are 2 X 12s spaced 12" o.c. If they install a second layer of wood underlayment (3/8″ plywood or thicker), the guys would use 1/4″ CBU on top. A 1/4″ thick, 3 x 5-foot CBU panel costs about $11, or a little less than $0.75 per square foot. The floor calculator can also be used to calculate the material properties of a non-rectangular floor by breaking the overall shape up into regular rectangles and calculating each rectangle individually (Fig 3).

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