Table 1-Minimum Shrinkage and Temperature Reinforcement steel for non-SES floors or SES floors with a secondary liner. Lay down wire mesh or rebar on top of the sub-base if necessary. The percentage of reinforcing refers to the cross-sectional area of the steel for a given width of slab divided by the cross-sectional area of the slab area considered. I was thinking of going with the same spacing. lengths of rebar to just below. The main reinforcement of the slab panel “A” is marked as (1). Unique fastening system ensures accurate positioning of rebar, to code, during concrete placement. Rust is visible where some of the bottom bars are at the bottom of the slab, and some rebar ridges are faintly visible. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. In order to calculate this, you need to input the length and width. (i) The maximum spacing between two parallel main reinforcing bars shall be 3dor 300mm or whichever is less, and. Come learn how you can build your own shed! In this video I cover all you need to know about rebar for your concrete shed foundation slab. Similarly, a 4 inch slab of 4,000 psi concrete, 4 feet by 8 feet, with reinforcing mesh can hold up to 45,000 lbs. Use a groover to cut grooves about 25% into the depth of the concrete. ) Second, contraction joints are rarely used in post-tensioned (PT) slabs although the Post-Tensioning Institute found that neither random cracks, which are common, nor. You'll also need vertical rebar hooks protruding at least 6” into the footing and out at least 18” every 48”, or less. 2-1/4 inch rebar high chair is designed to hold rebar in place during concrete applications. Use a metal-cutting blade or disc in a reciprocating saw, circular saw or grinder to cut the rebar. Where: As = cross-sectional area in square inches of steel per lineal foot of slab width t= thickness of slab in inches fr = tensile strength of concrete (psi) = 0. New concrete slabs must conform to the above stated properties before installation of. For a flat slab, such as a driveway, consider placing the rebar in an 18 inch grid spacing, keeping the edge rebar at the same distance from each side. 43/30 = 0. The 2021 IRC® contains many important changes such as: Braced wall lines must be placed on a physical wall or placed between multiple walls. How big is a sheet of concrete mesh? Standard sheet sizes range from 4m (length) x 2m (width) 8m2 up to 6m (length) x 2. 72 percent. Suppose you have a concrete slab with dimensions 10 feet by 8 feet by 6 inches, and you plan to use #4 rebars with a spacing of 12 inches. Designed to be extremely strong yet able to straddle a lower rebar mat, these chairs have a wide, stable base with a footprint that. Thickening the structure along the perimeter by another will serve as an integral footing, adding strength where the loads are. Size 18 rebar has a diameter of 2 1/4 inches. For example, let’s find the number of 5′ x 50′ rolls of mesh required to reinforce a slab that is 25′ by 25′. I’d probably recommend good old fashioned #4 metal bar on a 2’ grid. For slabs 200 mm thick or greater the bar size and spacing should be limited to control the crack width and reference should be made to section 7. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar. Use wire mesh for driveways that are 4 to 5 inches thick, and rebar for those that are 5 inches or more. 1: Calculate The Main bars. The installation of the rebar is critical for the success of the overall project. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. : In ACI 302. I've only ever called out a single layer in a 8" s-o-g. How to calculate the rebar quantity from concrete? Convert your longitude estimation into inches: 15 x 12 = 180. The appropriate rebar size depends on the project, with #3 and #4 being common choices. No. 15 per cent of the gross sectional area. Typically, for residential construction, you might use #4 (1/2 inch) or #5 (5/8 inch) rebar spaced at 12 inches on center for a 4-inch thick slab and closer spacing for a 5-inch thick slab. To truly reinforce concrete, the percentage. For a 400 square foot slab, the man hours required to finish a two-car concrete garage slab is about 13 hours. This spacing will provide the maximum reinforcement of the. A typical concrete slab costs $4 to $8 per square foot with most homeowners spending between $5. They are 4 feet in height and 10 inches in width (diameter), or 4' x 10". 65*6) = 1. Spacing of bar supports depends upon the size of the reinforcing bar being supported. All 3/4 inch diameter anchors must be a minimum of 6 inches away from any expansion seams, control joints or other inconsistencies in the concrete. 65*6) = 1. The formula is, Number of bars = (length ÷ spacing) + 1. Set the forms at the proper height before bringing in the last lift. Wood sole plates at all exterior walls on monolithic slabs, wood sole plates of braced wall panels at building interiors on monolithic slabs and all wood sill plates shall be anchored to the foundation with minimum 1 / 2-inch-diameter (12. A. 125" clear between bars. For patios, a grid spacing of 24 inches is. 12. For example in a slab of 6-inch depth, a rebar of 6/8 inch will be used. Minimum concrete cover over (and to the sides) of the reinforcing bars is 1 1/2-inches, whereas the minimum concrete cover under the rebar is 3-inches. The typical depth for rebar placement for slabs is 2-4 inches. Common practice is to place supports 2 to 3 feet apart. 75-in x 1. Rebar Spacing; D2-8F: 4. Designed for #4 and #5 rebar,. Step-4: Rebar Calculation Process Of The Slab Panel-A 4. 3 For walls with thickness greater than 10 inches, except singleLap Splices. Determine the amount of rebar needed for the footings. 15% for mild steel bars. Generally, rebar has an immense impact on concrete. If the slab in question is just for a patio or a similar purpose,. BAND—Group of reinforcing bars distributed in a slab or wall or footing. The plastic chairs are designed for the rebar rods to snap easily into. Labor Costs. 7 mm). For example, if the percentage is 0. Slabs, walls/dividers, and joists – 11 bars and littler – ¾ inch. Joint distance (D) or tank diameter in feet based on Steel Schedule Minimum end area (As) of steel (in2) for slab thickness, t= 5 inch * Anchor bolts are located a minimum of 1 3 / 4 inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate. To calculate the amount of rebar per square foot, you will need to convert the 6 foot length to a linear foot, and the 50 pounds to pounds per linear foot. Common size of rebar used for 4 inch slab, it may vary from size. Each rod of the rebar is engraved with a marking with a code instructed by the American Society for Testing and Materials. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. For an unreinforced slab, control joints should be spaced in feet 2 to 3 times the slab thickness in inches. If you chose to put rebar in a four inch garage slab, your rebar should be spaced at least four inches and up to twelve inches apart. Add one more length to allow for that extra, giving you a total of 18. When spacing the rebar, it is important to ensure it is evenly distributed and in accordance with the local building codes. a weak concrete has a compression. Drive 12-in. This is because rebar is comparatively thicker than galvanized mesh reinforcement. Benefits of Using Rebar in a 4-Inch Slab. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. 5 range tops, and control joints are formed either with preformed joint material or sawcut within the first 24 hours and be sure that the curing conditions are good, at least 50 F. Beams and columns: 1½ inches. Never put a shop on a slab less than 6" thick. 5 to determine you will need 120 feet of rebar. Tying should include bars near the ends of the bridge and bars near the curbs. Rebar Spacing OC + Waste / OverlapWith this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). Guidance for joint spacing to minimize out-of-joint. Expansion grooves should be cut into the wet concrete to provide additional crack resistance. Vertical rebar every 16 inches. of Main bars = (Width of Slab/Spacing) + 1. Rebar Spacing; D2-8F: 4. Build forms. The design of one-way slab is simple and can be carried out easily. 4" is plenty, be sure the base is good - compacted, free draining, etc use a relatively tight mix, ie low water to cement ration, slump in the 3 to 3. 5 mm) for concrete slab depth ≤12 inch (304. 4 inch Joist Spacing SLAB MESH THICKNESS SIZE 3 in. 1R-89, "Guide for Concrete Floor and Slab Construction," ACI Committee 302 does not recommend keyed joints for slabs thinner than 6 inches, and also doesn't provide guidance for dowels in slabs thinner than 5 inches. 5 range tops, and control joints are formed either with preformed joint material or sawcut within the first 24 hours and be sure that the curing conditions are good, at least 50 F. Common practice is to place supports 2 to 3 feet apart. 34 inch (8. 1%. Non-reinforced slabs – where no. 84 m; grid. inches thick and about 4 x 4 inches square. The spacing of the rebar is also determined by the weight and size of the slab. Concrete needs rebar to be as strong as possible; however, if poured thin enough and used only for walking, you can quickly go without rebar. Generally, #4 rebar (1/2 inch in diameter) is the most common size used for slab on grade applications. If the slab is expected to bear heavier loads, such as from heavy vehicles, then larger diameter rebar or closer spacing may be required. For a 4 inches slab, rebar is not necessary. Rebar will hold a force in tension. 4 and by diameter in inches above No. If the slab is going to support extra weight, such as the weight of a vehicle or the weight of the soil for a retaining wall, then stronger rebar such as #5 (5/8-inch diameter) or #6 (3/4-inch diameter) might be. 1. 34 and $7. The Engineer shows a 4″ Slab 3500psi with 6×6-W1. 6. For example, a 4 inch slab of 3000 psi concrete, 4 feet by 8 feet, with reinforcing mesh will hold up to 34,800 lbs. Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. Step-4: Rebar Calculation Process Of The Slab Panel-A 4. First, you need to consider the size of the rebar and the spacing between them. What should be the size rebar for a 4-inch slab?. How do you calculate rebar for a slab? Layout of Rebar for Concrete Slabs. If your concrete will be stamped, ask about the best ways to avoid interrupting the pattern. 10% reinforcing, the slab joint spacing should be the same as for an un-reinforced slab. This translates to roughly 5/8 inch rebar and must be spaced equally along the slab to create a proper grid. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. In addition, the spacing of the bars will also vary by the project. In order to calculate this, you need to input the length and width of your slab. 12% for HYSD bars and 0. However, generally, a 6mm rebar is suitable for a 4 inch slab. It’s crucial to ensure that welded wire mesh be placed on chairs of the proper height. Besides, do you need rebar for 4 inch slab? What are the problems with rusting rebar in concrete? Crack and Rebar Problems Problem #1 – Rusting rebar loses structural strength As rebar rusts, it slowly loses its strength and deteriorates. 2-1/4 inch rebar high chair is. the calculator will give you the default spacing values (for rebar – rebar it’s 40cm, and for edge – grid it’s 8cm). 73 per square foot for concrete installation. REBAR SPACING: GP‐7 SERIES MODELS: 4‐1/ 4" 3000 PSI / 28 Day Aging #6 Rebar: 12 in: XPR‐9 SERIES MODELS:. Do not go less than 4-inches thick. It has a procedure for using rebar to reduce slab thickness, and if I remember right for increasing joint spacing. And the rebar details of (1) is 10mmØ @ 8″ c/c. When you build a 4-inch slab, you’ll need a higher grade of rebar. A 4" slab should have joints 8-12 feet apart. of 2500 psi however. No, you do not need rebar for a 4-inch slab of concrete on grade. 17 per square foot, or $113 to $126 per cubic yard for both materials and installation. Shafts and segments – 1½ inches. Advertise Here. What size rebar do I need for a 4 inch slab? You will need a #3 rebar for a 4-inch slab. Suppose the foreman accidentally uses #3 bars instead of #4 at a 5 inch center-to-center spacing. Conclusion. 525 mm. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. For example, a 4″ slab should have control joints placed a maximum of 12 feet apart. If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h, 18 inches, l w /3. Second, most designs require’spacing rebar’ of two inches. Provide Construction Joints (ie, transverse joint) @ 40'-0" intervals if you have a long driveway. Proper installation that provides maximum strength requires the mesh to be raised off the ground so that when the concrete sets, it’s in the lower third of the slab depth. If the concrete slab in question is meant to be the footing of a house, then #5 rebar with a. 75-in x 1. For a 6 in. (Rebar Calculation Formula) No. Horizontal rebar starting at 12 inches and at 18 inch intervals after to the top. 5 inches up to 12 inches. The concrete contractors said that these rebar chairs were a great idea, but the execution and labeling of the product was very poorly thought out. basement foundations). For the slab's longer dimension, you'll need 360 inches divided by 14, which gives you 25 plus a bit left over. For example, a 4-inch slab should have joints no more than 8-12 feet apart. I will drill with a hammer drill and a 3/8 bit through the expansion material and into the existing slab about 6 inches. 33 inches. ( W) Width of the slab. 375 inches, which is equivalent to 9. Prices for your concrete slab will vary significantly depending on many factors, including the slab’s thickness, concrete type, and size. 2. 3) If your rebar is somehow perfectly placed in the center of the slab (unlikely) and your large aggregate is the typical 3/4" or 7/8", then think about the top 1-1/2" of concrete right over the rebar after you finish it. Control joints can be added to your concrete slab extension in two ways: Create a control joint when the concrete is still wet using a grooving toolRebar is best used in a driveway for which 5-6 inches of concrete can be poured. The typical depth for rebar placement for slabs is 2-4 inches. Raise the form sides 1/2-inch to create a slab that is a full 4 inches thick. For beams, these distances are 300 mm, 180 mm and 150 mm for grades of main reinforcement of Fe 250, Fe 415 and Fe 500, respectively. The spacing will depend upon the wire size and the wire spacing. Second level 6 inches thick 9 feet tall. It has stood up to some really heavy equipment for 25 years. Step 5 – Place the Mesh. Anchor bolts are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate. 73 per square foot, with an average cost of $6. Tie in the Rebar to Strengthen the Slab. Then use a “gauge board”—a 1×4 with blocks screwed to it—to position the other side. Tie two bands of 1/2-inch steel reinforcing rods (rebar) to stakes set about four inches from the perimeter of the forms. 1 Type A - The dowel structure shall comprise a single metallic material meeting the requirements of AASHTO M 255M/M 255, AASHTO M 334, ASTM A276, ASTM A312, or ASTM A1035 (CS, CM and CL). For example, a size 4 rebar will have a diameter of 4/8” or ½ inches. However, depending on the intended purpose of. x 6 · W4. 34 inch (8. The spacing will depend upon the wire size and the wire spacing. These dowels could be straight or have a hook in the bottom and only need to be a minimum of 16 inches high above the finished concrete. By understanding these basic fundamentals of inserting and spacing rebar in a concrete slab, one may ensure that their project will be protected against cracking or. Tying rebar at joints and positioning it in the middle of the slab is essential for proper reinforcement. Content intended for mature audiences. 5 (1), or as specified by engineered design accepted by the building official. The 6mm rebar should be arranged in a grid pattern, spacing out the rebar at 6 to 12 inches. Figure 2 shows the minimum bar extensions given in ACI 318-14, Building Code Requirements for Structural Concrete and Commentary, Figure 8. For example, a slab that is 6 inches thick might have rebar marked as size 6 or 3/4-inch. Rebar is recommended on concrete measuring 5 – 6 inches thick. For slabs. And a cross-sectional area of 0. For a standard 6-inch thick concrete slab, you will need between 6 and 7 pounds of rebar per square foot. What size rebar for 4 inch slab. 6 bars and bigger – 2 inches. 73 per square foot for concrete installation. The proper way to use rebar reinforcement is to ensure that it is laid in the center or slightly above the center of the slab's thickness. Generally, for a 4-inch slab, a #4 rebar is usually recommended due to. Mainly, heated slabs radiate outward rather than downward, so insulation on the edges of the slab is most important. Similarly, a 4 inch slab of 4,000 psi concrete, 4 feet by 8 feet, with reinforcing mesh can hold up to 45,000 lbs. The insulation phase is crucial for a radiant floor. 2. e. Increasing the thickness from 4 inches to 5 inches will add approximately 20% to your concrete cost, but will also boost your. Excavate the perimeter 1 foot deep and 1 foot wide to form a deeper trench around the excavated area. standard concrete slab reinforcing requirements consist of using #4 bars at 12” spacing, which is adequate for most residential. Rebar being #4 grade 60. MINIMUM VERTICAL REINFORCEMENT AND SPACING (INCHES) b, c: Soil classes and lateral soil load d (psf per foot below grade) GW, GP, SW and SP soils 30: GM, GC, SM, SM-SC and ML soils 45:. 78. Adequacy of curing. In conjunction with the bar callouts in Figure 1, minimum extensions for the top and bottom reinforcing bars in the column and middle strips must be provided. For example, #8 rebar = 8/8 inches (or 1 inch) in diameter. For garage slabs, two rows of #4 rebar are recommended around the perimeter, one above the other. Place concrete at a minimum thickness of 4 inches. The tensile strength of concrete is typically taken as 10 to 15% of the compressive strength, so only about 400 or 500 psi. Once you input these values, you will have your grid length dimensions, it’s that easy. We followed all of those and 2 years later we're glad we did!1. For a slab this thin you would use wire mesh instead. The important part is the use of support to achieve proper placement within the slab. For a patio you can use a grid spacing of 24 inches. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. CRSI’s Reinforcement Anchorage and Splices includes tables of required lap splice lengths based on these variables. 9_sqrt (Pt), with P representing the percentage of steel required and t representing the thickness of the slab. number up to No. To form consistent, parallel sides for a curved sidewalk, build one side first. Generally, you do not need rebar for a 4-inch slab. 5. The main reinforcement of the slab panel “A” is marked as (1). For slabs of septic tanks, you usually use #3 and #4 bars. 11. The installation of the rebar is critical for the success of the overall project. Main reinforcement which is based on the maximum bending moment shall not be less than 0. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal. For a 4-inch concrete slab-on-ground, this would be equivalent to #4 rebar spaced at 10 inches each way. Workmanship and jobsite conditions. If you have expansive soil or a significant frost depth, #4 rebar at no more than 12 inches on center is a good choice. If the slab is more than 24 inches thick, #5 (#5/8 inch diameter) rebar may be required. Main bar is also called as shortest span bar usually used at bottom of slab having spacing 4 inch between the two bar. transverse wire spacing with smooth No. 6 x 6 8/8 minimum reinforcing. 5. For very thick slabs, such as those 8 inches or more in thickness, half-inch rebar or larger is used. B3030. Anchorage shall be in accordance with Section R403. For instance, the ACI 318-19 specifies minimum slab thickness that satisfies deflection. Use 2” rebar chairs to support the rebar in the center strata of the pad. Rebar Spacing for Concrete Slab: What is the Correct Rebar Grid Spacing For Concrete Slab? The. spacings: #4 bar = 27. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal thickness. To reinforce a 4” concrete slab or driveway with steel rebar, determine the grid spacing and rebar size – #3 or #4 in a 12” to 18” grid. 59 per square foot. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. 0 CONCENTRATED LOAD 2000 lbs. Cover the fill with a layer of 6-mm plastic sheeting. To get the rebar in the bottom 1/3rd of the slab, a 1" chair would been perfect for a 4" slab, a 2" would be good for a 6" Slab, and a 3" for something crazy thick like 8"+. Fiber and welded wire are only used for shrinks cracks, non structure cracks, cosmetic cracks. spacings: #4 bar = 18. The minimum thickness of reinforced concrete pavements should be 6 inches, except that the minimum thickness for driveways will be 5 inches and the minimum thickness for reinforced overlays over rigid pavements will be 4 inches. Number of cubic yards = 64 cubic feet ÷ 27. The important part is the use of support to achieve proper placement within the slab. Video of the Day. 4. For a 4 inches slab, rebar is not necessary. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. The string will act as a guide to keep the form boards straight. To use our rebar calculator, simply input the dimensions and specifications of your project. #6 bars and larger – 2 inches #5 bars or smaller – 1½ inches. Do you require gravel under concrete?The minimum spacing of rebar in slabs varies depending on the application, with typical spacing distances between 5 and 6 inches on center. Have a helper add or remove concrete in. Rebar is short form of reinforcing bar, it is steel bar or Steel wire provided as tension bar, used in. 1: Calculate The Main bars. Proper and even spacing is also important. 23 inches For a 4" thick slab with GR60 bars I get the following max. approximately the bar diameter in eighths of an inch [whole millimeters], used to designate the reinforcing bar size. 4xW1. A good compacted base below the concrete is equally important. For thin slabs, such as those less than 4 inches thick, the most common size of rebar used is 5/8 inch. Ask Your Own Structural Engineering Question. How to calculate the rebar quantity from concrete? Convert your longitude estimation into inches: 15 x 12 = 180. Commonly called “rebar,” these 1/2-inch-diameter steel rods are embedded in the center of the slab to create a grid that extends lengthwise and crosswise to help the concrete better resist pulling and bending forces. Vertical placement tolerance for reinforcement in slabs-on-ground is ± 3/4 inch from the specified location. Include 1/3 to 1/2 the sq footage of the shop in exterior concrete - a large apron in front of the door for outside work on vehicles and generous walkways along the sides. Table 3 contains the maximum number of bars that can fit in a single layer for various beam widths based on Grade 60 reinforcement, the overall reinforcing bar diameter, 1. 2 mm in diameter. 19 rebars for the slab. 33 ft). Generally, #4 rebar (1/2 inch in diameter) is the most common size used for slab on grade applications. If you are in a climate subjecting the floor to freezing, get air added to the concrete. Slab footing Rebar may be easily determined with the help of the footing Rebar calculator. Slabs, walls, and joists: #14 and #18 bars: ½ inch. However, if the slab is subject to heavy load or if it’s used as a structural support, you may need to go larger, such as #6 (3/4-inch diameter) or even #7 (7/8-inch diameter). 5x the maximum aggregate size. 6. Prices for your concrete slab will vary. 10%. See STRIPS. For distribution bars the maximum spacing is specified as 5 times the effective depth or 450 mm whichever is less. 5x the maximum aggregate size. A cubic yard of concrete—equivalent to 27 cubic feet—will cover an 81-square-foot area with 4-inch-thick concrete and cost $113–$126. If the wall exceeds four feet in height, footings should be poured separately. If the steel placer is a little sloppy and places the bars at 5-inch spacing. For a 4-inch slab, you’ll need a higher grade of rebar. Above 12 1/4” they have a single cover height per chair. What size rebar for 4 inch slab. What should be the size rebar for a 4-inch slab? For a 4-inch slab, the thickness of the rebar should be ⅛ of the slab. e. For example, a Grade 60 #8 rebar with a 1/2-inch center-to-center spacing and encased in 4 inches of 6,000 PSI concrete can hold approximately 59,000 PSI. Emergency escape and rescue openings require a clear 36-inch-wide path to a public way. 0. 2-inch midspan c a m b e r, the beam delive r ed to the jobsite might have a 13⁄ 4-inch cam-b e r. 17 inches (18" controls) #3 bar = 10. For example, for a six inch garage floor, you would want to space your rebar at least six inches apart but no more than eighteen inches apart. Anchor bolts are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate. You’ll pay about $1,200 for a 6-inch slab that measures 10 inches by 20 inches. C. 2. Rebar Chair is a patented polypropylene support system ideal for concrete applications requiring a 6 in. 1 (a) (5) of ACI 318-19, nominal maximum size of coarse aggregate shall not exceed the least of (i), (ii), and (iii): (i) one-fifth the narrowest dimension between sides of forms. Typically, for residential construction, you might use #4 (1/2 inch) or #5 (5/8 inch) rebar spaced at 12 inches on center for a 4-inch thick slab and closer spacing for a 5-inch thick slab. For a patio you can use a grid spacing of 24 inches. Nail the corners together, and place the form on the graded gravel, making sure it doesn’t rock. 72 percent. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. 11. The general rule of thumb is that control joints should be place no more than 3X the slab thickness (in inches). Most DOT's use double layers in their decks. When a load is applied it bends the concrete on end, this is how the crack starts, the point of failure. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. We always recommend that you have a system in place to strengthen the concrete, though, to ensure the best results. Again, without mesh this drops to 34,300 lbs. Do you need rebar for 4 inch slab? No, you do not need rebar for a 4 – inch slab of concrete on grade. B3030. of Main bars = (3000)/150 + 1. Then I’d make sure that slab gets cut up the very next day after the pour so it can crack where you want it to. Rebar counteract this force. With rebar this thick, a four-inch slab will be more durable and last longer. ( rS) Rebar Size (2,3,4,5,6,7,8,9,10,11,12,14,16,18,20) Use Size "0" for. With our rebar calculator, you can eliminate. Space joints (in feet) no more than 2-3 times the slab thickness (in inches). Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. However, if the concrete slab is meant to be the footing of a small structure, #4 rebar with a diameter of 1/2-inch should be used. No, you do not need rebar for a 4-inch slab of concrete on grade. of Main bars = 20 + 1 = 21 Nos. 561 kg/m. Similarly, rebar with a size 15 will be 15/8. I just got off the phone with a local contractor after picking his brain a bit and he typically will use a #4 bar @ 48" o/c. Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. Step 1: – Calculate numbers of distribution rods. /18 in. 16 wire longitudinally and smooth No.