To increase the structural integrity of your slab, use 2 layers of rebar with the spacing staggered in the second layer. The grade shall be as specified by the. 75-in x 1. Generally speaking, a. Rebar Spacing OC + Waste / OverlapWith this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). In order to calculate this, you need to input the length and width of your slab. Slabs, walls, and joists: #11 bars and smaller: ¾ inch. Choose Round Column (or Round Slab) on the calculator; Enter Height 4 ft (or 48 in) Enter Diameter 10 in; Calculate and the answer is 0. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. My steel building plans call for wire mesh in the upper 1/3 of my 4 inch slab, and 2 continuous rebar running the lenght of the bottom of the footer with a min of 1' overlap, but for the rebar in the turn down the plans states "rebar plans by others". 375 inches, which is equivalent to 9. For example, let’s say the project requires a 4 inch thick slab, made of 6 foot rebar and a total of 50 pounds of rebar. 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. Vertical rebar every 16 inches. Every concrete slab should have a minimum. 7. The laps should be tied together with wire. Placing more rebar/less spacing than required leads to higher crack width formation in slab because the higher weight of rebar would lead to higher deflection. B3030. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. Tables indicate foundation walls reinforcement supporting concrete above grade walls 5. 5-inch cover to the beam stirrups, dagg = 3⁄4. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is. e. If you want to combine rods of two diameters, there would. Moreover, chloride ions from marine salt. Place the holes at the 2. inches thick and about 4 x 4 inches square. Use a metal-cutting blade or disc in a reciprocating saw, circular saw or grinder to cut the rebar. Generally, #4 rebar (1/2 inch in diameter) is the most common size used for slab on grade applications. 5. 6 rebar spaced 4 inches on center is P = 8. For garage slabs, two rows of #4 rebar are recommended around the perimeter, one above the other. Methods used for finding slab thickness varies for different types of slabs. I am filling a 12 ft x 12 ft sunken lounge are with 12" of Geofoam as filler and a 4" concrete slab. In order to calculate this, you need to input the length and width. 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. 15% for mild steel bars. Main reinforcement which is based on the maximum bending moment shall not be less than 0. 65*6) = 1. 6. Above 12 1/4” they have a single cover height per chair. The appropriate rebar spacing for most of the slabbing is 12-inches. For a 400 square foot slab, the man hours required to finish a two-car concrete garage slab is about 13 hours. Rule #5: For better crack control keep the maximum distance between joints in feet at 2 to 2. (For example, 0. Generally, rebar has an immense impact on concrete. 0. Plan out your control joint spacing 24-36 times. For example, a size 4 rebar will have a diameter of 4/8” or ½ inches. /18 in. Most reinforcing bars bearing a Metric diameter markNow, divide each measurement by the 14-inch spacing. This will provide adequate reinforcement for most applications. Furthermore, if the concrete. Similarly, rebar with a size 15 will be 15/8 inches. Dosage amounts shall be from 0. o Minimum 6 inch thick continuous concrete footings not less than 18 inches wide and reinforced with two continuous #4 rebar rods. The appropriate rebar size depends on the project, with #3 and #4 being common choices. I will drill with a hammer drill and a 3/8 bit through the expansion material and into the existing slab about 6 inches. of Engineers (Army TM 5-809-12) that you can download for free from thier website. Concrete rebar calculator plan view diagram. First, find the area of the slab. This is because rebar is comparatively thicker than galvanized mesh reinforcement. Generally speaking, it’s recommended to use #5 rebar if the slab is 4 to 6 inches thick and is being used for residential construction. If the concrete thickness is greater than 8 inches, the spacing of the rebar may be increased in order to prevent lateral buckling of the rebar. You might be interested: Readers ask: Pavers Vs Concrete? The size of rebar that is needed for a 6 inch slab will depend on a few things, such as the type of load the slab is being used for and the spacing of the rebar. Spacing of bar supports depends upon the size and placing of the rein-forcing bar being supported. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. 1: Calculate The Main bars. Rebar helps prevent cracks from growing wider largely by preventing cracked slabs from moving apart. 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. Provide 21" minimum rebar splice laps. For one layer of 6x6 W1. It's not a problem to get two layers in on an interior 8" elevated slab where the bottom cover is 3/4". Hercules 3 in. 4 Application range of post-installed rebar As a consequence of what has been declared in the previous chapter, the application range of post-installed rebar is limited by EOTA TR 023 [15] to: (a) Overlap joint for rebar connections of slabs and beams and overlap joint at aFor most residential slabs, such as patio slabs and sidewalks, #4 rebar (1/2-inch diameter) spaced 12 inches apart is recommended. Generally, concrete reinforcement mesh is available in a variety of sizes, including 6×6-inch, 8×8-inch, 10×10-inch, 12×12-inch and 14×14-inch. 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. Running Bar Points (Length - Left to Right): Running Bar Points (Width - Top to Bottom): Calculate Rebar Quantity and Mesh From Total Slab Area and Perimeter. Create contraction joints every 4-6 feet. 87 d Spacing of bar = Design of Continuous Slab Suppose a slab is supported at the ends and also at intermediate points on beams, the maximum sagging and hogging moments to which the slab is subjected to due to uniformly distributed load, can be computed as follows: Let = intensity of dead load per square metre. What size rebar for 4 inch slab. Convert the weight of the bag to the volume. New concrete slabs must conform to the above stated properties before installation of. The main reinforcement of the slab panel “A” is marked as (1). 2. 87 (round up to 13) Add one rebar to your result: 13 + 1 = 14. (UBC), may require the use of rebar in 4-inch concrete slabs. Emergency escape and rescue openings require a clear 36-inch-wide path to a public way. For a 4-inch slab, #3 rebar should be spaced 12 inches apart on center. ( rS) Rebar Size (2,3,4,5,6,7,8,9,10,11,12,14,16,18,20) Use Size "0" for. For multi sided slab, first draw the shape: 1: Hit Clear + Start and enter Side Length of first side to draw, then hit appropriate direction (Arrow) button to draw. Do you need rebar for 4 inch slab driveway? It depends. Concrete rebar calculator plan view diagram. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Fiber length shall be 1 / 2 inch to 2. Before beginning a concrete project, consult a professional engineer to determine the code requirements and what size and spacing of rebar will best meet. For beams and walls, the spacing should be closer and is usually 3-4 inches apart. Run twine between the stakes. So for example if you take a 6 inch slab times 2 is twelve feet or times 3 is 18. #4 rebar is perfect for adding strength to highways and can give columns and slabs. Do you need rebar for 6 inch slab? Rebar is recommended for. This thicker rebar will improve the durability of a 4-inch slab and therefore its lifetime. They're compatible with rebar sizes #3 to #5 and can elevate your rebar either 1 1/2 inch or 2 inches off the ground. Step 2 - Twist the Wire Pieces. Common size of rebar used for 4 inch slab, it may vary from size. That means placing the wire on chairs to hold it at the correct height (see below). For ½“ rebar the inside of the bend should have a diameter of at least 3 inches. This type of rebar is typically 6mm in diameter and can span up to 24. It has stood up to some really heavy equipment for 25 years. A. The important part is the use of support to achieve proper placement within the slab. The spacing of the rebar should increase to between 18 and 24 inches apart for slabs between four and six inches thick. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. 33_2_0. Step-4: Rebar Calculation Process Of The Slab Panel-A 4. 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. If rebar is used what should the spacing and size be?What size rebar do I need for a 6 inch slab? The size of rebar that you need for a 6 inch slab depends on a variety of factors including the type of construction and the specific design of your structure. However, many engineers and. 1. How do you calculate rebar spacing? Find the rebar-to-spacing multiplier with the formula M = 0. e. And rebar is sized by eights of an inch. Drag a straight 2×4 (screed board) across the top of the concrete forms to level the concrete. This means 2x 3/8 inch rebar makes 3/4 inch of steel. Do you need rebar for 4 inch slab? No, you do not need rebar for a 4 – inch slab of concrete on grade. 2 only if the steel reinforcing is greater than 0. For a 4-inch slab, you’ll need a higher grade of rebar. Tie in the Rebar to Strengthen the Slab. This video shows different aspects of selecting rebars for a driveway:. Great for use when pouring concrete slabs. (This convention begins to break down for bar diameters above #8. Fig 4: Rebar Tying details. Figure 2 shows the minimum bar extensions given in ACI 318-14, Building Code Requirements for Structural Concrete and Commentary, Figure 8. Fa b r ic may also be supported at the center of the slab, or it may be installed in two flat layers with the top layer (nega-t i v e steel) extending on either sideInterlocking PVC spacers to provide 1-1/2" spacing between ducts and 3" cover of concrete for the outer ducts, spaced 5 feet on centers will be used. But to get two layers in an 8" slab-on-grade where the bottom cover is 3" would might violate the bar to bar spacing between layers. Convert your longitude measurement into inches: 15 x 12 = 180. thick slab, the maximum joint spacing should be. 2(a) and 3-6. All thick slabs can be categorized into:. My driveway is 4 inch thick concrete. 10” or so around the edge and 4” everywhere else. Product Details. 1. 2. Horizontal rebar starting at 12 inches and at 18 inch intervals after to the top. Minimum reinforcement is 0. Raise the form sides 1/2-inch to create a slab that is a full 4 inches thick. The standard rebar is Grade 32 and is used for a 3-inch slab. MAX and #5 top placed at center of slab" I installed the #3 dowels 12" apart and 6" into the existing surrounding floor. 34 and $7. Before beginning a concrete project, consult a professional engineer to determine the code requirements and what size and spacing of rebar will best meet. 2 Spacing s of longitudinal bars in precast walls shall not exceed the lesser of 5h and 18 inches for exterior walls and 30 inches for interior walls. 9_sqrt (Pt), with P representing the percentage of steel required and t representing the thickness of the slab. 5x the maximum aggregate size. 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. 65 and the thickness of the slab is 6 inches, M = 0. Concrete doesn't dry out; it undergoes a chemical curing process that creates a dry, solid mass. Concrete can be mixed in a wheelbarrow, mortar pan, or mixer. Generally speaking, a. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. For a 4-inch slab, #3 rebar should be spaced 12 inches apart on center. 3a, for two-way slabs without interior column. 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. Unique fastening system ensures accurate positioning of rebar, to code, during concrete placement. You’ll pay about $1,200 for a 6-inch slab that measures 10 inches by 20 inches. 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. 17 per square foot, or $113 to $126 per cubic yard for both materials and installation. According to this method, you will need two rebars for a footing width of 16 inches, four rebars for a footing width of 24 inches, and so on. 9. I am confused about the grid. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. to 8 in. Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. The pitch of the main bars shall not exceed the following:This is done by inserting #4 rebar dowels a minimum of 6 inches into the center of the footing’s wet concrete, spaced typically at 4 feet on center. 1: Calculate The Main bars. Common practice is to place supports 2 to 3 feet apart. I used no. The 6mm rebar should be arranged in a grid pattern, spacing out the rebar at 6 to 12 inches. 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. 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. The appropriate rebar spacing for most of the slabbing is 12-inches. Concrete volume calculator plan view diagram. The top surface needs to remain wet while the curing process takes place. Rebar Spacing. Read more on low-shrinkage concrete mixes in the Concrete Mix Design section. Wilkerson, PE. 45 to 1. 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. The #3 rebar has a weight per length of 0. Splices not shown on the plans will be permitted in slabs no more than 15 in. Benefits of Using Rebar in a 4-Inch Slab. Generally, you do not need rebar for a 4-inch slab. Size 18 rebar has a diameter of 2 1/4 inches. Space joints (in feet) no more than 2-3 times the slab thickness (in inches). Calculate Rebar Spacing, Layout and Weight in a Concrete Slab To calculate Concrete and Total Rebar in a multi sided slab see: Calculate Concrete and Rebar in Multi Sided Slabs 16 Bars @ 11'- 6" 10 Bars @ 19'- 6" Total Length 420 ft Includes 10% waste / lap Exact Spacing Length 16" mid 10" Width 16" mid 10" 21 x 20 ft Lengths $ (Enter Cost per Bar) See full list on everything-about-concrete. To do this, concrete pros prop up the rebar. Main bar is also called as shortest span bar usually used at bottom of slab having spacing 4 inch between the two bar. Click HERE for spec sheet. 2. 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. 16000 lbs divided by 144 is 111 pounds per square inch. I was thinking of going with the same spacing. Determine the amount of rebar needed for the footings. I would suggest 3000 psi concrete if cracking and wearing is a concern, but 2500 psi is ok. The reinforcing steel sagged during placement between the support chairs, causing the 3/4-inch spacing to be infringed upon. 058 percent, which is only enough for crack containment. Main bar is also called tension. 7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps. If the forms are belowground, place stakes no more than 3 ft. Originally Answered: Do you need rebar for 4 inch slab? Reinforcement can be either wire mesh or ½- inch (#4) steel rebar. 4 Minimum Thickness . 5000 PSI concrete can safely support 5000 pounds per square inch (PSI) minimum before its compressive strength is overcome. For example, if the percentage is 0. Tractor. Generally, lighter-duty applications require a rebar spacing of 8-12 inches (20-30 cm), while heavier-duty applications require a closer spacing of 6-8 inches (15-20 cm). In order to calculate this, you need to input the length and width of your slab. 33_6_0. Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. In general, 6 inch (150mm) slab thickness is considered for residential and commercial buildings with reinforcement details as per design. 78. Sub-Grade and. With rebar this thick, a four-inch slab will be more durable and last longer. 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. 4 wire mesh in a 4-inch slab, P = 8. 6, Figure R404. The formula is, Number of bars = (length ÷ spacing) + 1. longitudinal and transverse. View More. A six inch slab can handle some thin spots - a 4" slab can't. 4 mm) diameter wire at 10 inches (254 mm) on center vertically. To calculate your concrete needs multiply the length by the width of your shed, then multiply by the thickness; remembering to change inches to feet (4” ÷ 12” = 0. Then, the new slab needs to be left alone. The top surface needs to remain wet while the curing process takes place. How do you calculate rebar for a slab? Layout of Rebar for Concrete Slabs. 15 per cent of the gross sectional area. com First, enter the concrete slab sizes: length = 6 m, width = 4 m. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. Here’s a complete chart of different rebar sizes, their diameters, and weight: Rebar markings. And a cross-sectional area of 0. What is the minimum reinforcement in slab? 2- Slab Reinforcement Details. Therefore, you will need approximately 2. And a cross-sectional area of 0. 19 rebars for the slab. For foundations that are taller than 8 feet and slabs thicker than 8 inches, the minimum spacing should range from 7. The exact size rebar you will need for a 4 inch slab will depend on several factors, including the application, the load being carried, and any seismic or other environmental considerations. If the steel placer is a little sloppy and places the bars at 5-inch spacing. Great for use when pouring concrete slabs. I'd go #4 rebar at 18-inch max spacing. As well as that, the calculator will also tell you. basement foundations). With our rebar calculator, you can eliminate. These rebar chairs, also known as rebar stands, are extremely versatile. vapor retarders - some times referred to as vapor barriers, insulation, etc. If you are working on a project that requires reinforcing concrete that will be exposed to the elements, then it is recommended to use a heavier mesh, such as 10×10-inch or 12×12-inch. Additionally, it plays a crucial role in preventing cracking and shrinkage, ensuring long-term reliability. 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. And rebar is sized by eights of an inch. Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. 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. In addition to a foundation's ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. (ii) one-third the depth of slabs. 11-22-2006, 08:16 PM. Tie two bands of 1/2-inch steel reinforcing rods (rebar) to stakes set about four inches from the perimeter of the forms. Suppose the foreman accidentally uses #3 bars instead of #4 at a 5 inch center-to-center spacing. The size of the rebar depends on the specific application, but typically #4, #5, #6, and #8 rebar are used. How do you calculate rebar spacing? Find the rebar-to-spacing multiplier with the formula M = 0. 5 inches of thickness at the edge of the pool. This will be based on the loads and desired strength of the concrete. For example, if you’re calculating rebar for a slab, input the slab dimensions, reinforcement spacing, and desired rebar size. When spacing the rebar, it is important to ensure it is evenly distributed and in accordance with the local building codes. The size of the rebar depends on the specific application, but typically #4, #5, #6, and #8 rebar are used. Similarly, rebar with a size 15 will be 15/8. The tensile strength of concrete is typically taken as 10 to 15% of the compressive strength, so only about 400 or 500 psi. concrete is good in compression but not tension. 25 inches (13 to 56 mm) in length. Rebar Spacing; D2-8F: 4. number up to No. If your footings are 16 inches wide, you will need to add two sticks of rebar along the width of the footing; however, if your footings are 24 inches wide, you will need three sticks. The rebar needs to be correctly. That's 144 square 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′. This gives the following information: You need the given quantity, 18, rebar, size 5 (5/8 inch diameter), with 9 bars laying in each direction, the top rows perpendicular to the bottom ones. _____ Bar Supports Bar supports are required in a number of locations on bridges. 1. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. Add one more length to allow for that extra, giving you a total of 18. However, many engineers and contractors use a rule of thumb of keeping the rebar spacing to 2 – 3 times the. (inches) Slab Bolster 3/ 4 to 3 high; Supports lower slab SB 2, 3, 12, 36 long reinforcing steel; also comes in circular shape for architectural work. According to 26. 10. The same slab without mesh can hold up to 25,400 lbs. 3. For slab thicknesses 12 inches or less, the concrete cover tolerance is - 3/8 inch. What should be the size rebar for a 4-inch slab?. ±3/8 inch (±9. Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. As well as that, the calculator will also tell you. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Finally, take a look at the calculation results: grid length = 5. #5 bars are 5/8”. Tying should include bars near the ends of the bridge and bars near the curbs. Add rebar for reinforcement, Ralston places rebar every 16” on center. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required . The dowels will then be embedded in the ICF wall concrete. Most reinforcing bars bearing a Metric diameter mark Now, divide each measurement by the 14-inch spacing. Each rod of the rebar is engraved with a marking with a code instructed by the American Society for Testing and Materials. Highway bridgework may require more stringent. When arranging joints, skilled contractors will often use them to create an attractive diamond pattern. 5. . If the wall exceeds four feet in height, footings should be poured. 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). The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal. spacings: #4 bar = 27. Construction joints also have this spacing for strip placement of the concrete. 2 mm in diameter. 11 in. INSTRUCTIONS: Choose units and enter the following: ( L) Length of the slab. 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. 5. 7 mm). 73 per square foot for concrete installation. Acorn International 2. 15 percent of total cross-sectional area. 6, the designer can exceed the CJ spacing in Table 10. Additionally, any slab poured over 4 inches should also be bonded with mesh fabric to the 2 preceding layers of clear of construction joint material to ensure the slab is adequately supported. It is also important to consult a structural engineer or professional mason to ensure the optimal rebar spacing is being achieved for the specific concrete foundation. When a load is applied it bends the concrete on end, this is how the crack starts, the point of failure. The spacing of the rebar is typically 12” on center for most residential applications. A 12-foot two-by-four and an 8-foot two-by-four on each long side. 8 mm) ±1/2 inch (±12. Number 4 rebars spaced 12 inches on center (center-to-center distance) on both the top and bottom faces and in each way as well, i. If the slab is thicker, then re-bar should be used. A 4-inch concrete slab with a 2-inch road base and #3 rebar at 16-inch spacing can provide a reasonably strong foundation for a patio structure such as a patio cover or gazebo. (Rebar Calculation Formula) No. (Video) Rebar Spacing, Made Easy (DesignBuildDoug). They cannot hold a load factor. Spacing of bar supports depends upon the size of the. on 2 feet- 6 inch square area (office building) 4000 lbs. Tractor. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. B3030. Do You Need Rebar For A 4 Inch Driveway Slab? A 4 inch concrete driveway slab is too thin for rebar. No. Driveway : The total cost of a concrete driveway will depend on size. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar construction and traditional tape measurement results. 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. lengths of rebar to just below. View More. You can multiply the bar size by 1/8 to get the nominal diameter in inches. User note: About this chapter: Chapter 4 provides requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. The rated separation for two-family dwellings is 1 hour whether or not a lot line exists between units. 2(1) shall be air entrained as specified in Table R402. If your concrete will be stamped, ask about the best ways to avoid interrupting the pattern. So, whether you are constructing a four- or five-inch slab, what size of rebar you will need is determined by the purpose or application of the slab. 65*6) = 1. This is the formula: mesh needed = slab area ÷ mesh area. The size of rebar that is needed for a 6 inch slab will depend on a few things, such as the type of load the slab is being used for and the spacing of the rebar. The main reinforcement of the slab panel “A” is marked as (1). 8" - 3/4" (top cover) - 2" (4-#4 bars) - 3" (bottom. 5 bars or littler – 1½ inches. For a 4-inch concrete slab-on-ground, this would be equivalent to #4 rebar spaced at 10 inches each way. inches thick and about 4 x 4 inches square. 7 mm) anchor bolts spaced a maximum of 6 feet (1829 mm) on center or approved anchors or anchor straps. #4 is 4/8”, or 1/2”. 10% reinforcing, the slab joint spacing should be the same as for an un-reinforced slab. But if one should choose to reinforce their concrete patio, the reinforcement bar they should use should be a size #3, which is 3/8 in diameter. Then, the new slab needs to be left alone. 6 for the recommended CJ spacing for unreinforced concrete slabs-on-ground as follows: Note that CJ spacing in a 4-inch slab should be between 8 feet and 13 feet. Space the joints no more than 2-3 times (in feet) of the slab’s thickness (in inches). To find the exact size of the slab by slab Rebar calculator. How to install rebar in slab footings: To install rebar in slab footings, follow these steps: Its rebar size in inches is 0. 5 to determine you will need 120 feet of rebar.