65 and the thickness of the slab is 6 inches, M = 0. For example, if the percentage is 0. To truly reinforce concrete, the percentage has to. In general, you’ll want a slab that is at least 4 inches thick, but 6-8 inches is even better. Rebar of ten forms a st eel skeleton-like framew ork within footings, walls, slabs, columns, roofs, bridges, driveways, highways, and other concr ete. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal. 5 mm) for concrete slab depth ≤12 inch (304. 7. Step 4: To determine the number of crossing bars you will need, divide the length of the driveway by the rebar grid spacing. Position a rebar grid or 4. 73 per square foot for concrete installation. For slab thicknesses 12 inches or less, the concrete cover tolerance is - 3/8 inch. Most 4-in. Convert the weight of the bag to the volume. But if you feel that the slab is in a sensitive position and extra protection is needed, you can add rebar to it. The installation of the rebar is critical for the success of the overall project. For example, a size 4 rebar will have a diameter of 4/8” or ½ inches. 1. 74 equals 1824 lbs per sq feet. For aboveground forms, space stakes 16 in. That way you can use the forms themselves as a guide for the final base height. Joint spacing in the topping should be coordinated with joint spacing in the base slab. In other words, for a 4-inch slab, space the joints 8 to 12 feet apart. You'll also need vertical rebar hooks protruding at least 6” into the footing and out at least 18” every 48”, or less. 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. If you are in a climate subjecting the floor to freezing, get air added to the concrete. On average are required, for 10 square meter with 12cm thick slab, 19 strips of 3/8” rods (9ml each one), are 171 ml. Compare that to the tensile strength of Grade 60 rebar, which is 60,000 psi. So for example if you take a 6 inch slab times 2 is twelve feet or times 3 is 18. #4 is 4/8”, or 1/2”. Figure 2 shows the minimum bar extensions given in ACI 318-14, Building Code Requirements for Structural Concrete and Commentary, Figure 8. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. For example in a slab of 6-inch depth, a rebar of 6/8 inch will be used. Rust is visible where some of the bottom bars are at the bottom of the slab, and some rebar ridges are faintly visible. 1. 10” or so around the edge and 4” everywhere else. 74 sq feet 5000/2. 2(1) requires that half the calculated span. 2: Repeat and continue to draw complete (closed) shape. It has a procedure for using rebar to reduce slab thickness, and if I remember right for increasing joint spacing. 65 and the thickness of the slab is 6 inches, M = 0. So if you have, say a 3/4" max. For 0. ( D) Depth of slab. (i) The maximum spacing between two parallel main reinforcing bars shall be 3dor 300mm or whichever is less, and. 1. 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. Divide 27 cubic feet of concrete in a cubic yard by the volume of the concrete bag. 34 and $7. 5. You can use regular fencing material with 2' x 4' or 2' x 6' mesh. Set the forms at the proper height before bringing in the last lift. Therefore, you will need approximately 2. 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. 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. In general, it will be necessary to provide supports for reinforcing steel in deck slabs and overhangs, railings, bent diaphragms, intermediate diaphragms, bent caps, approach slabs and culvert slabs. 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. 375 inches, which is equivalent to 9. 6 x 6 8/8 minimum reinforcing. Its rebar size in inches is 0. As a minimum, #4 rebar (1/2 inch) is spaced vertically at 36 inches on center, continued to within 8 inches of the top of the wall, placed on the tension side -- the inside face -- of the wall. Reading time: 4 minutes. Use unwashed material that has a top size of 11/4 inches and includes smaller sizes right down to the fines; the irregular shapes and sizes interlock nicely when compacted. 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. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. slabs are actually the 3-1/2-in. 2-inch chairs at the sup-p o r ts for a 31⁄ 2-inch slab; 2-inch chairs for a 4-inch slab; 21⁄ 2- i n c h chairs for a 41⁄ 2-inch slab and 3-inch chairs for a 5-inch slab. To se- If the slab in question is just for a patio or a similar purpose, #3 rebar with a diameter of 3/8-inch will do just fine. Slabs, walls, and joists: #14 and #18 bars: ½ inch. 1. The formula is, Number of bars = (length ÷ spacing) + 1. If the concrete slab in question is meant to be the footing of a house, then #5 rebar with a. 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. 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). Raise the form sides 1/2-inch to create a slab that is a full 4 inches thick. 5 to determine you will need 120 feet of rebar. Do you need rebar for 6 inch slab? Rebar is recommended for. These rebar chairs, also known as rebar stands, are extremely versatile. 84 m; grid. Use wire mesh for driveways that are 4 to 5 inches thick, and rebar for those that are 5 inches or more. Second level 6 inches thick 9 feet tall. Minimum vertical rebar for 6" flat wall foundations is 4@48" on center 3. the calculator will give you the default spacing values (for rebar – rebar it’s 40cm, and for edge – grid it’s 8cm). 43/30 = 0. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal. 7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps. However, it is better if 10mm or 12mm diarebar can be used with spacing of 100-125mm (4-5’’) between rebar. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. From 3” to 12 1/4” in height, each chair has two cover heights. “Reinforce the concrete with 6×6-10/10 wire mesh. A 4" slab should have joints 8-12 feet apart. Say your forklift has a contact area of 1 square foot. Concrete shall have a minimum specified compressive strength of ƒ' c, as shown in Table R402. Concrete strength also comes into play, but most slab concrete is around 3000 to 4000 psi, so it's not a major factor. ) = 0. 33_6_0. We typically advise using at least two pieces of #4 rebar (1/2-inch diameter) placed vertically in an 8-inch-diameter. Each rod of the rebar is engraved with a marking with a code instructed by the American Society for Testing and Materials. 3 For walls with thickness greater than 10 inches, except singleLap Splices. Concrete is not strong in tension and the rebar is. The Engineer shows a 4″ Slab 3500psi with 6×6-W1. 7. Tractor. For building footings I would use a #5 (5/8 inch) rebar. Contractors sometimes use the “1/8 Rule,” meaning the size of the rebar is 1/8 the thickness of the slab. Tractor. 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. If you have a 5 inch slab and multiply it by 24 to 32 you will find that your joints should be placed every 120 to 180 inches or 10 to 15 feet; Or another way to figure this out is to times it by 2 or 3 in feet. 3. Beams and columns: 1½ inches. PROWORX 3-in x 60-in x 3-in Steel Slab Bolster. For flat slabs, grid spacing of 18 inches for driveways and 24 inches for patios is recommended. _____ Bar Supports Bar supports are required in a number of locations on bridges. Horizontal rebar is. When long slabs are used, special consideration must be given to joint design and sealant require-ments. For example, let’s find the number of 5′ x 50′ rolls of mesh required to reinforce a slab that is 25′ by 25′. 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. 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. If the wall exceeds four feet in height, footings should be poured separately. Most homeowners can expect to pay between $4. 33 inches. (i) The maximum spacing between two parallel main reinforcing bars shall be 3dor 300mm or whichever is less, and (ii) The maximum spacing between two secondary parallel. To form consistent, parallel sides for a curved sidewalk, build one side first. The spacing and quantity of the rebar will depend on factors such as the load the slab needs to support and local building codes. There has been some research in recent years to look into this as a bridge deck with no rebar is a bridge. Does a 4 inch slab need rebar? No, you do not need rebar for a 4-inch slab of concrete on grade. To do this, concrete pros prop up the rebar. This will be based on the loads and desired strength of the concrete. The spacing will depend upon the wire size and the wire spacing. 0 pounds per cubic yard (0. 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. Concrete reinforcement can be either wire mesh or ½-inch (#4) steel rebar. 5 bars or littler – 1½ inches. Lay down wire mesh or rebar on top of the sub-base if necessary. of 2500 psi however. 1%. 7 mm). Q: Can rebar rust in concrete? A: Rebar can rust in concrete if it is exposed due to cracking or delamination. Once you input these values, you will have your grid length dimensions, it’s that easy. 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. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. Great for use when pouring concrete slabs. The Rebar and Concrete in a Slab calculator computes the total length and weight of rebar and the volume of concrete needed for a slab. 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. 375 inches, which is equivalent to 9. Expansion grooves should be cut into the wet concrete to provide additional crack resistance. inches thick and about 4 x 4 inches square. For an unreinforced slab, control joints should be spaced in feet 2 to 3 times the slab thickness in inches. For example, if the percentage is 0. Rule #5: For better crack control keep the maximum distance between joints in feet at 2 to 2. B3030. With 3-inch screws, attach the two-by-fours to the stakes: A 12-foot two-by-four on each short side. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is less. However, many engineers and. Horizontal rebar starting at 12 inches and at 18 inch intervals after to the top. Build forms. For example in a slab of 6-inch depth, a rebar of 6/8 inch will be used. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. 2. 1. Great for use when pouring concrete slabs. 4. The Rebar calculator for slab is best to find the Rebar size. What size rebar for 4 inch slab. A little more cash now is worth no cracks later but I always overkill. 10%. 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. 4 wire mesh in a 4-inch slab, P = 8. 3. Video of the Day Step 2: Dig Out the Area Excavate the concrete pad area 6 inches deep to prepare the ground for the concrete. My driveway is 4 inch thick concrete. 7 mm) anchor bolts spaced a maximum of 6 feet (1829 mm) on center or approved anchors or anchor straps. 5. 0. Concrete volume calculator plan view diagram. Step 5 – Place the Mesh. For a 4 inch slab, I really wouldn’t space the bars further apart than 12 inches. 1. In order to calculate this, you need to input the length and width of your slab. 12. This spacing will provide the maximum reinforcement of the. 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. to 8 in. Divide your result by the spacing measurement: 180 / 14 = 12. The standard rebar is Grade 32 and is used for a 3-inch slab. 33 inches. ±3/8 inch (±9. Emergency escape and rescue openings require a clear 36-inch-wide path to a public way. The spacing and quantity of the rebar will depend on factors such as the load the slab needs to support and local building codes. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required . 9_sqrt (0. 0 inches use 4 inch Schedule 40 PVC duct and internal joining coupling for 4 inch I. These new concrete slabs are designed as " s tand alone " and do not take. Here: Multiply the measurements together to calculate the square footage of the area. spacings: #4 bar = 18. 4/1. 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. I believe the rebar should be 1/4 to 1/3 of the slab thickness from the bottom. 4. Thick slabs Thick slabs are concrete slabs with an overall thickness of 4-6" or greater and can be either grade level (slab on grade) or below grade (i. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. 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. On average are required, for 100 square feet with 5 inches thick slab, 19 strips of 3/8” rods (30 ft each one), are 570 ft. of Main bars = (Width of Slab/Spacing) + 1. Again, without mesh this drops to 34,300 lbs. 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. 1% reinforcement in a 4-inch thick slab is #3 bars in both directions at 24-inches. The 6mm rebar should be arranged in a grid pattern, spacing out the rebar at 6 to 12 inches. Minimum reinforcement in either direction shall be 0. 34 inch (8. The rebar needs to be correctly. 08 cubic yards for one concrete tube; Multiply 0. 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. If the slab in question is just for a patio or a similar purpose,. Use 2” rebar chairs to support the rebar in the center strata of the pad. 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. 59 per square foot. A concrete slab costs between $4. 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. 2-1/4 inch rebar high chair is designed to hold rebar in place during concrete applications. Prices for your concrete slab will vary significantly depending on many factors, including the slab’s thickness, concrete type, and size. View More. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is. All thick slabs can be categorized into:. Rebar of the size specified in the Rebar Schedule will be placed in the duct bank, located as. #4 rebar is perfect for adding strength to highways and can give columns and slabs. 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. We would like to show you a description here but the site won’t allow us. The maximum height of a 4-inch (102 mm) load-bearing masonry foundation wall supporting wood-frame walls and floors shall be not more than 4 feet (1219 mm). On average, a 60-pound bag of concrete covers about 0. Wilkerson, PE. For beams and walls, the spacing should be closer and is usually 3-4 inches apart. Tie two bands of 1/2-inch steel reinforcing rods (rebar) to stakes set about four inches from the perimeter of the forms. And a cross-sectional area of 0. Suppose the foreman accidentally uses #3 bars instead of #4 at a 5 inch center-to-center spacing. 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. No, you do not need rebar for a 4 – inch slab of concrete on grade. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. 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). If you have any concerns about the soil or drainage in your yard, you may need to pour an even thicker slab. 2. 72 percent. Vertical placement tolerance for reinforcement in slabs-on-ground is ± 3/4 inch from the specified location. It’s crucial to ensure that welded wire mesh be placed on chairs of the proper height. For example, 4 inches patio slab will need rebar. A confused student is a good student. 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. The details of slab reinforcement are given below. 5x the maximum aggregate size. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. In inches the diameter of a #5 rebar is 5/8″ and that of a #4 rebar is 1/2″. Most reinforcing bars bearing a Metric diameter markNow, divide each measurement by the 14-inch spacing. If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h, 18 inches, l w /3. 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. Rebar Spacing OC + Waste / OverlapWith this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). 1. Concrete Floor Rebar Spacing. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. 17 per square foot, or $113 to $126 per cubic yard for both materials and installation. concrete is good in compression but not tension. Rebar should be placed evenly throughout the project. You’re likely to pay between $1,800 and. Reinforcing concrete slabs with rebar is an excellent way to prevent slab failure, as long as the slab is not over 4 inches thick. buildings and industrial projects) a spacing of 8” to 12” is more. For example, one-way slab thickness. 8 mm) ±1/2 inch (±12. See Figures 3-6. First, find the area of the slab. (UBC), may require the use of rebar in 4-inch concrete slabs. No, you do not need rebar for a 4-inch slab of concrete on grade. Fig 4: Rebar Tying details. spacings: #4 bar = 27. Often, the placement drawings are specific, such as "18 (number 5) rebar, 11 foot (3. For garage slabs, two rows of #4 rebar are recommended around the perimeter, one above the other. Dosage amounts shall be from 0. The spacing of the rebar is also determined by the weight and size of the slab. A. That's 144 square inches. #4 Rebar ; The #4 rebar is often used in residential and commercial projects to add strength in slabs and columns. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. The 2021 IRC® contains many important changes such as: Braced wall lines must be placed on a physical wall or placed between multiple walls. There are three different sizes of rebar typically used for home construction projects. Use 2” rebar chairs to support the rebar in the center strata of the pad. Horizontal-need 2 rebars each run with 3 or 4 runs of rebar 2 feet apart and rebar size 1/2 inch or 5/8 inch. CONTROL JOINT SPACING. 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. Second, most designs require’spacing rebar’ of two inches. 6. If you prefer to calculate the number of bags of concrete needed, you can use the weight of the bags as a reference. Fiber and welded wire are only used for shrinks cracks, non structure cracks, cosmetic cracks. Provide 21" minimum rebar splice laps. Thread starter matt_isserstedt; Start date Feb 18, 2015; Replies 30 Views 72,127 1; 2;. It’s best to check with a. on 3 feet- 6 inch square area (office for some codes) CONCRETE MIX Top size of the coarse aggregate should not exceed 3/4inchor as dictated by applicable codes. 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. With our rebar calculator, you can eliminate. Use wire mesh for driveways that are 4 to 5 inches thick, and rebar for those that are 5 inches or more. 2. That way you can use the forms themselves as a guide for the final base height. The rebar should form a neat grid. Generally, rebar has an immense impact on concrete. 4 bar at 48 inches (1220 mm) on center horizontally grouted in place. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. 7 mm) anchor bolts spaced a maximum of 6 feet (1829 mm) on center or approved anchors or anchor straps. You can use Grade 40 or Grade 50 rebar for a 4-inch slab. 525 mm. approximately the bar diameter in eighths of an inch [whole millimeters], used to designate the reinforcing bar size. With rebar this thick, a four-inch slab will be more durable and last longer. You’ll pay about $1,200 for a 6-inch slab that measures 10 inches by 20 inches. For ½“ rebar the inside of the bend should have a diameter of at least 3 inches. For very thick slabs, such as those 8 inches or more in thickness, half-inch rebar or larger is used. Furthermore, if the concrete. 5 times the slab thickness in inches. Why Rebar Spacing is Crucial. In addition, the spacing of the bars will also vary by the project. Splices not shown on the plans will be permitted in slabs no more than 15 in. 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. anchor bolts and the 4 inches (102 mm) φ pipes. For example, if both slabs have rebar mats that are spaced at 18 inches and use No. It has stood up to some really heavy equipment for 25 years. 4 wire mesh in a 4-inch slab, P = 8. Having installed thousands of slab on grade foundations over some 26 years as an ironworker, I can say that if it was my driveway, I would probably do 5 inch thick concrete with #4 rebar at 18 to 24 inches each way at center of slab in other words 2" chairs or dobies at every intersection and deepened perimeter footings. 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. With our rebar calculator, you can eliminate. This video series w. ±3/8 inch (±9. (3) #4: Three number 4 rebars (usually used when the rebar perpendicular to the detail) #3 ties @ 9 OC, (2) per set: Number 3 rebars used as stirrups, spaced at 9 inches on center. If you have expansive soil or a significant frost depth, #4 rebar at no more than 12 inches on center is a good choice. anchor bolts and the 4 inches (102 mm) φ pipes. com First, enter the concrete slab sizes: length = 6 m, width = 4 m. 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. Rebar is recommended on concrete measuring 5 – 6 inches thick. 2. (This convention begins to break down for bar diameters above #8. Similarly, rebar with a size 15 will be 15/8 inches. 12. How to install rebar in slab footings: To install rebar in slab footings, follow these steps: Its rebar size in inches is 0. 058 percent, which is only enough for crack containment. Having more bar would only increase the strength of the slab, as long as. Step 1: – Calculate numbers of distribution rods. Product Details. Finally, take a look at the calculation results: grid length = 5. 4 inch of p r otection. Find the number of concrete bags in the most popular sizes in the chart below: Bag Size. In either case, blocks should be used under the reinforcement to keep centered. For example: A #5 [#16] bar is approximately 5/8 inch [16 millimeters] in diameter: a #9 [#29] bar is approximately 9/8 inches [29. And a cross-sectional area of 0. Driveway : The total cost of a concrete driveway will depend on size. However, the stone has been compacted to the top of the rails, which corresponds to only 2. that is 2. 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. 37 cubic yards of concrete for a 4×4 slab that is 4 inches thick. Acorn International 2. Rebar is recommended on concrete measuring 5 – 6 inches thick. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. In the case of the RCC slab, the maximum spacing between two secondary parallel wires should be 5D or 450 mm or whatever. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. but what spacing do I use between the turned rebar and how far down the 18" turndown. The typical depth for rebar placement for slabs is 2-4 inches. Matt, You need to tie the new footing and foundation wall into the existing structure's footing and foundation wall, so yes drill and epoxy the rebar in. Make multiple passes if needed to create a flat, evenly filled area. Labor Costs. 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. For a patio you can use a grid spacing of 24 inches. Sub-slab details (i. For a 4-inch RCC (Reinforced Concrete) slab, using #3 (3/8-inch diameter) or #4 (1/2-inch diameter) rebar is typical. Rebar Spacing. 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.