Having more bar would only increase the strength of the slab, as long as. For a patio you can use a grid spacing of 24 inches. However, many engineers and. If the steel placer is a little sloppy and places the bars at 5-inch spacing. Common Rebar Sizes. (Rebar Calculation Formula) No. Placing WWR in Two-Course WorkGenerally, a #4 (1/2-inch diameter) or #5 (5/8-inch diameter) rebar should be sufficient for most residential and commercial applications over a 6-inch slab. of Main bars = 20 + 1 = 21 Nos. Use a metal-cutting blade or disc in a reciprocating saw, circular saw or grinder to cut the rebar. the calculator will give you the default spacing values (for rebar – rebar it’s 40cm, and for edge – grid it’s 8cm). I was thinking of going with the same 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. Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. 0 pounds per cubic yard (0. Most masons just round up to 5 inches. This will be based on the loads and desired strength of the concrete. Beams and columns: 1½ inches. The spacing of the rebar is typically 12” on center for most residential applications. 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. Cover the fill with a layer of 6-mm plastic sheeting. 4 x Modulus of Rupture fs = allowable working stress of the reinforcement (psi) T =range of temperature the slab is expected to be subjected to (F o) Stretch a string between two screws installed at the edge of both ends of the form boards. Per ACI 332. Rebar is recommended on concrete measuring 5 – 6 inches thick. Reading time: 4 minutes. Second level 6 inches thick 9 feet tall. The 2021 IRC® contains many important changes such as: Braced wall lines must be placed on a physical wall or placed between multiple walls. 33 inches. The same slab without mesh can hold up to 25,400 lbs. construction projects. For flat slabs, grid spacing of 18 inches for driveways and 24 inches for patios is recommended. For a. An 8-inch slab or thicker is required for CJ’s spaced up to 20 feet. Minimum vertical rebar for 6" flat wall foundations is 4@48" on center 3. 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. Fiber length shall be 1 / 2 inch to 2. 5. 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. #4 is 4/8”, or 1/2”. These rebar chairs, also known as rebar stands, are extremely versatile. in thickness, columns, walls, and parapets. 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. Adequacy of curing. Check for level on all sides. As per the present market rates, the average cost of concrete for a 400-square foot slab, the typical size for a two-car garage, ranges between $583 and $637 or between $1. Four legs allow easy placements of multiple layers of steel. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. For distribution bars the maximum spacing is specified as 5 times the effective depth or 450 mm whichever is less. To form consistent, parallel sides for a curved sidewalk, build one side first. User note: About this chapter: Chapter 4 provides requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. 6, Figure R404. The string will act as a guide to keep the form boards straight. The plastic chairs are designed for the rebar rods to snap easily into. (This convention begins to break down for bar diameters above #8. The thickness of rebar should be no more than 1/8 that of the slab, so a 4” slab shouldn’t have steel greater than #4 or 1/2″ bar. First, find the area of the slab. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar construction and traditional tape measurement results. To find the exact size of the slab by slab Rebar calculator. 1%. Position a rebar grid or 4. 2(1) shall be air entrained as specified in Table R402. 33_6_0. 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. Secure your rebar in place when pouring concrete with our Plastic Rebar Chairs. Most homeowners can expect to pay between $4. Anchors are located a minimum of 13/4 inches (45 mm) from the edge of the concrete parallel to the length of the track. 2(a) and 3-6. 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. First, Get The Number Of Required Bars. There are three different sizes of rebar typically used for home construction projects. 5 bars or littler – 1½ inches. Spacing of bar supports depends upon the size and placing of the rein-forcing bar being supported. For commercial loaded slabs I go 3000 psi minimum, and usually 4000 psi. Rebar Spacing. However, for thicker slabs, such as those between 4 and 8 inches thick, 3/4 inch rebar is usually used. Column spacings are 48 feet center to center. With 3-inch screws, attach the two-by-fours to the stakes: A 12-foot two-by-four on each short side. A little more cash now is worth no cracks later but I always overkill. d. You can't get that in a four inch slab. Anyhow, the rebar chairs are relatively cheap. 561 kg/m. ,). 9_sqrt (Pt), with P representing the percentage of steel required and t representing the thickness of the slab. How to install rebar in slab footings: To install rebar in slab footings, follow these steps: Its rebar size in inches is 0. anchor bolts and the 4 inches (102 mm) φ pipes. Rebar Spacing. Rebar should be placed evenly throughout the project. 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). 43/30 = 0. 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. If your concrete will be stamped, ask about the best ways to avoid interrupting the pattern. Set the forms at the proper height before bringing in the last lift. 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. 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 thickness. 24-foot joint spacing. 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, if both slabs have rebar mats that are spaced at 18 inches and use No. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. ACI 360R-10 (ACI 360), as referenced by ACI 318, as referenced by IBC, includes Figure 6. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. 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. 6 rebar spaced 4 inches on center is P = 8. Highway bridgework may require more stringent. The ends of the bars should be two or three inches from the sides of the form to protect the rebar from the elements. You can use regular fencing material with 2' x 4' or 2' x 6' mesh. Tie in the Rebar to Strengthen the Slab. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. For a 4-inch concrete slab-on-ground, this would be equivalent to #4 rebar spaced at 10 inches each way. Ask Your Own Structural Engineering Question. Every concrete slab should have a minimum. Leave a few inches of space between the mesh and the edges of the forms to prevent rust. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. 4 wire mesh, I would like to use rebar in place of the wire mesh as in my experience wire mesh usually ends up in the bottom of the slab, I also do not think a 4″ slab is enough for a shop that will have 80,000lb trucks in it. The appropriate rebar size depends on the project, with #3 and #4 being common choices. Many other styles of supports are available and effective. 4. 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. Great for use when pouring concrete slabs. 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. C. To find the exact size of the slab by slab Rebar calculator. spacings: #4 bar = 27. 1. 1. 6 x 6 8/8 minimum reinforcing. The gauge, or diameter, of the rebar is selected based on the purpose and the load-bearing requirements of the structure: For standard residential concrete slabs, #3 (3/8 inch diameter) to #5 (5/8 inch diameter) rebar is typically used. 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. Likewise, the top reinforcing mat is to be tied to the bottom reinforcing mat on a 4 foot grid in floors of concrete slab bridges. Joint spacing in the topping should be coordinated with joint spacing in the base slab. The reinforcing steel sagged during placement between the support chairs, causing the 3/4-inch spacing to be infringed upon. Second, most designs require’spacing rebar’ of two inches. 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 *1. Concrete rebar calculator plan view diagram. 78. 668 pounds; Applications: Residential foundations, thin concrete structures, and masonry walls. For a 6" thick slab with GR60 bar per the ACI318 I get the following max. 7 mm). Whatever you do, please don’t pour a gigantic slab of concrete with no. 1. 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. No, you do not need rebar for a 4-inch slab of concrete on grade. The 6mm rebar should be arranged in a grid pattern, spacing out the rebar at 6 to 12 inches. Tables indicate foundation walls reinforcement supporting concrete above grade walls 5. 13-4. 1. I've only ever called out a single layer in a 8" s-o-g. For 0. 74 sq feet 5000/2. 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. Tables are for 2500 psi concrete and Grade 60,000 psi rebar 4. On average, a 60-pound bag of concrete covers about 0. The bar size in English units is roughly its diameter, in eights of an inch: a #8 bar has a one inch diameter. Do you need rebar for 6 inch slab? Rebar is recommended for. A 4" slab should have joints 8-12 feet apart. Prices for your concrete slab will vary significantly depending on many factors, including the slab’s thickness, concrete type, and size. 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. Concrete Thickness. The main reinforcement of the slab panel “A” is marked as (1). Proper and even spacing is also important. Horizontal rebar starting at 12 inches and at 18 inch intervals after to the top. vapor retarders - some times referred to as vapor barriers, insulation, etc. 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). 26 inches (18" controls) #3 bar = 15. Space joints (in feet) no more than 2-3 times the slab thickness (in inches). Rebar Spacing for Concrete Slab: What is the Correct Rebar Grid Spacing For Concrete Slab? The. 2: Repeat and continue to draw complete (closed) shape. 0 inches use 4 inch Schedule 40 PVC duct and internal joining coupling for 4 inch I. (UBC), may require the use of rebar in 4-inch concrete slabs. This means 2x 3/8 inch rebar makes 3/4 inch of steel. And rebar is sized by eights of an inch. of Engineers (Army TM 5-809-12) that you can download for free from thier website. 1 in2. 2(1) requires that half the calculated span. 6 feet is equal to 72 inches, which is divided by 12 to get the 6. 75-in x 1. Concrete doesn't dry out; it undergoes a chemical curing process that creates a dry, solid mass. 34 inch (8. 35 to $6. For a 4" slab on grade house, what would you say about #3 vs #4 rebar, and the spacing? I was going to do #4 at 12" - Answered by a verified Structural Engineer. The appropriate rebar spacing for most of the slabbing is 12-inches. 33_2_0. See STRIPS. The spacing will depend upon the wire size and the wire spacing. That means placing the wire on chairs to hold it at the correct height (see below). Excavate the perimeter 1 foot deep and 1 foot wide to form a deeper trench around the excavated area. A. New concrete slabs must conform to the above. 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. However, clause 9. 4. Concrete Slab Rebar Spacing Guideline By Terry Smith. For the short side, 240 inches divided by 14 inches gives you 17 lengths of 20-foot rebar plus a bit left over. the calculator will give you the default spacing values (for rebar – rebar it’s 40cm, and for edge – grid it’s 8cm). 25" 3,000 PSI / 28 Day Aging #6 Rebar: 12 in: D2-10 Models: 4. To find the Bar Bending Schedule for Slab we use the following formula, No. This type of rebar is typically 6mm in diameter and can span up to 24. approximately the bar diameter in eighths of an inch [whole millimeters], used to designate the reinforcing bar size. Increasing the thickness from 4 inches to 5 inches will add approximately 20% to your concrete cost, but will also boost your. For flat slabs like driveways and patios, spacing is roughly 18″ to 24″. Does a 4-inch slab need rebar? By: Olin Wade (Remodel or Move Stuff) Watch This Video To Learn More About Using or Not Using Rebar For Concrete Driveway Watch on It. The formula is, Number of bars = (length ÷ spacing) + 1. Placement of Rebars. The appropriate rebar spacing for most of the slabbing is 12-inches. Once you input these values, you will have your grid length dimensions, it’s that easy. (i) The maximum spacing between two parallel main reinforcing bars shall be 3dor 300mm or whichever is less, and. e. 59 per square foot. What size rebar do I need for a 4 inch slab? You will need a #3 rebar for a 4-inch slab. With rebar this thick, a four-inch slab will be more durable and last longer. 10. 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. 75-in 500-Pack Polypropylene Rebar Chair. The architect's instructions on the plan are: “New conc slab with #3 transverse bars at 12” O. 4xW1. 2. ±3/8 inch (±9. Generally, rebar spacing in slab footings ranges from 12 to 24 inches, both for horizontal and vertical bars. Having more bar would only increase the strength of the slab, as long as. For patios, a grid spacing of 24 inches is. rebar strength is in tension, so by adding rebar to BOTTOM of foundation, it counter acts the load of compression. 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. Slabs for septic tanks may require the use. 33 ft). Then, the new slab needs to be left alone. The diameter of bar generally used in slabs are: 6 mm, 8 mm, 10 mm, 12mm and 16mm. #5 bars are 5/8”. 65 and the thickness of the slab is 6 inches, M = 0. Convert your longitude measurement into inches: 15 x 12 = 180. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. Generally, #4 rebar (1/2 inch in diameter) is the most common size used for slab on grade applications. 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. For example, if the percentage is 0. With our rebar calculator, you can eliminate. A. slabs, walls, and joists - #14 and #18 bars - ½ inch; Slabs, walls, and joists - #11 bars and smaller - ¾ inch ; Beams and columns - 1½ inches ; 2. 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. Above 12 1/4” they have a single cover height per chair. Our plastic rebar support “High Chairs” range in size from 3” to 14” in height. Another beam might have a 11⁄ 2-or 2-inch camber. 014/4 = 0. Here: Multiply the measurements together to calculate the square footage of the area. Use a groover to cut grooves about 25% into the depth of the concrete. The spacing of the rebar is typically 12” on center for most residential applications. If the steel placer is a little sloppy and places the bars at 5-inch spacing rather than 4-inch spacing, the product's strength will be reduced by 20%. a car weight about 5000lb. I was thinking of the following: basement wall 8 inches thick 10 feet high backfilled up to 7 to 8 feet. Rebar Spacing for Concrete Slab. These rebar chairs are so strong, you can step on them and they. B3030. You’ll pay about $1,200 for a 6-inch slab that measures 10 inches by 20 inches. Shafts and segments – 1½ inches. D. If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h, 18 inches, l w /3. 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. 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. 5” to 12”. Create contraction joints every 4-6 feet. These new concrete slabs are designed as " s tand alone " and do not take. 1% reinforcement in a 4-inch thick slab is #3 bars in both directions at 24-inches. The important part is the use of support to achieve proper placement within the slab. Place the holes at the 2. 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. In general, you’ll want a slab that is at least 4 inches thick, but 6-8 inches is even better. slab, including floors, sidewalks, driveways and many others. My driveway is 4 inch thick concrete. spacings: #4 bar = 27. If the slab is thicker, then re-bar should be used. 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. Its rebar size in inches is 0. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. Slabs, walls, and joists: #11 bars and smaller: ¾ inch. 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. 3. Most residential slabs contain reinforcement of less than 0. For a patio you can use a grid spacing of 24 inches. Stocked in half inch increments between 6. It has a foot print of four tires about 10 inches by 10 inches time 4. Rebar is about 15x stronger than concrete in compression, and way more than that in tension. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is. For flat slabs like driveways, a grid spacing of 18 inches is recommended, with the edge rebar placed at the same distance from each side. This video shows different aspects of selecting rebars for a driveway:. What size rebar for 4 inch slab. To find the exact size of the slab by slab Rebar calculator. Spacing of bar supports depends upon the size of the. So if you have, say a 3/4" max. Calculates approximate Rebar Length from total slab area and perimeter. 5 inches of spacing (18" + 1/2" diameter of the rebar). 65*6) = 1. 5 mm) for concrete slab depth ≤12 inch (304. Rebar Spacing; D2-8F: 4. Emergency escape and rescue openings require a clear 36-inch-wide path to a public way. What should be the size rebar for a 4-inch slab?. spacings: #4 bar = 18. How do you calculate rebar spacing? Find the rebar-to-spacing multiplier with the formula M = 0. Step 2 - Twist the Wire Pieces. The general rule of thumb is that control joints should be place no more than 3X the slab thickness (in inches). 5 (1), or as specified by engineered design accepted by the building official. 5. _____ Bar Supports Bar supports are required in a number of locations on bridges. 561 kg/m. 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. The spacing and quantity of the rebar will depend on factors such as the load the slab needs to support and local building codes. Rebar being #4 grade 60. Reinforcement for Slab. The plastic chairs are designed for the rebar rods to snap easily into. The grade shall be as specified by the. In slabs with an average thickness of less than 6 inches, the spacing should be. Concrete shall have a minimum specified compressive strength of ƒ' c, as shown in Table R402. 65 and the thickness of the slab is 6 inches, M = 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. Rebar is recommended on concrete measuring 5 – 6 inches thick. ±3/8 inch (±9. For example, if the area is 10 feet long and 6 feet wide, the square footage is 60 feet. The tensile strength of concrete is typically taken as 10 to 15% of the compressive strength, so only about 400 or 500 psi. For thin slabs, such as those less than 4 inches thick, the most common size of rebar used is 5/8 inch. 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. 1. In that case, a layer of rebar near the bottom or at. For a 6 in. In addition to a foundation's ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. Tractor. The grade shall be as specified by the. 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. Generally speaking, a 4-inch slab of normal weight concrete (145-165 pounds per cubic foot) with a 28-day compressive strength of at least. rebar spacing in a slab Shakesplitter | Posted in Construction Techniques on January 5, 2006 09:50am I was wondering if there were any rules of thumb for the. Great for use when pouring concrete slabs. Labor Costs. ( D) Depth of slab. 2 mm in diameter. By understanding these basic. 1: Post holes for pole buildings: 1For 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. 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. 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. And a cross-sectional area of 0. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Ridges in the surface of the rebar allow the concrete to adhere to it and create one solid structure. For a 4 inches slab, rebar is not necessary. Generally, it is recommended to have at least the. Generally speaking, a. 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. 73 per square foot, with an average cost of $6. Determine the amount of rebar needed for the footings. However, the stone has been compacted to the top of the rails, which corresponds to only 2. 75-in 500-Pack Polypropylene Rebar Chair. 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. The gauge, or diameter, of the rebar is selected based on the purpose and the load-bearing requirements of the structure: For standard residential concrete slabs,. 2. Tie in the Rebar to Strengthen the Slab. For example, if both slabs have rebar mats that are spaced at 18 inches and use No. The size of the rebar depends on the specific project, with #3 rebar suitable for driveways and patios, and #4 rebar recommended for walls, piers, or columns. 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). Wilkerson, PE. Average: Rebar in Concrete Slab Estimator. 11. 5x the maximum aggregate size. Add 5%-10% additional material for some waste or spills. Divide your result by the spacing measurement: 180 / 14 = 12. Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. This spacing will provide the maximum reinforcement of the. We would like to show you a description here but the site won’t allow us. Run twine between the stakes. For a slab this thin you would use wire mesh instead. 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. 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. First, you need to consider the size of the rebar and the spacing between them. Cover the fill with a layer of 6-mm plastic sheeting. The installation of the rebar is critical for the success of the overall project. A confused student is a good student. 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. 23 inches For a 4" thick slab with GR60 bars I get the following max. spacing and 12-in. I am filling a 12 ft x 12 ft sunken lounge are with 12" of Geofoam as filler and a 4" concrete slab. 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. o Minimum 3-1/2 inch thick continuous concrete slab footings not less than 48 inches and reinforced with approved fibers, or with 10 gage 6 inch x 6 inch wire fabric. Contact splices. Q: Can rebar rust in concrete? A: Rebar can rust in concrete if it is exposed due to cracking or delamination. For example, a size 3 rod has a diameter of 3/8-inch. 1: Calculate The Main bars. It is essential to check local codes and regulations before starting any construction project. 1 in2. 4m2. Set the forms at the proper height before bringing in the last lift. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Suggested applications - concrete slabs, precast, tilt-up, bridge deck, and other heavy applications. If the slab is more than 24 inches thick, #5 (#5/8 inch diameter) rebar may be required. 6 bars and bigger – 2 inches. Second level 6 inches thick 9 feet tall. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. Rebar counteract this force. You don’t need an 8mm Rebar on your 4” thick slab. 9_sqrt (0.