Rebar is typically calculated at a rate of 1 for every 8 inches of footing width. The reinforcing steel sagged during placement between the support chairs, causing the 3/4-inch spacing to be infringed upon. 4500lb mix with 4-5% air entrainment. longitudinal and transverse. Concrete has great compression strength, but it can crack or br eak under. 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. 5. Concrete strength also comes into play, but most slab concrete is around 3000 to 4000 psi, so it's not a major factor. 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. If the slab is expected to bear heavier loads, such as from heavy vehicles, then larger diameter rebar or closer spacing may be required. If you’re making a slab 4 inches tall, use Grade 40 or Grade 50 rebar. Workmanship and jobsite conditions. The national average cost of a concrete slab is $6. For M15 concrete, lever arm = 0. 5-inch cover to the beam stirrups, dagg = 3⁄4 inch, #3 stirrups used with #4, #5, and #6 longitudinal bars, and #4 stirrups used for #7 and larger longitudinal bars. area = 25′ × 25′. Common Rebar Sizes. The exact spacing for the expansion joints is dependent on the size and design of the slab, and should be determined by a professional engineer familiar. A little more cash now is worth no cracks later but I always overkill. concrete is good in compression but not tension. 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). Methods used for finding slab thickness varies for different types of slabs. 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. If the steel placer is a little sloppy and places the bars at 5-inch spacing. I am confused about the grid. 2. 72 percent. Common size of rebar used for 4 inch slab, it may vary from size. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. Re: rebar dowel size and spacing. 1. 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. The cover required is 2 inches for foundation walls, or walls exposed to. Rebar can be beneficial and provide added strength in a 4” inch slab drive way. Proper and even spacing is also important. Using the rebar tying tool, twist wires around the intersections of the bars. For thin slabs, such as those less than 4 inches thick, the most common size of rebar used is 5/8 inch. For residential slab on grade applications, the minimum spacing of grade 60 #3 or #4 rebar is typically 4 inches on center. If you prefer to calculate the number of bags of concrete needed, you can use the weight of the bags as a reference. The diameter size is given in eighths of an inch. Non-reinforced slabs – where no. 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. 2. You don’t need an 8mm Rebar on your 4” thick slab. A lap is when two pieces of reinforcing bar (rebar) are overlapped to create a continuous line of rebar. Generally, rebar has an immense impact on concrete. 5. Joint spacing in the topping should be coordinated with joint spacing in the base slab. the calculator will give you the default spacing values (for rebar – rebar it’s 40cm, and for edge – grid it’s 8cm). With rebar this thick, a four-inch slab will be more durable and last longer. standard concrete slab reinforcing requirements consist of using #4 bars at 12” spacing, which is adequate for most residential. Drag a straight 2×4 (screed board) across the top of the concrete forms to level the concrete. For example, 4 inches. There are three different sizes of rebar typically used for home construction projects. Spacing of bar supports depends upon the size and placing of the rein-forcing bar being supported. For a 4-inch slab, #3 rebar should be spaced 12 inches apart on center. (This convention begins to break down for bar diameters above #8. thick slab, the maximum joint spacing should be. 33_6_0. 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. 1 in2. We typically advise using at least two pieces of #4 rebar (1/2-inch diameter) placed vertically in an 8-inch-diameter. e. Rebar Chair is a patented polypropylene support system ideal for concrete applications requiring a 6 in. 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. Create contraction joints every 4-6 feet. )(100)/(6 in. 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. Here: Multiply the measurements together to calculate the square footage of the area. I'd go #4 rebar at 18-inch max spacing. Concrete Slab Rebar Spacing Guideline By Terry Smith. 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. 4/1. /18 in. Rebar is recommended on concrete measuring 5 – 6 inches thick. 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. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal. If you do want to increase joint spacing, I recommend looking at Concrete Floor Slabs on Grade Subject to Heavy Loads by the Corps. Rebar is about 15x stronger than concrete in compression, and way more than that in tension. Add one more length to allow for that extra, giving you a total of 18. The overall strength of the structure will decrease by about 35%. 35 to $6. (Rebar Calculation Formula) No. and type of reinforcement bars are crucial to the success of any project. For unbonded topping, the minimum thickness is 75 mm. 4 wire mesh in a 4-inch slab, P = 8. 5 mm) for concrete slab depth ≤12 inch (304. 5 inch line of your patio slab to keep the dowels in the upper portion of the slab. Labor Costs. The general rule of thumb is that control joints should be place no more than 3X the slab thickness (in inches). If the slab is thicker, then re-bar should be used. Rebar Spacing; D2-8F: 4. e. The tolerances on rebar position, as defined by ACI 117, “Tolerances for Concrete Construction and Materials,” are shown in the table. Then, the new slab needs to be left alone. of Main bars = (3000)/150 + 1. 2-1/4 inch rebar high chair is. 668 pounds; Applications: Residential foundations, thin concrete structures, and masonry walls. 6. Reinforcing concrete slabs with rebar is an excellent way to prevent slab failure, as long as the slab is not over 4 inches thick. 60 per square foot for materials and labor. 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. The installation of the rebar is critical for the success of the overall project. 13-4. 5 bars or littler – 1½ inches. Generally speaking, when pouring a 6 inch slab, #4 or #5 rebar is used. However, generally, a 6mm rebar is suitable for a 4 inch slab. 25" 3,000 PSI / 28 Day Aging #6 Rebar: 12 in: D2-10 Models: 4. 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. The grade shall be as specified by the. . This is the formula: mesh needed = slab area ÷ mesh area. The insulation phase is crucial for a radiant floor. 74 sq feet 5000/2. #3 bar = 10. Rebar grid for concrete Slab Foundation. The architect's instructions on the plan are: “New conc slab with #3 transverse bars at 12” O. 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. 16 wire longitudinally and smooth No. For slabs of septic tanks, you usually use #3 and #4 bars. 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. 4 wire mesh in a 4-inch slab, P = 8. Second level 6 inches thick 9 feet tall. Rebar Spacing for Concrete Slab: What is the Correct Rebar Grid Spacing For Concrete Slab? The. So if you have, say a 3/4" max. Rust is visible where some of the bottom bars are at the bottom of the slab, and some rebar ridges are faintly visible. area = 625. buildings and industrial projects) a spacing of 8” to 12” is more. For example, if a 6-inch-thick slab is used with #3 rebar at 18 inches on center, the percentage of steel for a 12-inch width would be: (0. Rebar is recommended on concrete measuring 5 – 6 inches thick. In inches the diameter of a #5 rebar is 5/8″ and that of a #4 rebar is 1/2″. The top surface needs to remain wet while the curing process takes place. 84 m; grid. The plastic chairs are designed for the rebar rods to snap easily into. For a 4-inch slab, #3 rebar should be spaced 12 inches apart on center. And a cross-sectional area of 0. 0 inches use 4 inch Schedule 40 PVC duct and internal joining coupling for 4 inch I. Lay down wire mesh or rebar on top of the sub-base if necessary. A slab with this joint spacing may be reinforced with bars (ASTM A 615, A 616, A 617, or A 706) or WWF (ASTM A 185 or A 497). Most homeowners can expect to pay between $4. 440 2 2. 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. 2)(12 in. For concrete not exposed to weather or in contact with the ground: slabs, walls, and joists – #14 and #18 bars – ½ inch. 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. o Minimum 6 inch thick continuous concrete footings not less than 18 inches wide and reinforced with two continuous #4 rebar rods. Provide Construction Joints (ie, transverse joint) @ 40'-0" intervals if you have a long driveway. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar. to 8 in. I believe the rebar should be 1/4 to 1/3 of the slab thickness from the bottom. That way you can use the forms themselves as a guide for the final base height. For example, a size 4 rebar will have a diameter of 4/8” or ½ inches. Whatever you do, please don’t pour a gigantic slab of concrete with no. 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. 5 inches up to 12 inches. For example, for a one-way solid slab with #5. Place the holes at the 2. 1. Concrete moisture conditions and drying rate. That way you can use the forms themselves as a guide for the final base height. Our calculator will instantly calculate the quantity of rebar required. Conclusion. 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. 2: Repeat and continue to draw complete (closed) shape. However, there is no need to tie the garage slab to the new foundation, and in fact a strong case against doing so. 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. The rated separation for two-family dwellings is 1 hour whether or not a lot line exists between units. If the slab is expected to bear heavier loads, such as from. Calculate the rebar size, spacing, and number: Use the structure’s specifications to determine the rebar size needed for the concrete. construction projects. 34 and $7. 1. The main reinforcement of the slab panel “A” is marked as (1). The standard rebar is Grade 32 and is used for a 3-inch slab. That means placing the wire on chairs to hold it at the correct height (see below). 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. 9_sqrt (Pt), with P representing the percentage of steel required and t representing the thickness of the slab. User note: About this chapter: Chapter 4 provides requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. Moreover, chloride ions from marine salt. Ask Your Own Structural Engineering Question. For footings that are poured before the slab, two #4 horizontal pieces of rebar are required – one 3” from the top and the other 3” from the bottom. 74 equals 1824 lbs per sq feet. 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. 34 inch (8. Our calculator will instantly calculate the quantity of rebar required. 1. For that job, we poured a thick concrete foundation featuring #9 rebar. And the rebar. 375 inches, which is equivalent to 9. Low cement. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. Next, divide the total square footage by the size of the rebar. 9 3 in. 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. 65*6) = 1. Stocked in half inch increments between 6. 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. To truly reinforce concrete, the percentage has to. 33 inches. (see below for more information on contraction joints)Second, most designs require’spacing rebar’ of two inches. Many other styles of supports are available and effective. 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. 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. Do you need rebar for 6 inch slab? Rebar is recommended for. 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. But if you feel that the slab is in a sensitive position and extra protection is needed, you can add rebar to it. A 6" slab is quite minimal for most bridge deck applications. 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. 3. 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,. 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. The 6mm rebar should be arranged in a grid pattern, spacing out the rebar at 6 to 12 inches. C. I’d probably recommend good old fashioned #4 metal bar on a 2’ grid. surface. 10” or so around the edge and 4” everywhere else. 37 cubic yards of concrete for a 4×4 slab that is 4 inches thick. Down here in gator country my architect would typically prescribe: drill and epoxy 36" #5s 24" o. The #3 rebar has a weight per length of 0. Concrete slabs-on-ground shall contain micro- or macro-synthetic fiber reinforcement. 4. Common practice is to place supports 2 to 3 feet apart. 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%. However, depending on the intended purpose of. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. This translates to roughly 5/8 inch rebar and must be spaced equally along the slab to create a proper grid. To calculate Total Area of a multi sided slab, first divide the shape into rectangles or squares. A concrete slab costs between $4. 8" - 3/4" (top cover) - 2" (4-#4 bars) - 3" (bottom. 72 percent. It’s best to check with a. On top of that form up a thickened edge slab. 6 feet is equal to 72 inches, which is divided by 12 to get the 6. 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. 15 per cent of the gross sectional area. #4 Rebar ; The #4 rebar is often used in residential and commercial projects to add strength in slabs and columns. 59 per square foot. 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. A. (Video) Rebar Spacing, Made Easy (DesignBuildDoug). If you have expansive soil or a significant frost depth, #4 rebar at no more than 12 inches on center is a good choice. 2 mm in diameter. If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h, 18 inches, l w /3. 34 inch (8. The plastic chairs are designed for the rebar rods to snap easily into. For columns and beams, the minimum spacing should be 6 inches. 8 mm) ±1/2 inch (±12. No, you do not need rebar for a 4-inch slab of concrete on grade. A good compacted base below the concrete is equally important. 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. spacings: #4 bar = 27. The Rebar calculator for slab is best to find the Rebar size. Add rebar for reinforcement, Ralston places rebar every 16” on center. When overlapping rebar, the length of the overlap should be at least 40 bar diameters. 3. Check for level on all sides. 75-in x 1. See STRIPS. Works with all sizes of rebar. Can I pour concrete directly on dirt?Placing 0. Generally, for a 4-inch slab, a #4 rebar is usually recommended due to its versatility and strength. diameter. The spacing and quantity of the rebar will depend on factors such as the load the slab needs to support and local building codes. Suggested applications - concrete slabs, precast, tilt-up, bridge deck, and other heavy applications. Rebar Spacing. 7. The spacing of the rebar is also determined by the weight and size of the slab. 11. 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. For example, a size 4 rebar will have a diameter of 4/8” or ½ inches. ±3/8 inch (±9. Prices for your concrete slab will vary. Every concrete slab should have a minimum. BAND—Group of reinforcing bars distributed in a slab or wall or footing. 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. For example, if both slabs have rebar mats that are spaced at 18 inches and use No. 5. #6 bars and larger – 2 inches #5 bars or smaller – 1½ inches. When you build a 4-inch slab, you’ll need a higher grade of rebar. For example, if you’re calculating rebar for a slab, input the slab dimensions, reinforcement spacing, and desired rebar size. So for example if you take a 6 inch slab times 2 is twelve feet or times 3 is 18. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. 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. Why Rebar Spacing is Crucial. 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. 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. Rebar Spacing for Concrete Slab. 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. Slabs, walls, and joists –. Regardless of beam spacing, the top mat must be tied to the forms or the bottom reinforcing mat at 4 foot spacing. 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. To increase the structural integrity of your slab, use 2 layers of rebar with the spacing staggered in the second layer. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. What size rebar do I need for a 4 inch slab? You will need a #3 rebar for a 4-inch slab. a car weight about 5000lb. For the slab's longer dimension, you'll need 360 inches divided by 14, which gives you 25 plus a bit left over. 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. Use a metal-cutting blade or disc in a reciprocating saw, circular saw or grinder to cut the rebar. Read more on low-shrinkage concrete mixes in the Concrete Mix Design section. Great for use when pouring concrete slabs. Others say rebar in the middle is a waste. approximately the bar diameter in eighths of an inch [whole millimeters], used to designate the reinforcing bar size. Per ACI 332. No, you do not need rebar for a 4-inch slab of concrete on grade. #4 rebar is perfect for adding strength to highways and can give columns and slabs. Add one more length to allow for that extra, giving you a total of 18. Advertise Here. Acorn International 2. Slabs for hot tubs generally are 8 feet by 8 feet. 12% for HYSD bars and 0. In that case, a 4-inch slab of higher strength concrete could typically support upwards of 15,000 PSF. 34 and $7. Content intended for mature audiences. A six inch slab can handle some thin spots - a 4" slab can't. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. The process for putting rebar in concrete is relatively straightforward. INSTRUCTIONS: Choose units and enter the following: ( L) Length of the slab. So if you have, say a 3/4" max. This illustrates a common problem for the concre t e s u b c o n t ra c t o r : How do you place a l e v el slab of uniform thickness ove r steel beams that can va r y in eleva-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: SC, ML-CL and inorganic CL soils 60: 6 feet 8 inches: 4 feet (or less) #4 at 48 #4 at 48 #4 at 48: 5 feet #4 at 48 #4 at 48 #4 at 48: 6 feet 8 inches #4 at. For patios, a grid spacing of 24 inches is. ±3/8 inch (±9. For example, if a 6-inch-thick slab is used with #3 rebar at 18 inches on center, the percentage of steel for a 12-inch width would be: For enough reinforcing to accomplish. 5 to determine you will need 120 feet of rebar. For example, if the percentage is 0. Our plastic rebar support “High Chairs” range in size from 3” to 14” in height. For slabs. The Engineer shows a 4″ Slab 3500psi with 6×6-W1. 7. 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. Space the joints no more than 2-3 times (in feet) of the slab’s thickness (in inches). A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. 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. 25" 3,000 PSI / 28 Day Aging #6 Rebar: 12 in:. The spacing of the rebar is typically 12” on center for most residential applications. 6 rebar spaced 4 inches on center is P = 8. The appropriate rebar spacing for most of the slabbing is 12-inches. The 2021 IRC® contains many important changes such as: Braced wall lines must be placed on a physical wall or placed between multiple walls. Most reinforcing bars bearing a Metric diameter mark Now, divide each measurement by the 14-inch spacing. This video series w. Similarly, rebar with a size 15 will be 15/8. For example, if both slabs have rebar mats that are spaced at 18 inches and use No. 2. Horizontal rebar starting at 12 inches and at 18 inch intervals after to the top. However, clause 9. For building footings I would use a #5 (5/8 inch) rebar. Nathaniel P. Generally, you do not need rebar for a 4-inch slab. Tie in the Rebar to Strengthen the Slab. 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. 78 kg/m 3) in accordance with the manufacturer’s recommendations. To use our rebar calculator, simply input the dimensions and specifications of your project. 2. 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. 78. 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. To truly reinforce concrete, the percentage. Concrete Slab Rebar Spacing Guideline. 4 m) 6 inches (15. 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. Raise the form sides 1/2-inch to create a slab that is a full 4 inches thick. 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. 5” to 12”. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. If your concrete will be stamped, ask about the best ways to avoid interrupting the pattern.