Content intended for mature audiences. 5 inches up to 12 inches. We followed all of those and 2 years later we're glad we did!1. Per ACI 332. Pour footings and wall. Nathaniel P. For example, a size 4 rebar will have a diameter of 4/8” or ½ 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. Thickness of concrete slab depends on loads and size of the slab. 6 feet is equal to 72 inches, which is divided by 12 to get the 6. Rebar Spacing OC + Waste / OverlapWith this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). 9. View More. For beams and walls, the spacing should be closer and is usually 3-4 inches apart. Minimum sub-base (stone) under slab shall be 4 inches for both Table 1 and Table 2. 4. Thread starter matt_isserstedt; Start date Feb 18, 2015; Replies 30 Views 72,127 1; 2;. The rebar should form a neat grid. 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). 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. We would like to show you a description here but the site won’t allow us. 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. Spacing of bar supports depends upon the size and placing of the rein-forcing bar being supported. 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. Concrete shall have a minimum specified compressive strength of ƒ' c, as shown in Table R402. A typical concrete slab costs $4 to $8 per square foot with most homeowners spending between $5. Place the holes at the 2. The national average cost of a concrete slab is $6. For example, if the engineer calls for rebar spaced every 4 inches, you need to place three bars for every 12 inches of the form. For a 4-inch RCC (Reinforced Concrete) slab, using #3 (3/8-inch diameter) or #4 (1/2-inch diameter) rebar is typical. If you prefer to calculate the number of bags of concrete needed, you can use the weight of the bags as a reference. 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. For foundations that are taller than 8 feet and slabs thicker than 8 inches, the minimum spacing should range from 7. 1 in2. 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. 5 mm) for concrete slab depth ≤12 inch (304. Generally, one stick of rebar per 8 inches of footing width will suffice. 9_sqrt (Pt), with P representing the percentage of steel required and t representing the thickness of the slab. Here’s a complete chart of different rebar sizes, their diameters, and weight: Rebar markings. Concrete slabs-on-ground shall contain micro- or macro-synthetic fiber reinforcement. Concrete Thickness. Determine the rebar gauge. 75-in 500-Pack Polypropylene Rebar Chair. 65 and the thickness of the slab is 6 inches, M = 0. 7 mm) anchor bolts spaced a maximum of 6 feet (1829 mm) on center or approved anchors or anchor straps. The size of the rebar depends on the specific application, but typically #4, #5, #6, and #8 rebar are used. So for example if you take a 6 inch slab times 2 is twelve feet or times 3 is 18. 440 3. These new concrete slabs are designed as " s tand alone " and do not take. First, Get The Number Of Required Bars. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is less. Prices for your concrete slab will vary significantly depending on many factors, including the slab’s thickness, concrete type, and size. Stocked in half inch increments between 6. 5x the maximum aggregate size. 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. d. Do you need rebar for 4 inch slab? No, you do not need rebar for a 4 – inch slab of concrete on grade. Anchors are embedded into concrete a minimum of 7 inches (178 mm). Concrete rebar calculator plan view diagram. 2. Sawcut Joints. When a=4. 1: Calculate The Main bars. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar construction and traditional tape measurement results. Rebar spacing in a slab footer will depend on the size of the slab, the load it will support, and local codes. 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. 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. I like to use a #3 (3/8 inch) piece of deformed rebar, 18 inches long. The architect's instructions on the plan are: “New conc slab with #3 transverse bars at 12” O. Anchorage shall be in accordance with Section R403. This spacing will provide the maximum reinforcement of the. 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). To get the rebar in the bottom 1/3rd of the slab, a 1" chair would been perfect for a 4" slab, a 2" would be good for a 6" Slab, and a 3" for something crazy thick like 8"+. Rebar is recommended on concrete measuring 5 – 6 inches thick. Use a metal-cutting blade or disc in a reciprocating saw, circular saw or grinder to cut the rebar. Generally speaking, a. 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. For a patio you can use a grid spacing of 24 inches. (For example, 0. Rebar being #4 grade 60. 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. 5000 PSI concrete can safely support 5000 pounds per square inch (PSI) minimum before its compressive strength is overcome. 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. 11. Retaining Walls: The most commonly used. a car weight about 5000lb. Concrete doesn't dry out; it undergoes a chemical curing process that creates a dry, solid mass. H3: #8 Rebar (8 rebar size). For a 6" thick slab with GR60 bar per the ACI318 I get the following max. apart. For residential slab on grade applications, the minimum spacing of grade 60 #3 or #4 rebar is typically 4 inches on center. First, Get The Number Of Required Bars. spacings: #4 bar = 18. Do you need rebar for 4 inch slab? No, you do not need rebar for a 4 – inch slab of concrete on grade. The spacing of the rebar should increase to between 18 and 24 inches apart for slabs between four and six inches thick. 59 per square foot. On average are required, for 10 square meter with 12cm thick slab, 19 strips of 3/8” rods (9ml each one), are 171 ml. Concrete reinforcement can be either wire mesh or ½-inch (#4) steel rebar. 10% reinforcing, the slab joint spacing should be the same as for an un-reinforced slab. The Rebar calculator for slab is best to find the Rebar size. 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 main reinforcement of the slab panel “A” is marked as (1). For that job, we poured a thick concrete foundation featuring #9 rebar. The spacing of the rebar is also determined by the weight and size of the slab. 2. Tie two bands of 1/2-inch steel reinforcing rods (rebar) to stakes set about four inches from the perimeter of the forms. Methods used for finding slab thickness varies for different types of slabs. aggregate, you'd need 1. It has stood up to some really heavy equipment for 25 years. 2: Repeat and continue to draw complete (closed) shape. For a 4-inch concrete slab-on-ground, this would be equivalent to #4 rebar spaced at 10 inches each way. For the slab's longer dimension, you'll need 360 inches divided by 14, which gives you 25 plus a bit left over. For larger slabs, cut control joints into the surface to accommodate shrinkage and changes in temperature. 2-1/4 inch rebar high chair is designed to hold rebar in place during concrete applications. 23 inches For a 4" thick slab with GR60 bars I get the following max. 25" 3,000 PSI / 28 Day Aging #6 Rebar: 12 in: D2-10 Models: 4. If the wall exceeds four feet in height, footings should be poured separately. 4xW1. Step 5 – Place the Mesh. I will drill with a hammer drill and a 3/8 bit through the expansion material and into the existing slab about 6 inches. To form consistent, parallel sides for a curved sidewalk, build one side first. Table 1-Minimum Shrinkage and Temperature Reinforcement steel for non-SES floors or SES floors with a secondary liner. 5 inch line of your patio slab to keep the dowels in the upper portion of the slab. Slabs, walls, and joists: #11 bars and smaller: ¾ inch. transverse wire spacing with smooth No. Ridges in the surface of the rebar allow the concrete to adhere to it and create one solid structure. Rule of thumb is to have the minimum clear spacing between bars be 1. 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. 1%. 5 inches of spacing (18" + 1/2" diameter of the rebar). 26 inches (18" controls) #3 bar = 15. 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. 7 mm). See Figures 3-6. 4 m) 6 inches (15. Convert your longitude measurement into inches: 15 x 12 = 180. The plastic chairs are designed for the rebar rods to snap easily into. Generally, for a standard residential foundation, the minimum spacing between rebar should be at least 4 inches. 08 cubic yards for one concrete tube; Multiply 0. 4. I'd go #4 rebar at 18-inch max spacing. Have a helper add or remove concrete in. Others say rebar in the middle is a waste. 3 Joints in Unbonded Topping Slab. The evaluation of rebar spacing results shows that the maximum standard deviation for rebar spacing is 0. 2(1) requires that half the calculated span. 33_2_0. However, many engineers and contractors use a rule of thumb of keeping the rebar spacing to 2 – 3 times the. 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. However, it is better if 10mm or 12mm diarebar can be used with spacing of 100-125mm (4-5’’) between rebar. 8 wire transversely). A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is. If shear reinforcement is required for in-plane strength, s shall not exceed the smallest of 3h, 18 inches, l w /3. 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. This video series w. surface. inches thick and about 4 x 4 inches square. Use 2” rebar chairs to support the rebar in the center strata of the pad. Place concrete at a minimum thickness of 4 inches. 65*6) = 1. 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. The appropriate rebar size depends on the project, with #3 and #4 being common choices. These rebar chairs, also known as rebar stands, are extremely versatile. It create a bending of the slab. Provide Construction Joints (ie, transverse joint) @ 40'-0" intervals if you have a long driveway. The #3 rebar has a weight per length of 0. If the slab is expected to bear heavier loads, such as from heavy vehicles, then larger diameter rebar or closer spacing may be required. 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. To increase the structural integrity of your slab, use 2 layers of rebar with the spacing staggered in the second layer. 11 in. When arranging joints, skilled contractors will often use them to create an attractive diamond pattern. Wow, everyone is all over the board with the spacing on the rebar. 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. Run twine between the stakes. Provide minimum vertical reinforcement of one No. The plastic chairs are designed for the rebar rods to snap easily into. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not. How to calculate the rebar quantity from concrete? Convert your longitude estimation into inches: 15 x 12 = 180. 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 few rules of thumb for control joints: Space them 2 to 3 times in feet the thickness of the slab in inches (4" slab = 8' to 12' max); Joints should create nearly square sections; joints should be struck or sawn to a depth of 1/4 the slab thickness; Sawn joints need to be cut before shrinkage cracks occur, no more than 12 hours. Slabs, walls, and joists: #14 and #18 bars: ½ inch. For a patio you can use a grid spacing of 24 inches. Plan out your control joint spacing 24-36 times. ( D) Depth of slab. 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. 16 wire longitudinally and smooth No. To use our rebar calculator, simply input the dimensions and specifications of your project. If the slab is 4 inches or less than it should not be reinforced. 2(a) and 3-6. Lay out and dig the footings. Legs on other types of. This will provide adequate reinforcement for most applications. It’s crucial to ensure that welded wire mesh be placed on chairs of the proper height. The rated separation for two-family dwellings is 1 hour whether or not a lot line exists between units. 5. As well as that, the calculator will also tell you. Spacing of bar supports depends upon the size of the reinforcing bar being supported. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. The dowels will then be embedded in the ICF wall concrete. In other words, for a 4-inch slab, space the joints 8 to 12 feet apart. For example, for a one-way solid slab with #5. The same slab without mesh can hold up to 25,400 lbs. Add rebar for reinforcement, Ralston places rebar every 16” on center. I was thinking of going with the same spacing. It has a procedure for using rebar to reduce slab thickness, and if I remember right for increasing joint spacing. The size of the rebar depends on the specific application, but typically #4, #5, #6, and #8 rebar are used. 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. 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. construction projects. For example, 4 inches. Finally, reinforcing mesh can replace bars if needed, but it must be spaced according to manufacturer’s guidelines. No, you do not need rebar for a 4-inch slab of concrete on grade. Step 1: – Calculate numbers of distribution rods. 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. It's not a problem to get two layers in on an interior 8" elevated slab where the bottom cover is 3/4". You don’t need an 8mm Rebar on your 4” thick slab. Tie two bands of 1/2-inch steel reinforcing rods (rebar) to stakes set about four inches from the perimeter of the forms. Reinforcing concrete slabs with rebar is an excellent way to prevent slab failure, as long as the slab is not over 4 inches thick. Common size of rebar used for 4 inch slab, it may vary from size. Rebar should be placed evenly throughout the project. 2 only if the steel reinforcing is greater than 0. 2. slabs are actually the 3-1/2-in. Rebar is about 15x stronger than concrete in compression, and way more than that in tension. For unbonded topping, the minimum thickness is 75 mm. Q: Can rebar rust in concrete? A: Rebar can rust in concrete if it is exposed due to cracking or delamination. A confused student is a good student. 16000 lbs divided by 144 is 111 pounds per square inch. In either case, blocks should be used under the reinforcement to keep centered. 1 in2. depth of standard 2x4s. In general, you’ll want a slab that is at least 4 inches thick, but 6-8 inches is even better. 1. Emergency escape and rescue openings require a clear 36-inch-wide path to a public way. 1. For slab thicknesses 12 inches or less, the concrete cover tolerance is - 3/8 inch. Highway bridgework may require more stringent. 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. Slabs, walls/dividers, and joists – 11 bars and littler – ¾ inch. First, you need to consider the size of the rebar and the spacing between them. Proper and even spacing is also important. The diameter of bar generally used in slabs are: 6 mm, 8 mm, 10 mm, 12mm and 16mm. 2-1/4 inch rebar high chair is. They are 4 feet in height and 10 inches in width (diameter), or 4' x 10". The important part is the use of support to achieve proper placement within the slab. Make multiple passes if needed to create a flat, evenly filled area. buildings and industrial projects) a spacing of 8” to 12” is more. 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. 46 and $1. 16 inches for a number three bar. 6. For one layer of 6x6 W1. Additionally, it plays a crucial role in preventing cracking and shrinkage, ensuring long-term reliability. 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. I was thinking of going with the same spacing. Great for use when pouring concrete slabs. Expansion grooves should be cut into the wet concrete to provide additional crack resistance. 6 rebar spaced 4 inches on center is P = 8. Read more on low-shrinkage concrete mixes in the Concrete Mix Design section. 7 mm) anchor bolts spaced a maximum of 6 feet (1829 mm) on center or approved anchors or anchor straps. Concrete has great compression strength, but it can crack or br eak under. inches thick and about 4 x 4 inches square. The dowels will then be embedded in the ICF wall concrete. I poured a full 4. Down here in gator country my architect would typically prescribe: drill and epoxy 36" #5s 24" o. Similarly, rebar with a size 15 will be 15/8. 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. The spacing of the rebar is also determined by the weight and size of the slab. It is not necessary to use rebar for a 4 inch slab, as concrete’s compression strength alone is enough to hold a 4 inch slab in most cases. (This convention begins to break down for bar diameters above #8. 043 pounds; Applications: Residential and commercial slabs, beams, and columns. Fiber length shall be 1 / 2 inch to 2. area = 625. 3. The length of the lap varies depend on concrete strength, the rebar grade, size, and spacing. With our rebar calculator, you can eliminate. How do you calculate rebar for a slab? Layout of Rebar for Concrete Slabs. How to lay a concrete slab. For example, if the percentage is 0. 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. 7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps. Guidance for joint spacing to minimize out-of-joint. A 4 – inch -thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Workmanship and jobsite conditions. 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. If your concrete will be stamped, ask about the best ways to avoid interrupting the pattern. spacings: #4 bar = 27. 34 and $7. Adequacy of curing. Why is rebar spacing crucial?11. The maximum weight of fly ash, other pozzolans, silica fume, slag or blended cements that is included in concrete mixtures for. Whatever you do, please don’t pour a gigantic slab of concrete with no. 9_sqrt (0. Concrete can be mixed in a wheelbarrow, mortar pan, or mixer. “Reinforce the concrete with 6×6-10/10 wire mesh. Our plastic rebar support “High Chairs” range in size from 3” to 14” in height. 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. 78 kg/m 3) in accordance with the manufacturer’s recommendations. The splices should have at least 2 ft overlap into the new pour. Minimum reinforcement is 0. Tables are for 2500 psi concrete and Grade 60,000 psi rebar 4. Many other styles of supports are available and effective. Here:The size of rebar needed for a 4-inch slab depends on several factors, such as the type of material used for the slab, the type of project, and the size and weight of the load it will be required to carry. (Rebar Calculation Formula) No. Nail the corners together, and place the form on the graded gravel, making sure it doesn’t rock. For slab thicknesses 12 inches or less, the concrete cover tolerance is - 3/8 inch. The structural engineer specified 3/4-inch cover for the bottom bars and a 3/4-inch aggregate mix. The size of the rebar you need for a 4-inch slab depends on a variety of factors such as the type of slab, the environment it is located in, the amount of load and stress the slab will be subjected to, as well as the size of the area and how thick the slab is meant to be. What size rebar for 4 inch slab. What size rebar do I need for a 4 inch slab? You will need a #3 rebar for a 4-inch slab. 45 cubic feet. 2. 3. So for example if you take a 6 inch slab times 2 is twelve feet or times 3 is 18. Determine the amount of rebar needed for the footings. of 2500 psi however. No, you do not need rebar for a 4-inch slab of concrete on grade. Construction joints also have this spacing for strip placement of the concrete. into an existing footer with a min. Add rebar for reinforcement, Ralston places rebar every 16” on center. And a cross-sectional area of 0. For example, one-way slab thickness. Lay down wire mesh or rebar on top of the sub-base if necessary. Use a groover to cut grooves about 25% into the depth of the concrete. 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. Main bar is also called tension. The concrete contractors said that these rebar chairs were a great idea, but the execution and labeling of the product was very poorly thought out. The formula is, Number of bars = (length ÷ spacing) + 1. Before beginning a concrete project, consult a professional engineer to determine the code requirements and what size and spacing of rebar will best meet. You can use Grade 40 or Grade 50 rebar for a 4-inch slab. 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. ) = 0. 78. of Main bars = (3000)/150 + 1. Designed to be extremely strong yet able to straddle a lower rebar mat, these chairs have a wide, stable base with a footprint that. in thickness, columns, walls, and parapets. However, clause 9. 65 and the thickness of the slab is 6 inches, M = 0. I've only ever called out a single layer in a 8" s-o-g. New concrete slabs must conform to the above stated properties before installation of. Rebar Spacing; D2-8F: 4. Allow concrete to cure. #4 Rebar ; The #4 rebar is often used in residential and commercial projects to add strength in slabs and columns. Size 18 rebar has a diameter of 2 1/4 inches. For a 6 in. No, you do not need rebar for a 4-inch slab of concrete on grade. This type of rebar is typically 6mm in diameter and can span up to 24. 73 per square foot, with an average cost of $6. 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. It’s best to check with a. Great for use when pouring concrete slabs. 73 per square foot for concrete installation. Rebar size is first number - 4,5 or 6, second number, in inches, is vertical on center spacing 2. Concrete strength also comes into play, but most slab concrete is around 3000 to 4000 psi, so it's not a major factor. However, for thicker slabs, such as those between 4 and 8 inches thick, 3/4 inch rebar is usually used. spacing and 12-in. 058 percent, which is only enough for crack containment. 5% of the slab cross-sectional area. For the slab's longer dimension, you'll need 360 inches divided by 14, which gives you 25 plus a bit left over. Most concrete slabs last 30–40 years and can last up to 100 years if properly installed and sealed. They cannot hold a load factor. 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. The design of one-way slab is simple and can be carried out easily. 8. e. 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. 4 inch of p r otection. MATERIALS The materials used to construct the dowel bar shall meet the following requirements: 4. Again, without mesh this drops to 34,300 lbs. 08 x 50 = 4 total cubic yards of concrete for 50 tubes4. Often, the placement drawings are specific, such as "18 (number 5) rebar, 11 foot (3. 13-4. Drag a straight 2×4 (screed board) across the top of the concrete forms to level the concrete. Concrete doesn't dry out; it undergoes a chemical curing process that creates a dry, solid mass. Supporting the rebar during the concrete pour is. Generally, for a 4-inch slab, a #4 rebar is usually recommended due to its versatility and strength. 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. 8" - 3/4" (top cover) - 2" (4-#4 bars) - 3" (bottom. e. That's 144 square inches. 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 rated separation for two-family dwellings is 1 hour whether or not a lot line exists between units.