FLOOR SLABS M. 2. /18 in. each way at center of slab construction joint for same shall not be more than 3000mm apart. 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. In the case of the RCC slab, the maximum spacing between two secondary parallel wires should be 5D or 450 mm or whatever. The support for reinforcing steel in floor slabs is shown in figure 7-24. The diameter of reinforcing bars shall not exceed one-eighth of the total thickness of the slab. Step 1. First, it avoids that the column transmits to the slab a concentrated force, which would cause large stresses in the concrete slab and likely large damage. 006 inch; 0. 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. shear stresses at the columns and bending moments in the slab con-3 trol the design. 8 mm) when subjected to 50 pounds (23 kg) applied over 1 inch square (645 mm) of material and are greater than 1/ 8 inch (3 mm) in thickness in the uncompressed state shall not extend beneath walls, partitions or columns, which are fastened to the floor. The type of rebar used in the construction of a given section of concrete will depend on several. 1 of the 2021 International Building Code (IBC) specifies that the thickness of concrete floor slabs supported directly on the ground shall not be less than 3 1/2″. One-Way Joist Slab Concrete Floors are constructed in a range of sizes with conventional spans. Most residential slabs contain. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed. 6) Calculation of top rebar Please refer to the method in construction site as follows because it is very difficult to explain in theory. The provision of adequate reinforcement, slab thickness, and. The depth of slab needs to be increased if slab panel size (b) increases, but rebar requirement remains the same for slab (refer to point 3). Rebar should be minimum Grade 40 reinforcing steel. The spacing of such shrinkage-temperature steel cannot exceed 18 in. See full list on everything-about-concrete. I am filling a 12 ft x 12 ft sunken lounge are with 12" of Geofoam as filler and a 4" concrete slab. Use f’c = 28 MPa and fy = 414 MPa for main rebars and fy = 276 MPa for shear reinforcement. For general purpose concrete slabs with 2,500 pounds compression strength, like patios, use a 1:2:4 concrete mix ratio. 11 in. With some limitations, reinforcement for slabs can be sized using the Subgrade Drag Theory in order to increase the spacing of control or construction joints. 3rd. SLAB ON GROUND—A type of foundation with a concrete floor which is placed directly on the soil. No, you do not need rebar for a 4-inch slab of concrete on grade. 5 cm) thick footing, the rebar mat is usually placed about 4 inches (10. Slab may be supported on walls or beams or columns. Concrete Slab Rebar Spacing Guideline Report an Issue. When arranging joints, skilled contractors will often use them to create an attractive diamond pattern. 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). With this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). The spacing of the rebar should increase to between 18 and 24 inches apart for slabs between four and six inches thick. In this article, we will examine the importance of reinforcing concrete with rebar and the proper steps. S. I was thinking of the following: basement wall 8 inches thick 10 feet high backfilled up to 7 to 8 feet. 2 – Contraction joints, states the following: “ (d) Joint depth shall be a minimum of ¼ the slab thickness for formed or tooled joints, or dry-cut sawed joints in hardened concrete (e) Joint depth shall be a minimum of 1 in. 5 inches up to 12 inches. We would like to show you a description here but the site won’t allow us. Floors shall be a minimum 3 1 / 2 inches (89 mm) thick (for expansive soils, see Section R403. 11. We can also pinpoint the depth of every object we locate in concrete with an accuracy of +/- 10-15%. Compressible floor-covering materials that compress more than 1 / 32 inch (0. b) Slab depth does not exceed 200 mm when the steel grade is 460. #LonbicooltvUsing the search function should turn up a lot of info. Summarize and show schedule of the design outputs such as beam dimensions, main rebars diameter and quantity, and shear rebar diameter and spacing. This design is particularly effective for structures with consistent loads. Rebar (short for reinforcing bar ), known when massed as reinforcing steel or reinforcement steel, [1] is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Maximum spacing: The maximum spacing of main bars is limited to 3d or 300 mm (whichever is less). 375 inches, which is equivalent to 9. The imposed loads considered for various types of buildings can be. The size of the rebar depends on the specific application, but typically #4, #5, #6, and #8 rebar are used. 2 and 9. The floor has been designed with two mats of steel, 7 1/2" total concrete thickness and 50 ksi steel beams with a single row of shear studs on the beams. Thank ForSubscribeLikesShare. • Edge beams act as L-beams, and interior. Enjoy the Rebar Calculator for Slab. Main bars in the slabs should not be less than 8 mm if you are using the H. . Theoretically, so long as the horizontal spacing is sufficient, the number of layers shouldn't be much of a problem, but the more layers you have, the greater the odds that the vibrator will accidentally touch the rebar (which it shouldn't). Corner angle. 4. Input all the dimensions in the input section of the above calculator. If the weight of each steel beam is 62 lb/ft, determine the dead load in lb/ft supported by any interior beam. I am pouring a slab for radiant heat next week and I have been given a variety of advice on whether or not to use rebar. If a concrete slab is 4 inches thick, the depth of the control joint should be 1 inch. 2 m top bars @ discontinuous edge Compute temperature bars 250 Using 10 mm f bars:. ACI 332, Section 10. 36 Live load Canopy = 1. The roof of a concrete home can be used as a slab-on-grade floor for the wood frame on the second story. Minimum thickness of concrete structural elements based on ACI 318-14, IRC 2009, IS 456 2000, and UBC. First, Get The Number Of Required Bars. The installation of the rebar is critical for the success of the overall project. If the floor is designed as a reinforced-concrete slab requiring rebar in the tension zone, the designer should specify the correct rebar position. #5 rebar on a 6X6 grid, No cracks in that, poured the same time as the slab in the heated addition. If Steel grade 60 is to be used, the minimum slab thickness is taken as L/20 where L is the span of slab. 1. Similar “uncontrolled” or “random. Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of this section or ACI 332. Place these positioners at a spacing that will not allow the rebar to bend or deflect enough to reduce the coverage you wish to obtain with the concrete you place in you forms. Prepare and Place Reinforcement for Slab. #TwoWaySlab #Basic #ConstructionWatch Basic Concept with its Practical Application by Construction AnimationJoin as member to support the channel. As ready-mix trucks arrive. Concrete is strong under compression, but has low tensile strength. 2 cm) from the bottom of the concrete, and side clearances range from 2 to 4. Foundation and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1808. One Way Slab Bar Bending Schedule Calculation. For this case, the lift should not be installed without written authorization from theIt has stood up to some really heavy equipment for 25 years. This table is span based since the bottom reinforcement is designed span by span. A 6-mil. The more layers of rebar you have, the harder it becomes to properly vibrate the concrete. slab opening det. In either case, blocks should be used under the reinforcement to keep centered. 2-way slab rebar arrangement method 1-way slab rebar arrangement method Slab main bar arrangement type classification Bent bar type. Scanning and Detecting Rebar in Concrete. Figure 5. 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. An example is shown in Fig. I am confused about the grid. STRENGTH REINFORCEMENT REBAR SPACING GP‐7 SERIES MODELS 4‐1/4” 3000 PSI / 28 Day Aging #6 Rebar 12 In. They want one expansion. Finally, take a look at the calculation results: grid length = 5. There are two types of Grade slabs: Usually after casting Plinth beams. Reading time: 4 minutes. It illustrates and explain. , interior beam dimensions = 14 in. Now, divide each measurement by the 14-inch spacing. x 27 in. Here, ∅ is the bar diameter. Essentially a early age concrete shrinkage problem (cement paste not reaching full strength/bond with aggregate and restraint on the concrete member due to rebar. 15% of the slab’s cross-sectional area), the spacing of tendons in at least one direction shall not exceed the smaller of eight times the slab thickness and 1. Slabs for septic tanks may require the use. You should still use reinforcement material, but there are other options besides rebar. PSI means per square inch. Concrete slabs-on-ground shall contain micro- or macro-synthetic fiber reinforcement. Rebar is typically used to provide additional strength and rigidity to concrete slabs, so if the slab is intended. 53 m). The minimum spacing between two reinforcement bars should be at least equal to the maximum coarse aggregate dimension plus a margin of 5 mm. A 4" slab should have joints 8-12 feet apart. 1: Calculate The Main bars. Steel fibers, at 1. It has Spanish language descriptions, labels and diagrams and it also has default units in the metric system (SI). (b) A flat slab which is the same as a flat plate except the areas around the columns have. Concrete slabs-on-ground containing 6 × 6 W1. The three different sizes of rebar used for home projects are usually #3, #4, and #5. We’ll run through these ties now: Saddle ties:As per clause 11. A basic rule to follow when judging how deep a control joint should be is that it should be roughly 1/4 the depth of the concrete. g. 53 Compute moments At support: ( - ) M1 = 3. 2. area elements and go to Assign > Shell/Area > Opening to create holes in the slab. Pour 6" fiber reinforced concrete over it. Consequently, building such slabs requires rebar spacing knowledge. 73 Therefore, use 12 mm bars @ 0. 2. This is one of the types of concrete slabs. 3. If 1 span is 8,000mm, 4,000mm will be center part and add 40times (40d) + rebar thickness is the length of top rebar in center part & end. c) Slab reinforcement percentage less than 0. 🕑 Reading time: 1 minuteEstimation of steel reinforcement quantity for concrete slab, footing and column, beams etc. Ordinarily, the rebar supplier details, fabricates, and delivers to the site, as required. This type of slab is used on the Basement floor. 5 rebar, then measure and mark for your dowels at a 18. #5 bars are 5/8”. Steel reinforcement bar size for footing of G+2/ 3rd floor building:- we will assume a structure of G+2 (three storey) residential building, using standard 4″ thick walls, according to general thumb rule, use of mesh bar of 12mm or number 4 (#4) size (diameter) of steel reinforcement as main and distribution bar (T12@6″C/C of Fe500) is most suitable for. to 9. Design of Floor Slabs (fc' = 28 MPa, fy = 276 MPa) Common design parameters: 0. In t e r p r etations of the ACI 318 code re q u i r ements (Ref. Vertical rebar every 16 inches. Study Resources. 113. . If you want, you can cut out of a section of the steel for testing too. 3 Slabs-on-ground with turned-down footings. a) Slab depth does not exceed 250mm when the steel grade is 250. At a maximum spacing of 120 inches (3048 mm). 3. 3 For long, narrow panels, place rebar at 0. x 20 in. But if the slab is a patio or driveway, it will need rebar. What size rebar do I need for a 6 inch slab? The size of rebar needed for a 6 inch slab would depend on the specific application and requirements. get your rebar grid down, i would use 1/2" on 12" center. The article elaborates the elastic and inelastic methods for design of. 00 m to 6. 6: 20mm clear cover in slab is sufficient. 2ND FLOOR CRACKING WIDTH. However, some specific rules and requirements need to be met. 3 Storey Building: Larger diameter rebars, such as 16mm and 20mm, may be used to accommodate the. For slabs of septic tanks, you usually use #3 and #4 bars. Floors shall be a minimum 3 1 / 2 inches (89 mm) thick (for expansive soils, see Section R403. The load needs, and the span of the slab decide the spacing, size, and placement of the bars. Here, ∅ is the bar diameter. 75 to 3. FIrst, find number of rods required for main reinforcement and distribution. For a 12 inch (30. The thickness of RCC roof slab is vital. Ridges in the surface of the rebar allow the concrete to adhere to it and create one solid structure. AI Homework Help. 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. 120 m Length of shorter side of building = 12. Minimum clear cover to reinforcements in slab depends on the. 4. A 6-mil (0. Round up the value of n to the next whole number to find the nominal rebar size required for that spacing. For example, The #3 bar size is 3/8″ diameter of the solid section, the #4 bar size is 4/8″ diameter of the solid section, and the #5 bar size is 5/8″ diameter of the solid section. Because of this, the Building Code places limitations on the size and spacing of rebar in gunite & shotcrete. 5 try 100 mm Dead load Slab weight = 2. For this case, the lift should not be installed without written authorization from the building. Industry Practitioners. In some cases, concrete needs reinforcement with steel mesh. For slabs. C. Unfortunately, rebar can cause extensive damage to construction tools if you are performing coring or concrete cutting work. Patio slabs are used in pathways. , interior beam dimensions = 14 in. 30% carbon cont ent and only. Crack Control – when crack widths are not checked by calculations No Further Checked Required. 5 m) with mini-mum slab thicknesses of 6 to 10 in. 3, No. Floor Under Solids or Semi- solids and Single Axle load (15,000 lbs. I have 10 in. 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 side of the support for one-quarter of the span (See Fi g u r e 1). 3 bars may be used, for constructability and handling reasons it is common practice to use no. Once you have determined that the foundation of the house is strong enough to sustain a concrete floor, lay down wood sheeting. How far apart must rebars normally be spaced? There should be a clear distance at least equal to the bar diameter between parallel bars but never less than one inch. ** For alternate steel schedules and/or slab thickness determine As (end area of steel, in2) as shown below and use USDA NRCS Standard Drawing ES-46 to select bar size = and spacing that meets or exceeds the computed end area of steel. Generally, rebar has an immense impact on concrete. MINIMUM VERTICAL REINFORCEMENT AND SPACING (INCHES) b, c: Soil classes and later soil load d (psf per foot below grade) GW, GP, SW and SP soils 30: GM, GC, SM, SM-SC and ML soils 45:Concrete Floor Slabs On Grade Course# ST-702 EZ-pdh. Contact*: Severity*: Description*:Problem #3 – Shrinkage cracks that allow moisture to reach the rebar. Rebar. 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). 0 pounds per cubic yard (0. 5. ) is going to be 5'-6' for 4 ksi concrete anyways. 6 For two‐way slabs, maximum spacing of bars shall not exceed two times the slab thickness h nor 450 mm. Garage floors that are at least six inches thick should have rebar because it provides the best support, but garage slabs thinner than that do not need rebar. The typical depth for rebar placement for slabs is 2-4 inches. The concrete floor will be reinforced according to WAC 246-359-430. Our calculator will instantly calculate the quantity of rebar required. I was thinking of the following: basement wall 8 inches thick 10 feet high backfilled up to 7 to 8 feet. c. In that case, a layer of rebar near the bottom or at. Place the second bar parallel to the first bar and 1 inch beyond (see Figure 2). 21 = 183. 4m x. I have some question regarding the placement of the expansion joints. And the rebar details of (1) is 10mmØ @ 8″ c/c. 2. For M15 concrete, lever arm = 0. Slab depths are typically between 4”-10” (10. Note: Unless otherwise specified, all code references for elevated slabs are to ACI 318-14/ACI 318-11. 3. Two layers of steel bar reinforcement are needed for secondary containment floors because tank loads induce both positive and negative bending moments in the floor. The national average cost of a concrete slab is $6. R403. ( W) Width of the slab. Maximum spacing of main bar is restricted to 3 times effective depth or 300 mm whichever is. A typical installation uses 6-inch by 6-inch woven wire mesh, which is supported on rebar chairs so it is positioned near the center of the finished slab. Rebar being #4 grade 60. In summary the design procedures for beams and floor slabs are similar with the following differences: (a) Minimum steel. south d c rebar i 306" i #7,7/8" dia ---j r--rebar j. ) 400 dowel 400 250 %$56 $6 6+2:1 %277 %$56 # 2 & slab occurs mid-depth of slab [ /21* $7 723 bott. This assumes that the concrete will contain aggregate that is no more than three-fourths of these distances; otherwise the aggregate. In the case of the RCC slab, the maximum spacing between two secondary parallel wires should be 5D or 450 mm or whatever. Often, concrete contractors don’t have solid runs of rebar anyway. Concrete volume calculator plan view diagram. Some brands of forms have preformed chases that run the length of each. Add the third side. For 2,000 LBV soil or greater, two-story buildings may have 12-inch minimum wide footings. The result is a lightly reinforced slab designed to offset the effects of temperature and shrinkage of the concrete. Size and spacing of rebar;secondary containment floor slabs on grade. 4 bars in the middle third of the footing depth. 7. 2. Steel shall be located within 2” of the top or the upper 1/3 of the slab. 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. Figure 5. 8 ). Number of Distribution Bars = Lx / spacing + 1 = 3000/150 + 1 = 21 nos. 1. You will be able to add radiant floor heat any time. longer than the length of the slab. For Greece, the. First, Get The Number Of Required Bars. By Theodore Neff. 3. A good compacted base below the concrete is equally important. Section 13. C. Construction joints also have this spacing for strip placement of the concrete. In the farwestern states, the rebar supplier also ordinarily places the bars, In the New York City area,…. Level, straighten and brace the second form board. 525 mm. 87 (round up to 13)Add one rebar. then use 1/2 PEX tubing and create about 5 floor heating circuits, bring all of them to a convenient access point in the shop. E. MAX and #5 top placed at center of slab" I installed the #3 dowels 12" apart and 6" into the existing surrounding floor. 00 m 21 reinforced concrete slab 3 mm for every 3. Typically, once the concrete in the foundation wall has set, install the floor system. 87 d Spacing of bar = Design of Continuous Slab Suppose a slab is supported at the ends and also at intermediate points on beams, the maximum sagging and hogging moments to which the slab is subjected to due to uniformly distributed load, can be computed as follows: Let = intensity of dead load per square metre. 6 of the International Building Code. The maximum size of reinforcement shall be No. If your two slabs have different spacing for their rebar mats, measure and mark so your dowels fall in the middle of the spacing of the second slab. Grade 40 means that the yield strength is 40,000 psi and the code allowed strength is 20,000 psi. The design of slabs for imposed loads and live loads is based on the type of the building. x 27 in. diameter) for a house construction are not that many. com) 3. Normally, it is assumed changes in deck slabs, and sloped slabs over beams. Larger diameter bar will allow a wider spacing of the bar, our designs went from 3/8 on 12 inches to 1/2 on 18 inch when we started to build pesticide storage facility's. Tie the slab rebar into the footing. That has held up great over the last 8 years, no cracks at all. The support for reinforcing steel in floor slabs is shown in figure 7-24. 1. However, we want to use slabs for the floor elements in this model. A. or slab change soffit typical detail for beam 400 dowel 250 300 (typ. Most homeowners can expect to pay between $4. By Concrete Construction Staff. Measure the cover depth of embedments. The Rebar Calculator is now available in Spanish. CONTROL JOINT SPACING. #4 is 4/8”, or 1/2”. dustrial floor slab. The floor finishing is. Two-Way Concrete Floor Slab with Beams Design and Detailing Design the slab system shown in Figure 1 for an intermediate floor where the story height = 12 ft, column cross-sectional dimensions = 18 in. 12mm. Tie pieces together with rebar ties. The second table describes the negative (mid-span) moment demand and the bottom reinforcement. Therefore net area of slab = 201. The height of the slab bolster is determined by the required concrete protective cover. The specified compressive strength of concrete shall be as set forth in Section R402. Floor slab of bottom-most SS or NS and floor slab of NS located above an SS: (i) Slab reinforcements at both external face and internal face shall be H13-. Tying the rebar is crucial to ensuring the rebar stays in place and functions as it should. Narrow panels Fig. Detail B: “Wrap and Snap Tie” (diagram upper right) is normally used when tying vertical wall reinforcement to hold the bars securely into. For example, at Column I-4 between the basement and first floor, building plans required four pieces of horizontal rebar through the column in both directions to connect it to the slab. 5 The second-floor layout of an office facility is shown in Figure P2. 10. Ekberg, Jr. 2nd. #3 is most commonly used for patios and driveways, #4 for columns and walls, and #5 for foundations and footers. NOTE: Section 1907. Total Length of rebar in feet. -l. Reinforcing bars that are spaced too far apart could result in relatively large flexural crack widths. 4 welded wire reinforcement fabric located in the middle to the upper one-third of the slab. Retaining Walls: The most commonly used rebars in retaining walls are #3, #4 and #5. For distribution bars the maximum spacing is specified as 5 times the effective depth or 450 mm whichever is less. Methods used for finding slab thickness varies for different types of slabs. First step of the fixing of slab reinforcement was placed the bottom most R/F (B1) of the slab. We had twisted square bars in our 1911 second floor slab. The top surface needs to remain wet while the curing process takes place. I was thinking of going with the same spacing. vapor retarders - some times referred to as vapor barriers, insulation, etc. 24-foot joint spacing. 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. The compaction UNDER the slab is more important than the thickness of the slab. 1 shows the design detail for a secondary containment floor slab with two layers of reinforcing. Two layers of steel bar reinforcement are needed for secondary containment floors because tank loads induce both positive and negative bending moments in the floor. The openings are square in shape and range in size from 2 ft to 5 ft. Understanding the Importance of 2nd Floor Slab Thickness for Building Safety and Stability in the Philippines The safety and stability of a building depend on various factors, and one of the most crucial is the thickness of the second-floor slab. In either case, blocks should be used under the. , interior beam dimensions = 14 in. If you are trying to put a new concrete slab on your small-scale domestic project; 6mm (#19), 8mm (#25), and 10mm (#32) rebars will do the job nicely. 9 cm)-round bar 05 = part of second floor plan designated by the number 5. Avoid using air contents over 3% for interior slabs. Joints shall be spaced at 24 to 30 times the slab thickness but this need to be confirmed by a structural engineer. The structural design of the concrete floor slab on-ground is dominated by the sub-grade conditions and the floor loadings. a car weight about 5000lb. 2L at the intermediate support. It requires input values for the dimensions of the slab, the size and spacing of rebars, and other parameters, providing an estimate of the required rebar quantities. Properly compacted sub-grades can reduce needs for reinforcement – as well. 1. . The simplest type of two-way slab to construct is known as a flat plate. Unless you are going to park a very large truck on the slab the 2'x2' oc #4 rebar is over kill IMHO. Dowel bars transmit the weight from one slab to its neighboring slab. A one-way concrete joist slab, employed in building construction, is a structural system featuring a reinforced concrete slab supported by parallel, slender joists. Q. 1. 3. Concrete doesn't dry out; it undergoes a chemical curing process that creates a dry, solid mass. 5-TM 5-809-1/AFM 88-3, Chap. The most commonly used rebar sizes for slabs up to six inches thick are #5 and #4. diameter), spaced at a maximum of 24 in. For slabs (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. To maintain strength and longevity, concrete slab rebar spacing must fit together like a jigsaw puzzle. 1 Introduction: A structural member used for covering spaces in the form of roof or floor is called a slab. 6mm. However, the boilers I have been recommended is the Electro boiler (30,000. The two design options are a ground-bearing slab, or a pile supported suspended slab. 5 bar or two No. The spacing of the main steel in a slab should not exceed the following: First, the American Concrete Institute (ACI) Residential Code Requirements for Structural Concrete (ACI 332-14) requires contraction joints and provides a table to determine joint spacing for plain and reinforced concrete containing up to 0. Concrete slab reinforcement design and code checks can be performed based on the following codes: ACI 318-19. For flat slabs like driveways and patios, spacing is roughly 18″ to 24″. The steel rods help reinforce the strength of the concrete slabs giving the structure a strong form. Shrinkage cracks are probably the most common type of cracks in concrete. I'm in the process of designing a elevated composite concrete and metal deck floor slab for a warehouse. 1R-15 Guide to Concrete Floor and Slab Construction, American Concrete Institute, ACI 360R-10 Guide to Design of Slabs-on-Ground, American Concrete Institute,. If the maximum diameter for slab thickness is 75 mm, so the diameter of reinforcing bars should be 8 mm. 42d. The tendency is to lay rebar the way one’s. Also, a small hole in the concrete will be totally fine, given the fact that there is a rebar grid. Such applications usually involve the placement of large numbers of bars with close spacing. Steel reinforcement bar size for footing of G+1/ 2nd floor building:- we will assume a structure of G+1 (two storey) residential building, using standard 4″ thick walls, according to general thumb rule, use of mesh bar of 12mm or number 4 (#4) size (diameter) of steel reinforcement as main and distribution bar (T12@6″C/C of Fe500) is most. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. Retaining Walls: The most commonly used rebars in retaining walls are #3, #4 and #5.