The number ranges from 10-to. 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. . The commentary R26. 27. This guide is not a standard nor a specification, and it is not intended to be included by refer-ence in construction contract documents; ACI 330. 1 Storey Building: Typically, smaller diameter rebars like 10mm or 12mm might be suitable, depending on the specific design requirements. 75 to 3. 00 m to 6. Parking lots have most loads imposed on interior slabs sur-11. The no. spacing requirements and to repeat bar size and spacing as often as possible. 04 Required spacing, s = 242. 8. 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. As can be seen from the figure-2 below, the tension reinforcement are 100% at the mid-span of the beam and slab, while it is curtailed at the distance of 0. Contact*: Severity*: Description*:Problem #3 – Shrinkage cracks that allow moisture to reach the rebar. Sixteen gauge wire is used to tie. However, for post-tensioned (PT) slabs, this can be mistakenly regarded as difficult, expensive, and. Easiest way to go. Our engineers wanted to make sure that big yellow boots fit between the rods so the workers did not stand on the rod and bend or. The floor system of the classroom shown in Figure 2. In the process, install bar chairs (various types are available) in cores where vertical rebar must be installed. Before placing the re-bar, correct spacing given in the detailing drawing were marked by using piece of choke on the slab formwork. 5" 3,000 PSI / 28 Day Aging. Level, straighten and brace the second form board. 1 For longerfloor slab rebar' • ~ #4 19 mk402 "rll ~ ii i i i i i i i i i i i i i i i i i i i k '&y ih:' ii~. In Seismic Design Categories D 0, D 1 and D 2, slabs-on-ground cast monolithically with turned-down footings shall have not fewer than one No. 00 m to 6. 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. 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. 600-2 DETERMINATION OF BUILDING WIDTH A. (not reducing for cover/spacing, etc. We would like to show you a description here but the site won’t allow us. Here, ∅ is the bar diameter. The spacing of the rebar is also determined by the weight and size of the slab. 1) for con-c r ete cover over re i n f o rc e m e n t h a v e not been consistent. Report Application Issues or. For the trapezoidal, dovetail, and reentrant composite slabs, and RC slab, welded rebar meshes with Φ 8 ribbed bars were selected, and bar spacing was 200 mm in both directions. 1 the spacing of links along the FULL HEIGHT shall not exceed 6 times diameter of smallest longitudinal bar or 150mm. Rebar would be absolutely required in a footer located near the frost line or in the areas subject to moisture changes in shrink/swell soil areas. 4: Two-way slabs having multiple spans; The purpose of the code is to design the total amount of reinforcement steel rebar into principal directions in the slab system. , interior beam dimensions = 14 in. Clear cover of the slab = 25-mm. • Edge beams act as L-beams, and interior. It says that floor slabs were patent designs back in the 1920's. Pool construction crews must place each steel bar and drop of concrete with precision to avoid future structural problems. x 18 in. If the slab is more than 24 inches thick, #5 (#5/8 inch diameter) rebar may be required. Enjoy the Rebar Calculator for Slab. Learn the steps to pour a concrete floor inside an existing garage, house or shed. Tie the slab rebar into the footing. The diameter of reinforcing bars shall not exceed one-eighth of the total thickness of the slab. 5. The second table describes the negative (mid-span) moment demand and the bottom reinforcement. , interior beam dimensions = 14 in. 006 inch; 0. Rebar is recommended on concrete measuring 5 – 6 inches thick. Crazing is a result of poor surface curing and only visible in hard troweled slabs. The architect's instructions on the plan are: “New conc slab with #3 transverse bars at 12” O. Much of the time, the depth that finishers install control joints is less than what is normally recommended. Suspended slab/Two-way slab/One-way slabToday's video answers the questions I get asked most frequently: - How do you read or interpret slab reinforcement pl. 2. Rebar spacing calculator is perfect to indicate how much Rebar is needed. Slab may be supported on walls or beams or columns. Input all the dimensions in the input section of the above calculator. Also, a small hole in the concrete will be totally fine, given the fact that there is a rebar grid. But if the slab is a patio or driveway, it will need rebar. 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. 83-6. Important Points. 74 sq feet 5000/2. 2-way slab rebar arrangement method 1-way slab rebar arrangement method Slab main bar arrangement type classification Bent bar type. Sudip Shrestha. Reinforcing steel should be properly tied with wire to rigidly support it in its proper. However, some specific rules and requirements need to be met. Detail A: “Snap Tie” (diagram upper left) is the simplest and is usually used for rebar in a flat horizontal position. 2. • A beam-and-slab system, with a one-way slab, and beams cast compositely with the slab, is a highly efficient floor system. diameter), spaced at a maximum of 24 in. 2. 00 m span 3. No, you do not need rebar for a 4-inch slab of concrete on grade. Design Rules - Footing/Pile Cap Rebar. Clear span of the two way slab = 5000 mm. 4, and No. Maximum spacing of bars for slabs • Main bars: 3h ≤ 400mm (in areas of concentrated loads 2h ≤ 250mm) • Secondary bars: 3. CONTROL JOINT SPACING. long-term deflections of the slabs. As ready-mix trucks arrive. Rebar is recommended on concrete measuring 5 – 6 inches thick. 5 Slabs on Grade - “the purpose of isolation joints in slabs on grade is to allow horizontal and vertical movement between the slab and adjoining structures such as walls, columns, footings, or specially loaded areas (machinery bases). Rebar Spacing. Finally, take a look at the calculation results: grid length = 5. The minimum Sub-Base thickness shall be as shown in the table. I'd use: 8" thick concrete wall with #6 rebar at 12" oc EACH WAY with the VERTICAL rebar placed 3/4" clear from the face of the INTERIOR BASEMENT ROOM. normal rebar sizes (e. extension of existing reinforced concrete (R/C) structural elements such as slabs, walls, and columns (Figure 3), either to facilitate expansion of floor space or to address other functional changes in the use of the structure. In either case, blocks should be used under the reinforcement to keep centered within the concrete. For Greece, the. 15 1-1 CHAPTER 1 INTRODUCTION 1-1. rebar spacing o. Concrete slabs-on-ground shall contain micro- or macro-synthetic fiber reinforcement. We recommended to use 5″ rcc roof slab thickness 1, 2 and 3 storey building. Insert plate. c. However, if the concrete slab is meant to be the footing of a small structure, #4 rebar with a diameter of 1/2-inch should be used. 2. Advertise Here. Except for Type F slabs, all slabs are expected to remain essentially uncracked under applied loads. Expert Guide to 2nd Floor. The article elaborates the elastic and inelastic methods for design of. The diameter of bar generally used in slabs are: 6 mm, 8 mm, 10 mm, 12mm and 16mm. south d c rebar i 306" i #7,7/8" dia ---j r--rebar j. 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. ) slabs are plate elements used to form the floors of buildings. The elevation to the top of the decking (bottom of the concrete waffle slab) for forming of the second floor above-grade slab is ___. Industry Practitioners. Step 1. For the slab's longer dimension, you'll need 360 inches divided by 14, which gives you 25 plus a bit left over. #5 bars are 5/8”. Minimum width and length of slab: See new slab table & figures below. , and unfactored live load = 100 psf. Joint spacing normally ranges between 12 to 18 feet depending on the amount of reinforcement the slab has. Rebar Spacing; D2-8F: 4. 76 Slab designation: CS1 Check if one-way or two-way slab 1 Slab is one way since it is catilever slab Minimum slab thickness min t = 69. The numbers range from #3 (smallest) to #18 (largest). The maximum weight of fly ash, other pozzolans, silica fume, slag or blended cements that is included in concrete mixtures for garage floor slabs and for exterior porches, carport slabs and steps that will be exposed to deicing chemicals shall not exceed the percentages of the total weight of cementitious materials specified in Section 19. Rebar should be minimum Grade 40 reinforcing steel. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. I recommend use of M20 grade of concrete. Methods used for finding slab thickness varies for different types of slabs. STRENGTH REINFORCEMENT REBAR SPACING GP‐7 SERIES MODELS 4‐1/4” 3000 PSI / 28 Day Aging #6 Rebar 12 In. 375 inches, which is equivalent to 9. standard rebar lenght is normally 12m or 6m each. The spacing of the rebar should increase to between 18 and 24 inches apart for slabs between four and six inches thick. How far apart should rebar be spaced? approximately 12 inches Place rebar in a grid pattern with a spacing between bars of approximately 12 inches. UB 610 x 179_BP_Pinned. a) Slab depth does not exceed 250mm when the steel grade is 250. Once the wood sheeting is down, add a covering of plastic. Rebar in patios, basement floors, footings and driveways may vary from size 3 to 6. Concrete slab reinforcement design and code checks can be performed based on the following codes: ACI 318-19. One reason is simple ease of construction. 4 × W1. Total Length of rebar in feet. The existing rebar spacing is @ 16 in. 3. Rebar being #4 grade 60. Standard concrete floor slab thickness in residential construction is 4 inches. For corrosion protection, however, most specifications require a minimum depth of concrete cover that usually ranges from 1 inch to 2 inches. ) 400 dowel 400 250 %$56 $6 6+2:1 %277 %$56 # 2 & slab occurs mid-depth of slab [ /21* $7 723 bott. t + DWhen a concrete slab is stressed by the post-tensioning method, it means the steel is being tensioned and the concrete is being compressed. The maximum size of reinforcement shall be No. . For Greece, the maximum aggregate grains dimension for usual concrete, is 32 mm and for self-compacting. In the Philippines, buildings face various environmental challenges such as strong typhoons, earthquakes, and floods. 113. REBAR SPACING: GP‐7 SERIES MODELS: 4‐1/​4" 3000 PSI / 28 Day Aging #6 Rebar:. Development length Ld = 45-d. These slabs are supported directly by the columns and have a completely flat soffit. 1. Minimum thickness of concrete structural elements based on ACI 318-14, IRC 2009, IS 456 2000, and UBC. The top of the wall will need "hooks" in the rebar in order to fasten the wall to the garage slab. 3 bars may be used, for constructability and handling reasons it is common practice to use no. 2 Spacing s of transverse barsUse min 3/8 inch 24 inch on center rebar (wired together) not mesh. We had twisted square bars in our 1911 second floor slab. 00 m shorter span one-way floor slabs under 3. 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. There are three (3) materials used in constructing a composite floor slab; steel decks, reinforcing bars and concrete. ICF Foundation and One ICF Story – The sequencing here is to build the foundation walls first, place concrete, and then build the above-grade walls second. 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,. Spacing (Rebar) A-7 4-1/2” 4000 psi with 28 day aging #6 rebar 12 in. 8. A good GPR survey and interpretation should give you the rebar spacing and pattern. AI Homework Help. 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. x 27 in. Shrinkage cracks are probably the most common type of cracks in concrete. Enter the slab dimensions, desired rebar spacing and the spacing from the edge to quickly find how to lay out the rebar grid. Pouring of floor 2's slabThe dead loads include the self-weight of the slab, floor finishes, walls, grills, etc. Concrete is strong under compression, but has low tensile strength. 20 Plant-applied External Fusion Bond Epoxy Coating [Abrasion-Resistant Overcoat] for Steel Pipe (CSA Group, formerly the Canadian Standards1) Except as provided in Sentences (2) and (3) and in Articles 9. 1) provides the code basis. 2. This steel runs vertically and should lap the same size reinforcing steel out of the footing. 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. The minimum size and grade of rebar for slabs depends on a variety of factors, such as the thickness of the slab, the loads it supports, seismic requirements and other factors. 10mm, 12mm, 16mm, 20mm. Joint spacing that is greater than 15 feet require the use of load transfer devices (dowels or diamond plates). Most residential slabs contain. AS3600-2009 P P Lsy. e. Use 3/8 min repair frame in the footing. Cut a second board to the width of the slab. 3 Factored live load = 3. T F 8. , F. Once you have determined that the foundation of the house is strong enough to sustain a concrete floor, lay down wood sheeting. vapor retarders - some times referred to as vapor barriers, insulation, etc. The second marker expresses the bar size and is demonstrated by a number. The load needs, and the span of the slab decide the spacing, size, and placement of the bars. However, the boilers I have been recommended is the Electro boiler (30,000. With this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). Prices for your concrete slab will vary. 1 of ACI 318-111 identifies a two-way slab as a slab system designed for flexure in more than one direction. 9. In this video, you will learn the Spacing between the. is crucial for the cost evaluation for the construction. Fo r decades ACI 318 has re q u i r ed high-Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of ACI 332 and this section. Compression is a force that squeezes or crushes, and tension is a force that pulls something apart. Specify the spacings: rebar-rebar spacing = 40 cm, edge-grid spacing = 8 cm. or >) The minimum floor thickness shall be 6 inches. On average are required, for 100 square feet with 5 inches thick slab, 19 strips of 3/8” rods (30 ft each one), are 570 ft. Multiple layers of c r ossing bars cause these pro b - l e m s . • Basement floor slabs with integral footings must provide for 5000 psi concrete in that portion of the slab acting as a footing. 00 m 14 over 6. rebar strength is in tension, so by adding rebar to BOTTOM of foundation, it counter acts the load of compression. #5 rebar on a 6X6 grid, No cracks in that, poured the same time as the slab in the heated addition. Section 13. You can use regular fencing material with 2' x 4' or 2' x 6' mesh. Rebar mesh: Cut and lay 6-inch rebar mesh across the site, covering all areas except for a 3-inch band on the outside. Also note while no. HollowCore floor slab systems provide construction flexibility, fire separation, vibration isolation, and the structural support required to span almost any challenge that large or small multi-deck buildings require. For driveways and patios, #4 (1/2 inch diameter) rebar is a common. Specify the spacings: rebar-rebar spacing = 40 cm, edge-grid spacing = 8 cm. 5% reinforcement (reproduced here as Table 1). Figure 5. . Its rebar size in inches is 0. C. Size and spacing of rebar;secondary containment floor slabs on grade. Foundation and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1808. 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. or slab change soffit typical detail for beam 400 dowel 250 300 (typ. for concrete floor construction are found in ACI 360R for slabs-on-ground, ACI 223R for shrinkage-compensating concrete floors, and ACI 421. In this video, you will learn the Spacing between the Main and Distribution steel bar. mk . In low- to. It has Spanish language descriptions, labels and diagrams and it also has default units in the metric system (SI). 12% for HYSD bars and 0. 2)(12 in. ACPA Guide Specification | Dowel Bars for Concrete Street and Highway Pavement | ACPA M254-21 April 8, 2021 | Page 4 of 11 CSA-Z245. There should be a minimum of 3 inches of clear cover from the fi nished surface of the slab. 2—Slabs-on-ground 5. Five to six inches is recommended if the concrete will receive occasional heavy loads, such as motor homes or garbage. Ridges in the surface of the rebar allow the concrete to adhere to it and create one solid structure. Generally, #4 rebar (1/2 inch in diameter) is the most common size used for slab on grade applications. 4 cm) based on the span to depth formula. cedures used to design and construct slab-on-grade such as streets, highways, and floors. The slab is constructed on well compacted granular fill, crushed stone or marl. in concrete slabs. 40 (default) and 60 are common. Since this is a patio, you could use 6x6 10/10 wire mesh instead of the rebar. Minimum aging of new concrete slab: 28 days (cure time) Minimum width and length of slab: See new slab table & figures below MIN W L R S1 & S2 D I LIFT MODELS SLAB MIN. Where, d is the diameter of the bar. General Approach to the Design of Post-Tensioned. The spacing of such shrinkage-temperature steel cannot exceed 18 in. dustrial floor slab. 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. shear stresses at the columns and bending moments in the slab con-3 trol the design. Concrete slabs-on-ground containing 6 × 6 W1. Second, the slab is allowed to elongate freely in the whole length of DFR, thus reducing its strain to the value. I was thinking of going with the same spacing. Here, ∅ is the bar diameter. Modeling floor diaphragms. 5. Rebar SizesOn studying the drawing, Length of longer side of building = 16. 1 m) and post-tensioned spans of 13’-28’ (3. longer than the length of the slab. For a 400 square foot slab, the man hours required to finish a two-car concrete garage slab is about 13 hours. Finally, you pour the concrete into the molds. make sure rebar is in the center of the slab, or close to it. 5 bars; There shall be a minimum clearance between parallel reinforcement bars of 2 1/2 inches; Bars larger then # 5 increase the chances of shadowing (voids behind rebar) Always use the larger of the two. An example is shown in Fig. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. There are many variables that influence the decision of how much space to leave, including the maximum load the slab is likely to. Building Width for Use of Appen-dix B Tables. In t e r p r etations of the ACI 318 code re q u i r ements (Ref. 1 in2. #IScodes #Concrete #Concretetechnology Recent & Related Videos Concrete. Prior to the placement of reinforcement for concrete floor slab construction, inspect and check forms to confirm that the dimensions and the location of the concrete members conform to the structural plans. It create a bending of the slab. ACI 318-08. For this case, the lift should not be. Sunitha K Nayar, gives the grouping of slabs-on-grade based on the design philosophies and a brief overview of the different design methods, the commonalities between design strategies in terms of the input parameters, assumed and estimated parameters, and the relevance of each. To define design strip rules, click the Slab Design Rules button on the Data Entry toolbar. This type of slab is used on the Basement floor. Two-story buildings require a minimum of 15-inch wide footings for 1,500 LBV soil. #Lonbicooltv Using the search function should turn up a lot of info. Whether the frame is precast, cast-in-place, masonry, or structural steel it can be accompanied by a HollowCore floor slab system. These provisions are not meant to prohibit the use. 4 rebar in the upper part and one piece of No. 5 bar or two No. The result is a lightly reinforced slab designed to offset the effects of temperature and shrinkage of the concrete. Added to that, the forms shall be properly cleaned and oiled but not in such amount as to run. The #3 rebar has a weight per length of 0. 46 and $1. 🕑 Reading time: 1 minute The design of reinforced concrete (RC) column is carried out by following certain procedures. The three different sizes of rebar used for home projects are usually #3, #4, and #5. C. (a) A flat plate which is a two-way slab supported on a column grid without the use of beams. Avoid using air contents over 3% for interior slabs. 2 and 9. When two slabs are moved together, the impact loading created by the slab is reduced. These slabs require more load-bearing capacity than other slabs. ** 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. 🕑 Reading time: 1 minuteEstimation of steel reinforcement quantity for concrete slab, footing and column, beams etc. girder sides & slab on grade - 1 reinforced concrete beams 6 mm for every 4. The imposed loads considered for various types of buildings can be. 3 -SPACING OF TRANSVERSE REINFORCEMENT 11. In summary the design procedures for beams and floor slabs are similar with the following differences: (a) Minimum steel. 6. E. Number of Main Bars = Ly / spacing + 1 = (4000/150) + 1 = 27 nos. (I think someone touched on this) Your floor covers some span. h. Suresh, Professor, Civil Engineering Department, NIE, Mysore (Ph:9342188467, email: gss_nie@ yahoo. The distribution bars are installed in the slab’s top layer, with a minimal cover distance of 15mm from the slab’s top. 1R-92 (Ref. 40ft x 15ft dumpster pad, 8" thick with double mat of #4 rebar 16" OC Each way. 64 mm) between longitudinal rebar 2 and 3, which is the same as the rebar construction and traditional tape measurement results. However, no matter how basic or complex. It is not hurting anything by putting it in a floor slab, but unless it is in the bottom third of the slab, it is providing zero strength, just keeping the pieces together if it cracks. ** 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. Here: Bar Tying Requirements. square poured concrete beams and columns. (ii) The maximum spacing between two secondary parallel bars shall be 5dor 450 mm or. What Size Rebar for Concrete Slab? This usually depends on the intended workload. 3. Rebar in a concrete slab reinforces it against weather and other external loads. Slabs, walls, joists: No. Setting a Max Bending Check value controls the rebar which the program chooses for the slab design. Calculate how much rebar you need to reinforce a concrete slab. The edge of the slab is usually thicker and acts as the footing for the walls. of the bars. A 6-mil (0. c) Slab reinforcement percentage less than 0. 6 For two‐way slabs, maximum spacing of bars shall not exceed two times the slab thickness h nor 450 mm. Thickness of concrete slab depends on loads and size of the slab. 3. Concrete Slab Rebar Spacing Guideline Report an Issue. Divide your result by the spacing measurement: 180 in / 14 in = 12. The simplest type of two-way slab to construct is known as a flat plate. 5 rebar, then measure and mark for your dowels at a 18. Design of Floor Slabs (fc' = 28 MPa, fy = 276 MPa) Common design parameters: 0. I am constructing a 10 unit 2 story condo building with concrete block and 10in. D bar or 10 mm if you are using Plain bars. The typical depth for rebar placement for slabs is 2-4 inches. These new concrete slabs do not account for second floor installations or installations in a ground floor with a basement beneath. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. In terms of steel I was going to go with 2% of the slab cross-sectional area in each direction, with a maximum rebar spacing of say 12" to 16" to keep the crack widths small. Annex. vided in the slab under the net. 8 inches. The steel rods help reinforce the strength of the concrete slabs giving the structure a strong form. Carbon steel. x 27 in. 7736 m 2. Crack Control – when crack widths are not checked by calculations No Further Checked Required. Compressible floor-covering materials that compress more than 1/ 32 inch (0. Generally, rebar has an immense impact on concrete. Its primary purpose is to increase the tensile strength of the concrete, helping it resist cracking and breaking. last quarter of 2014, the prices i got for the rebars (12m lenght) are: 9mm deformed rebar - P110 10mm - P138 12mm - P205 16mm - P385. I have an exiting two way concrete slab in which it is required to introduce new openings. ( rS) Rebar Size (2,3,4,5,6,7,8,9,10,11,12,14,16,18,20). 1. Typically, once the concrete in the foundation wall has set, install the floor system. Input the number of mesh in slab rebar. Consider. You’ll also need vertical rebar hooks protruding at least 6” into the footing and out at least. Y. The maximum diameter of bar used in slab should not exceed 1/8 of the total thickness of slab. Minimum. 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. Section 13. At a maximum spacing of 120 inches (3048 mm). 5 m) with mini-mum slab thicknesses of 6 to 10 in. To assign a Slab element to the floor, go to Assign>Wall/Slab/Deck sections. 1. Wet your concrete after the pour. In this video i will show you about 2nd Floor Slab Rebar. Rebar is tied together, using wire, to hold it in place. Number of Required Bars Formula = (Length of slab / spacing) + 1. Concrete blocks made of sand-cement mortar can be used in place of the slab bolster.