CONSTRUCTION ESTIMATING I BCT 1770 CHAPTER 5 CONCRETE CSI DIVISION 3

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1 Be able to read blueprints, diagrams, floorplans, and other diagrams used in the construction process. Marilyn vos Savant CONSTRUCTION ESTIMATING I BCT 1770 CHAPTER 5 CONCRETE CSI DIVISION 3 48

2 CONCRETE Components of Concrete Take-Offs Include: Formwork Reinforcement Cast in place concrete Finishing Formwork Cost includes the install and removing of forms Formwork for footings is usually omitted when excavation is in very hard earth, however, most specification requires that footing forms be used Forms are figured to be re-used Depends on material used Types of coatings Care during stripping Forms should be: Strong and rigid Well braced Oiled or coated Based on surface of forms actually in contact with concrete Referred to as the square feet of contact area - S.F.C.A. Small jobs: 2 x 4 frames ¾ plywood panels Concrete reinforced with galv. Strips Larger jobs: 49

3 Prefabricated panel forms Formwork Take-Off Concrete footings, basement walls, & retaining walls may be estimated by determining the number of square feet of contact area, however, it is more accurate and necessary to have a detailed breakdown in building formwork. Formwork (Footings) 2 X material for the stringers (7% waste) SOL X 2 X waste divided by length Stakes - 2 X 2 X 4 o.c. (12% waste) SOL divided by 4 X 2 X waste Spreader ties - 1 X 4 o.c. (7% waste) SOL divided by 4 X waste FORMWORK (STUDS AND BRACING) Studs - Compute by dividing the SOL of the wall by the stud spacing 2 X 12 o.c. (7% waste) SOL X 2 X waste Plates - 2 X 4 (7% waste) SOL X 4 X waste divided by length Plyform - ¾ (5% waste) SOL X 2 X 8 X waste divided by 32 Bracing - placed at a 45 0 angle - the height of the wall X X 4 o.c. (10% waste) SOL divided by 4 X waste X 2 Formwork (Studs and Bracing) Walers - double 2 X 4 members running horizontally or vertically and spaced as closed as necessary to resist the lateral pressures on the wall form The number - height or SOL divided by 2 SOL X number X waste X 2 divided by length 2 X 4 o.c. (7% waste) Form ties Horizontal spacing - 32 o.c. 50

4 Vertical spacing - 16 o.c. Number of ties = H X Lt h L H = height of wall Lt = total length of wall h = vertical spacing of ties L = horizontal spacing of ties Waste - 5% Formwork (Studs and Bracing) Nails Reinforcement 6 d common used to fasten the plywood to the studs and plates - 15 lbs. Per 1,000 sq.ft. (10% waste) Sq.ft. x 15 X waste divided by 1, d common used to nail the plates to the studs - 20 lbs. Per 1,000 bd.ft. of plate (10% waste) 16 d duplex nails used for easy removal in fastening the bracing to the form and the stakes - 10 lbs. Per 1,000 bd.ft. of bracing material Anchor bolts 6 o.c. (5% waste) - add two extra bolts for each corner Rebar - total length X the weight per lf. For particular bar sizes Concrete is strong in compression and shear, however, weak in tension Types of reinforcement - wire mesh and rebar Estimated in lbs. and tons Size is based on the number of eighths of an inch in diameter - #3 = 3/8 diameter Weight per foot for steel bar = 2.67 D 2 D = the diameter of the steel bar in inches Example - W = 2.67 (0.75) 2 = lbs/ft. Designed so that the separate parts act as a single unit Types of splices Lapped Welded Mechanical 8% waste to cover extra for lapped joint 51

5 SOL X quantity X weight X waste Weights of Standard Reinforcing Bars Bar # Bar Nominal Area Weight (PLF) Size Diameter (sq.in.) 3, / , / , / , / , / , , / , / , / , / , / Minumum Laps Bar Number Minimum Lap (50D) Cast In Place Concrete Includes cost of the concrete for specific item and the cost of the labor and equipment or mixing and placing it Finishing Includes finishing, curing and protection Curing Leave forms in place 4 or 5 days Curing compound - spray or brush Damp Burlap Sand 52

6 Sawdust Depends on the finish specification The unit of measure for concrete, or some of the ingredients of concrete (coarse and fine aggregate), is the cubic yard, which contains 27 cubic feet. Foundations Foundations for residential structures are made up of four basic parts 1. Footings 2. Foundation walls 3. Piers and column footing 4. Concrete slabs Footings Footings transmit the superimposed load of a structure to the soil 53

7 Foundation Walls Foundation walls are usually made of concrete or masonry block, they form the perimeter of a basement or crawl space and transmit the load from the structure above the to the footings Pier and Column Footings Piers and column footings are concrete and usually square in shape. They also help support the building load through wood and steel posts placed on top of them. Concrete Slab Concrete slab are used for residential construction primarily in temperate climates, such as found in western and southern states. They carry the live and dead load weights of people, furniture, and equipment placed in the home. 54

8 Estimating Concrete Volume The following formula can be used to determined the amount of concrete needed for any square or rectangular area. Cubic Yard Volume = Thickness X Width X Length in feet in feet in feet 27 For example, for a volume of concrete that is 4 thick by 40 wide and 60 long, how many cubic yards of concrete would be required? The thickness of 4 is 1/3 of a foot and may be expressed in the problem as follows: Cu.Yd. =.333 X 40 X 60 = 2400 = 800 CU.FT. 800 = OR 29.6 CU.YD. OF CONCRETE 27 Converting Slab Thickness Measures 55

9 Square Foot Area A square foot is the surface area covered by 12-inch by 12-inch square without regard to its thickness. Two Methods There are two methods that can be used to find the number of square feet in a building. 1. The positive areas are added together 2. The largest width dimension must be multiplied by the largest length dimension, and the negative areas must be subtracted Postive Method 56

10 Negative Method The building shape in the previous examples have been given in even foot measurement. The following table will help an estimator find the square footage of buildings that are not dimensioned in even feet. Find the Square Footage in the Following: 57

11 Lineal Foot Measurement A lineal foot is a line designated by length in feet lineal feet or 10 lin.ft. Lineal feet is the measurement used to designate the perimeter of a building (the perimeter is the distance around the outside of the building) Procedure for Estimating Concrete Volume of Footings and Foundations Walls Check the foundation plan for the size of footings and foundation walls From Table 10-3, select the cubic foot volume that corresponds to the footing and foundation wall sizes Calculate the lineal feet of footing and foundation walls Multiply the lineal feet of footing and foundation wall by cubic foot volume per lineal foot Divide the cubic feet of form content by 27 for cubic yards 58

12 Example Problem Find the cubic feet and cubic yards of concrete for the following foundation problem Procedure Rules for Estimating Concrete Walls and Floor Slabs Another method used to estimate the volume of a concrete wall or floor slab is to consult Table 10-4, which designates how many square feet a cubic yard of concrete will cover at a certain thickness 59

13 Example Problem Estimate the cubic yards of concrete in the slab. Rules for Estimating Concrete Piers 60

14 Example Problem How many cubic yards of concrete are there in the piers illustrated below? Procedure Trianglar Area The area of a triangle equals ½ the area of a rectangle of the same length and width. Estimate the amount of concrete needed in the following triangular slab: 61

15 Estimating Foundation Bolts The building code requires that the mudsill or the bottom wall plate on a slab be held down with bolts embedded in the concrete. The usual recommendation is for one bolt within one foot of each corner, exterior door openings or wall plate splice and a maximum span of 6 0 for bolts falling between corners. Wood Foundation Construction Slab Construction Procedure for Estimating Foundation Bolts Calculate the number of bolts for the exterior corners of the building. Two bolts are used for the inner and outer exterior corner. For the bolts between the corners, divide the exterior perimeter by six. (six-foot maximum spacing allowed) Add the number of bolts for the corners and between the corners. The result will be the number of bolts needed. If the building has long walls with many plate splices and if there are mire than the usual number of exterior door openings, add a few extra bolts. 62

16 Compute the following: EXERCISE II 1. The number of pieces required for the 2 X 6 X 16 stringers in forming the footings. Apply the waste factor of 7%. Convert your results to board feet. 2. The lumber required for the spreader ties placed 4 o.c. around the length of the footing. Apply a waste factor of 7% and give the number of 1 X 3 X 8 that will be required. Convert your results to board feet. 3. The number of pieces required for the stakes, which are 2 X 2 X 18 spaced 4 o.c. Use a waste factor of 12% and convert your results to board feet. 4. The number and board feet of 2 X 4 X 16 plate material using a waste factor of 7%. 5. The number and board feet of 2 X 4 X 8 stud 12 o.c. in the forming of the basement wall using a waste factor of 7%. 6. The number of sheets and square feet of 4 X 8 plyform using a waste factor of 5%. 7. The number and board feet of 2 X 4 X 16 waler material using a waste factor of 7%. 8. The number of tie h- 32 o.c. and v-16 o.c., using a waste factor of 5%. 9. The number and board feet of 2 X 4 X 10 bracing 4 o.c. Apply a waste factor of 10% 10. Pounds of 6 d common nail using a 10% waste factor. 6 d common nails are used to fasten the plywood to the studs and plates. Figure 15 lbs of 6 d common nails for every 1,000 sq.ft. of plyform required. 11. Pounds of 16 d duplex nail using a 10% waste factor. The 16 d duplex nails are used for easy removal in fastening the bracing to the form and to the stakes. Figure 10 lbs of 16 d duplex nails for every 1,000 board feet of bracing required. 12. Pounds of 16 d common nail using a 10% waste factor. The 16 d common nails are used to nail the plates to the studs. Figure 20 lbs of 16 d common nails for every 1,000 board feet of plates required. 13. The number of anchor bolts spaced 4 o.c., using a waste factor of 5%. Note: add two extra bolts for each corner. 14. Pounds of #5 rebar for the footing (horizontal only) using a waste factor of 8% to over laps and waste. 15. Pounds of #5 rebar for the basement walls (horizontal and vertical steel, including that which goes down into the footing lf.), using a waste factor of 8%. The vertical steel is spaced 2 o.c. around the length of the basement wall. 16. Cubic yards of concrete for the footing using a waste factor of 8%. 17. Cubic yards of concrete for the basement wall using a waste factor of 8%. 63

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