Quantity Takeoff. Dr. Ahmed Elyamany

Transcription

1 Quantity Takeoff Dr. Ahmed Elyamany 1

2 Outline Importance of Quantity Takeoff Preparation of Quantity Takeoff Measurement Units Measuring excavation, P.C footings, Beams, Columns, slabs, and stairs. Solved Example 2

3 Quantity Takeoff Quantity takeoff is an activity performed by General Contractors, Subcontractors, Cost Consultants, and Quantity Surveyors as part of the construction process. It involves counting the number of items associated with a particular construction project 3

4 Quantity Takeoff Quantity Takeoff is performed by: General Contractors, Subcontractors, Cost Consultants, Quantity Surveyors Counting the number of items associated with a particular construction project Determining the associated materials and labor costs Preparing an estimate as part of the bidding process. Applied to the pricing process. 4

5 Quantity take-off: Why? Owner perspective: Initial estimate of the project costs at the different stages of the project. Preparing the BOQ as a requirement of the contract documents. Estimating the work done for issuing the contractor payments. Contractor perspective: Pricing different work items. Identifying the needed resources (Labor, Equipment, etc.). Project schedule. Preparing invoices for work done. Subcontractors payments. Review and control of crews production rates. 5

6 Quantity Takeoff The quantity takeoff process is typically done manually using a printout, a pen, and a calculator. 6

7 Quantity Takeoff New Trend is Building Information Modeling (BIM) Provide a solution that generates a set of takeoff elements (counts, measurements, conditions that affect cost) enables estimators to more quickly and more accurately perform takeoff for bidding or pricing. 7

8 Quantity Takeoff Important to specify the type of ; Imported materials Suppliers Equipment Labors Work in project Important to know project budget Important to know activities logic 8

9 Quantity Takeoff Criteria It must be as accurate as possible Should be based on all available engineering and design data. Use of appropriate automation tools is highly recommended. The Quantity Takeoff is an important part of the cost estimate. 9

10 Quantity Takeoff Input Documents Input from the client (task description). Conditions (general, special, supplementary). Drawing and specifications. Addenda. Agreement form. Modifications. 10

11 Quantity Development Guidelines Coordinate the quantity takeoff process and plan with the estimator. Include a list of materials in quantity takeoffs. Utilize a process that easily records the quantity Check scales and dimensions on each drawing sheet. Highlight drawing areas where quantities have been determined to ensure all elements is captured but not double counted. 11

12 Quantity Development Guidelines Consider items that have no material but still require cost, e.g., job office overhead, task setup, training and certifications. Add a certain amount of waste, loss, drop off, or length related to the material purchases for a bulk order. Coordinate with designers if the design appears in error.. 12

13 Takeoff Sheet & Bill Of Quantities Quantity Takeoff Sheet مقايسات كميات Estimated Quantities Actual Quantities Bill Of Quantities (BOQ) مقايسات أعمال تقديرية مقايسات أعمال فعلية مقايسات تثمينية 13

14 Quantity Takeoff Sheet Item Item Unit Quantity Length Dimension Width Height Part Subtraction Addition Total

15 Bill Of Quantities Price Notes Item Item Unit Quantity Unit Total

16 Bill of Quantities classification The Bill of Quantities is classified into the following work groups: Civil works Sanitary works Electrical works Mechanical works 16

17 Bill of Quantities classification Civil works: Earth works: leveling, excavation, backfilling, transportation of excavated soil) Foundation works: plain concrete reinforced concrete piling foundations 17

18 Bill of Quantities classification Civil works: Brick works: Internal brick work External brick work Skelton reinforce concrete: Columns, Beans, Slabs Stairs 18

19 Bill of Quantities classification Civil works: Finishing: Water proofing Staircases Plastering Flooring Painting Metal works: Windows Doors Accessories 19

20 Bill of Quantities classification Sanitary works: Water feeding systems Internal and external plumbing works Finishes of plumbing works Electrical works: Electrical cables Wiring; Accessories Internal connections Mechanical works: Air conditioning systems Elevators 20

21 Work order Items in takeoff sheets are organized in the same construction sequence. Order of items in the same chapter: Items estimated in (m3) Items estimated in (m2) Items estimated in (m) Items estimated in (unit) Items estimated in (ton) Items estimated in (L.S.) 21

22 Measuring Units The units of measurements for civil engineering works are mainly categorized for their: Nature Shape Size and Payments to the contractor. There are a number of standard codes and methods of measurement that are available. 22

23 Measuring Units Cubic meter (m 3 ) Used for items such as: Excavation Backfilling Concrete Brick walls ( 25 cm thick) Square meter (m2) Used for items such as: Brick walls (<25 cm thick) Plastering Flooring Painting 23

24 Measuring Units Linear meter (m) Used for items such as: Pipe lines Canals Stair steps Windows sills Number (unit) Used for items such as: Electric outlets Doors and windows Sanitary fixtures Precast concrete 24

25 Measuring Units Lump sum(l.s.) Item is subcontracted when the contractor does not have enough experience to construct it or there is an item which has a small quantities of many work items such as: Manholes Lifts Some electrical and plumbing works Weight (Ton): Metallic works Reinforcement steel 25

26 Preparation of Quantity Takeoff Check the availability of drawings Check the axis and dimensions Check building levels and link it to structural drawings. Check doors and windows model numbers Check ground water levels 26

27 Preparation of Quantity Takeoff Check architectural against structural drawings Check foundation design and foundation levels Check construction members dimension and reinforcement. Review the contract conditions and specifications 27

28 Formulas Square Rectangle Parallelogram Trapezoid Trapezium 28

29 Formulas Triangles Regular Polygons Circle Parabola Ellipse 29

30 Formulas 30

31 Formulas 31

32 Formulas 32

33 Formulas 33

34 Formulas 34

35 Formulas 35

36 Earth works Excavation Quantities are calculated based on the dimensions of the foundation in plans from the owner perspective. Contractors should consider the excess of material excavated to all for safe operations. Prices differ based on the soil type, deep of excavation, ground water level, site location, shoring system, Equipment used, etc. Unit of measurement is cubic meter (volume). Consider the example in the following slide: 36

37 Earth works Excavation The length of excavation = (4.4 2) 2 = 15.6 m Depth of excavation = 1.8 m Width of excavation = width of plain concrete footing = 1.0 m Volume = = 18.8 m3 37

38 Earth works Backfilling Unit of measurement is cubic meter (volume) Consider the example shown in previous slide, the volume of backfilling could be calculated as follow: Volume of backfilling = excavation concrete brick Volume of concrete = = 6.24 m3 Volume of brick = = m3 Volume of backfilling = 18.8 ( ) = m3 38

39 Earth works Site leveling & Soil transportation Site leveling: Measured in m2 (area) if thickness < 30cm. Measured in m3 (volume) if thickness > 30cm. Soil transportation: Transported soil = Vol. of exc. Vol. of backfilling + additional soil at site Add swelling factor based on the soil type: 5% sandy soil. 15% clayey soil and 25% for demolition material. (owner or contractor) 39

40 Concrete works Plain concrete & Reinforced concrete Plain concrete (PC): Measured in m2 (area) if thickness < 20 cm. Measured in m3 (volume) if thickness 20 cm. Average thickness should be mentioned when measurement is done by area. Reinforced concrete (RC): All RC elements measured by volume (m3) except hollow block slabs measured by area (m2). Domes, cylindrical roofs and shells measured by area in the horizontal projection. 40

41 Concrete works Plain Concrete Footing Quantity of P.C footing = No. of footings for a specific model * length * width * depth Total quantity of P.C footings = summation of P.C footing models RC Footing PC Footing 41

42 Concrete works Ground Beams Quantity of ground beam = No. of ground beams for a specific model * length * width * depth Total quantity of ground beams = summation of ground beam models Ground Beam RC Footing PC Footing 42

43 Concrete works Columns Quantity of columns = No. of columns for a specific model * length * width * height Total quantity of columns = summation of columns models Columns RC Footing PC Footing 43

44 Concrete works Slabs Solid slabs: Quantity of slab = length * width * thickness Flat slab: Quantity of slab = length * width * thickness Beams: Quantity of beam = length * width * height 44

45 Brick works Measured in m2 (by area) if thickness <25 cm. Measured in m3 (by volume) if thickness 25cm. Deduct all openings. Deduct half the area (volume) of arches. Deduct all Concrete elements. Separate item for each brick type 45

46 Stairs Quantity of stairs = inclined length * width * height + stair section area * stair width * No. of stairs stair section area 46

47 Plastering Internal Plaster: Engineering measurement by area (m2). All openings are deducted. All openings sides are added. Inclined slabs are calculated based on their horizontal projection. 47

48 Plastering External plaster: Measured by area (m2). Openings with areas < 4 m2 are kept with deduction. Deduct half the area of the openings 4 m2. Openings with areas < 4 m2 are kept with deduction. Cantilever slabs < 1 m projection not added. Add half the area of cantilever slabs 1 m. 48

49 EXAMPLE 1 Substructure Taking-off List Site preparation Removing trees and shrubs Lifting turf Top soil/removing/preserving Excavation Reduce levels/disposal of excavated material Excavating trenches/disposal of excavated Material/Filling/Surface treatments Concrete Foundations Beds/formwork/damp-proof membrane Masonry Brick walls Forming cavities Filling to cavities 49

50 EXAMPLE 1 Substructure Site levels Top soil cannot be used for backfilling as it would, over time, cause damage to the substructure. The usual default depth for topsoil is 150 mm Next figure is a 5 m grid of a survey of levels taken on a site. The site is required to be reduced to a level of and in order to calculate the volume of excavation required the average level of the site must be determined. This can be easily done by weighting the levels as follows starting at the top left-hand corner of the site (35.90) and working from left to right. 50

51 EXAMPLE 1 Substructure Site levels Level Total Level Total Number of Points = 40 Average site level = / 40 = Reduced level = Average Excavation depth = =

52 Example 5.6m ع ١ ك ٢ ع ١ 15cm 7ɸ10/m 4.8m ك ١ 7ɸ12/m ك ١ A A ع ١ ك ٢ ع ١ 52

53 ك Example سفلي عدل و الكانات 6ɸ8/m الغطاء الخرساني 4ɸ16+ علوي 2ɸ16 ٢.٥ سم 0.3m x 0.5m قطاع الكمرات ك ١ ٢ 0.3m x 0.3m 3.0m قطاع العمود ع ١ ارتفاع العمود ع ١ قطاع السمالت 0.3m x 0.5m منسوب األرض الطبيعية 1.2 m القواعد المسلحة 1m x 1m x 0.4m 53 Section A-A القواعد العادية 1.6m x 1.6m x 0.3m

54 Example It is required to estimate the quantities of the following jobs: (كميات الحفر) Excavation (خرسانة القواعد العادية) Plain Concrete Footings (خرسانة القواعد المسلحة) Reinforced Concrete Footings (خرسانة السمالت) Ground Beams concrete (كميات الردم) Filling (خرسانة األعمدة) Columns concrete (خرسانة البالطة وكمرات السقف) Slab and beams Concrete حديد تسليح البالطة وكمرات ( Reinforcement Slab and beams (السقف 54

55 Excavation 1.6 m 4.8 m 1.2 m 1.6 m.15 m 5.6 m.15 m 1.6 m m 3.7 m

56 Excavation No. Item Unit Number Length Width Depth Total 1 Excavation m

57 PC Concrete Footings No. Item Unit Number Length Width Depth Total 2 PC Concrete m m 0.3 m 1.6 m 57

58 RC Concrete Footings No. Item Unit Number Length Width Depth Total 3 RC Concrete m m 0.4 m 1.0 m 58

59 Ground Beams No. Item Unit Number Length Width Depth Total 4 Ground Beams m m السمالت 4.8 m 4.5 m 0.3 m 0.15 m 5.6 m m 0.3 m 59

60 Filling No. Item Unit Number Length Width Depth Subtotal Total 1 Excavation m PC Concrete m RC Concrete m Ground Beams m Total Concrete m Filling m

61 Columns No. Item Unit Number Length Width Depth Total 6 Columns Concrete m m 3.0 m االعمدة 3.0 m 61

62 Slab & Beams No. Item Unit Number Length Width Depth Total 7 Slab & Beams m m 5.0 m 0.5 m 4.2 m 15 cm 4.8 m 4.5 m 0.3 m m 5.6 m m

63 Take-off Summary Table No. Item Unit Number Length Width Depth Total 1 Excavation m PC Concrete m RC Concrete m Ground Beams m Filling m Columns Concrete m Slab & Beams m Total Concrete

64 ك Reinforcement Takeoff 30cm 0.3m x 0.5m 4ɸ16+ علوي 2ɸ16 قطاع الكمرات ك ١ ٢ سفلي عدل و الكانات 6ɸ8/m الغطاء الخرساني ٢.٥ سم 2.5cm 2.5cm 25cm 7ɸ10/m 7ɸ12/m 50cm 45cm 64

65 Reinforcement Takeoff Unit No. of Length Total Unit Total (kg) bars length Weight Weight 16 upper (beams) lower (beams) long (Slab) short (Slab) stirrup (beams) Total Steel

66 66 Questions?