Lecture 6 Quantity Surveying PDF

Lecture 6 Quantity Surveying 6.1-Introduction Once a construction project is completed or depending on the form of contract upon completion of certain parts of the work, the contractor must be paid for appropriately completed works. This would then require that the actual works done be somehow...

Lecture 6 Quantity Surveying 6.1-Introduction Once a construction project is completed or depending on the form of contract upon completion of certain parts of the work, the contractor must be paid for appropriately completed works. This would then require that the actual works done be somehow estimated or measured for payment purposes. On the other hand to estimate how much a civil engineering project may cost, the actual quantities of materials, labor, equipment etc. that is needed for the construction work must be calculated at the beginning of the work. Such work of calculating the amount of materials and other incidentals necessary for the realization of the work is called quantity surveying. 6.1-Introduction Quantity surveying is a term or processes used in the construction industry to take measurements of civil works, prepare specifications, and estimate the cost of works either for each trade of work or for the whole project. The term “surveying” means to inspect, study, review, investigate, asses, and hence “to measure” therefore the term “quantity surveying” means “quantity measuring” as applied to civil engineering projects. Quantity surveying is the application of standard methods of measurement to quantify the amount of various items in a construction project, for the undertaking of valuation, and certifying payments. 6.1-Introduction The following tasks are covered in quantity surveying. A. Preparation of Specification B. Taking measurements of civil works (Taking off quantities and preparing BOQ) C. Preparation of approximate (preliminary) cost estimate at the very early stage of the project D. Preparation of detail cost estimate at different stages (taking as built measurements and preparing payment certificates or approval of payment certificates prepared by taking measurements) E. Valuation of property  6.2-Purposes of Quantity Surveying The purposes of quantity surveying hence the preparation of Bill of quantities are: I. Assist the client to have an accurate estimate of the volume of work as well as the required budget. II. To assist in the accurate preparation of tenders, by providing uniform measurement of quantities. III. To give an accurate checklist of work accomplished IV. To assist in the certification of payments V. To give insight into the required variation work amounts. 6.3-Measurement of Civil works Measurement of civil works includes the billing of each trade of work either from drawings or the building itself for defining the extent of works under each trade. In order to avoid ambiguity in measuring quantities, there is a recommended principle of measurement in construction activities. Many professional organizations publish recommendations on units of measurement, degree of accuracy etc. this assists in setting a common parameters so that dispute is avoided. 6.3-Measurement of Civil works Principles of Measurement The following are list of the basic principles of quantity surveying, applicable to all items of work. Each work section of a bill shall contain a brief description of the nature and location of work. Work shall be measured net as fixed in position. Measure the full work area and adjust deductions later. Items which are to be measured by area shall state the thickness or such other information as may be appropriate. Items which are to be measured by length or depth shall state the cross- sectional size and shape, girth or ranges of girths or such other information as may be appropriate. Items which are to be measured by weight shall state the material thickness and unit weight if appropriate ( Ex. Duct work) 6.3-Measurement of Civil works Principles of Measurement Piece of work shall be taken in numbers. For items of pipe work it shall be stated whether the diameter is internal or external. Mass voluminous and thick works shall be measured in volume (cubic meter) Thin, shallow and surface work shall be measured in area (meter square) specifying the thickness. Long and thin work shall be measured in length (linear measure, running meter) Bills are deemed to include labor, materials, goods and plant and all associated costs for fixing, assembling, etc. 6.3-Measurement of Civil works Units of Measurement Depending on the prevailing system of measurement in any locality, quantities may be measured in the Foot- Pound- Second (FPS) system or the metric system. The most common unit of measurement is the International System of Units, or the metric system of units in which the various items are measured as follows: For the measurement of length Meter (m) For the measurement of mass Kilogram (Kg) For the measurement of Area Square Meter (m2 ) For the measurement of Volume Cubic Meter (m3 ) For measurement of piece Number(No.) 6.3-Measurement of Civil works Dimension Unit Example Length M, ML, MR Skirting Area M2 Plastering, waterproofing Volume M3 Concrete, Excavation Weight Kg, Ton Steel Reinforcement Number item No. Doors, Windows Complex /Specialties LS (Lump sum) Pump Room 6.3-Measurement of Civil works Degrees of accuracy in Measurement All dimensions measure to the nearest 0.01m Thickness of slab measure to the nearest 0.005m Wood work measure to the nearest 0.002m Road work measure to the nearest 0.005m Areas measure to the nearest 0.01 meter square Steel work areas measure to the nearest 0.001 meter square Volume measure to the nearest 0.01 meter cube Wood work volume measure to the nearest 0.001 meter cubes Weights measure to the nearest 1 kg 6.4-Types of Quantity Surveying Types of Quantity Surveying (QS) Contractor QS Consultant QS 6.5What is MasterFormat Master lists of titles and section numbers for organizing data about construction requirements, products, and activities. By standardizing such information, MasterFormat facilitates communication among architects, specifies, contractors and suppliers, which helps them meet building owners’ requirements, timelines and budgets. 6.6 Master format Divisions PROCUREMENT AND CONTRACTING REQUIREMENTS GROUP: 00- Division 00 — Procurement and Contracting Requirements SPECIFICATIONS GROUP General Requirements Subgroup 01-Division 01 — General Requirements Administrative & Procedural Requirements Temporary Facilities & Controls Performance Requirements Life Cycle Activities 6.6Master format Divisions Facility Construction Subgroup Division 02 — Existing Conditions Division 03 — Concrete Division 04 — Masonry Division 05 — Metals Division 06 — Wood, Plastics, and Composites Division 07 — Thermal and Moisture Protection Division 08 — Openings Division 09 — Finishes Division 10 — Specialties Division 11 — Equipment Division 12 — Furnishings Division 13 — Special Construction Division 14 — Conveying Equipment Division 15 – 19 — (RESERVED) 6.6 Master format Divisions Facility Services Subgroup: Division 20 — (RESERVED) Division 21 — Fire Suppression Division 22 — Plumbing Division 23 — Heating Ventilating and Air Conditioning Division 24 — (RESERVED) Division 25 — Integrated Automation Division 26 — Electrical Division 27 — Communications Division 28 — Electronic Safety and Security Division 29 — (RESERVED) 6.6 Master format Divisions Site and Infrastructure Subgroup: Division 30 — (RESERVED) Division 31 — Earthwork Division 32 — Exterior Improvements Division 33 — Utilities Division 34 — Transportation Division 35 — Waterway and Marine Division 36 — (RESERVED) Division 37 — (RESERVED) Division 38 — (RESERVED) Division 39 — (RESERVED) 6.6 Master format Divisions Process Equipment Subgroup: Division 40 — Process Integration Division 41 — Material Processing and Handling Equipment Division 42 — Process Heating, Cooling, and Drying Equipment Division 43 — Process Gas and Liquid Handling, Purification and Storage Equipment Division 44 — Pollution Control Equipment Division 45 — Industry-Specific Manufacturing Equipment Division 46 — Water and Wastewater Equipment Division 47 — (RESERVED) Division 48 — Electrical Power Generation Division 49 — (RESERVED) 6.7 MasterFormat Numbering 6.7 MasterFormat Numbering 6.8 Uniformat Level 1 Categories Introduction A Substructure B Shell C Interiors D Services E Equipment and Furnishings F Special Construction and Demolition G Building Site work Z General 6.8 Uniformat 6.8 Uniformat 6.8 Uniformat 6.8 Uniformat 6.9 Uniformat/Masterformat 6.10 The Process of Quantity Surveying I. Bill of Quantities (BOQ) Definition The BOQ is an itemized list of building materials, their units, quantities and associated and costs. Also it may contain work items (non- material) such as mobilization, site preparation and other kind of expenses. A BOQ is used mainly in Tendering.  6.10 The Process of Quantity Surveying There are four clearly defined steps in preparation of Bill of Quantities: I. Taking off II. Squaring III. Abstracting IV. Writing the final Bill of Quantity I. Taking Off This is a process of measuring or scaling dimensions from drawings and recording all dimensions in an easily understood format. This is coupled with the descriptions in the drawings and specification. In this task the quantity surveyor “take off” the quantities from the drawings and determines the volume of work to be done for the various components. These quantities are calculated in a specially prepared format, as to aid accurate preparation and enable checking/rechecking or adjusting of amounts and correcting errors if any. These special formats are called “Take off sheets” or “Dimension Paper”. The dimension paper used for taking off is usually double-ruled as shown 6.10 The Process of Quantity Surveying I. Taking Off Column 1 is used for stating the number of times an item occurs and is called the timising column. Column 2 is called dimension column as it is used to enter the dimensions of the items of works. The dimensions are entered in the order indicated below: Length, Width, Height or Thickness. Column 3 is called squaring column. The stated dimensions in column 2 are multiplied to determine the quantity of the work either in ml, m2, m3 or in Pcs. or No. Column 4 is called description column and description of the work item is briefly stated. 6.10 The Process of Quantity Surveying A separate sheet (Bar Schedule) is used to prepare reinforcement quantities as shown below. 6.10 The Process of Quantity Surveying I. Taking Off II. Squaring The dimensions entered in Column 2 are squared or cubed as the case may be, multiplied by the timising factor, and the result entered in Column 3. This task is called squaring. All squared dimensions should be carefully checked by another person before abstracting, and if correct the item should be ticked with red. Use two decimal places. III. Abstracting The squared dimensions are transferred to abstract sheets and all similar dimensions are collected in the same category to obtain the total quantity of each item. IV. Writing the final bill After the abstract sheets have been completed and checked, the final bill of quantity is written. The dimensions are copied from the abstracts, and as each item is transferred it should be ticked by a vertical line from the abstract sheets. The description of each item in the final BOQ should be short, precise and descriptive as per the specification. 6.11BOQ Format Items are usually grouped into Divisions or Groups according to an international standard such as the Master Format, Uniformat and RICS. Sometimes a design consultant will produce his own format or combine several formats together. But the best way is to use just one standard that everyone can read and understand. 6.12The WBS(Work Breakdown Structure ) It is used to breakdown the project from one main and relatively big entity into smaller, defined, manageable and controllable units, usually called work groups (packages) or tasks, or, at the finest level of detail (which is undesirable) activities. Each work packages should be: A. Manageable Specific authority and responsibility can be assigned. B. Independent With minimum interfacing or dependence on other elements. C. Measurable In terms of progress. 6.13The Project Cost System Objectives of Establishing Project Cost System: Keep the construction costs of the project within the established budget. Develop labor and equipment productivity information for estimating the cost of future work. Cost Code for stripping concrete formwork for bridge deck (Labor) 6.13The Project Cost System 1. Project Number(9708B ) Eighth project in 1997(Bridge) 2. Area code (05) Geographic location or Associate Field Cost to Specific supervisor or Management 3. Work type code (03157.20) 03157.20 Wood Concrete Formwork for Deck 4. Distribution code (3) Total Material Labor Equipment Sub-Contract 6.14WBS Samples 6-15:Basic principles of taking Off Basic principles of taking Off The following tasks are part of the Taking Off: Describing the item Bracketing (relating the description to the quantity) Timising Dotting on (adding to the timising factor) The Ampersand (ditto) Waste calculations Deduction of items Correction of dimensions (nullifying) 6-15:Basic principles of taking Off 1. Drawings shall be fully understood and clearly detailed. 2. Works, which cannot be measured accurately, shall be expressed as provisional quantity (PQ) and will result in provisional sum (PS) and lump sum (LS) 3. There shall be the understanding that measurements are taken to the nearest cm. 4. Built items shall generally include all possible entrants like labor, materials (including storing, loading, unloading and handling), fixing, use of plant and equipment, wastage of materials, equipment; which will result in a better process for establishing prices and profit. 5. Prior knowledge of the regulations is necessary (For E.g. roofing is measured in horizontal projection). 6. Measurements of civil works shall be carried out in such a way that it can be easily checked and audited. Lecture 7 ESTIMATING EARTHWORK 7.1Earthwork Earthwork includes: 1. Excavation 2. Grading & Leveling: Moving earth to change elevation 3. Temporary shoring 4. Back fill or fill: Adding soil to raise grade 5. Compaction: Increasing density 6. Disposal 7.2Units of Measuring Earthwork Earth work measured in Cubic Meter (bank, loose, or compacted) Bank (BCM): Material in its natural place before disturbance (in Place or In situ) Loose (LCM): Material that has been disturbed or loaded. Compacted (CCM): Material after compaction 7.3-Swelling and shrinking of excavated materials Swelling: soil increases in volume when it is excavated Shrinkage: soil decreases in volume when it is compacted 7.4:Swell Factor and Shrinkage Factor The swell Percentage is calculated as follows: Shrinkage: soil decreases in volume when it is compacted 7.4:Swell Factor and Shrinkage Factor The swell Percentage is calculated as follows: Shrinkage: soil decreases in volume when it is compacted  Example The loose density of soil is 1,250 Kg/cm, bank density is 1,500 Kg/cm and the compacted density is 1,700 Kg/cm. The excavation calculated net quantity is 1,000 cm and the calculated backfilling net quantity is 750 cm. Assuming: 1. 5 $/cm excavation cost. 2. 10 $/cm hauling cost 3. 20 $/cm for importing & compacting the backfilling material. Find: D. Earthworks total cost. E. Excavation & hauling unit cost F. Backfilling & compaction unit cost  Swelling Percentage = ((1,500/1,250) – 1 )) x 100 = 20 % Swelling factor = 1,500 / 1,250 = 1.2 Shrinkage Percentage = (1 – (1,250 / 1,700)) x 100 = 26.47 % Shrinkage factor = 1 – 26.47 = 0.74 Excavation Cost = 1,000 Cm x 5 $/m3 = 5,000 $ Disposal Cost = (1,000 Cm x 1.2) x 10 $/Cm = 12,000 $ Total Excavation & disposal cost = 17,000 $ Backfilling & compaction Cost = (750 Cm / 0.74) x 20 $/Cm = 20,400 $ A. Earthworks total Cost = 17,000 + 20,400 = 37,400 $ B. Total Excavation & disposal Unit Cost = (17,000 / 1,000) = 17.00 $/cm C. Total Backfilling & compaction Unit cost = (20,400/ 750) = 27.20 $/cm 7.5:Typical Soil Volume Conversion Factors 7.6:Excavation Allowance is added for measuring excavation for working space, e.g. nearly 0.5 m allowance should be added around footings and foundations walls for erecting and removing formwork. Allowance is added for sloping the sides of excavation for stability vary with type of ground (most common 45°). 7.7:Approximate Angle of Repose For Sloping Sides of Excavation 7.8Trimming and grading Trimming and grading generally measured in square meter. And should be considered separately. Hand (manual) excavations required to finish the bottom to the desired level. Since machines cannot always work to the required degree of accuracy. 7.9Temporary shoring Temporary shoring : required where ever excavating vertical surfaces are unstable. Temporary shoring costs includes the cost of labor required to erect and remove the shore (props) and the cost of material required for shoring. Temporary shoring is measured by the area of the excavation surfaces that are supported by shoring. 7.10Backfilling Backfilling of excavated materials: is required in most projects. In some cases native excavated materials are unsuitable for backfilling. therefore, filling materials should be imported. Like excavation, backfilling materials measured in cubic meter net in place. In the estimate, the total net volume of the required backfilling material are deducted form the total net volume of the excavated material. (Excavated – backfilled = X) If the result is positive (surplus) X is total net volume for disposal. If the result is minus quantity, more backfilling materials required than excavated. And the difference is total net volume of imported materials required. The actual total quantity of backfilling required will be greater than the total net quantity (Bank Quantity) calculated. Depending upon the type and moisture content of backfilling material specified, and the degree of compaction required. Lecture 8 Measuring Concrete Work 8.1-Measuring Concrete Concrete is generally measured in CUBIC Meters. Concrete costs are affected by location in the building. Concrete is a mixture of aggregate, cement and water One cubic meter of cement is about 1510 kg One bag of cement contains 50kg of material One cubic meter of concrete is about 2400 kg Strength of concrete is usually expressed in terms of the 28-day compressive strength 8.2-Types of Concreting Activities and Concrete Costs of labor, equipment, and materials are relatively high Two major Categories: Plain concrete Reinforced concrete Examples of activities: foundation, slab, column, beam, stairway, etc. Types of Concrete Cast-In-Place Concrete: consists of five major operations: Form preparation Reinforcement placement Concrete placement Curing Form removal Precast Concrete: formed, placed, and cured in a manufacturing plant 8.3Concrete Material Expressed as the volume of concrete required. Usually obtained from a ready-mix concrete supplier. If mixing is conducted on site, quantities of cement, sand, gravel must be taken off Concrete mixture is expressed as a ratio (e.g., 1:2:3): 1 Volume unit of cement 2 Volume unit of fine aggregate 3 Volume unit of coarse aggregate To obtain 1 m of concrete, a total volume of 1.5 m3of dry materials is required. Example: a concrete mix contains cement, sand & gravels in ratios of 1:2:3. Calculate each component quantity. Cement = 1/6 x 1.5 = 0.25 m3 Sand = 2/6 x 1.5 = 0.5 m3 gravel = 3/6 x 1.5 = 0.75 m3 Waste factors: 5 to 10% cement, 8.4-Take-Off Methods for Concrete Concrete quantity is expressed in terms of concrete volume Volume = length x width x height Section Area = Length x Width Three methods are used to determine the volume of concrete: The unit method The perimeter method The centerline method 8.4-Take-Off Methods for Concrete 1-Unit Method Given the height of the walls is 3 m, then: Concrete Volume = 2 (6 x 0.3 X 3) + 2 (7.4 x 0.3 x 3) = 24.12 m3 8.4-Take-Off Methods for Concrete 2-The Perimeter method Given the height of the walls is 3 m, then: Concrete Volume = (2 x 6) + (2 x 7.4) x 0.3 x 3 = 24.12 m3 8.4-Take-Off Methods for Concrete 3-The centerline method Given the height of the walls is 3 m, then: Concrete Volume = (2 x 5.7) + (2 x 7.7) x 0.3 x 3 = 24.12 m3 8.5-Formwork Formwork is a part of most concrete work and is a large part of its cost Formwork is temporary work and not incorporated to the building. So, it is rarely shown on the drawings. Formwork is generally measured in square meter of the actual concrete surfaces. And the ,major cost of formwork is labor costs, since formwork is reusable as much as possible. Plywood formwork could be reused up to twenty to thirty times. And steel formwork could be used much longer. Deduction No deduction shall be made for voids in form work up to 0.25m2 in area 8.6-Steel Reinforcement From the drawings, determine total linear meter of each size bar Waste for lapping and splicing is about 10% Determine the weight of each size bar Weight per linear Meter D is the diameter of Circular bars in MM Lecture 9 Measuring Masonry, Water Proofing and Metal works 9.1-Masonry works Masonry work shall be differentiated for material and: - Above and below grade work Straight and tapering surfaces Face finish Mortar type The unit of measurements are: - Stone wall by volume Stone paving by area specifying thickness Brick & block wall by area specifying thickness Deductions No deducts shall be made in masonry work for opening up to 0.25m2 in area. 9.2-Roof Water Proofing Method of Measurement Roofing & water proofing shall measured by area, without addition for laps and seams. Decorative (reflective) coat to roofing shall be measured separate. 9-3: Metal Work Measurement Floor plates, duct covers, suspension profiles, ladders metal corner protection and linings shall be measured by length stating sizes. Stairway and balustrade rails shall be measured by length stating girth. Protective grills fixed to windows and doors shall be measured by area. Doors and windows shall be enumerated stating sizes. Curtain walls shall be measured by area. No addition or deductions shall be made for deviation in measurement of up to 50mm in length, width and height. Lecture 10 Measuring Plastering Pointing and Painting works 10-1:Plastering and Pointing Methods of Measurement Plaster shall be measured in successive coat with two backing coats measured as an item and the final coat measured separate. Plaster work shall be measured by area identified by the surface of the material it is to be applied to. Plasterwork shall be measured flat with out addition for edges and returns. Plaster to ribbed or corrugated surfaces shall be measured flat. Curved, spherical and conical surfaces shall be measured along the surface. Internal and external surfaces shall be measured separate. 10-2:Painting General Painting, wall papers, plastic and fabric shall be measured by area. Special application to edge shall be measured in length, by stating the girth of the surface exposed for painting. Paints to metal surface shall be measured by area or the weight of the metal to be used. Classification Painting and other decorative finishes shall be classified as follows: - Walls, columns and beams. Ceiling which shall include Soffits of beams, Slabs, staircases and in joinery. Floors. Staircases risers and treads. Skirting. Balustrades and rails. Doors, windows, curtain walls and partition. Metal surfaces