6 - Construction Estimates Flashcards
The cost of construction facility to the owner include:
- Initial capital cost
* Operation and maintenance cost
Initial Capital Cost
- Land acquisition
- Planning and feasibility studies
- Architectural and engineering design
- Construction, including materials, equipment and labor
- Field supervision of construction
- Construction financing
- Insurance and taxes during construction
- Owner’s general office overhead
- Equipment and furnishing of facility
- Inspection and testing
Operation and Maintenance Cost
- Land rent
- Operating staff
- Labor and materials for maintenance and repair
- Periodic renovations
- Insurance and taxes
- Financing cost
- Utilities
- Owner’s other expenses
area of engineering practice where engineering judgment and experience are utilized in the application of scientific principles and techniques to the problem of cost estimation, control and profitability
Cost Engineering
establishes the baseline of the project at different stages of development of the project
Cost Estimate
one of the most important steps in project management
Cost Estimation
a complex process of collecting available and pertinent information about project scope, expected resource consumption, and future changes in resource cost
Cost Estimation
Process of Cost Estimation
- Collection and review of detailed plans, specs, site data, resource data (labor, materials, equipment), contract documents, gov’t regulations
- Synthesis of information through visualization of the construction process
- Conversion of information to forecast cost of facility
Qualifications of cost estimator
- Extensive knowledge of construction
- Knowledge of construction materials & method
- Knowledge of construction practices & contracts
- Ability to read & write construction documents
- Ability to sketch construction details
- Graphic & verbal communication
- Strong background in business & economics
- Ability to visualize work items
- Broad background in design & code requirements
Types of Cost Estimate (general)
- Conceptual or approximate estimate
2. Detailed estimate
Classification is dependent on:
Cost Estimate (general)
- available information
* extent of effort
Used at the outset of the project when scope are in early stages of development
Conceptual estimate
Used to assess potential cost to determine economic desirability
Conceptual estimate
Quick techniques usually employed: (Conceptual estimate)
- Utilize one project parameter such as floor area, length (roads & bridges), or output (barrels per day)
- Use historical cost information
Estimates that are prepared after scope of works of project are clearly defined
Detailed estimate
Requires effort in gathering information and forecasting cost
Detailed estimate
Prepared for bid purposes or definitive budgeting
Detailed estimate
Fairly accurate projections of construction costs
Detailed estimate
Used for decision making and commitment
Detailed estimate
Types of Cost Estimate (function)
- Design Estimate
- Bid Estimate
- Control Estimate
used by the owner or design professional during the planning and design stage
Design Estimate
used before design and thus rely cost data of similar facilities built in the past
• Screening estimate
based on the conceptual design of the facility
• Preliminary estimate
made when the scope of works is clearly defined and essential features of facility are known
Detailed estimate
based on completed plans and specifications and used by the owner to solicit bids from contractors
Engineer’s estimate
4 types of Design Estimate
• Screening estimate
• Preliminary estimate
Detailed estimate
Engineer’s estimate
used by the contractor for submission to the owner either for bidding or negotiation
Bid Estimate
consists of direct construction cost, job site and general overhead and profit margin
Bid Estimate
Bid Estimate may be derived from:
1 Subcontractor quotation
2 Quantity takeoffs
3 Construction procedures
basis of cost estimate for tasks that are subcontracted by the gencon
Subcontractor quotation
estimate of materials and labor for tasks that will be performed by the gencon based on plans provided by owner
Quantity takeoffs
assess the actual cost of construction considering actual procedure to be used if the project is different from typical desig
Construction procedures
used by the owner for planning long term finances
Control Estimate
used by the contractor for monitoring expenses during construction
Control Estimate
4 Methods of Cost Estimation
- Simple Unit Cost
- Labor, Material & Equipment Cost
- Allocation of Joint Cost
- Estimate Based on Engineer’s List of Quantities
Proration of joint cost to various elements of the project in proportion to element’s cost
Allocation of Joint Cost
_____ are indirect costs which cannot be directly charged to an activity
Joint costs
Joint Costs activity:
- field supervision
- field office cost
- general operating overhead
• Based on a list of items and associated quantities from which the total construction cost is derived
Estimate Based on Engineer’s List of Quantities
• List is made available to bidders and unit prices are solicited from each bidder
Estimate Based on Engineer’s List of Quantities
Refers to various human craft or skill resources that actually build the project
Labor Resource
Cost of labor:
1 wage rate
2 labor productivity
3 labor cost per physical unit of work
Identify skill to be used & determine hourly cost
wage rate
Estimate rate of work
labor productivity
Divide labor rate by productivity
labor cost per physical unit of work
total hourly expense for a particular craft or task
– expressed in pesos per hour (dollars/hr)
Labor rate
– output per unit of labor input
– expressed in output per unit time (e.g. m3/day)
Labor productivity
may either be purchased or leased
• Equipment
Equipment selection criteria:
- Functional performance
- Project flexibility
- Companywide operations
- Economics
Equipment selection criteria - capacity & speed
Functional performance
Equipment selection criteria – multiple uses
Project flexibility
Equipment selection criteria equipment can be used in other projects
Companywide operations
Equipment selection criteria production or hourly cost
Economics
• Equipment economics include:
Production rates
Equipment cost
output per unit time
Production rates
includes direct and indirect equipment cost
Equipment cost
– cost of ownership and operation of equipment
Direct cost
costs that occur in support of the overall fleet of the equipment but cannot be specifically assigned to a particular equipment
Indirect cost
Estimator must be able to read & interpret drawings & specs to develop a complete list of materials required
Materials Estimate
• Estimator identifies the cost of materials including purchase price, shipping, handling & taxes.
Materials Estimate
_______ are simplified to reduce the probability of committing error when several digits are being used.
Measurements
contractor is responsible in establishing the mix that will achieve required strength and workability as specified in the plan
Designed Mix
the design engineer specifies the mix proportion. Contractor’s responsibility is to provide a properly mixed concrete containing the right proportion as prescribed in the plan.
Prescribed Mix
categorized as conceptual estimate
• given a floor area, one can generally have an idea of the total volume of concrete of the structure
Concrete estimate by Floor Area
- all concrete structures are estimated using its volume
- know the dimension of the structure by referring to the plan
- neglect the volume occupied by the reinforcement
• Concrete estimate by Volume Method
_____ has three void cells and two half cells, making it four void cells
Standard concrete hollow block (CHB)
Concrete hollow block (CHB) has standard dimensions of _________
400mm length (16”) and 200mm height (8”). Thickness varies according to use, typically 75mm to 200mm (3” to 8”)
We want to know quantity of materials for a certain masonry work made of CHB, which generally comprises the following:
- CHB
- Cement and sand (mortar) for block laying
- Cement, sand and gravel for filling hollow cores and pouring stiffener columns and beams
- Reinforcing steel bars
- Tie wires
Quantity for plastering depends on the_______
area (area method) and thickness of plaster
______ are temporary materials that are used to hold liquid concrete
Formworks
Due to the __________, its behavior is considered in getting the amount of formworks to be used
liquid property of concrete
Estimates are based on the commercial sizes of materials (formworks)
- Plywood – 4ft x 8ft (1.2m x 2.4m)
* Lumber – 10ft, 15ft, 20ft, 25ft (3m, 4.5m, 6m, 7.5m)
• Units of measure: (Formworks)
- Plywood in pc
- Lumber in lgth or bd-ft
- Nails in kg
Estimating Formworks
• In big construction projects,______ are not directly estimated
overlaps
• Estimators multiply a factor _______ to account for overlaps and material wastage due to cutting of commercial sizes
(from 1.05-1.15)
• The goal is to minimize ______ from cutting sizes of forms in the one whole board
wastage of board
Estimators come up with the most efficient way of cutting rebars accounting for the commercial size of rebars. This is incorporated in a _______
cutting list
is a list of rebar requirements of a project which contains lengths of cut to be used in specific parts of the structure. It also accounts for material wastage minimization
Cutting list
___ refers to gauge No. 16 galvanized iron wire popularly known as G.I. tie wire
Tie wire
______ is used to hold steel bars into its designed position in contact with other bars
Tie wire
circumference of Tie wire
900mm
Length of Tie wire per kg
53m
The most common roofing material is the ______
G.I sheet
G.I sheet is either:
plain, corrugated or ribbed
Commercial sizes for GI sheets:
- Plain: 0.90m x 2.40m
- Corrugated: 0.80m x 1.50-3.60m
- Ribbed: Same as corrugated, width varies depending of the type of rib
