ESTIMATING
BILL OF QUANTITIES
BILL OF MATERIALS

COMMON ACRONYMS
BOQ, BOM, SMM

SOURCES OF INFORMATION/ COMMON STANDARDS OF PRACTICE

1. Practice Standard for Project Estimating - Second Edition (2019), by Project Management Institute (PMI)
2. Civil Engineering Standard Method of Measurement (CESMM), by Institution of Civil Engineers (ICE)
3. MasterFormat by The Construction Specifications Institute (CSI)
4. UniFormat by Construction Specifications Canada (CSC)
5. Royal Institution of Chartered Surveyors - RICS
6. Business Network International
7. Marshall & Swift
8. R.S. Means
9. Engineering News Record
10. Association for the Advancement of Cost Engineering International (AACE)
11. American Society of Professional Estimators (ASPE)
12. International Cost Engineering Council

DEFINITION
An estimate is an approximation of the value of a project before execution of work from the best information available.

The BOQ is a document or a spreadhseet that provides measured (or estimated/ approximated) quantities of work in an itemised way. The BOQ shows estimated quantities (of activities, materials, resources and labor) required to fully complete items of work. It is advisable to use Standard Methods of Measurement (SMM) while preparing a BOQ. (Click to read more about SMM)

Bill of Materials (BOM), on the other hand is a detailed list with quantities of raw materials required for each and every assembly and sub-assembly deemed necessary to manufacture a product.

BOQ and BOM are inter-related. A BOQ takes information from the BOM. BOM is the formula/ recipe. BOQ is the shopping list. BOQ is prepared by quantity surveyors, estimators or cost consultants. BOM is prepared by Manufacturing Engineers and Technicians. In Construction industry, "Material take-off" is similar to BOM.

CLASSIFICATION
Bill of quantities can provide information in many ways depending on the estimation methods used. Various organisations have published classes of estimation with different codes and names. Estimation is performed according to one or some combination of the following basic approaches.

1. EMPIRICAL ESTIMATE (Class 5): Also known as Order of Magnitude. It is normally based on an expert and wild guess and hence also called guesstimate, hybrid of a guess, SWAG or PIDOOMA. It comes from a combination of factors including historical knowledge, long experience in the industry, general thumbs-rules, and very quick mental calculations. At this point a very broad range is proposed with a few high level assumptions. The estimate accuracy at this stage could be +100% and -50%. The project scope/ design at this stage is considered 0-2% defined.
2. PARAMETRIC ESTIMATE (Class 4): Also known as Intermediate, Comparison Estimating, Unit Base, Ball Parking or Benchmarking. It considers parameters like No of Hotel Keys, No of Hospital Beds, No of Court rooms in a courthouse, No of students in a school. Comparison estimating uses analogies and historical information on total costs from past projects of similar building types. The estimate accuracy at this stage could be +50% and -30%. The project scope/ design at this stage is considered 1-15% defined. Some other techniques used are as follows.
1. Elemental Estimating: The elemental method considers the major elements of a building and provides an order of cost estimate based on an elemental breakdown of the building project. Typical elements are design, pre-works, substructure, superstructure, finishing, equipment, services, external works etc.
2. GFA Estimating: Also known as Plinth Area Estimate. This can be done when Gross Floor Area or the Space Program of the building or buildings has been finalised, but designs are still not available. Historical information on total costs from past projects of similar building types is used for estimating.
3. Cube Estimating: This can be done when Gross Floor Area or the Space Program of the building or buildings has been finalised, Storey Heights are known, and Number of floors are established, but designs are still not available. Historical information on total costs from past projects of similar building types is used for estimating.
3. PRELIMINARY ESTIMATE (Class 3): It is normally estimated/ developed when the scope/ design is considered 10-40% defined, design drawings are not fully completed, and specifications are still to be developed. This estimate can show assemblies as line items. It can be used to acquire initial budget approval to proceed further to studies and design stages. It also forms the basis of budget control for rest of the life cycle of the project. The estimate accuracy at this stage could be +30% and -20%.
1. Provisional Estimate: It contains activity items with provisional (hypothetical) quantities and issued to tenderers on the basis that the quantities will be remeasured during construction where they differ from the actual quantity. This type of BOQ is normally used where the designs, drawings and specifications cannot be finalised prior to calling tenders. Incomplete designs and Minimum/ Guide specifications may be attached to the Request for Bids. It has the advantage of reducing the documentation period and allows the Contractor to commence work earlier.
2. Specified Estimate: Instead of having a seperate document for specifications, every line item in the list shows the specifications too. Specifications maybe written as notes in the preamble at the start of the estimate; or specifications for an item is written as a part of every line item. Provisional (hypothetical) quantities are issued to tenderers on the basis that the quantities will be remeasured during construction where they differ from the actual quantity.
4. SUBSTANTIVE ESTIMATE (Class 2): It is based on detailed system and component design where all systems and componewnts are defined 30-75% with necessary objectives, scope, design, specifications and deliverables. At this stage project may be sent to bidders for lumpsum pricing.
5. FINAL ESTIMATE (Class 1): Also called the Firm Estimate or Final BOQ, the requirements, scope, specifications and deliverables are described precisely. Project is considered 65-100% defined, and quantities are +15 to -10% accurate. Material take-offs are done for every work section and/or trade. Market quotations are acquired to understand trade requirements, inclusions, exclusions and prices. As a result, Firm BOQ can be priced without adding many risks and assumptions, providing maximum reliability and a good financial control. Costs of changes can be accessed easily.
1. Trade BOQ/ Package Based Estimate: Work items are grouped as trades. Typical trades are earthworks, ground improvements, concrete, masonry, HVAC, MEP, landscaping etc.
2. Sub-Trade BOQ/ Section Based Estimate: Work items are grouped as sections. It is similar to trade BOQ but has more groupings to cater to sub-trades. Work Section BOQ is most favored by Contractors. Instead of listing Concrete as a single line (as is done in trade BOQ), the Work Section BOQ will list In-situ Structural concrete, Precast Structural concrete, Architectural Concrete, etc., as seperate line items.

There is a direct co-relation between the design details and the accuracy of estimate. As design becomes more detailed and mature the accuracy of estimate increases. Various standards exist in the world, and various terminologies and thresholds are used to define the co-relation. The most commonly used co-relation is shown below;

Empirical Estimate

Parametric Estimate

Preliminary Estimate

Substantive Estimate

inal Estimate/ take-off

Empirical Estimate

Design Definition at 0-2%

Parametric Estimate

Design Definition at 1-15%

Preliminary Estimate

Design Definition at 10-40%

Substantive Estimate

Design Definition at 30-75%

Final Estimate/ take-off

Design Definition at 65-100%

Design Definition at 0-2%

Estimate Accuracy -50%, +100%

Design Definition at 1-15%

Estimate Accuracy -30%, +50%

Design Definition at 10-40%

Estimate Accuracy -20%, +30%

Design Definition at 30-75%

Estimate Accuracy -15%, +20%

Design Definition at 65-100%

Estimate Accuracy -10%, +15%

Bill of materials can be classified as follows;

1. Manufacturing BOM: It comprises all the assemblies and parts required to construct a finished item ready to be shipped. It also incorporates the packaging materials required to send the product to the customer. It contains processes that require execution on the product prior to completion and stores all the information required for manufacturing activities.
2. Engineering BOM: It defines the design of the finished product. It includes all alternative and substitute part numbers and parts contained in the drawings and drawing notes.
3. Explosion BOM: It displays an assembly at the highest level broken down into its individual components and parts at the lowest level
4. Implosion BOM: It displays the linkage of individual parts at the lower level to an assembly at the higher level

WHY
A BOQ is issued to bidders to provide their prices against the quantities given for every work item. A BOM is a centralized source of information containing a list of items used to manufacture a product and the instructions on how to do so. A BOQ or a BOM helps the construction/ production process is many ways, some of which are given below;

1. Comprehensive Planning of the Project
2. Eliminates Guesswork
3. Saves Time & Cost of Construction
4. Assists in Procurement of materials
5. Communication between teams/ stakeholders
6. Fair and accurate system for tendering.
7. Reliable base for budget control and accurate cost reporting
8. Low risk tendering environment
9. Basis for the valuation of variations
10. Assists in Preparation of interim payments and finalazing accounts
11. Cashflow forecasts

WHEN
Preparing and issuing a comprehensive (firm) bill of quantities requires that the scope is well defined, design is complete, and a specification has been prepared. But this is not always the case. Sometimes an early engagement with the market/ contractors is required, especially in a fast track environment. Sometimes the designs are still not complete, designs are at conceptual stages, and designs are to be left for the contractor to complete while starting early works. Sometimes it is important to acquire lastest technologies from the market rather than limiting options. In all cases it is necessary that the description of the works to be done is complete while the quantities may be approximate. The way a BOQ is prepared and issued to the bidders also depends on the form of contract to be used. e.g. Firm BOQs are commonly used in Lumpsum contracts, whereas approximate BOQs are commonly used in re-measurable contrats.

HOW
A typical table for Bill of Materials has the following information.

1. Serial Number
2. Product code
3. Part name
4. Part number
5. Part revision
6. Part description
7. Quantity
8. Unit of Measure
9. Unit Size/ Dia
10. Unit Length
11. Unit Weight
12. Quantity
13. Unit Rate (if priced)
14. Rate Reference (if priced)
15. Amount (if priced)
16. Related Specifications
17. Related Drawings
18. Remarks

A typical table for Quantity Take off Sheet has the following information.

1. Serial Number
2. Project WBS Code
3. MasterFormat Code
4. Item Description
5. Item Sub - Description
6. Work Type
7. Location
8. Reference Doc/ Dwg
9. Qty
10. Units
1. Materials
1. Times
2. Times
3. Length
4. Width
5. Height/ Depth
6. Quantity
7. Units
8. Rate (if priced)
9. Rate Reference (if priced)
10. Materials Amount (if priced)
2. Equipment
1. Times
2. Times
3. Quantity
4. Units
5. Rate (if priced)
6. Rate Reference (if priced)
7. Equipment Amount (if priced)
3. Manpower
1. Times
2. Times
3. Quantity
4. Units
5. Rate (if priced)
6. Rate Reference (if priced)
7. Manpower Amount (if priced)
4. Subcontractors
1. Times
2. Times
3. Quantity
4. Rate (if priced)
5. Rate Reference (if priced)
6. SubContractor Amount (if priced)
11. Remarks

A typical table for BOQ has the following information.

1. Serial Number
2. Project WBS Code
3. MasterFormat Code
4. Nature of work (Supply/ Install)
5. Item Description
6. Item Sub - Description
7. Sub-Item Description
8. Inclusions
9. Exclusions
10. Location
11. Reference Doc/ Dwg
12. Total Quantity
13. Rate (if priced)
14. Rate Reference (if priced)
15. Total Amount (if priced)
16. Remarks

It is important to prepare the tables using a standrad methodology or standard of practice to eliminate/ minimise errors. Common erors are given below;

1. Incorrect measurement of the quantities
2. Not considering deductions for openings
3. Not considering reusable materials
4. Insufficient/ Non-quantifiable information given in the descriptions, scope documents or specifications
5. Leaving room for assumptions/ interpretations
6. Any Changes made are overlooked
7. Incorrect assumptions
8. Omission of temporary works/ access requirements
9. Omission of wastage
10. Duplications and Omissions
11. Arithmetic errors
12. Change in currencies
13. Change in units of measurement
14. Inclusion of irrelevant preliminary items
15. Exclusion of relevant preliminary items/ indirect costs
16. Exclusion of Contingencies, Overheads, Profits
17. Exclusion of depreciation/ inflation for long term projects
18. Exclusion of Duties, Customs fees, shipping charges, delivery conditions
19. Adding too many options and exclusions
20. Not considering inclusions and exclusions provided by subcontractors or suppliers
21. Past performance used to assume future productivity
22. Incorrect understanding of the work method/ procedure
23. Incorrect understanding of employers requirements
24. Incorrect understanding of required standards
25. Incorrect understanding of durations and resources required to acquire approvals from AHJ

EXAMPLES

#

Location

Reference

WBS

CSI

Work Type

Description

Sub-Description

Quantity

Units

Rate (USD)

Amount

#

1

Location

North

Reference

DWG-00090-0987

WBS

XYZ-00001-0000

CSI

09000000

Work Type

Supply & Install

Description

Stone Masonry

Sub-Description

Complete with Mortar and Pointing

Quantity

149.00

Units

CBM

Rate (USD)

2.00

Amount

298.00

#

2

Location

South

Reference

DWG-00090-0987

WBS

XYZ-00001-0000

CSI

09000000

Work Type

Supply & Install

Description

Stone Masonry

Sub-Description

Complete with Mortar and Pointing

Quantity

1650.00

Units

CBM

Rate (USD)

2.00

Amount

3,300.00

DOWNLOADS

1. Activity Quantity Take-off Sheet
2. Resource Quantity Take-off Sheet