2.1 Preparation of Abstracting Sheet

Abstracting is the stage of quantity surveying, under the traditional method of bill preparation, in which the squared dimensions from the taking-off sheets are collected together under their item descriptions, so that all quantities for the same item are gathered in one place, added up and, after deductions, reduced to a single net quantity. The abstract sheet is the working paper on which this is done: it is ruled into columns, headed with item descriptions and arranged in the order the items will appear in the bill of quantities. A well prepared abstract makes billing quick and accurate, and it provides a clear audit trail from every bill item back to the original dimensions. This topic covers the formats of abstract sheets, how to organise measurements on them, how the standard methods of measurement shape the abstract, and how to review it for accuracy.

2.1.1 Abstracting formats

An abstracting format is the layout of the abstract sheet: its size, ruling, headings and the way each item column is divided for additions and deductions. Traditionally, abstracts are prepared on large ruled sheets (often A3 or double foolscap) divided into vertical columns, each column holding one item, with sub-columns for additions and for deductions marked "Dd". Today, the same layout is reproduced in spreadsheets or quantity surveying software, but the principles remain. Example: a quantity surveying firm preparing the bill for a county assembly office block uses a spreadsheet abstract that copies the traditional columns, with each item's description at the head and its plus and deduction quantities below.

Parts of an abstract sheet

• Sheet heading: Project name, section or element (for example "Substructure" or "Concrete work"), sheet number and the name of the abstractor.
• Item columns: Vertical columns, each headed by one item description and its unit.
• Addition and deduction sub-columns: Each column is split so that positive quantities and deductions (Dd) are entered separately.
• Dimension references: Beside each quantity, the taking-off sheet and item number it came from, such as 4/7 for sheet 4, item 7.
• Totals and net quantity: Space at the foot of each column for the total additions, total deductions and the resulting net quantity.

Typical layout of an abstract column

Formats in use

2.1.2 Organizing measurements for clarity

Organizing measurements means arranging the item columns and the entries within them in a logical, consistent order so that anyone can follow the abstract and transfer it to the bill without confusion. The usual rule is to follow the order of the bill: by work section or element, then within each section in the order of the standard method of measurement, and within each group from cubic to square, linear and enumerated items. Entries are written neatly, referenced, and kept aligned so additions and deductions are never mixed. Example: an assistant quantity surveyor abstracting the substructure of a teachers' housing project for a church-sponsored school lists excavation items first, then disposal, filling, concrete, formwork, reinforcement and masonry, matching the bill order.

Principles for organizing the abstract

• Follow the bill order: Arrange columns in the order of the work sections or elements of the bill.
• Order by unit within a section: Place cubic items first, then square, linear and enumerated items.
• One item per column: Never mix items with different descriptions or units in one column.
• Keep additions and deductions separate: Enter every deduction in the Dd sub-column.
• Reference every entry: Write the dimension sheet and item reference beside each quantity.
• Tick off dimensions: Mark each squared dimension on the taking-off sheet as it is abstracted, so none is missed or entered twice.

Steps in setting out an abstract sheet

1. Head the sheet: Write the project, section, sheet number and your name.
2. Plan the columns: List the items expected in the section in bill order.
3. Write column headings: Enter each item description in short form with its unit.
4. Rule addition and deduction sub-columns: Divide each column into Add and Dd.
5. Leave space for new items: Allow blank columns where extra items may arise.
6. Abstract dimension by dimension: Enter each squared quantity in its column with its reference.
7. Tick the taking-off sheets: Mark each dimension once abstracted.
8. Continue sheets in order: Number continuation sheets and carry headings forward.

2.1.3 Applying SMM/CESMM standards

The Standard Method of Measurement (SMM) for building works and the Civil Engineering Standard Method of Measurement (CESMM) set out how work is divided into sections, classified, described and measured, and in which units. Applying them to the abstract means grouping items into the correct work sections or classes, keeping items separate wherever the standard requires separate measurement, using the stated units and following the standard's order, so that the abstract converts directly into a compliant bill. In Kenya, building projects commonly use the Standard Method of Measurement of Building Works for East Africa, while civil engineering contracts such as roads and water works use CESMM. Example: on a water supply project for a rural water company, the abstract follows CESMM classes, keeping pipework (Class I) separate by diameter and depth band as CESMM requires.

How SMM and CESMM shape the abstract

• Work sections or classes: Columns are grouped by the standard's sections, such as excavation, concrete and masonry under SMM, or CESMM classes such as E (earthworks), F (in-situ concrete) and I (pipework).
• Units of measurement: Each column uses the unit the standard specifies, such as m³ for excavation, m² for formwork and tonnes for reinforcement.
• Separate items: Items the standard requires separately, such as excavation in different depth stages or pipes of different diameters, each have their own column.
• Item descriptions: Column headings follow the standard's classification and wording.
• Order of items: Columns follow the standard's sequence within each section, matching the final bill.
• Rules for deductions: Voids and openings are deducted only where the standard's rules require it.

Steps in applying the standard to the abstract

1. Identify the standard in use: Confirm whether the contract uses SMM or CESMM and which edition.
2. List the sections or classes: Prepare abstract sheets for each section or class in order.
3. Check measurement rules: Read the rules for each item to decide which items stay separate.
4. Set units: Head each column with the unit the standard requires.
5. Word headings to the standard: Use the standard's classification in each column heading.
6. Apply deduction rules: Enter deductions only where the standard permits them.
7. Check the order: Confirm the columns follow the standard's sequence before billing.

2.1.4 Reviewing abstracting accuracy

Reviewing abstracting accuracy means checking the completed abstract to make sure every squared dimension has been transferred once and only once, into the correct column, with the correct sign, and that all columns have been added correctly. Errors at this stage pass straight into the bill and can cost the client or the contractor heavily, so a systematic check, preferably by a second person, is essential before billing. Example: before issuing the tender bill for a dairy processing plant, the senior quantity surveyor checks a junior's abstract, finds a deduction for a door opening entered as an addition and corrects it before billing.

Common errors in abstracting

• Missed dimensions: Squared dimensions not transferred to the abstract.
• Double entries: The same dimension abstracted twice.
• Wrong column: A quantity placed under the wrong item or unit.
• Sign errors: Deductions entered as additions or the reverse.
• Casting errors: Mistakes when adding up columns.
• Missing references: Entries without sheet references that cannot be traced.

Steps in reviewing an abstract

1. Check all ticks: Confirm every squared dimension on the taking-off sheets is ticked as abstracted.
2. Check entries against dimensions: Compare a sample, or all, of the abstract entries with their referenced dimensions.
3. Check column allocation: Confirm each entry is under the correct item and unit.
4. Check signs: Make sure deductions are only in the Dd sub-columns.
5. Re-add every column: Recast the additions and deductions, using a calculator or a second checker.
6. Check headings and order: Confirm descriptions, units and sequence follow the standard.
7. Mark checked work: Initial and date each checked sheet.
8. Record and correct errors: Correct mistakes neatly and note them for the record.

Worked example: checking the casting of an abstract column

Given: The column "Concrete Class 20 in foundations (m³)" has additions of 12.60, 4.32 and 3.15 m³ and a deduction of 0.54 m³. The abstractor recorded total additions of 19.97 m³. Check the casting.

Total additions = 12.60 + 4.32 + 3.15

Total additions = 20.07 m³

Answer: The recorded total of 19.97 m³ is wrong by 0.10 m³; the correct total additions are 20.07 m³, with deductions of 0.54 m³ carried separately for reduction.