27 July 2019: Partly split to different pages.
23 Dec 2014: Created.
The traditional manual processes of measurement and billing are:
Take-off (measure dimensions)
Square (calculate products and sums)
Transfer (carry forward quantities)
Bill (describe and list)
Transfer (bring forward quantities)
With the use of BQ production software, squaring, transferring, and abstracting can be combined by linking the dimensions with the final BQ items.
The dimension by dimension taking off may be replaced with CAD or BIM measurement.
However, the processes still exist implicitly though taking a different form.
The process of measuring the quantities of items of work is called "taking-off" or "quantity-take-off" or "QTO" whereby the dimensions of the items of work are (traditionally) written down on a dimension sheet.
Person(s) taking-off are called "Taker(s)-off".
Long hand manual dimension sheets 長式手工計算紙
- Calculations may be set out in the usual arithmetical form:
- This uses less paper, but is difficult to trace, compare and inspect for errors.
Traditional manual dimension sheets
- Traditional dimension sheets used to take-off quantities take the following form:
- Dimensions are set in vertical stack, in the order of length, width and breadth.
- A line is used to separate each set of dimensions.
- Timesings are written on the left column.
- In this column, "/" means multiply, not divide.
- ". " means add, an action called "dotted on".
- The products are given in the right column.
- The descriptions are very much abbreviated to reduce writing.
- The calculation in the description column is the build-up of one of the dimensions.
- It is called a "waste calculation" or "side-cast".
- The annotations "bm B1", "bm B2" in the description column are to identify the locations of sets of dimensions.
- This action is called "sign-posting".
Another kind of manual dimension sheets
- Another kind of dimension sheets is to lay out the dimensions horizontally as follows:
- The products of dimensions are not written one by one.
- Only the total of the products is entered at the bottom.
- This is made feasible with the popular use of electronic calculators with memory function.
- It would be faster to calculate once more than write down all the products before summing up.
- Laying out the dimensions horizontally actually improve the presentation and make comparison of dimensions easier.
- Deductions are indicated by putting brackets to enclose the set of dimensions, and write them in red:
- The right hand columns can be utilized as rate and extension columns for final account purposes.
Manual taking-off schedules 計算表
- Dimension sheets require descriptions against group of dimensions.
- To reduce writing descriptions, dimensions of all quantities of the same item should be measured in one go and this requires greater experience.
- For measurement of group of items which have a lot of inter-related dimensions, use of dimension sheets would be cumbersome.
- A taking-off schedule would be preferred.
- The schedule sets out inter-related dimensions and items in a systematic manner.
- This reduces the need to repeat descriptions.
- This enables measurement of more than one items at the same time.
- This makes comparison and identification of errors easier.
- The following schedule for the same dimensions above measures concrete and formwork at the same time sharing the same set of dimensions:
- The following schedule puts all finishes items sharing the same primary dimensions together and enables easier understanding of their inter-relationship:
- "/" = Times
- () = Deduct
- Deductions are written in red or, if black and white photocopying is anticipated, marked with a minus sign or with brackets.
- The number of columns for each set of dimensions is flexible.
- For items measured Cube, four columns are allocated.
- Since the width of a sheet of paper is limited, a column needs to be shared by more than one item, e.g. two types of floor finishes, and colouring of the boxes is used to distinguish dimensions of different items.
- The process of calculating the products of dimensions and totals on dimension sheets and taking-off schedules is called squaring.
- The person is called a "Squarer" or "Comptometer".
- To ensure correctness, each calculated total entered by a Squarer must be counter-checked and initialled by another Squarer.
- Squaring is a tedious process even with the help of electronic calculators before the use of computer spreadsheets or BQ production software.
- Dimension sheets or taking-off schedules measure more than one item on the same sheet or schedule.
- The same BQ item may appear on more than one sheet or schedule.
- Therefore, it is necessary to collate the individual quantities of the same BQ item appearing on more than one sheet or schedule together to arrive at the grand total of the item.
- A summary schedule is used to bring together the individual quantities to add up the grand total.
- The process of transferring the individual quantities from dimension sheets or taking-off schedules to the summary schedule is called "abstracting".
- The items in the summary schedule are then transferred to the draft BQ pages in the correct sequence with the descriptions expanded in full without abbreviations.
- This process is called "billing" and requires experienced Surveyors to do.
- The whole process from squaring to billing is called "working up".
- Information is transferred from the dimension sheets or taking-off schedules to the summary schedule to the draft BQ.
- Every transfer of descriptions, units and quantities has to be counter-checked by another Surveyor.
- The actions are called "transferring" and "transfer-checking" or "to check transfer".
Cut and shuffle 洗牌式
- Abstracting and working up are tedious processes involving a lot of transferring and transfer checking.
- More movements of information from one to another will increase the chances of making errors
- A method has been devised whereby:
- each dimension sheet only contains one item
- when the taking-off is finished, dimension sheets of the same BQ item are collated and stapled together
- if taking-off schedules are used, the totals are transferred to the respective dimension sheets
- squaring is done to obtain the grand total which is written on the front dimension sheet
- short descriptions are expanded to full descriptions on the front dimension sheets
- the dimension sheets are then shuffled according to the intended BQ sequence
- headings are added as appropriate
- BQ is directly typed from the dimension sheets which have headings, descriptions, unit and total quantities.
- The number of processes is greatly reduced.
- A drawback of this system is that when the dimension sheets are shuffled, the original sequence and logic of measurement are lost.
- Therefore, when the system was originally invented, the dimension sheets came together in 4 on one sheet of paper and were backed with a self impressed carbon copy.
- After taking-off in a logical sequence, the front sheet (A4 size) was taken out and cut into 4 vertical pieces or 2 horizontal pieces which were shuffled and sorted with other sheets.
- The carbon copy was kept in the original sequence to facilitate future reference
- Electronic spreadsheet software like Excel can be used as dimension sheets or taking-off schedules.
- However, using electronic spreadhseets to imitate dimension sheets would require the defining of many calculation formulae.
- If the formulae cannot be consistent defined to enable copy-and-paste repeatedly, the defining process will be tedious and prone to errors.
- Using electronic spreadsheets to imitate taking-off schedules is more suitable.
- However, taking-off schedules when put into an Excel worksheet will become too wide to view on screen.
- It is suggested to set out the dimensions using less columns in the following manner:
- Instead of adding columns for different items of work, codes are used to represent items row by row.
- Note that Columns B and I and Rows 4, 16, 18, 24 and 26 have been reduced to narrow widths and heights respectively.
- They will be used as the boundaries of ranges of columns or rows used in formulae such that any insertion of columns or rows within the boundaries would not go outside the defined ranges unexpectedly.
- The PRODUCT(range) function has been used in the following tables to calculate the Qty.
- Note that the range is from the narrow Column B to Column I.
- Within the defined range, empty cells are regarded as having value 1.
- “$” is used to anchor the columns in case the Qty column is copied to some other places without the intention to change the referred columns.
- The SUM(range) function has been used in the following table to calculate the total.
- Note that the range is from the narrow Row 4 to Row 16.
- The SUMIF(range to check, criteria, range to sum if criteria matched) function has been used in the following table to calculate the total qty per code.
- In the above table, if a cell value in the range to check is equal to the criteria, e.g. a cell value in the range to check “J$4:J$16” matches the value of cell J20, then the cell value on the same row in “K$4:K$16” will be added to the sum.
- “$” has been used to anchor the rows such that when the formula is copied down to other rows, the defined range will not change as shown in the following table:
- Column J may need to be anchored as well if the same formula is copied sideway to other columns.
- To ensure that the sum of all sub-totals equal to the grand total, another check total should be calculated.
- Note that in the following table, the upper boundary of the range to sum is Row 19 the heading row instead of Row 18 the narrow row.
- This serves the same purposes of bounding the ranges.
- An advantage is that Rows 19 to 25 can be moved to elsewhere independent of Row 18.
- It is important that insertion must be by rows or columns not by cells, and copying and pasting of cell values to other places are preferred to cutting and pasting, to avoid corrupting the formulae.
- Formulae must be refreshed by copying the correct ones to the other corresponding cells.
- There must always be a double-check of the totals using alternative method or formula to ensure no omission or duplication.
Paper based table
- When doing quick measurement without using Excel, users may use coloured rows to highlight rows to be added using manual calculator to obtain the total.
- Individual qty per row may be skipped to save time.
- It is important to calculate the totals twice to ensure no error.
- With substantial portion of taking-off information given in taking-off schedules in tabulated and inter-related manner, the portion of taking-off directly on dimension sheets is greatly reduced.
- The need for carbon copy to keep the original taking-off sequence and logic is also reduced
- "Cut" is also no longer required, one independent sheet can be used for one BQ item, leaving the "shuffle" behind.
- Taking-off directly onto these dimension sheets which can be shuffled immediately for billing is called "direct billing"