Types of drawings according to their stages of development
Sketch design drawings or outline design drawings
Preliminary design drawings.
BD (Buildings Department) submission drawings.
Construction drawings or working drawings or variation drawings issued under post contract instructions.
Shop drawings, fabrication drawings or installation drawings prepared by Contractors.
As-built drawings by Contractors.
Types of drawings according to their contents
Site location plan
Site survey plans
Architectural elevations and sections
Architectural detailed drawings
Structural detailed drawings
M&E schematic drawings
M&E detailed drawings
Manage Tender Drawings
Characteristics of issuing drawings:
Drawings are usually not issued in one batch
Revised drawings are usually issued during the course of taking-off
Revised drawings are usually not given a revision number during the pre-contract stage
Therefore, a system should be implemented for identification of drawings
Upon receipt of drawings:
Check whether they are complete according to the covering letter
Chase for omitted drawings
Stamp drawings received with a date-received chop
Register the drawings to facilitate following-up
Dispatch to the relevant team members after registration
Check Sufficiency of drawings 图纸的齐全性
Upon receipt, drawings should be checked to see whether they are sufficient for the purposes. If there are insufficient drawings or details, the Architects and Engineers shall be liaised with to pursue the outstanding drawings
Use Drawing Register 图纸登记录
A Drawing Register should be set up to record the drawings received
The format of the Drawing Register can be as follows:
During the course of taking-off, Surveyors should check that they are using the latest versions of drawings
The Drawing Register is useful for tracking revised drawings for use. If drawings are provided late, measures should be taken to resolve the issue
The Drawing Register may be adapted as the Schedule of drawings to be included in the Tender Documents
The Drawing Register may also be used for the management of drawings in the construction stage
Use dimensions shown on drawings
Use marked dimensions in preference to scaling from the drawings.
With drawings drawn by hand without using CAD, it may be possible that the draftsman makes the last minute change to the dimensions without changing the drawn sizes.
Verify the correctness of the dimensions shown before using them:
The total of running dimensions should match the overall dimension.
The actual scale (printed drawings or on screen) should match the stated scale without enlargement or reduction.
The scale in one direction should match the scale in the perpendicular direction without distortion.
The same object should not have different dimensions on different drawings.
Use scale rule to help the above verification.
Use correct scale rule
Scale rule may be used when:
Counter-checking the dimensions.
Dimensions are insufficient.
The shape is complex without adequate dimensions.
The unit rate for a work item is low with minor cost implication in case of some tolerance in measurement.
The drawings will usually state the scale (1:10, 1:20, 1:100, etc.) of the drawings. Older drawings may draw a scale rule on the drawings.
When using scale rule:
Check the overall or critical dimensions on the drawings to ensure that there is no enlargement, reduction or distortion in either direction to the scale stated on the drawings or on screen.
Use the correct scale on the scale rule matching the true scale of the drawings, e.g. use 1:100 scale rule for 1:100 scale drawings, and do not use 1:50 scale rule.
Avoid conversion of scales, e.g. converting from 1:10 to 1:30.
Use simple scales like 1:1, 1:10 or 1:100 instead of 1:20, 1:25, 1:30 if conversion cannot be avoided.
In special circumstances where the matching scale rule is not available, conversion from the dimensions measured to the actual dimensions represented must be done very carefully with the conversion factors double checked before use.
Note that on a scale of 1:100:
A length measured 1 unit would mean 100 units.
A square measured 1 x 1 unit would represent 100 x 100 square units.
A cube measured 1 x 1 x 1 unit would represent 100 x 100 x 100 cubic units.
Therefore, on a scale of 1:X:
The linear conversion = 1: X
The area conversion = 1: square X.
The volume conversion = 1: cubic X.
Failure to recognize this exponential effect will lead to serious errors.
For example, when using 1:100 scale rule to measure 1:200 drawings:
All readings on the scale rule should be multiplied by 2 to obtain the actual linear measurement
It should also be noted seriously that the multiplying factor to obtain the area is 2 x 2 = 4
计面积时，若按1:100读数先计面积才转换，要小心换算率乃2 x 2 = 4
The conversion factor for scaled area measurement is the square of the conversion factor for scaled linear measurement. 平面换算率是直尺换算率的2次方
The conversion factor for scaled volume measurement is the cube of the conversion factor for scaled linear measurement. 立方换算率是直尺换算率的3次方
Use accurately calibrated measurement instruments
Other measurement instruments may also be used:
Curvimeter: a mechanical or digital instrument with a wheel for measuring lengths (some stationery stores may still have this on sale)
Planimeter: an instrument with a number of arms for measuring areas (it may be difficult to find it now on sale)
Digitiser: an electronic tablet with a pen for measuring lengths and areas (this is available from some computer hardware stores); a PC computer equipped with digitising software is required for use
CAD software: for measuring the numbers, girths and areas directly from the CAD drawings
Every time before using these electronic or mechanical instruments:
The scale should be set to the same scale as the drawing
The accuracy should be verified
When conversion is unavoidable, calculate the conversion factor carefully
To signify that things on drawings have been measured：
Parts of the drawings should be coloured as and when those parts have been measured；for example, when a beam on a structural framing plan has been measured, the beam is coloured; when the finishes inside a room have been measured, the area inside the room is coloured
Either the area or the perimeter may be coloured
The same colour should be consistently used for the same kind of materials or construction; for example, red colour is used to colour brick walls and green colour is used to colour concrete walls
Shades or crosses can be used in case the number of colours available is not sufficient
Tracing and distinguishing those measured from those not yet measured
Checking visually that the extent measured is correct
Creating a little bit of fun when measuring
If this practice is maintained, then if a certain part of a drawing has not been coloured, it would readily mean that it has not yet been measured
Therefore, it is important that the drawings should not be coloured before measurement, since one may easily forget that he has not yet measured the coloured parts.
If a drawing is full of texts, lines and figures and is too condensed that some advance colouring is desirable to help reading the drawings, then partial colouring or colouring the boundary only should be adopted before measurement. After measurement, the full colouring is put in to signify completion of measurement
When a thing shown on the drawings is to be measured several times for different things, e.g. measuring concrete and formwork first and then reinforcement later, then use partial colouring to indicate different phases of measurement
Line through notes on drawings
Notes and annotations on drawings should be taken into consideration in the measurement or writing BQ descriptions
As soon as this is done, a note or an annotation should be lined through
Example of lining through:
Lining through should be done by lining along the notes and annotations using coloured pencils in bright colours, e.g. yellow or orange. Dark colours which may cover up the notes or annotations should not be used
Fountain pens, ball pens or felt pens, which use permanent ink, should not be used since they appear to be crossing out the Annotations and figures in a permanent manner
Coloured pencils should be used because any wrong marking can be erased, but marking of useful information should not use easily erasable coloured pencils
Fountain pens, ball pens or felt pens should be reserved for making permanent changes on drawings. Red ink should be used
Upon completion of taking-off, the presence of any note or annotation on drawings but not yet lined through may mean that they have not yet been taken into account
Some objects on drawings may have repeating annotations on the same drawings, e.g. a reinforcement bar may be annotated more than once. When the object has been measured, the first annotation is to be lined through. When the next repeating annotation is encountered, instead of lining through, a loop may be drawn over it to signify that the object has already been measured once and this annotation is not measured again. Such practice will help ensure that the same object will not be measured more than twice
Example of looping:
Drawings superseded should be marked with the words "SUPERSEDED" at conspicuous location on the drawings, usually against the drawing number
Superseded drawings which have not been used should be thrown away
For superseded drawings which have been used and have information marked on, the information should be transferred to the updated drawings before throwing away the superseded drawings
If there are a lot of information marked on the superseded drawings, the superseded drawings should be kept and stapled at the back of the updated drawings
The drawings actually used for taking-off are called "Taking-off drawings" or "BQ drawings"
The BQ drawings should become the Tender Drawings
Tender Drawings and Contract Drawings
Upon completion of taking-off, the Drawing Register should be checked against the drawings actually used for taking-off and the Register can be transformed to a Schedule of Tender Drawings showing a consolidated list of the drawing numbers, titles and the last dates of receipt. Such Schedule of Tender Drawings will be included in the Tender Documents for the reference of the Tenderers and the drawings so listed will become the Contract Drawings
Theoretically, the contents of Tender Drawings actually issued to Tenderers for tendering or made available for Tenderers to inspect should be the same as those used for taking-off and listed in the Schedule of Tender Drawings, and the contents of Contract Drawings actually bound should be the same as the Tender Drawings. However, because the Architects and Engineers may still be making changes during the course of taking-off through the construction stage, it is very usual that the contents of Contract Drawings are more up-to-date than Tender Drawings which are more up-to-date than those used for taking-off
Theoretically, the Architects and Engineers should make sufficient copies of the drawings issued to the Quantity Surveyors as reserve for use as Tender Drawings and sufficient copies of Tender Drawings for use as Contract Drawings. However, this is often forgotten. In practice, the BQ drawings instead of the Tender Drawings or Contract Drawings are used for measuring omissions for variations
With the popular use of CAD software, the discrepancy could be eliminated by making backup copies of the CAD files. Of course, co-ordination by the Quantity Surveyors with the Architects and Engineers and co-operation from them are required