Sunday, January 31, 2016

Internal measured surveys - You have to draw the line somewhere!

Errors or omissions in a drawing can result in serious consequences which can manifest themselves into confusion and disagreement, delays, additional costs and ultimately disputes. These problems can be avoided by ensuring that those who undertake measured surveys are adequately trained and supervised.

Drawings are arguably the most effective form of communication within a construction project and are used at all stages.  It is therefore fundamentally important that all of those who are responsible for taking measurements and preparing drawings understand the significance of what they are doing. The 'life' of a drawing will be developed throughout a project and will vary depending upon the complexity and type of project.  For example concept drawings may be required, which can then become initial design drawings, followed by detailed design drawings.  From this stage the drawings could then be developed into construction drawings and used for tendering and also contract drawings.  Eventually, the drawings will become 'as built' and will be included into a Health & Safety File, a requirement under the Construction (Design & Management) Regulations 2015. The above examples of where drawings could be used in a construction project is not exhaustive, however demonstrates their importance.

Errors or omissions in a drawing can result in serious consequences which can manifest themselves into confusion and disagreement, delays, additional costs and ultimately disputes.  These problems can be avoided by ensuring that those who undertake measured surveys are adequately trained and supervised.  It would be very unwise to assume that undertaking a measured survey is a simple process and a skill that everyone should naturally have.  This is because buildings differ significantly in size, construction and form and the amount of information needed will vary depending on the scope of the project. One thing however that is for certain is that undertaking a measured survey is far more than just obtaining dimensions! A common issues I often found with my surveyors when undertaking an internal measured survey would be that they would sometimes miss key information such as floor to ceiling heights, window cill height, joist direction, services intake of a building, diagonal check measurements and sometimes even forgetting to note wall construction. If a re-visit is necessary to collect missing information then this will be a cost to the business and can impact on profitability.

It is important that the right measuring equipment is taken and used. This will include a folding measure and 5 or 10 metre steel tape (or both) for measuring shorter distances and 25 metre tape and a trundle wheel for measuring longer distances.  Nowadays a digital measure will also be taken which can also be used to obtain, rooms sizes (sqm) as well as single dimension measurements.  When using measuring equipment the 'Surveyor' should be fully aware of the limitations of the equipment and also have an appreciation of distance to be able to discern whether digital dimension are accurate or not.  This is because inaccurate readings can be obtained from a digital measure when the laser comes into contact with reflective surfaces or glass.  If the Surveyor was to write down the measurement without asking themselves if the reading is reasonable, they will have problems when they return to the office and start to prepare their drawings.

Whilst undertaking a measured survey on site the Surveyor must appreciate that either they, or maybe somebody else like an Architectural Technologist will have to interpret the information that has been collected on site in order to prepare the drawings.  Many times I have witnessed Surveyors and Technologists look with complete dismay at a piece of paper in the office that has been given to them by someone who has undertaken a measured survey.  This is because what they are looking at is a rain drenched, smudged, excuse for a drawing that is so 'busy' with lines, dimensions and other information that it is difficult to tell the difference between each!, and they are expected to produce an accurate drawing from this!

To help minimise omissions and errors in drawings there are some simple basic techniques that can be very useful when undertaking measured surveys.  Firstly, I always advised my Surveyors to draw the building footprint (in pencil) first, before taking any dimensions, The pencil could then be overdrawn in pen later.  This would ensure that the drawing was well proportioned and avoid 'squashing' information into a small corner of a piece of paper, because there is no room left on the sheet, toward the end of the survey.  Next, use different colour pens for recording information.  It is much easier to interpret a drawing if say the building outline is in black, dimensions are in red, construction details are in green, sockets, switches and radiators are in blue etc.  Next, when using measuring tapes particularly for longer distances, ensure that there are no twists in the tape and that it is a tight as possible to avoid deflection.  Surveyors must also ensure that dimensions are taken at the same height.  For example is one Surveyor is holding the tape just above the skirting board and at the other end the Surveyor is holding the tape half way up the wall this could result in a significant inaccuracy in a single dimension.

The importance of a comprehensive and accurate measured survey cannot be understated, which can only be achieved through appropriate training and supervision.  Organisations should ignore this at their peril!

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1 comment:

  1. Encourage the use of running dimensions to avoid accumulative error. Review survey before leaving site, have a got everything covered, can I cast a section, do I have all the information I need? Take measurements of face brickwork and joints, this will help when counting courses externally to gauge eaves heights, stack heights etc. Take plenty if photographs too. When I started the cost of film and developing was always a factor, now with digital photography it's snap away until your heart is content.