Sunday, November 1, 2015

MODES OF MEASUREMENTS in DESIGN EXECUTION

Post 130   by Gautam Shah

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There are two major processes in design execution: Checking the quantity and quality of work. Both of these deal with vast number of items and their variants. The items’ variations persist in procedures like estimating, specification writing, rate quotations, task supervision (productivity of human and machine resources) and billing. The immediate efficiency can occur by reducing the number of items (types).

 Wikipedia image by Author Martinvl

Major job agencies like Public Works Departments, Railways, shippers etc. dictate the job market, and evolve their own 'Game Rules' for measuring and paying for the works. The rules are very practical, as have evolved through years of experience. The rules may vary in minor details from one agency to another, and one geographical region to another. Over the years, however, a common System of Taking Measurements comes into being.
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SOME CONSIDERATIONS FOR MODE OF MEASUREMENTS:

Use of Appropriate Technology: Measurement taking must occur with the appropriate technology on hand. A steel fabrication job ideally needs to be paid by weight, but it is not possible to weigh a complex fabricated object on the site. Earthworks on contoured terrain can only be measured in terms of truckloads of soil moved or hours an excavator operates at a site. Intricately shaped and massive concrete structure cannot be measured in volume and must be paid in terms of concrete poured in. Painting work on a complex steel structure cannot be measured in surface area, so is paid per volume of paint applied. Earthworks on a small and remote location are measured in multiple lengths of the pick axe handles (approx. 750 mm), rather than using measure tapes or automatic measuring devices.

 Wikipedia image by Author: Own Work (de:Benutzer:Suricata)

Commercial Value and Frequency of the item: The effort expended in measuring an item also depends on the commercial value and frequency of its occurrence. Items of low commercial value are measured in larger measure modules. An item is considered costly if its labour, material or techniques of installation are rare, or difficult to procure. An item is also costly, if it forms a large component of the total cost of the scheme. Frequently occurring items are measured thoroughly, once, and its product is used as a basis.

Identity in time and Space: An item forms a distinct identity depending on the nature and time of execution. Frames for doors and windows are fitted in masonry, before the plaster work begins, the shutters are installed after the plaster and flooring work, whereas fittings-fixtures hardware, are fixed after painting and polishing work. Here the item is the same, but likely to be paid in parts at different time schedules.

Multiple modes of measurements: Some items require multiple modes of measurements. A design office, supplier, manufacturing workshop, and the site supervisor, all have distinctly different ways of dealing with the same item. For example a flat-coiled spring that is used in a sofa can be readily measured in a linear measure, but real cost can only be estimated in a weight measure, (by which it is purchased). Similarly furnishing fabric may be estimated in square measures (area) but must be resolved into lengths (of woven fabric widths) for purchase. Leather may be estimated in square measure (area), but can be purchased in weight measures only. A designer tends to estimate the item in the form represented in the drawing, whereas the site-in-charge person would estimate the item in terms of its market form.


wikipedia image by Author JKBrooks85
Applying same Mode of Measurement: Some work items are reclassified so that can be measured using the same mode of measurement. RCC slabs are paid in square measures (area), beams and columns paid in linear measures, and other massive works like foundations paid in cubic measures. Such multiplicity of measures can be avoided by awarding all RCC items in volumetric quantity and by separately awarding the form work and casting labour.

Newer Modes of Measurements: Traditional markets do not readily accommodate the changes in tools, technology, or labour inputs that happen over a period. Yet, newer modes of measurements do come up, for example, marble flooring was once made mostly from factory cut pieces. On-site cutting was rare, as it required cutting with a chisel and manual edge-dressing (old technique). Each splitting (cutting with a chisel also required post dressing of two edges) was charged in double lengths. But with small rotary cutting machines (now commonly used) both split edges get a clean (polished) cut in a single effort. Earlier practice of charging marble floor-fixing by square measures, and splitting + edge dressing by length are not commercially valid or viable any longer. Now the marble flooring work is charged through one all-inclusive rate. Often this rate (square measure) also includes providing and laying the substrate as well as polishing the floor. And, in many instances to save the labour of billing etc. a certain percentage for skirting work (which earlier was a linear measure) is added to the floor work (square measure).

 Wikipedia image

New work items: Newer work items require a very different attitude for mode of measurement. Cleaning a site (installations, furniture, furnishings) after the work is over, is a problem, for which no organized labour contractor is available. For this work no traditional mode of measurement practice exists. So a lump sum amount, or a percentage amount over the cost of painting is charged for the job of final cleaning of the site. This is a non-traditional item, but depending on the relevance, a logical solution has been achieved.

Mode of measurement and billing: These two are intimately linked. When all sub items within a bill are dealt in one mode of measurement, and priced by a single or similar rates, the updating, revision or scrutiny becomes easier.

Abstracting the modes of measurements: Mode of measurement of one type is generally transferable into another type (linear to square to cubic) (volume to the mass) (speed to distance and time). RCC slabs can be paid in square or cubic measure. A taxi driver may charge you on per kilometre basis, or on per day travel basis (that may include the cost of waiting). Where, for any reason, such transfers are not possible, permissible or illogical, the mode can be generalized into a neutral denominator like Monetary Value. Such abstracted modes are absolute in nature and provide a common ground for evaluation of many dissimilar entities.

Wikipedia image of Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea

Usefulness of Mode of Measurement: Mode of measurement is a very critical tool for efficient use of resources. Saving (in monetary terms) of 7.5 to 12% can be achieved by efficient mode of measuring and related accounting methods. An efficient and logical measurement practice can reduce the labour and time involved in estimating and billing a job. Reduce the total number (types) of items and number of different rates for them, (by suitable accommodation of minor variations and acceptable methods of generalizations). Eliminate chances of disputes at all levels. In many instances extra items are eliminated, and where such items do appear, a clear basis for their identity is available.
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