Construction Measurement : Chapter 3 PDF

# Chapter 3: Measurement ## Accuracy in Measurement - Accuracy in measurement is very important and depends on the prevailing rate of the material (itemwise) and the unit of payment. - The higher the rates, the greater should be the accuracy with which the quantities are calculated. - The dimensio...

# Chapter 3: Measurement ## Accuracy in Measurement - Accuracy in measurement is very important and depends on the prevailing rate of the material (itemwise) and the unit of payment. - The higher the rates, the greater should be the accuracy with which the quantities are calculated. - The dimensions should be accurate especially when the rates are high and to be paid on per unit basis. - The quantities in such cases should be worked out upto at least two places of decimal. - In case, where the rates are low and paid for percent to percentage unit accuracy to perfection may not be needed. - In case of wall where masonry is paid per cubic metre, a little difference in measurement does not make much a difference in the total amount. - In case of width or thickness of wall every small deviation from the actual measurement can make a considerable difference to the total amount. - It becomes necessary to take such measurements accurate upto two places of decimal. - Practically, dimensions must be measured to the nearest cm (0.01 m) areas should be calculated to the nearest 0.01 m² and cubic contents should be calculated to the nearest 0.01 m³. - It is always better to take the thickness of slabs, partitions etc. and sectional dimensions of columns, pillars, beams etc. to the nearest half centimetre (0.005 m). ## 3.1 Units of Measurement in Metric System - The principle for dimensions and measurements is to use millimetre(mm) for very minute dimensions, centimetre(cm) for small dimensions and in case of large dimensions metre(m) should be used. - Distances are generally measured in kilometres(km). ## 3.1.1 Principle of Units for Various Items of Works - The units of different works depend upon the nature of work, project size and shape. - In general, the units of different items of work depend upon the following principles: - Works with heavy volumes or large scale works are taken in cubic unit or volume. The measurements of length, breadth and depth/height are taken to calculate the cubic contents or volume. - Shallow, thin and surface works are taken in area (square metre). The measurements of length and breadth/height are taken to calculate the area. - Long and thin works are taken in linear or running unit and the linear measurement must be taken. - Jobwork or Jobs with precision, piecework, etc. are taken in number. - The units of payments and measurements of various items of work in metric system are same except for earthwork. - Earthwork is measured in cum but payment is made per 100 cum (per % cu m). ## 3.1.2 Units of measurements and payments for various items of works and materials | S. No. | Particulars of Items | Units of measurement in MKS | Units of payment in MKS | Units of payment in FPS | | :------ | :----------------------------------------------------------------- | :----------------------------- | :----------------------- | :----------------------- | | 1 | Earthwork : | | | | | | Earthwork in excavation in ordinary soil, earthwork in mixed | cu m | per % cu m | % cu ft | | | soil with kankar, bajri etc. earthwork in hard soil | | | | | 2 | Rock excavation | cu m | per % cu m | % cu ft | | 3 | Earthfilling in excavation in foundation | cu m | per % cu m | % cu ft | | 4 | Earthfilling in foundation trenches (Usually, not measured and | cu m | per % cu m | % cu ft | | | not paid separately) | | | | | 5 | Earthfilling in plinth | cu m | per % cu m | % cu ft | | 6 | Earthwork in banking, cutting, in road and irrigation channel | cu m | per % cu m | % cu ft | | 7 | Surface dressing and levelling, cleaning, etc. | sq m | per sq m | % sq ft | | 8 | Cutting of trees (Girth specified) | no. | per no. | per no. | | 9 | Puddling, puddle clay core | cu m | per % cu m | % cu ft | | 10 | Sandfilling | cu m | per cu m | % cu ft | | 11 | Quarrying of stone or boulder | cu m | per cu m | % cu ft | | 12 | Blasting of rock (Blasted stone stacked and then, measured) | cu m | per cu m | % cu ft | **Note:** For earthwork, normal lead is 30 m and normal lift is 1.5 m. **Concrete:** | S. No. | Particulars of Items | Units of measurement in MKS | Units of payment in MKS | Units of payment in FPS | | :------ | :---------------------------------------------------------------------------------- | :----------------------------- | :----------------------- | :----------------------- | | 1 | Lime Concrete (L.C.) in foundation | cu m | per cu m | % cu ft | | 2 | Lime Concrete (L.C.) in roof terracing, thickness specified (May also be in volume basis as practice in U.P.) | sq m | per sq m | % sq ft | ## 3.1.4 Standard Modular Bricks - Size of standard modular bricks : Sizes of standard modular bricks as established by Indian Standard Institution are as given below. These standard bricks are being manufactured and used these days. (Standard modular bricks with frogs, all dimensions are in centimetres) | Type of brick | Actual size | Nominal size | | :---------------------- | :-------------------- | :------------------ | | Standard modular brick | 19 cm × 9 cm × 9 cm | 20 cm × 10 cm × 10 cm | | Standard modular brick-tile | 19 cm × 9 cm × 4 cm | 20 cm × 10 cm × 5 cm | - Thickness of wall with standard brick: | Wall | 1/2 brick | 1 brick | 1 1/2 brick | 2 brick | 2 1/2 brick | 3 brick | | :-------------- | :------- | :------ | :---------- | :------ | :---------- | :------ | | Thickness of wall | 10 cm | 20 cm | 30 cm | 40 cm | 50 cm | 60 cm | - Actual thickness of wall with 1 cm mortar joint is 9 cm is 1/2 brick, 19 cm for 1 brick, 29 cm for 1 1/2 brick, 39 cm for 2 brick, 49 cm for 2 1/2 brick and 59 cm for 3 brick. - The thickness of wall is taken as multiple of 10 irrespective of the actual thickness for estimating and payment. - Above 3 brick wall the thickness of wall is measured after construction for payment but for estimating the thickness is generally taken as multiple of 10. - Thickness of R.B. lintel and slab with standard brick: | Layer | Thickness | | :----------- | :-------- | | 1 flat brick | 10 cm | | 2 flat brick | 20 cm | | 3 flat brick | 30 cm | | 4 flat brick | 40 cm | - Using brick tile in combination with brick the thickness of R.B. lintel and slab is taken as 15 cm, 25 cm, 35 cm, etc. ## 3.2 Rules For Measurement - Measurement of work holds the key in planning and execution of any project. - It plays an important role from estimate to execution. - The methods of measurement may differ from state-to-state or sometimes within the states. - Therefore, for convenience, need of adopting a uniform method for all measurements arises. - Therefore, a uniform method to be adopted for measurement was framed based upon the Indian standards - I.S. 1200. ## 3.2.1 General Rules of Measurement - **General rules of measurement are as the following:** - All measurements shall be itemwise and the description in respect to material, labour fabrication, tools, plants and transportation, etc. must be mentioned. - To make the work self explanatory incidental charges for finishing the work to the required specifications must be mentioned. - While booking the dimensions, a specific pattern shall be observed i.e. the order has to be in sequence of length, breadth and height/depth/thickness. - All jobs must be measured to some standard tolerances or as per specifications given. The standard tolerances are as the following: - Dimensions measured must be to the nearest 0.01 m. - Areas measured must be to the nearest 0.01 m². - Cubic contents measured must be upto the nearest 0.01 m³. - Identical natured works under different conditions and nature must be measured under separate items. - There must be full description of materials, proportions, workmanship, accuracy etc. in the bill of quantities. - Works which require site visits for measurement must be described as provisional. - Works from foundation to plinth level, plinth level to first floor, subsequent floorwise measurement must be measured separately. - The units of different work items are based on the following principles: | S. No. | Work | Unit | | :------ | :--------------------------------------------- | :------------------------------------------ | | 1 | Mass, voluminous thick | cubic units/volume | | 2 | Shallow, thin, surface work | square units/area | | 3 | Long, thin | linear/running units | | 4 | Piecework, jobwork | numbers | - For computing, the measurement of length, breadth and height are taken to calculate volume whereas length and breadth are taken to calculate area. ## 3.3 Methods Of Building Estimate - To calculate the dimensions of length, breadth and height/depth, the plan, elevation and section of the building drawing is studied carefully from the study, we can imagine the shape of the building and can have a clear picture in mind. - This helps to take the dimensions correctly. - The main purpose of studying the drawing is to have accurate dimensions. - It is very important to give special attention to junction of walls at the corners and at the meeting points of walls. - All depends upon imagination as there is no hard and fast rule to find out the dimensions from the working drawing. - The quantities of different items can be worked out by any one of the following methods: - Centre-line method - Crossings method - Out-to-out and in-to-in method. ## 3.3.1 Centre-Line Method - In this method, the centre-line length is measured and is used for computing the quantities of different items. - This method requires special consideration at the junctions, meeting points of partition or cross walls, etc. - It is mainly used for rectangular, circular or polygonal building having no cross walls. - For buildings having junctions, the following rule applies: - To arrive at the net centre-line length, deduct the total centre-line length by (one-half breadth x number of junctions) amount. - Following points in relation to the centre-line method are worth noting: - The meeting points of the cross walls with main walls is indicated by the term junction e.g. for one cross wall, there will be two junctions. - It is worth noting that no junctions are formed at the corners of a building. - In the estimate of a room, there is no junction. - For a square or rectangular building having no cross walls, no deduction from centre length will be required as there is no junction. - This is because some portions taken twice are counterbalanced by the same amount of portions left out. - This can be well explained in the following example: ## 3.3.2 Crossings Method - In this method, the centre line length is obtained by subtracting four times thickness of the crossings from the overall perimeter of the building. - This method is not used in today's ultra modern buildings as it is limited only for use in buildings which are perfectly square or rectangular with no junctions of cross walls. ## 3.3.3 Out-to-out and In-to-in Method - This is one of the simple and most practical method which can be used under all circumstances. - In this method, the horizontal walls are taken out-to-out and vertical walls are taken in-to-in. - Therefore, we can calculate the actual working or vertical walls can be accordingly done and payment is made accordingly. - This method is more preferable than other two methods because the other two methods are only applicable in case the buildings are nearly square or rectangular.