Taking-off Measurement for the Foundation

Taking-off Measurements

Estimating costs for particular construction work can be divided into categories as follows.

1. Method of construction
2. Detail drawings
3. Measurements
4. Specification of materials
5. Availability of material and market price
6. Quantity (Labour and Material)
7. Transport and operational expenses

Measurements are one of the most important parts in estimating the construction cost.  Estimate the materials, labor, transport, or whatever the expenses are prior to the quantities gathered from the drawings. Therefore, quantities must be very accurate to estimate the construction cost.

Taking-off measurement is called the process of recording dimensions in a standard way which is accepted by construction professionals. It is done in a particular sheet called TDS. Taking-off measurements and estimating the project quantities are time-consuming, but it is required to be done. Because to reduce errors and give a rational elucidation for the estimated quantity whenever necessary. The measurements entered are should be accurate while being clear and readable for others.

In this article, we will discuss how we take measurements for excavation work for the foundation in a building.

Foundation Detail

Foundation Layout

According to the given details in the drawings, we can find the centerline girth of the building.

Horizontal Lengths          = 3 x 20’-0” + 2 x 10’-0”

                                         = 60’=0” + 20’-0”

                                         = 80’-0”

Vertical Lengths              = 3 x 20’-0” + 2 x 12’-0”

                                         = 60’-0” + 24’-0”

                                         = 84’-0”

Centerline Girth            = 80’-0” + 84’-0”

                                        = 164’-0”

Let’s find the excavation volume of the rubble foundation with the following steps;

Excavation for Rubble Foundation            = 164’-0” x 1’-6” x 2’-0”

                                                                   = 492 Cu.ft

Ddt

For Column bases            = 8 x 3’-0” x 3’-0” x 2’-0”

                                         = (144 Cu.ft)

Therefore Total excavation for Rubble Foundation = 492 Cu.ft – 144 Cu.ft

                                                                                                    = 348 Cu.ft

                                                                                                   = 3.48 Cube

                                                                                                   = 9.85 m3

Excavation for Column Bases      = 8 x 3’-0” x 3’-0” x 3’-0”

                                                      = 216 Cu.ft

Total Excavation Work for the foundation of the Building = 348 Cu.ft + 216 Cu.ft

                                                                                                                = 564 Cu.ft

                                                                                                                = 5.64 Cube

                                                                                                                = 15.96 m3

                                      

Material Calculation for Concrete Mixing Designs

Introduction to Concrete

Concrete is an artificial stone which we used in construction. Concrete can be divided into two main categories as follows;

1. Mass Concrete
2. RCC Concrete

The only different between Mass concrete and RCC concrete is reinforcement. The mass concretes are designed without reinforcement while RCC concrete are designed with considerable reinforcement. The mass concrete are not being used as structural concrete. It is only used for leveling & as ground floor slabs and may be as some other architectural designs.

The concrete is basically made with cement, sand, metal and water to mix them together. The metal used for increasing the volume and also to give a considerable strength to the concrete. The sand used to fill the rest of the void which cannot be filled with metal. The cement is used in concrete will make these components attached well together with the jelly kind of thing that they produce in the mixing. Again the cement will make sure to fill other micro small voids which the sand cannot go through. 

Density of Cement  = 1440 kg/m3

Density of Sand      =  1920 kg/m3 

Density of Metal     = 1800 kg/m3

How to Find the cement, sand & metal quantities used in different type of  concrete mixing designs.

Calculations are based on the following assumption;

• Sand includes 15% wastage
• Cement Included 5% wastage
• No wastage includes for metal
• Contribution of the sand 65% per 1m3 of concrete by volume
• Contribution of metal 85%  per 1m3 of concrete by volume
• Contribution of cement 2% per 1m3 of concrete by volume

Nominal Mixing Designs

1. G15 (C:S:M = 1:3:6)
2. G20 (C:S:M = 1:2:4)
3. G25 (C:S:M = 1:1 1/2:3)
4. G30 (C:S:M = 1:1:2)

Contribution of material for 1 m3 of concrete = Sand 65% + Metal 85% + Cement 2%

                                                                          = 152 %

                                                                          = 1.52 m3

This means (1.52m3) to produce a 1m3 of solid concrete requires a 1.52 m3 of the actual quantity of the above material.

Hence, we can find the required material for the different type of concrete.

Required Material for G15 Concrete

1. G15 (C:S:M = 1:3:6)

Cement  = 1/10 = 0.1

Sand      = 3/10 = 0.3

Metal     = 6/10 = 0.6

Number of 50 kg cement bags per 1m3 = 0.1 x 1.52 m3 / Volume of cement bag

                                                             = 0.152 / 0.035

                                                             = 4.343 

                                                             = 4.343 x 1.05 

                                                             = 4.560 Nr

Therefore required number of cement bags per 1Cu = 4.56 x 2.83 Nr

                                                                                   = 12.91 Bags

                                                    Say Nr of Bags      = 13 Nos

 Required amount of Sand = 0.3 x 1.52 Cu 

                                           = 0.456 Cu

                                           = 0.456 x 1.15 Cu

                                           = 0.525 Cu

Say Required Amount of Sand      = 0.53 Cu

 Required amount of Metal = 0.6 x 1.52 Cu 

                                            = 0.912 Cu

Say Required Amount of Metal      = 0.91 Cu

Required material for G20 Concrete

2. G20 (C:S:M = 1:2:4)

Cement  = 1/7 = 0.14

Sand      = 2/7 = 0.29

Metal     = 4/7 = 0.57

Number of 50 kg cement bags per 1m3 = 0.14 x 1.52 m3 / Volume of cement bag

                                                             = 0.21 / 0.035

                                                             = 6.00 

                                                             = 6.00 x 1.05 

                                                             = 6.30 Nr

Therefore required number of cement bags per 1Cu = 6.30 x 2.83 Nr

                                                                                   = 17.83 Bags

                                                    Say Nr of Bags      = 18 Nos

 Required amount of Sand = 0.28 x 1.52 Cu 

                                           = 0.43 Cu

                                           = 0.43 x 1.15 Cu

                                           = 0.50 Cu

Say Required Amount of Sand      = 0.50 Cu

 Required amount of Metal = 0.571 x 1.52 Cu 

                                            = 0.87 Cu

Say Required Amount of Metal      = 0.87 Cu

Required material for G25 Concrete

3. G25 (C:S:M = 1:1.5:3)

Cement  = 1/5.5 = 0.18

Sand      = 1.5/5.5 = 0.27

Metal     = 3/5.5 = 0.55

Number of 50 kg cement bags per 1m3 = 0.18 x 1.52 m3 / Volume of cement bag

                                                             = 0.27 / 0.035

                                                             = 7.71 

                                                             = 7.71 x 1.05 

                                                             = 8.1 Nr

Therefore required number of cement bags per 1Cu = 8.1 x 2.83 Nr

                                                                                   = 22.92 Bags

                                                    Say Nr of Bags      = 23 Nos

 Required amount of Sand = 0.27 x 1.52 Cu 

                                           = 0.41 Cu

                                           = 0.41 x 1.15 Cu

                                           = 0.47 Cu

Say Required Amount of Sand      = 0.47 Cu

 Required amount of Metal = 0.55 x 1.52 Cu 

                                            = 0.836 Cu

Say Required Amount of Metal      = 0.87 Cu

Required material for G30 Concrete

4. G30 (C:S:M = 1:1:2)

Cement  = 1/4 = 0.25

Sand      = 1/4 = 0.25

Metal     = 3/5.5 = 0.50

Number of 50 kg cement bags per 1m3 = 0.25 x 1.52 m3 / Volume of cement bag

                                                             = 0.38 / 0.035

                                                             = 10.86 

                                                             = 10.86 x 1.05 

                                                             = 11.40 Nr

Therefore required number of cement bags per 1Cu = 11.40 x 2.83 Nr

                                                                                   = 32.26 Bags

                                                    Say Nr of Bags      = 31 Nos

 Required amount of Sand = 0.25 x 1.52 Cu 

                                           = 0.38 Cu

                                           = 0.38 x 1.15 Cu

                                           = 0.437 Cu

Say Required Amount of Sand      = 0.44 Cu

 Required amount of Metal = 0.50 x 1.52 Cu 

                                            = 0.76 Cu

Say Required Amount of Metal      = 0.76 Cu

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