Masonry

1. INSTRUCTIONAL MATERIAL
(CIEN 30272 - QUANTITY SURVEYING)
MODULE 2 – CONCRETING WORKS Part 1
Estimating Concrete and Formworks
Overview:
Concrete work in a project usually holds the maximum weightage in terms of overall
cost and work quantity. It therefore becomes an important step to calculate the concrete
related costs while preparing a project estimate. The cost of concrete depends upon the cost
of materials, mix design, workforce, and machinery.
Estimating the cost of new concrete involves much more than the price of concrete per
cubic meter. There are many variables to consider, such as surface prep, formwork,
reinforcing materials, and finish work, plus the cost of the ready-mix concrete, that will add up
to the total price of the job. Costs for specific items will vary from location to location or from
site to site, but you can get a rough estimate using some averaged amounts.
Learning Objective:
After successfully completing this module, the student should be able to:
1. Understand and learn what the considerations in estimating concrete and formworks
are.
2. Prepare a quantity take off of concrete, and form work
Course materials:
The concrete for a project may be either ready mixed or mixed on the job. Most of the
concrete used on commercial and residential work is ready mixed and delivered to the job by
the ready-mix company. For mixed on the job proportioning of concrete mixture is done in two
different ways: by volume or by weight method. The most common and convenient way is by
volume method using empty plastic bag of cement, or by using a box for sand and gravel.

2. Types of Concrete Structure
(1) (2)
1. Plain Concrete – artificial stone as a result of mixing cement, fine aggregates and water
(see figure 1).
2. Plain Concrete – artificial stone as a result of mixing cement, fine aggregates and water
(see figure 2).
Proportions of Concrete
Varying the amount of cement, fine and coarse aggregates and water in a given volume of
concrete results in different strenghts of the mixture. The quality of concrete to be used in a
given project is specified in different ways such as: by its water-cement ratio; weight of a given
volume; compressive strength after 28days and by the fixed proportion of cement, sand and
gravel, by volume, contained in the concrete mixture.
Table 1

3. Table 2
Table 1 and 2 shows the different class of concrete mixture with its corresponding mix
proportions. Note that the volume of sand and gravel for all classes of mixture is constant 0.50
and 1.0 cubic meter respectively.
ESTIMATING CONCRETE
Concrete is estimated by the cubic meter. Concrete quantities are measured in cubic meters
as it is the pricing unit of a ready-mix companies and even mix on the job volume is the needed
quantity for the concrete.
Procedures using formula based on the volume and class of concrete mixture to be used:
1. Compute the volume of the concrete member in cu.m., based from the plans and
detailed drawings of the project. Add allowance for wastage if necessary especially on
members with no forms (e.g. footing).
2. Ascertain the “class” or concrete mixture used for each concrete part being estimated.
This information can be found in the project’s specifications or indicated in the working
drawings/plans.
3. Substituting the estimated total concrete volume under the appropriate class of
concretes shown on table above, multiply it by the factors indicated to get the estimated
quantities of cement, sand and gravel required.

4. Sample Problem:
1. On Foundation (substructure)
Estimate the quantity of cement, sand and gravel for the column footing and wall
footing based on the foundation plan shown below using Class A concrete mixture.

6. SOLUTION:
Let A = area
B = Volume of Cement
C = Total Concrete Volume
A = Width x Depth
B = A x thickness
C = B x quantity

7. Therefore base on table 2 for Class A concrete mix:
Footing:
Cement (bags) = 7.43 x 9 = 66.87 ; say 67 bags
Sand (cu.m.) = 7.43 x 0.5 = 3.72 ; say 4 cu.m.
Gravel (cu.m.) = 7.43 x 1 = 7.43 ; say 7.5 cu.m.
Wall Footing:
Cement (bags) = 2.69 x 9 = 24.21 ; say 25 bags
Sand (cu.m.) = 2.69 x 0.5 = 1.35 ; say 1.50 cu.m.
Gravel (cu.m.) = 2.69 x 1 = 2.69 ; say 3 cu.m.
2. Estimate the quantity of cement , sand and gravel for the concrete slab on fill of
the foundation plan shown in example 1, using Class B concrete mixture.
Solution:
Note: in computation of slab on fill you may neglect the columns and consider only
inside dimensions, excluding thickness of the wall which is usually 150mm thick unless
otherwise stated in the specification.
Area 1 = 34.29
Area 2 = 28.32
Area 3 = 31.56
94.17 sq.m.
Therefore:
Gravel Fill = 94.17 x 0.075 = 7.06 cu.m.
Cement = 94.17 x 7.5 = 706.28 ; say 707 bags
Sand = 94.17 x 0.5 = 47.09 ; say 47.50 cu.m.
Gravel = 94.17 x 1 = 94.17 ; say 94.50 cu.m.

8. In BOQ format
FORMWORKS
The formwork operations involve a number of activities including fabricating and erecting the
forms, stripping, moving, and cleaning and oiling the forms for reuse. All of these activities and
the materials involved are allowed for in the pricing of the forms. The estimator measures the
surface area of the concrete that comes into contact with the forms; this is known as the
contact area. Because only the area of formwork is measured, the estimator does not have to
be concerned about the design of the forms at the time of the takeoff. All that need to be
established is which surfaces of the concrete require forms.
Estimating Formworks
1. Formwork shall be measured in square meter of contact area; that is, the actual
surface of formwork that is in contact with the concrete. In some cases, like in small
construction materials required to construct a formworks is being take-off rather
than the area.
2. Formwork is classified in the same categories as those listed for concrete. As an
illustration, consider a project with concrete footings, walls and columns, forms to
footings; forms to walls and forms to columns would each be described and
measured separately.

9. There are, however, a number of factors which may have no effect on the price
of the concreting operations but do affect the price of formwork and, therefore,
should be noted. For example, the volume of concrete in all walls, whether they
are straight or curved, will have the same price but the price of forms to curved
walls will differ from the price of straight walls, so the forms to curved surfaces must
be kept separate.
Plywood as a construction Form
Plywood is a versatile construction material used as wall partitions, cabinets, and furniture. It
is also utilized in boat building as well as forms for reinforced concrete constructions.
Plywood is manufactured in various thickness ranging from 4; 6; 12; 20 and 25 mm with a
standard commercial sizes of .90 x 1.80 and 1.20 x 2.40 meters.
Formula in finding the Materials for Square and Rectangular Form
In determining the materials for square and rectangular form, as stated above measured
square meter of the contact area is required and based on the area cost was generated.
However, if specific material is desired, e.g. plywood, refer to the formula and table below.
For Column:
P = 2 ( a + b ) + 0.20
Where:
P = lateral perimeter of the column
a = shorter side of the column
b = the longer side of the column
0.20 = constant value for the lapping of form joints
Steps:
1. Multiply P by the height of one column times the number of columns to get the total
area of columns.
2. Divide the total area found by 2.88 to get the number of plywood forms.
3. For Frame/Studs (bd.ft.), Multiply the number of plywood found (see table) to get the
board foot of frame required.

10. For Girders and Beams:
P = 2 ( d ) + b + 0.10
Where:
P = perimeter of two sides form
d = the two sides form
b = the bottom form
0.10 = constant value for the lapping of form
Steps:
1. Multiply P by the length and number of beams to get the total area of forms.
2. Divide the total area found by 2.88 to get the number of plywood forms
3. Multiply the number of plywood found by (see table) to get the board foot of frame
required.
Example:
Base on foundation plan in example above, compute for the required formworks. See elevation
plan below. Use 6mm thk marine plywood on a 2” x 2” wood frame.

11. Solution:
Let A = perimeter
B = Surface Area of 1 Column
C = Total Formworks
A = (Width + Depth) x 2
B = A x Height
C = B x quantity
Plywood needed for forms = 80.30 / 2.88 = 27.88; say 28 pcs
Board Foot of Frame/Studs = 28 x 20.33 = 569.24; say 567 bd.ft.
END OF MODULE 3

12. Activities/assessments:
1. Base on the given plan below. Estimate the quantity of Cement, Sand and Gravel and
Formworks needed for Columns and Beams and suspended Slab. Use Class A
concrete mix and assume 100mm thk for suspended slab (slab at second floor).

15. Schedule of Column