ESTIMATING FOR THE BUILDING TRADES
A TECH MATH MODULE
Hal Pierce
Rose High School
Greenville, NC
Business partner Jake Fine
Bill Clark Homes
Greenville, NC
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July 2008
PREFACE
This is a Tech Math project. The objective is for students to experience a practical
application of measurements and calculations done in the building trades. A construction
contractor will be necessary as a contact person for making measurements on the
property. Field trip permission forms will also be needed. This project is intended for a
Technical Mathematics I course in a high school. The module should take about 8 days.
Students will visit a construction site, make measurements and determine the amount of
materials needed and the cost of the materials. Measurements should be made during two
class periods.
Students will make a scaled drawing and show measurements and calculations.
After the phase of this construction is complete the contractor will come to school and
share the results with the class. He will share with us the actual number of bricks needed
and the cost.
My business contact is Jake a contractor at Bill Clark Homes in Greenville NC. Jake is
the director of risk management and safety. This is a large construction company that
builds houses in many different cities in NC an SC. It will be necessary for you to find a
business partner in your area for convenience.
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TABLE OF CONTENTS
Preface
Lesson 1 Measurement
Lesson 2 Scale Drawing
Lesson 3 Calculations
Notes
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Lesson 1
MEASUREMENT
OVERVIEW Students will visit the construction site and make measurements of the
exterior walls, doors and windows in order to determine areas. This is necessary in order
to determine the amount of materials needed in the construction process of a house or
garage. Use a building that is being constructed with standard bricks and has siding at the
gable ends.
TIMELINE This should take about 2 class periods 90 minutes each. It may be easier to
take a half-day field trip to the site depending on the location.
NCSCOS
Geometry and Measurement
Competency Goal 2
The learner will measure and apply geometric concepts to solve problems.
Objectives
2.01 Select and use appropriate tools to measure two- and three-dimensional figures;
interpret and communicate results with regard to precision.
2.02 Interpret and construct maps and scale drawings to solve problems.
2.03 Use the length, area, and volume of geometric figures to solve problems. Include arc
length, area of sectors of circles; lateral area, surface area, and volume of threedimensional figures; and perimeter, area, and volume of composite figures.
OBJECTIVE
The students will:
 measure the length and width of the exterior walls, doors and windows in
order to later determine materials needed.
 learn to read a tape measure.
 work with fractions and decimals
 use a tape measure to make measurements in feet and inches.
MATERIALS - pencils, note pad, tape measure, transportation provided by school to
the building site.
ASSIGNMENT - Student will measure the exterior walls, doors and windows
while working in groups of two or three
1. Make a rough sketch of the floor plan including doors and windows.
2. Use a tape measure calibrated in feet and inches to measure the length and width of
the exterior walls. Put the measurements of the walls on your sketch of the house or
garage.
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3. Measure the length and width of all the windows and doors in feet and inches. Transfer
the measurements of the windows and doors onto your sketch.
4. Make a table with length and width at the top of your chart. Windows, doors and walls
should be listed separate in a vertical column.
Sample Chart
Length
Width
Window # 1
Window # 2
Window # 3
Door # 1
Door # 2
Door # 3
Front wall
Back wall
End wall # 1
End wall # 2
Miscellaneous
walls
ASSESSMENT Data measurements should be included in a table in feet and inches.
Student will be assessed based on the data collected. The chart should be well organized.
Look at the table to see if correct units of measurement are used and measurements are
reasonable
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Lesson 2
OVERVIEW
TIMELINE
Scale Drawing
Student will make a scaled drawing in order to review proportions.
This should take about 3 class period 90 minutes each
NCSCOS
Geometry and Measurement
Competency Goal 2
The learner will measure and apply geometric concepts to solve problems.
Objectives
2.01 Select and use appropriate tools to measure two- and three-dimensional figures;
interpret and communicate results with regard to precision.
2.02 Interpret and construct maps and scale drawings to solve problems.
2.03 Use the length, area, and volume of geometric figures to solve problems. Include arc
length, area of sectors of circles; lateral area, surface area, and volume of threedimensional figures; and perimeter, area, and volume of composite figures.
OBJECTIVE
The student will:
 learn how to use proportions while making a scale drawing of a house
floor plan.
 make conversions using different units of measure.
MATERIALS pencil, ruler, calculator, paper, data table from lesson 1, rough sketch
ASSIGNMENT Construct a scale drawing. Be sure to include your key.
(see notes for other options)
ASSESSMENT Observe students while they are working and provide help as needed.
Check for neatness, organization, and correctly labeled parts.
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Lesson 3
CALCULATIONS
OVERVIEW Students will make calculations to determine the number of bricks needed
and the cost of materials and the cost of labor
TIMELINE This should take 3 class periods (90 minutes each)
NCSCOS
Geometry and Measurement
Competency Goal 2
The learner will measure and apply geometric concepts to solve problems.
Objectives
2.01 Select and use appropriate tools to measure two- and three-dimensional figures;
interpret and communicate results with regard to precision.
2.02 Interpret and construct maps and scale drawings to solve problems.
2.03 Use the length, area, and volume of geometric figures to solve problems. Include arc
length, area of sectors of circles; lateral area, surface area, and volume of threedimensional figures; and perimeter, area, and volume of composite figures.
OBJECTIVE
The student will:
 record measurements in the table in terms of feet.
 calculate the area of the windows, doors and walls.
 determine the number of bricks necessary for construction.
 determine the cost of labor.
 compare the number of bricks, cost of bricks and labor to the real
data provided by the contractor.
MATERIALS pencil, calculator, scale drawing
ASSIGNMENT
Students will determine the area of walls, doors and windows.
1. Calculate the area in square feet and include it in your table.
2. Calculate the area of each exterior wall, door and window to the nearest square foot
and place the information in the table. Use the formula for the area of a rectangle.
A=LxW
3. Add the area of all the exterior walls.
4. Add the area of all the doors and windows.
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5. Subtract the window and door areas from the total wall area. This is the space that will
need to be covered with bricks.
6. Calculate the number of bricks needed. There are 7 bricks per square foot for standard
brick.
Use the following example to determine how many bricks will be needed for this
construction project.
Example: Calculate the number of bricks for a 2 car garage. The floor plan dimensions
are 25’-0” x 25’-0”. The garage has a flat roof, the elevation is 10’-0”. There are two
floor to ceiling doors each 9’-0” wide in front of the garage.
Solution: Compute the area of the exterior walls. A=LxW
Since there are 4 walls 4x250= 1000 sq ft
25 x 10=250 sq ft
Now find the area of the openings A= LxW 9x10 = 90 sq ft
2x90=180sq ft
Deduct the area of the openings 1000- 180=820 sq ft
The rule of thumb is 7 bricks per square foot for standard bricks.
7x820=5740 bricks
In this example, you would need 5740 bricks.
7. Use the web or call the supplier to determine the unit cost of bricks. Once this has been
determined find the total cost of the bricks. (The teacher will contact the contractor to
obtain the supplier and type of brick)
Example: Find the cost of 5740 bricks if the price is $ 285 per 1000 and the tax rate is
7%.
Solution: 5740/ 1000= 5.74 thousand
5.74 x 285 = $ 1635.90
Tax: 1635.90 x .07 = $114.51
The cost of the bricks is $ 1750.41.
Example Calculate the number of bags of mortar mix and the cost necessary for 5740
bricks. The rule of thumb is 7 bags per 1000 bricks. Use the web or phone book to
contact a supplier for the cost per bag. Include the tax.
Solution: 5.74 x 7= 40.18 bags
In this example you need to buy 40 bags
The price per bag in this example is $7.80
Solution: 40 x 7.80 = $312.00
Tax: 312 x .07 = $21.84
In this example the total cost of the mortar mix is $333.84
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Example Determine the amount of mortar sand necessary for your 5740 bricks. The rule
of thumb is 1 cubic yard per 10 bags of mortar mix. Use the web or phone book to
research the cost of your mortar sand. In this example mortar sand is $180 per 12 cubic
yards.
Solution: 40/10= 4 cubic yards
In this example you should order 4 cubic yards
180/12 = $15.00 per cubic yard
4 x 15 = $60
In this example the cost of the mortar sand is $60.00
8. Teacher will obtain the labor rate for masonry work from the contractor and give to
students.
Example: Calculate the cost of labor for 5740 bricks if the fee is $450 per 1000 bricks.
Solution: 5.74 x 450 = $ 2583.00
The labor cost is $ 2538.00
Example: Calculate the total cost of this phase of the construction.
Solution: 1750.41 + 333.84 + 60.00 + 2583.00 = $4727.25.
ASSESSMENT
Contractor will come to class and share real values for the construction project. Students
that are not close will try to find their mistake and correct it. Discuss the importance and
consequences of what would happen if the wrong number had been ordered for the job. In
the discussion it should come out that the same procedure could be used for walkways,
patios and driveways.
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NOTES
1. Review how to change fractions to decimals
2. Review proportion and have student to practice drawing lines to a scale
3. You may want to measure the interior walls while at the construction site and you will
now have the necessary information to do similar things involving sheetrock, paint,
Carpet, tile etc
4. Draw the plan using the scale provided by the teacher. (The scale will be determined
by the teacher depending on the size of the building. Choose a scale that will fit on a
sheet of 8½ by 11 inch paper and give paper and scale to students.)
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