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Flashcards in Construction Math Deck (17)
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Calculate the number of cubic yards of asphalt to cover a dumpster pad with 6 inches of material, where the length of the pad is 20 feet and the witdth is 15 feet.

6 cubic yards
Multiply length x width to get the area (20x15 = 280 sq. ft.) Divide area by thickness in feet. To find the cubic ft. 280 x .5 = 150 cubic feet Convert to cubic yards: 150 / 27 = 5.55 cubic yards


A sidewalk 100' long slopes at 1/16" per foot. What is the total drop or rise at one end?



A blueprint is drawn to a scale of 3/16" = 1'-0". What will 4 1/2" on this drawing equal? (study guide)



An underground tank with inside dimensions of 8' 3/4" x 4' 1/2" and 4' deep will be filled with sand. The total cubic yards of sand required to fill the tank is___________. Make no allowance for compaction of sand.

Less than 5.00


Given: A 24' long x 52' wide, 8" thick slab on grade is to be edge-formed with pressure treated pine. How many board feet of pine will be required to construct a 2" thick edge-form for the slab on grade described above?

203 board feet


A contractor bids a job for $60,000, plus 10% for overhead and 8% profit on all costs. What will be the contractor's bid?



A 5 gallon bucket of concrete sealer covers 250 sq. feet. How many buckets will it take to seal a concrete slab that is 200' by 125'?



The courtyard of a condo complex contains 1,600 sq. feet of area. Each paver is 4" x 8". How many brick pavers will be required to cover the courtyard? Allow 5% for waste.

7,560 pavers


A commercial piece of property has to be re-seeded. The property is 1,500' x 1,800 '. The lot contains a two story building that is 150' x 150' and a one story building that is 40' x 40'. Also, there is a 100' x 200' parking area and 2,000 sq ft of entrance road and walkways. What is the cost to re-seed the property if seed is $27 per lb and covers 2,500 sq ft per lb? Add labor as 15% of the seed cost.



A building slab will be 25' x 90' x 8" How many cubic yards of concrete will be needed? (Note: assume that the grade will be perfectly level and that there will be no crown or slope in the slab do not include waste or accessing your estimate.)

56 yd.³
(25×90 = 2250 ft.²) , (multiply by 8 inches (.66) = 1485 ft.² , divide by 27


A cut stake is being set for the excavation of a trench using a building level (transit). The bottom of the trench will be at elevation 94.00 feet. A rod reading of 4.70 feet is taken on a benchmark whose elevation is 102.50 feet. The rod reading on the mark on the cut stake is 6.20 feet. What should the cut stake be marked

Construction Math: Add the reading of 4.7 to the benchmark elevation of 102.5 for a total of 107.2. Next add the 6.2 reading to the elevation of 94 for a total of 100.20. Subtract the 100.2 from the 107.2 for a total of 7


A subcontractor bids a unit price of $4.00 per square foot to place and finish fiber mesh concrete. The fiber mesh concrete cost the contractor $82 per cubic yard. Regular concrete is $75 per cubic yard and requires steel mesh to be installed, which cost $.10 per square foot. The subcontractor charges $3.75 per square foot to place and finish regular concrete with still mesh included. What is the LEAST expensive cost for the contractor to provide a 500 square foot slab that is 4 inches thick.


Construction Math: Always round up. They are trying to trip you up on this question. The first sentence states what work the contractor has bid on (providing and placing fibermesh concrete only). The next statement about the cost of regular concrete


A contractor bids a project based on: equipment equals $1,000; Direct labor equals $3,000; Material equals $6,000; Project Overhead equals 20% of direct labor; General Overhead equals 10% of direct labor and materials; profit margin equals 10% of all costs. The owner offers to pay $12,000. If the contractor accepts this offer, what would be the contractor's anticipated profit or loss?

A loss of $778

Equip, Labor and Materials = $10,000 Project Overhead = $600 General Overhead = $900 Sub Total (Costs) = $11,500 Profit Margin = Costs / (1-profit percentage) $11,500 / 1-10% (or .9) = $12,777.77 For a handy video about Profit MARGIN vs. Profit MARKUP -


The earth removed from a hole has a volume of 45 cubic yards and is found to have a compacted volume of 36 cubic yards. What is the percentage of shrinkage for this volume of earth?


The difference between the amount removed and it’s compacted volume is 9 cubic yards. When you divide that number (9) into the amount removed (45 cubic yards), the answer is .20% 9 / 45 = .2 or 20%


A subcontractor bids a unit cost of $19.50 per square foot for labor and materials to provide and install ceramic tile. The cost for the subcontractor to do the tile work breaks down to 50% split for profit and material. There is 2500 sq. ft. of floor tile in the project. The owner wants to upgrade the tile. The material will increase $2.25 per square foot. What is the amount of the change order to the original contract amount to upgrade the floor tile? The contract allows a 20% markup.


The line in this question about the 50% split is irrelevant to finding the answer. Multiply the increase per square foot by the square footage to get the total increase amount.$2.25 (increase amount) X 2,500 (sq. ft) = $5,625 Add the 20% markup by


A rectangular building with a gable roof will be 80' x 36'. The rafters will be spaced 32" on center. How many total rafters will be needed?


80 foot X 12inches = 960 total inches. 960 divided by 32 inches o.c.= 30 rafters. Need 2 rafters for the 36’ span = 60 Rafters. Plus the first outside set of rafters = 62.


An 18' long, 2" x 4" fir stud wall has double top plates, a single bottom plate and fourteen 8' studs. Fir costs $520 per thousand board feet. How much does the lumber for this wall costs? Do not allow for waste.


Board feet calculation is on page 63 in the Carpentry book. Number of pieces X thickness (inches) X width (inches) X length (feet) all divided by 12 18 x 3 = 54 54/8 = 6.75 = number of pieces for top and bottom plates (round up to 7 pieces) 14 studs So 21 pieces total 21 x 2 x 4 x 8 = 1344 1344/12 = 112 board feet total 1000 (board feet for pricing) / 112 (actual board feet) = 8.93 $520 (cost per 1000 bf) / 8.93 = $58.23 OR $520 / 1000 = $0.52 per board foot x 112 = $58.24