CONSTRUCTION | Estimates | 8 Questions (EASY)

CONSTRUCTION ESTIMATES

(8 Questions, Difficulty Level: EASY)

by Raison John J. Bassig

Q#1: Specify the total number of standard-sized plywood, 1/4" thickness, to be used as ceiling material for a 6.00m x 12.00m living room, to be mounted on 2" x 2" ceiling joists spaced at 0.40m x 0.40m on center.
a. 30 pieces
b. 25 pieces
c. 20 pieces
d. 15 pieces

Analyzing my given question, the only information necessary to solve it are the area of the material (plywood) and the area of where the material is to be installed ceiling of living room). The other data (plywood's thickness, joist material, and joist spacing) do NOT need to be factored into the equation.

Since a standard-sized plywood measures 4' x 8', its equivalent size in SI (metric) units is,

4' = 1.2192m (exact) or 1.22m (approx.)
8' = 2.4384m (exact) or 2.44m (approx.)

Area of Plywood = 1.22m x 2.44m = 2.97sqm (approx.)
*Note: Some commonly estimate the 4' x 8' plywood in metric units as 1.2m x 2.4m = 2.88sqm

Area of Ceiling = 6m x 12m = 72sqm

# of Plywood = Area of Ceiling / Area of Plywood
# of Plywood = 72sqm / 2.97sqm = 24.242 pcs

Since there is a fraction, and we cannot order fractional size of such plywood, then, we round up the calculated value to get the exact number of pieces, i.e., 24.242 pcs ==> 25 pcs.

If you use the commonly estimated value of 2.88sqm., then,

# of Plywood = 72sqm / 2.88sqm = 25 pcs

Therefore, the correct answer is b. 25 pieces.

Q#2: A concrete firewall of a building measuring 20 meters long and 12 meters high is to be coated with concrete neutralizer. According to the manufacturer's brochures, 1 pint of neutralizer is mixed with 2-1/2 gallons of water. 1 gallon of water can cover 30 square meters. How much concrete neutralizer will you exactly order.
a. 3 pints
b. 4 pints
c. 5 pints
d. 6 pints

Given Area of Wall = 20m x 12m = 240sqm

Required Volume of Water = Area of Wall x Coverage
Required Volume of Water = 240sqm x 1 gal/30sqm = 8 gallons

Required Neutralizer = Req'd. Vol. of Water x Mix Rate
Required Neutralizer = 8 gallons x 1 pint/2.5 gal = 3.2 pints

Since there is a fraction, and we cannot order fractional size of such neutralizer, then, we round up the calculated value to get the exact number of pints, i.e., 3.2 pints ==> 4 pints.

Note that you must NOT always round-off to the nearest value (especially if you are rounding the value DOWN).

For example, since 3.2 pints might be rounded to 3 pints, it will only cover [3 pints x 2.5 pints/gallon x 30 gallons/sqm = 225sqm of wall area]. This incorrect rounding will leave us with 15sqm of uncoated area since the total firewall surface is given at 240sqm.

Therefore, the correct answer is b. 4 pints.

Q#3: You asked for a quotation at your local hardware for prices of lumber. The store owner told you that their price is at P72.50/bd.ft. Which among the following line items in your bill of materials would be the cheapest?
a. 8 pcs - 2" x 4" x 8' Lumber
b. 9 pcs - 2" x 3" x 10' Lumber
c. 18 pcs - 1" x 2" x 14' Lumber
d. 10 pcs - 2" x 2" x 12' Lumber

Recall computation of Board Feet:

Bd.Ft. = Cross-Sectional Area (in sq.in.) x Length (in feet) / 12

Computing for the total board feet of the given choices, we have,

For Choice a.: 8 pcs x [2" x 4" x 8' / 12] = 8 pcs x 5.33 bd.ft. = 42.66 bd.ft.

For Choice b.: 9 pcs x [2" x 3" x 10' / 12] = 9 pcs x 5.00 bd.ft. = 45.00 bd.ft.

For Choice c.: 18 pcs x [1" x 2" x 14' / 12] = 18 pcs x 2.33 bd.ft. = 42.00 bd.ft.

For Choice d.: 10 pcs x [2" x 2" x 12' / 12] = 10 pcs x 4.00 bd.ft. = 40.00 bd.ft.

As it turns out, the 10 pcs of 2" x 2" x 12' lumber is the cheapest (smallest total bd.ft. among the choices), while the 9 pcs of 2" x 3" x 12' lumber is the most expensive (highest total bd.ft.).

Note that if the cost per bd.ft. is different for each item of material, then, we must solve for the actual prices of each to determine which one costs less.

Since all lumber in my given question is said to have the same price (cost per bd.ft.), then, just solving for the total bd.ft. is enough to determine which costs cheaper than the other (no need to compute for the actual price).

Therefore, the correct answer d. 10 pcs - 2" x 2" x 12' Lumber.

Q#4: You instructed your worker to cut five sections of pipe from a 13'-3" length PPR pipe. The lengths of the cut sections are 74-5/8", 19-3/4", 49-7/8", 4-1/4", and 2". What is the remaining pipe length from the original PPR pipe if the saw cut is 1/20" wide?
a. 3-7/8"
b. 0.25 foot
c. 0.6875 foot
d. 2.125 feet

For ease of computing, let's remove all fractions of the given data by converting all units to inches with decimals:

Original PPR pipe length = 13'-3" = 156" + 3" = 159"

Length of Cut Section 1 = 74-5/8" = 74.625"
Length of Cut Section 2 = 19-3/4" = 19.75"
Length of Cut Section 3 = 49-7/8" = 49.875"
Length of Cut Section 4 = 4-1/4" = 4.25"
Length of Cut Section 5 = 2"

Tot. Length of Cut Sections = 74.625" + 19.75" + 49.875" + 4.25" + 2" = 150.5"

We also need to consider the measurements lost due to the saw cuts,

Number of Saw Cuts = 5
Width (Length) of 1 Saw Cut = 1/20" = 0.05"
Total Length of all Saw Cuts = 5 x 0.05" = 0.25"

So,

Remaining Length = Original Length - Tot. Sections Cut - Total Length of all Saw Cuts
Remaining Length = 159" - 150.5" - 0.25" = 8.25" (or 8-1/4" or 0.6875 foot)

Therefore, the correct answer is c. 0.6875 foot.

Q#5: At a certain time of the day during your site visit, your client asked you to measure the height of the existing electrical post adjacent to his lot. Knowing that your measuring tape wouldn't reach the top of the post, you then began to measure the post's shadow on the ground, which is 2.35m long from the base of the post. Being resourceful, you also measured the tip of your own shadow (your head) being 421mm from the point where you are standing. If your height is 5'-7", how tall is the electrical post?
a. Approx. 10m
b. Approx. 9.7m
c. Approx. 9.5m
d. Approx. 9.2m

Let us first list all given values and convert them into same units:

Your height = 5'-7" = (5' x 12"/1') + 7" = 60" + 7" = 67"
(Converting to metric unit), 67" x 25.4mm/1" = 1,701.8mm
Your shadow length = 421mm
Electrical post shadow length = 2.35m = 2,350mm
Electrical post height = unknown = h

Using Proportion:

h / Your height = Electrical post shadow length / Your shadow length
h / 1,701.8mm = 2,350mm / 421mm
h = (2,350mm) x (1,701.8mm) / 421mm
h = 9,499.3586698mm (or approx. 9.5m)

Therefore, the correct answer is c. Approx. 9.5m.

Q#6: How many pieces of standard-sized CHB (Concrete Hollow Blocks) can cover up a one square meter (1 sq.m.) area?
a. 10.5 pieces
b. 8-3/4 pieces
c. 11.25 pieces
d. 12-1/2 pieces

Standard CHB (in the Philippine-setting) would have a surface area of a little less than 8" high (~200mm high) x 16" long (~400mm long), with CHB thickness usually available in 4" to 6".

In general, the 200mm x 400mm approx. surface area of each CHB already takes into account ample-sized grouting between the blocks.  So,

# of CHB = 1 sqm / (0.2m x 0.4m)
# of CHB = 1 sqm / 0.08sqm
# of CHB = 12.5 pcs

This means that 12-1/2 pcs of CHB is enough to exactly fill up 1 square meter of surface area (considering ample-sized grouting and standard-sized blocks).

Note that most estimators round up the 12.5 pcs/sqm to 13 pcs/sqm, for contingencies/wastage since one cannot logically order a half-piece CHB.

Therefore, the correct answer is d. 12-1/2 pieces.

Q#7: Given a circular room, the diameter of which measures 4.21m, calculate the number of flooring materials required if the specification calls for the use of 3mm thk x 150mm x 910mm vinyl strips.
a. 31 pcs
b. 102 pcs
c. 97 pcs
d. 131 pcs

Area of 1 Vinyl Strip = 0.15m x 0.91m = 0.1365sqm
*Note: Thickess given does NOT matter.

Area of Circular Room = πd² / 4
Area of Circular Room = 3.14159... x [4.21m]² / 4
Area of Circular Room = 13.92...sqm

# of Vinyl Strips Required = 13.92...sqm / 0.1365sqm = 101.98...pcs

Since there is a fraction, and we cannot order fractional size of such vinyl strip, then, we round up the calculated value to get the exact number of pieces, i.e., 101.98... pcs ==> 102 pcs.

Therefore, the correct answer is b. 102 pcs.

Q#8: An apprentice carpenter can construct all the cabinet works in the kitchen you designed in 17 days. A skilled carpenter can complete the same work in 12 days. A foreman can finish the same job in only 5 days. If you hire all three to work together, how long would it take the kitchen cabinets to be completed?
a. Under 3 days
b. A little above 11 days
c. Just a 1 day job
d. Approximately a week

Given the data from my problem, we have,

Kitchen Cabinet Job = 1
Work Rate of the Apprentice Carpenter = 1 job : 17 days
Work Rate of the Skilled Carpenter = 1 job : 12 days
Work Rate of the Foreman = 1 job : 5 days
Total Duration for Job = unknown = t

So,

Total Rate of Kitchen Cabinet Job = 1 job : t days = 1 / t

Since all 3 workers were hired with each of their individual work rates combined to complete one job, we now have,

Total Rate of Kitchen Cabinet Job = Sum of Workers Rates

1 / t = Apprentice Rate + Skilled Rate + Foreman Rate
1 / t = (1 / 17 days) + (1 / 12 days) + (1 / 5 days)
1 / t = 349 / 1020 days
t / 1 = 1020 days / 349
t = 2.9226... days

So, the total duration for the job when all 3 workers are combined, given their work rate, is UNDER 3 DAYS.

Therefore, the answer is a. Under 3 days.