Masonry: NASCLA Commercial General Building Practice Questions
Brick and concrete block units, mortar types and grout, reinforcement and ties, bonds and joints, cold and hot weather, wall bracing and the limited access zone, and block, brick and mortar counts.
Question 1
What are the actual dimensions of a standard 8 x 8 x 16 concrete masonry unit (CMU)?
Correct answer: 7-5/8 x 7-5/8 x 15-5/8 inches
Trade practice (masonry units)
Nominal sizes include a 3/8-inch mortar joint, so the unit itself is 3/8 inch smaller in each dimension.
Question 2
Calculation
Using 1.125 standard 8 x 16 blocks per square foot of wall (given), how many blocks are needed for a wall 80 ft long and 12 ft high with no openings, before waste?
Correct answer: 1,080 blocks
Estimating math (masonry)
Each 8 x 16 nominal block covers 128 sq in, or 0.889 sq ft, so there are 1.125 blocks per square foot. Dividing by 1.125 gives 853.
Worked solution
1
Formula
Wall area = 80 ft × 12 ft = 960 sq ft
2
Values
Blocks = 960 sq ft × 1.125 blocks per sq ft
3
Result
Blocks = 1,080 blocks
Question 3
Calculation
A CMU wall is 60 ft long and 10 ft high and has two openings of 3 ft by 7 ft and one of 6 ft by 4 ft. Using 1.125 blocks per square foot (given), how many blocks are needed before waste?
Correct answer: 601 blocks
Estimating math (masonry)
Subtract the openings from the gross area before multiplying, and round a partial block up. Ignoring the openings gives 675 blocks; dividing by 1.125 gives 475.
Blocks = 534 × 1.125 = 600.75, round up to 601 blocks
Question 4
Calculation
Modular brick runs about 6.75 bricks per square foot of wall (given). How many bricks are needed for 1,200 sq ft of veneer, adding 5% waste?
Correct answer: 8,505 bricks
Estimating math (masonry)
Multiply area by bricks per square foot, then add the waste allowance. Subtracting the waste gives 7,695.
Worked solution
1
Formula
Net bricks = 1,200 sq ft × 6.75 = 8,100
2
Values
With waste = 8,100 × 1.05
3
Result
Bricks = 8,505 bricks
Question 5
Which mortar type has the highest compressive strength and is often used below grade and for foundations?
Correct answer: Type M
Trade practice (mortar)
The ASTM C270 types from strongest to weakest are M, S, N and O (spelled out in "MaSoN wOrK"). Type N is the general-purpose above-grade mortar.
Question 6
Which mortar type is commonly used for general above-grade exterior walls and veneer?
Correct answer: Type N
Trade practice (mortar)
Type N is a medium-strength, workable mortar for above-grade walls and veneer; stronger is not always better because stiff mortar cracks more easily.
Question 7
How does masonry grout differ from mortar?
Correct answer: Grout is a fluid fill for cells; mortar bonds units in joints
Trade practice (grout)
Grout is placed at a high slump (roughly 8 to 11 inches) so it fills cells completely around the reinforcing bars; mortar is stiffer and laid in the joints.
Question 8
When grout is placed in lifts higher than about 5 ft 4 in, what must usually be provided at the bottom of the cells?
Correct answer: Cleanouts at the base of the cells
Trade practice (grout)
High-lift grouting needs cleanout openings at the base of grouted cells; they are closed after cleaning and inspection.
Question 9
Horizontal joint reinforcement in a CMU wall is commonly placed at what vertical spacing?
Correct answer: Every other course, about 16 inches
Trade practice (reinforcement)
Ladder or truss-type joint reinforcement every second course (16 in on center) is a common specification to control shrinkage cracking.
Question 10
In a brick veneer wall, what are wall ties used for?
Correct answer: To anchor the veneer to the backup wall
Trade practice (veneer)
Ties carry wind loads from the veneer to the structure; the veneer's weight is carried by the foundation or by shelf angles and lintels.
Question 11
Why are weep holes placed at the base of a masonry veneer wall just above the flashing?
Correct answer: To let water in the cavity drain out
Trade practice (flashing and weeps)
Masonry veneer is not waterproof; flashing collects the water in the cavity and weeps let it out.
Question 12
OSHA requires a limited access zone whenever a masonry wall is being built. How wide must that zone be?
Correct answer: Equal to the height of the wall plus 4 feet
29 CFR 1926.706(a)(2)
The zone runs the full length of the wall on the unscaffolded side, as wide as the wall height plus 4 ft; only the masons working on the wall may enter.
Question 13
Calculation
A masonry wall is being built to a height of 14 ft. How wide must the limited access zone be?
Correct answer: 18 ft
29 CFR 1926.706(a)(2)
Add 4 ft to the wall height. Using the height alone (14 ft) leaves too little room for a falling wall.
Worked solution
1
Formula
Zone width = wall height + 4 ft
2
Values
Zone width = 14 ft + 4 ft
3
Result
Zone width = 18 ft
Question 14
Under OSHA, masonry walls over what height must be adequately braced until permanent supporting elements are in place?
Correct answer: 8 feet
29 CFR 1926.706(b)
New walls are weak until mortar and grout cure and the roof or floors tie them in; walls over 8 ft must be braced against wind and collapse.
Question 15
In cold-weather masonry construction, what is a key precaution?
Correct answer: Keep materials from freezing and protect new work
Trade practice (cold weather)
Cold-weather provisions call for heated materials, windbreaks and covers; antifreeze admixtures are generally not allowed in mortar.
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Practice questions are written in our own words and cite code sections by number. Always study from your own copy of the code and the official candidate bulletin.