CBP Technical Measurements 3

Question 1

A stair has a total rise of 108 inches, and the IRC limits risers to 7-3/4 inches. What is the minimum number of risers?

Accepted Answer

14

Answer

108 / 7.75 = 13.94, which rounds up to 14 risers.

Question 2

Under the IRC, what is the minimum tread depth for residential stairs?

Accepted Answer

10 inches

Answer

IRC R311.7.5.2 requires a minimum tread depth of 10 inches.

Question 3

A gable end is a triangle with a 24-ft base and an 8-ft height. What is its area?

Accepted Answer

96 square feet

Answer

Triangle area = 1/2 x 24 x 8 = 96 square feet.

Question 4

A takeoff shows a dimension of 0.75 ft. What is that in inches?

Accepted Answer

9 inches

Answer

0.75 x 12 = 9 inches.

Question 5

What is the rafter length (to the nearest hundredth, no overhang) for a 12-ft run at a 6/12 pitch?

Accepted Answer

13.42 ft

Answer

Rise is 6 ft, so length = √(12² + 6²) = √180 ≈ 13.42 ft.

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