ICC Residential Building Inspector (B1) Exam: Practice Test & Licensing Guide

A habitable bedroom measures 12 feet by 14 feet. It will rely on natural light, not the artificial-light exception. What is the minimum aggregate glazing area required?

Answer: 13.44 square feet

Section R303.1 requires habitable rooms to have glazing of at least 8 percent of the floor area. Floor area = 12 x 14 = 168 sq ft, and 168 x 0.08 = 13.44 sq ft. The 6.72 sq ft answer (168 x 0.04) is the minimum openable area for natural ventilation, not the glazing area. The 8.4 and 16.8 answers use 5 and 10 percent, which are not IRC figures.

Reference: 2021 International Residential Code, Section R303.1

A second-floor bedroom has a casement window with a net clear opening 20 inches wide by 41 inches high, and a sill 40 inches above the floor. Does it qualify as the emergency escape and rescue opening?

Answer: No, the net clear opening area is less than 5.7 square feet

Net clear area = 20 in x 41 in = 820 sq in, and 820 / 144 = 5.69 sq ft. That is below the 5.7 sq ft minimum in Section R310.2.1. The 5 sq ft reduction applies only to grade-floor openings, not to a second floor. Width (20 in) and height (41 in, at least 24 in) meet Section R310.2.2. The sill at 40 in is within the 44-inch maximum in Section R310.2.3, so 36 inches is the wrong limit.

Reference: 2021 International Residential Code, Section R310.2.1

A deck walking surface is 32 inches above grade at its outer edge. What is the minimum guard height along that open edge?

Answer: 36 inches

Section R312.1.1 requires guards on open-sided walking surfaces more than 30 inches above the floor or grade below, measured at any point within 36 inches horizontally of the edge. This deck at 32 inches needs a guard. Section R312.1.2 sets the minimum guard height at 36 inches above the walking surface. 34 inches applies only to guards on the open sides of stairs, measured from the line of the nosings, and 42 inches is the IBC commercial guard height.

Reference: 2021 International Residential Code, Section R312.1.2

Using Table R403.1(1), what is the minimum concrete footing size (width x thickness) for a two-story light-frame house with a basement, a 30 psf ground snow load, and soil with a 1,500 psf load-bearing value?

Answer: 19 x 6 inches

In Table R403.1(1), go to the 30 psf ground snow load block, find the row "2 story - plus basement" and read across to the 1,500 psf column: 19 x 6 inches. The 16 x 6 answer is the 1-story-plus-basement row, 14 x 6 is the same row at 2,000 psf soil, and 21 x 7 is the 50 psf snow block. Section R403.1.1 also sets an absolute minimum of 12 inches wide by 6 inches thick.

Reference: 2021 International Residential Code, Table R403.1(1)

In an area where the frost line is not the controlling depth, what is the minimum depth of exterior footings below the undisturbed ground surface?

Answer: 12 inches

Section R403.1.4 requires exterior footings to be at least 12 inches below the undisturbed ground surface. Where frost applies, Section R403.1.4.1 may require greater depth (below the frost line in Table R301.2) or another frost-protection method. Measure from undisturbed ground, not from fill or finished grade that has been raised.

Reference: 2021 International Residential Code, Section R403.1.4

A plumber notched the top edge of a sawn-lumber 2x10 floor joist (actual depth 9 1/4 inches) 2 inches deep, about 3 feet from the bearing on a 15-foot span. The notch is not in the middle third of the span and is not at the joist end. What is your finding?

Answer: Does not comply, because the notch exceeds one-sixth of the joist depth

Section R502.8.1 limits notches in sawn joists to one-sixth of the depth, a length of no more than one-third of the depth, and no location in the middle third of the span. One-sixth of 9.25 in = 1.54 in, and the 2-inch notch exceeds it. The one-fourth limit (9.25 / 4 = 2.31 in) applies only to notches at the ends of the member, and this notch is 3 feet in from the bearing. Being outside the middle third is necessary but not enough on its own.

Reference: 2021 International Residential Code, Section R502.8.1

An enclosed attic has 1,500 square feet of vented space. Neither condition of the Section R806.2 exception is met. What minimum net free ventilating area is required?

Answer: 10 square feet

Section R806.2 requires a minimum net free ventilating area of 1/150 of the vented space: 1,500 / 150 = 10 sq ft. The 5 sq ft answer (1,500 / 300) is allowed only under the exception: a Class I or II vapor retarder in Climate Zones 6 to 8, plus 40 to 50 percent of the venting high in the attic within 3 feet of the ridge. 15 sq ft assumes a 1/100 ratio, and 7.5 sq ft assumes 1/200.

Reference: 2021 International Residential Code, Section R806.2

What is the deepest notch allowed in a 2x6 stud (actual depth 5 1/2 inches) in an exterior wall?

Answer: 1 3/8 inches

Section R602.6 limits notches in studs in exterior walls or bearing partitions to 25 percent of the stud depth: 5.5 x 0.25 = 1.375 in = 1 3/8 inches. 2 3/16 in (40 percent) is the notch limit for nonbearing partitions, and 3 5/16 in (60 percent) is the maximum bored-hole size. Deeper notches need an approved stud shoe or other repair.

Reference: 2021 International Residential Code, Section R602.6

An exterior bearing wall supports only a roof and ceiling on a 24-foot-wide building with a 30 psf ground snow load. A window needs a header spanning 6 feet. Using Table R602.7(1), what is the smallest two-ply (2-2x) sawn-lumber header, and how many jack studs are required at each end?

Answer: 2-2x10 with 2 jack studs

In Table R602.7(1), "Roof and ceiling" block, 30 psf snow, 24-foot building width: 2-2x8 spans 5-9 (too short for 6-0), 2-2x10 spans 6-10 with NJ = 2, and 2-2x12 spans 8-1. The smallest two-ply header that reaches 6 feet is 2-2x10, and the NJ column requires 2 jack studs at each end. The 2-2x8 answer uses the 12-foot building width (7-7). Full-height (king) studs at each end are a separate requirement in Table R602.7.5.

Reference: 2021 International Residential Code, Table R602.7(1)

No. 15 asphalt felt is being installed as the water-resistive barrier on exterior walls. How must it be lapped?

Answer: Applied horizontally, upper layer over lower at least 2 inches, with at least 6-inch laps at end joints

Section R703.2 requires No. 15 felt and ASTM E2556 barriers to be applied horizontally, shingle-fashion, with the upper layer lapped over the lower layer at least 2 inches. Where joints occur, the lap must be at least 6 inches. Lapping the lower layer over the upper (reverse lap) directs water behind the barrier.

Reference: 2021 International Residential Code, Section R703.2