Chapter 3 of 625% of exam

Core Trades Remodeling

CSLB weights Core Trades Remodeling at about 25% of the B-2 exam: plumbing, electrical, mechanical, interior walls, ceilings and trimwork, and flooring and stairs. This page is a short survey; the PrepPass B-2 Residential Remodeling study guide teaches the section with worked examples and a full practice exam at CSLB's weights.

Plumbing, electrical and mechanical fixtures

B-2 work is fixtures and minor alterations. Bath and kitchen code figures come from the 2025 codes as summarized by a California building department.

Toilet space
30 inches wide (15 each side of the centerline) and 24 inches in front.
City handout (2025 CPC 402.5)
Shower
Mixing valve 120 degrees F maximum; stall 1,024 square inches and a 30-inch circle.
City handout (2025 CPC 408)
Kitchen receptacles
No point along the wall more than 24 inches from a receptacle; 20 inches maximum above the counter.
City handout (2025 CEC 210.52)
Bath exhaust
Tub or shower bath needs a fan; 50 cfm intermittent or 20 continuous.
2025 CRC R325.2

Walls, ceilings and framing

Framing cuts have limits; fireblocking, under-stair protection and gypsum board follow the CRC.

Stud notches
25 percent (bearing) or 40 percent (nonbearing); bores 60 percent.
2025 CRC R602.6
Joist notches
One-sixth depth, one-third length, not in the middle third.
2025 CRC R502.8.1
Fireblocking
Vertically at floor and ceiling and horizontally at 10-foot intervals or less.
2025 CRC R302.11
Under-stair closet
1/2-inch gypsum board.
2025 CRC R302.7

Flooring and stairs

Flooring makers' instructions differ; stairs follow the CRC dimensions.

Riser and tread
Riser 7-3/4 inches maximum; tread 10 inches minimum; 3/8-inch variation in a flight.
2025 CRC R318.7.5
Handrail
34 to 38 inches high, on at least one side of four or more risers.
2025 CRC R320.2, R318.7.8
Width and headroom
36 inches clear; 6 feet 8 inches headroom.
2025 CRC R318.7.1, R318.7.2

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