Trade Knowledge and Construction Practices
The Trade Knowledge and Construction Practices domain tests field competence: code compliance, materials, sequencing, structural and MEP basics, inspections, and jobsite safety. DC enforces the ICC family of construction codes with local amendments, so answers must reflect both standard practice and DC's inspection model.
Codes, permits, and inspections
DC's construction codes are published in Title 12 DCMR and adopt the International Building Code, International Residential Code, International Existing Building Code, International Plumbing Code, International Mechanical Code, International Fire Code, International Energy Conservation Code, and NFPA 70. The Department of Buildings issues permits and conducts inspections. Concealing work before rough-in inspection, skipping special inspections, or failing to post a permit can trigger stop-work orders and rework.
Structural and materials basics
Follow the load path from roof to foundation. Concrete strength, curing, reinforcement placement, and soil bearing matter; framing must use correct grade, spacing, and fasteners. Moisture control, flashing, and drainage details are common failure points. Commercial and multi-family work generally follows the IBC; one- and two-family dwellings may follow the IRC where scoped.
MEP and life safety
Rough-in inspections are required before covering plumbing, mechanical, and electrical work. Pressure tests, drain slopes, GFCI protection, smoke and carbon monoxide alarms, firestopping, and egress dimensions are frequent inspection items. Accessibility requirements apply to covered commercial work.
Worked example
A stair has a total rise of 108 inches to the finished floor. The maximum riser height is 7¾ inches. Divide 108 by 7.75 to get 13.94, so use 14 risers. Actual riser height is 108 ÷ 14 = 7.71 inches, within the limit. With 13 treads at a 10-inch minimum run, the total run is 130 inches. Measuring to the rough floor or forgetting that the number of treads is one less than the number of risers are common errors.
Traps that cost marks
Using nominal lumber dimensions as actual; covering MEP work before inspection; applying IRC rules to commercial occupancies; ignoring DC amendments; and treating fireblocking or firestopping as optional finish work.