BOABC Level 2 cheat sheet

Dead load is the self-weight of permanent construction; live load is occupancy-driven and varies with use group; both are unfactored (nominal) values until load combinations are applied.

Basic ASD combination: D + L; basic LRFD/strength combination: 1.2D + 1.6L. Factored resistance must equal or exceed factored demand (φRn ≥ ΣγQ).

Allowable bearing pressure times footing area must exceed total service load; add footing self-weight and any soil overburden to the column load before sizing.

Deflection limits are expressed as a fraction of span: L/360 for floors with brittle finishes, L/240 for general floor members, L/180 for roof members with no ceiling.

Egress width: capacity is occupants × unit width, with 0.2 in (5 mm) per occupant for level components and 0.3 in (7.6 mm) for stairs and ramps.

Minimum ceiling height on an egress path is 7 ft 6 in (2286 mm); doors in a means of egress have a clear width of at least 32 in (813 mm).

Fire-resistance ratings are stated in hours and apply to assemblies, not materials; a rated wall must be continuous from the floor slab to the underside of the deck above.

Thermal bridging through framing reduces effective R-value; overall assembly U-factor is the area-weighted sum of component U-factors times their area fractions.

Slope for drainage on flat roofs is typically 1/4 in per foot (2%); roof drains and scuppers must handle the design rainfall intensity for the local 100-year storm.

A drainage fixture unit (DFU) is a measure of the waste-flow load of a fixture; a water supply fixture unit (WSFU) is a measure of its demand on the supply system.

A water closet has a DFU of 3 and a private lavatory has a DFU of 1; a floor drain is 2 DFU and a bathtub is 2 DFU under common code tables.

The building drain carries waste from the building to the building sewer; the building sewer begins 5 ft (1524 mm) outside the building wall.

A vent stack serves the drainage stack; a stack vent is the extension of the soil stack above the highest fixture branch. Every trap must be vented.

Trap seal depth is 2 to 4 in (51 to 102 mm); a fixture arm (trap-to-vent distance) is limited by pipe diameter, e.g., 1.5 in pipe at 1/4 in per foot slope allows about 6 ft.

Drainage pipe slope: 2 in and smaller at 1/4 in per foot (2%); 3 in at 1/8 in per foot (1%); 4 in and larger may use 1/8 in per foot where solids transport permits.

Water supply pressure: a residual pressure of about 8 psi (55 kPa) is needed at the fixture; a pressure-reducing valve is required when static pressure exceeds 80 psi.

Water hammer arrestors are placed at the end of long runs and near quick-closing valves; thermal expansion in the supply line is absorbed by an expansion tank on the cold side of the water heater.

Backflow prevention: an air gap is the highest protection; a reduced-pressure-zone assembly is required for high-hazard cross-connections, and a double check valve for low hazard.