NCCER Carpenter cheat sheet

OSHA construction rules require fall protection (guardrail system, safety net, or personal fall arrest) whenever a worker is 6 ft or more above a lower level.

Ladder setup rule: the base sits 1 ft out for every 4 ft of height (4:1), and an extension ladder must extend at least 3 ft above the landing surface.

Supported scaffold guardrails: top rail 42 in above the platform, midrail approximately 21 in, plus toe boards where workers or materials below are exposed.

Nominal vs. actual dressed sizes: 2x4 = 1-1/2 x 3-1/2 in; 2x6 = 1-1/2 x 5-1/2 in; 2x8 = 1-1/2 x 7-1/4 in; 2x10 = 1-1/2 x 9-1/4 in; 2x12 = 1-1/2 x 11-1/4 in.

Board feet = nominal thickness (in) x nominal width (in) x length (ft) divided by 12; a nominal 2x6 10 ft long contains 10 board feet.

All temporary 120-volt receptacles on a construction site require GFCI protection, which trips when current leaks to ground.

Before changing a blade, adjusting a guard, or clearing a jam, disconnect the power source (unplug the cord or remove the battery) on any power tool.

Never carry a pneumatic nailer with a finger on the trigger, and always disconnect the air hose before clearing a jam or making adjustments.

A lumber grade stamp shows species group, grade, moisture content, grading agency, and mill; span tables for joists and rafters depend on those values.

Square a corner with the 3-4-5 method (or multiples such as 6-8-10): 3 ft one way, 4 ft on the perpendicular, and adjust until the diagonal reads 5 ft; verify by comparing both diagonals of the rectangle.

Batter boards are set about 2 to 3 ft outside the building corners so the string lines marking the building lines can be restrung after excavation.

Footings must bear on undisturbed soil below the local frost depth and be sized for the soil bearing capacity and the wall load.

Minimum rebar cover: 3 in for concrete cast directly against the earth, 2 in for concrete exposed to weather.

Vertical wall forms are typically stripped 24 to 48 hours after placement; slab forms and shores stay until the concrete reaches the strength assumed in design, commonly about 7 days.

Saw-cut control joints are spaced about 2 to 3 times the slab thickness in feet, so a 4-in slab gets joints roughly 8 to 12 ft apart.

Read written dimensions rather than scaling the drawing; the title block gives the scale, date, and revision status of the sheet.

Concrete weighs about 145 to 150 lb per cubic foot, and 1 cubic yard equals 27 cubic feet.

An 8-ft wall framed with a 92-5/8 in precut stud, one bottom plate, and a double top plate measures about 97-1/8 in from subfloor to top of plate.

Common studs are spaced 16 in or 24 in on center; every rough opening gets king studs, jack (trimmer) studs, a header, and cripple studs at the common spacing.

Double top plates must lap at corners and at intersecting partitions so the wall line is tied together.

Header size is determined by span and load; jack studs transfer the header ends to the sole plate and king studs run full height.

Floor joists are installed crown up, and their maximum span comes from tables keyed to species, grade, size, spacing, and load.

The rim joist caps the joist ends, squares the floor system, and supports the subfloor edge and exterior wall plates; joist hangers are used where joists frame into headers.

Subfloor panels of 3/4 in tongue-and-groove plywood or OSB are glued and screwed, with ends staggered and about a 1/8 in gap left at panel edges.

Solid blocking or cross bridging is installed between joists at midspan and bearing lines to stop twisting and reduce floor bounce.

Walls are plumbed, aligned to the chalk line, and braced before the temporary braces are removed or sheathing is completed.

Roof pitch is stated as rise over 12 in of run; a 6/12 roof rises 6 in per foot of run, an angle of about 26.6 degrees.

Common rafter length = the square root of (run squared + total rise squared); the rafter table on a framing square gives unit lengths per foot of run.

Ridge height above the plate = run x (pitch/12); for a gable roof the run is half the building width.

The ridge board should be at least 1 in thicker than the rafters it receives, and its top edge establishes the ridge height.

The birdsmouth consists of a plumb cut and a seat cut; the seat cut depth should not exceed one-third of the rafter depth.

Roof sheathing panels are laid with the long dimension perpendicular to the rafters, with panel edges supported and fastened to the rafter spacing shown on the panel rating.

Drip edge is installed under the underlayment at the eaves and over the underlayment at the rakes.

Lap siding is fastened about 1 in above the bottom edge so the nail is covered by the next course and does not pass through both pieces.

Drywall thickness: 1/2 in for walls, 5/8 in for ceilings on 24 in framing, and 5/8 in Type X where a fire-resistance rating is required.

Drywall screws are placed 12 in on center in the field and 8 in on center at panel edges, about 3/8 in back from the edges.

Door rough opening = door slab width plus about 2 in and slab height plus about 2-1/2 in, allowing room for the prehung frame and shims.

Standard interior and exterior door height is 6 ft 8 in; a common exterior door width is 3 ft 0 in.

When hanging a prehung door, plumb and shim the hinge side first, level the head jamb, then adjust the latch side to an even gap of about 1/8 in.

Window installation sequence: sill pan flashing first, then set and level the unit, then side flashing and head flashing lapped so water sheds outward.

Trim joints: cope inside corners and miter outside corners; baseboard is commonly 1/2 to 3/4 in thick.

Drywall finishing requires a tape coat followed by two progressively wider finish coats with feathered edges.