Carpentry Basics

97 flashcards by MentisLibrary

Lumber dimensions and grades, wall and roof framing, stair layout, joinery, and fasteners, with the layout math worked out on the card. The fundamentals a first year apprentice is expected to know cold.

Why is a 2x4 not actually 2 inches by 4 inches?
Those are nominal dimensions, the rough green size before the mill surfaces and dries the board. A finished 2x4 measures 1 1/2 by 3 1/2 inches.
What are the actual dimensions of nominal 2x6, 2x8, 2x10 and 2x12 lumber?
1 1/2 by 5 1/2, 1 1/2 by 7 1/4, 1 1/2 by 9 1/4 and 1 1/2 by 11 1/4 inches.
How do you calculate a board foot?
A board foot is 144 cubic inches of lumber: thickness in inches times width in inches times length in inches, divided by 144.
What does S4S mean on a lumber order?
Surfaced four sides, meaning the piece has been planed smooth on both faces and both edges to its finished dimension.
List the common structural grades of dimensional softwood lumber from strongest to weakest.
Select Structural, No. 1, No. 2, No. 3. Stud grade is a separate grade intended for vertical use in walls, and Utility or Economy is non structural.
What is the difference between green and kiln dried lumber?
Green lumber is still above about 19 percent moisture content. Kiln dried lumber has been dried in a kiln, typically to 19 percent or less, and KD-HT or S-DRY on the stamp indicates it.
In which direction does lumber move most as its moisture content changes?
Across the grain. Boards shrink and swell in width and thickness, tangentially most of all, and almost not at all in length.
How do Douglas fir-larch, southern yellow pine and spruce-pine-fir compare for strength?
Southern yellow pine and Douglas fir-larch have the highest design values of the common framing species. Spruce-pine-fir, sold as SPF, is lighter and weaker and spans less.
How are the face veneers of plywood graded?
By letter, A through D. A is smooth and repairable for finishing, B allows tight knots and small repairs, C allows knotholes, and D allows the largest open defects.
How does OSB compare with plywood for sheathing?
OSB is made of oriented wood strands bonded with resin. It is rated for the same structural uses and is usually cheaper, but it swells more at cut edges and dries more slowly once wet.
What is LVL and what is it used for?
Laminated veneer lumber, thin wood veneers laid with all grain parallel and bonded under pressure. It is used for headers, beams and rim board.
What is PSL, and how does it differ from LVL?
Parallel strand lumber, made from long strands of veneer bonded under pressure. It is denser and stronger in bearing than LVL and is used for heavily loaded columns and long span beams.
What is a wood I-joist made of?
An I shape with LVL or solid sawn flanges top and bottom and an OSB or plywood web between them.
What is glulam?
Glued laminated timber, made by bonding graded dimensional lumber laminations face to face with the grain running lengthwise.
Why does pressure treated lumber require special fasteners?
Modern waterborne copper preservatives such as ACQ and CA are far more corrosive to steel than the old CCA treatment. Plain steel or electroplated fasteners corrode and fail.
What is the difference between platform framing and balloon framing?
In platform framing each floor is built as a platform and the walls for that story sit on it, one story at a time. In balloon framing the studs run continuously from the sill to the roof plate past the intermediate floors.
What is a sill plate and how is it attached?
The pressure treated plate bolted flat to the top of the foundation wall that gives the floor framing something to bear on and fasten to.
What is a rim joist?
The joist that runs on edge around the perimeter of the floor system, closing the ends of the floor joists and transferring load from the wall above into the joists and sill.
What controls how far a floor joist can span?
Species and grade, joist size, spacing, and the design live and dead load. You read it from a span table or an engineered layout, never from memory.
What does it mean to crown a joist or a stud?
To sight down the edge of the piece, find the slight bow, and install it with the high side of the bow up.
How is a subfloor installed over floor joists?
Tongue and groove panels, typically 23/32 or 3/4 inch, run perpendicular to the joists with end joints staggered, glued to the joist tops with construction adhesive and nailed or screwed.
Why are studs usually spaced 16 inches on center?
Because 16 divides evenly into the 48 inch width of a sheet of plywood, drywall or OSB, so every panel edge lands on a stud, and the spacing gives the strength and stiffness most walls need.
How do you lay out a wall plate so panel edges land on stud centers?
Hook the tape on the end of the plate, mark 15 1/4 inches, and put an X on the far side of the mark. From there mark every 16 inches. That puts the first stud's CENTER at 16 inches and the sheet edge at 48 inches on a stud center.
Why do walls get a double top plate?
The second plate laps the joints of the first, ties intersecting walls and corners together, and lets joists or trusses above bear anywhere along the wall rather than only over a stud.
Name the parts of a framed opening for a door or window.
The header spans the opening, king studs run full height on each side and are nailed to the header ends, jack studs (trimmers) sit inside the kings and carry the header down to the plate, and cripple studs fill above the header and below a window sill.
Why is a precut stud 92 5/8 inches long?
So a wall with one bottom plate and a double top plate frames to 97 1/8 inches, which lets an 8 foot sheet of drywall go up with room for the ceiling finish and a small floor gap.
What is the purpose of wall sheathing and bracing?
To resist racking, the tendency of a rectangular wall to distort into a parallelogram under wind or seismic load, and to tie the studs together.
What is the difference between blocking and fire blocking?
Blocking is any short piece of framing added between members for backing, bearing or stiffness. Fire blocking is specifically required material that closes concealed spaces so fire cannot travel through them.
How do you square a wall you have just framed on the deck?
Measure both diagonals corner to corner. When the two measurements are equal, the wall is square. Push the long corner until they match, then nail the sheathing or a temporary brace to hold it.
What are the code limits for notching and boring a solid sawn floor joist?
Holes may not exceed one third of the joist depth and must be at least 2 inches from the edges. Notches on the top or bottom may not exceed one sixth the depth, may not be in the middle third of the span, and end notches may not exceed one fourth the depth.