Woodworking and construction glossary

Definitions

Board Foot

A board foot is a US lumber volume of 144 cubic inches: a piece 12 inches wide, 12 inches long and 1 inch thick. Board feet = (thickness in × width in × length ft × pieces) / 12. One cubic metre is about 423.776 board feet. European yards quote cubic metres; the calculators store one physical volume and show it in the unit system you pick.

Nominal vs Actual Size

Nominal size is the name stamped on the board. Actual size is the dressed section you receive. A stamped 2×4 is typically 1½ in × 3½ in; a stamped 1×6 is often about ¾ in thick. Entering the stamp overstates board feet and cost. Metric shops still need the mill’s finished millimetres, not the marketing name.

On-Center Spacing

On-center spacing (O.C.) is measured from the centre of one framing member to the centre of the next. Common layouts are 16 in (406 mm) and 24 in (610 mm). Stud and joist counts are floor(length / O.C.) + 1, then extras for openings or beams. The convention stays 16/24 even when the wall length is shown in metres.

Rise and Run

Rise is the vertical height of a flight (floor to floor, including finishes). Run is the total horizontal going. A comfortable target riser is often 7–7¾ in (178–197 mm). The tool rounds total rise ÷ target riser to a whole number of risers; treads are one fewer because you step onto the landing. Stringer length is the hypotenuse of total rise and total run. Blondel’s 2R + T is a comfort check, not a code.

Roof Pitch

Roof pitch is rise per 12 inches of run: 6/12 is arctan(6/12) ≈ 26.6°. Run of a common rafter is half the span minus half the ridge. Rise follows the pitch ratio; the hypotenuse is birdsmouth-to-ridge length. The unit toggle converts span and overhang but leaves the 6/12 ratio alone — it does not become 6/300 in millimetres.

Miter and Bevel

Miter is the rotation of the saw table; bevel is the tilt of the blade. For crown moulding, spring is the angle between the wall and the back of the profile. A 52° spring on a 90° inside corner is about 31.6° miter and 33.9° bevel. Flat polygon rings need only a miter (180°/n from square) and no bevel. Always test on scrap; coping inside corners is often more accurate than two miters.

Overlay vs Inset

Overlay doors sit on the face of the cabinet and grow by the overlay on each edge (½ in / 13 mm is a common full overlay). Inset doors sit inside the opening and shrink by the reveal or gap. A pair splits the remaining width after one centre gap. Rails run between the stiles, so rail length is door width minus two stile widths (no tenon extra in that number).

Deflection (L/360)

L/360 is a stiffness target: deflection no greater than the span divided by 360. On a 36 in shelf that is 0.10 in (2.5 mm). For a simply supported rectangular shelf with uniform load, δ = 5WL³ / (384EI) where W is the total load, and I = bh³/12. Thickness dominates because it is cubed. MDF often fails L/360 sooner than plywood of the same size because its modulus E is lower. Brackets and fixed ends sag less than this conservative model.

Sphere Rule

The sphere rule is a guard opening limit: a 4-inch (102 mm) sphere must not pass between balusters or pickets. Some stairs use 4⅜ in; confirm the adopted code. Equal gaps mean n balusters create n+1 spaces: gap = (opening − n × width) / (n + 1). Posts are not counted — enter the clear opening between them. The same math spaces a fence if you raise the allowed gap.

Moisture Content

Moisture content (MC) is water in the wood as a percent of oven-dry mass. Across the grain, change ≈ width × coefficient × (end MC − start MC). Flatsawn uses the larger tangential coefficient; quartersawn uses radial. Negative change is shrinkage. Indoor winter EMC is often 6–11%. Leave the calculated movement as button-slot travel on tabletops — do not glue a solid top tight to the apron.

Waste Factor

Waste (sometimes called a cutting or compaction allowance) is a percent added to net quantity before you buy. S4S softwood often needs 5–10%; rough lumber, tile diagonals or gravel compaction often 10–15%. The calculators apply waste to volume or area, then round counts (sheets, bags, packs, studs) up. Order extra if dye lots may disappear or the room is out of square.

Cubic Yard

A cubic yard is 27 cubic feet — the US bulk unit for concrete, gravel, soil and mulch. Volume = length × width × (depth in inches / 12), then yards = cubic feet / 27. One cubic metre is about 1.308 cubic yards. Ready-mix is usually cheaper than bags above about 1 yd³ (0.76 m³). US 60 lb bags yield about 0.45 ft³ and 80 lb bags about 0.60 ft³; metric mode still uses those bag yields as a planning number.