Chapter 3 — Key Takeaways

Lumber Basics

• Nominal dimensions (2x4, 2x10) are rough-sawn sizes; actual dimensions are about 1/2 inch less in each direction (a 2x10 is actually 1.5" x 9.25").
• Major framing species: Douglas Fir-Larch (West), Southern Yellow Pine (Southeast), Spruce-Pine-Fir (Northeast/Canada). Species affects allowable span — check species-specific tables.
• Grade stamps appear on every piece of dimensional lumber; No. 2 is the standard framing grade for structural members. Stud grade is NOT appropriate for horizontal members (joists, rafters, headers).
• Engineered lumber (LVL, I-joist, glulam) provides greater spans, dimensional stability, and predictable performance. I-joists are the modern standard for floor systems.

Framing Types

If you have pre-1950 balloon framing: check for fire blocking at floor levels. Its absence is a code concern and a real fire hazard.

Wall Opening Components

Every door or window rough opening contains: - King studs — full-height, flanking the opening - Trimmer (jack) studs — shorter, directly supporting the header - Header — horizontal beam spanning the opening; must be sized for load in bearing walls - Cripple studs — above the header (to top plate) and below window sills - Rough sill — bottom of window opening

Headers in bearing walls must be sized by load and span. A rough guide: doubled 2x6 up to 3 ft, doubled 2x10 up to 7 ft, LVL for larger spans. Engineer specifies final sizing.

Load-Bearing Wall Identification

Likely load-bearing: - Runs perpendicular to floor joists - Located near building center, running the long axis - Continues through multiple floors at the same position - Is directly above a beam or post in the basement/crawlspace - Is an exterior wall

Likely non-bearing: - Runs parallel to floor joists - Has no structural element above or below it - Appears to be a space-dividing addition, not original structural framing

To be definitive: Open the wall or hire a structural engineer. The heuristics are useful; the stakes justify verification.

The Hard Rules

🔴 Never remove a wall without confirming it is non-bearing, or without engineer-specified header and shoring plan.

🔴 Never cut a roof truss member. Every member is structurally essential. Modifications require structural engineering.

🔴 Never cut ceiling joists in a stick-framed roof to create a cathedral ceiling without structural engineering — they resist outward roof thrust.

🔴 Never notch joist flanges (top or bottom) of I-joists. Never notch floor joists at mid-span or deeper than 1/6 of joist depth.

Floor System Key Points

• Girder (main beam) → floor joists → subfloor → finish flooring
• Floor joists span between bearing points; the standard deflection limit is L/360
• Notches and holes in joists are code-regulated: notches only in outer 1/3 of span, max 1/6 of joist depth; holes max 1/3 of joist depth, min 2 inches from edges
• I-joist flanges must NEVER be notched — see manufacturer's literature for web hole placement
• A damaged joist can be "sistered" — a new joist alongside the damaged one, properly fastened

DIY vs. Pro Framework for Framing

Next: Chapter 4 — The Building Envelope: Sheathing, Housewrap, Insulation, and Air Sealing