Framing: Spans, Notching & Boring
~13 min read · Apply joist/rafter span logic and the notching-and-boring limits that keep members structural.
Framing inspection lives on a few durable numbers: joists notched no more than a sixth of their depth and never mid-span, bores a third max and 2 inches from edges, studs notched a quarter (bearing) or 40 percent (partition). The plumber's chainsaw is the finding these rules exist to catch.
Joist rules
Sawn-lumber joists: notches limited to 1/6 the depth, no longer than 1/3 the depth, allowed only in the outer thirds — never the middle third of the span (where bending stress peaks); end notches at bearing up to 1/4 depth. Bored holes: max 1/3 the depth, at least 2 inches from top and bottom edges and from any other hole or notch. Violations concentrate where trades ran pipe and duct: under bathrooms and kitchens — sight along joists there.
- Notch: ≤1/6 depth, ≤1/3 long, outer thirds only
- Bore: ≤1/3 depth, 2-in edge and spacing margins
- Middle third is sacred — bending lives there
Studs, headers, and engineered lumber
Studs: notch up to 25% of width in bearing/exterior walls, 40% in non-bearing partitions; bores leave 5/8 inch to the edge — and the trap: the 60% bore figure applies ONLY to doubled studs (max two successive), not standard bearing studs. Headers: undersized ones announce themselves — sagging over openings, cracked drywall corners, binding doors (span tables are code-cycle material; the SYMPTOMS are the inspection finding). Engineered lumber (I-joists, LVL): follows manufacturer rules, not sawn-lumber rules — flange cuts are prohibited outright, web holes only per the hole chart; a cut I-joist flange is a structural referral like a cut truss.
- Studs: 25% bearing / 40% partition; 5/8-in bore edge
- 60% boring belongs to doubled studs only
- I-joist flanges are untouchable; webs per the chart
- Undersized headers show as deflection symptoms
Bearing and modifications
Joists need real bearing (on plates, beams, or hangers with full nailing — never drywall or air); look for shimmed, short-bearing, and hangerless connections. Amateur remodels are the finding factory: removed walls without headers, joists 'sistered' with inadequate lap/fastening, and load paths interrupted. Report cuts by rule violated, location, and structural significance; systematic violations under one bathroom get one systemic finding.
Worked example
Under a renovated bathroom: a 2×10 joist (9¼ in deep) carries a 3½-inch bore tight to the bottom edge mid-span; the neighboring joist has a 2-inch-deep notch cut into its middle third for a drain; and an LVL beam nearby shows a chunk cut from its bottom flange to clear a duct. Apply the rules.
Joist one: max bore = 9¼ ÷ 3 ≈ 3.08 in — the 3½-in hole exceeds it AND sits within 2 inches of the edge: double violation at mid-span where stress is highest. Joist two: notch depth limit = 9¼ ÷ 6 ≈ 1.54 in — a 2-inch notch is over-deep and it sits in the FORBIDDEN middle third: the worst-placed cut possible. The LVL: flange cuts are prohibited entirely — engineered lumber has no notch allowance; that member's capacity is compromised by manufacturer rule, not judgment. Report: systemic over-cutting during the plumbing/duct work (condition), reduced load capacity with deflection/failure risk under the tiled bath (implication), engineer or qualified-contractor repair — sistering/headers per design (action). The numbers made three findings in ninety seconds.
Common exam pitfalls
Applying sawn-lumber allowances to I-joists and LVLs.
Engineered lumber follows manufacturer charts — flanges are never cut, and web holes have their own geometry.
Quoting 60% as the stud-bore limit.
40% is the bearing-stud bore limit; 60% requires doubled studs (max two in a row) — the flattened version is wrong.
Missing the pattern for the single cut.
Trades cut in clusters — one violation under a bathroom predicts siblings; report the systemic condition.
Sixth notched, third bored, two from the edge, middle third untouched — and engineered lumber plays by its own book.
Recap
- Joists: notch ≤1/6 depth (outer thirds), bore ≤1/3 with 2-in margins
- Studs: 25% bearing / 40% partition notches; 5/8-in bore edge
- 60% bores = doubled studs only
- I-joist flanges never cut; webs per manufacturer chart
- Headers judged by deflection symptoms
- Cluster findings under wet rooms; refer significant cuts
Prove it: 10 questions on this topic
Every lesson ends with a ten-question check in the free course — your progress syncs between the web and the EstatePass app.