Structural & Non-Structural Framing

Table 1 maps the parts to interior and exterior walls. Subsections that apply only to interior or only to exterior walls carry an Applies to tag; untagged subsections apply to both. An Informs tag marks the subsections behind each decision above.

1 · Gravity: how load reaches the soil

Bottom line. Under clear-span trusses roof load goes to the exterior walls and floor load to whatever the joists bear on; the exception is a girder truss, which puts a concentrated roof reaction on an interior support.

Load follows an unbroken chain of members to the soil

Every pound of load reaches the soil through a chain of members, and each link is checked in bending, shear, bearing across the grain and deflection. A broken link does not remove the load; it moves it into something not sized for it.

Under a truss roof the chain has two branches for roof load and one for floor load (Figure 1):

• Typical truss. Roof covering → sheathing → top chord → truss heel → exterior wall → footing → soil.
• Girder truss. Carried trusses → hangers → girder truss → point load on an interior wall or post → floor framing → wall or post below → footing.
• Floor. Finish → subfloor → joists → bearing wall or beam → studs → plate → slab or foundation → soil. Floor load is unaffected by the roof framing type.

Area loads become line loads through tributary width

A member supporting joists from both sides receives half the span on each side. Joists spanning 13 ft on each side of a central wall give it 13 ft of tributary width, the same as an exterior wall under a 26 ft clear-span floor (Figure 2).

q area load · s₁, s₂ joist spans on either side

the load on each foot of beam is the floor load times the width of floor that leans on it.

Table 2 lists the design loads used in this guide.

A concrete tile roof is about 1.9 times the dead load of a shingle roof. That difference reaches interior walls only through girder trusses, but it reaches the seismic mass everywhere (Part 5).

Under clear-span trusses, interior walls carry floor load but not roof load

Informs D1

A truss is one engineered element spanning exterior wall to exterior wall, so roof load bypasses the interior. Three consequences follow, in different directions:

• Ground-floor interior walls still carry the second floor. Removing roof load does not make them non-structural; the reference case in Part 3 is exactly this condition.
• Second-floor interior walls usually carry nothing from above. The bottom chord clear-spans over them, so on the gravity axis they are the most freely movable walls in the house. Their lateral role is a separate question (Part 2).
• Field changes since construction (an attic storage platform, an equipment platform, a knee wall bearing on a bottom chord) add load the truss design did not include and can make a wall below bearing.

A girder truss delivers a concentrated roof reaction to an interior support

Informs D1 D2

Where the roof shape needs it (a hip, a valley, a change of span), a girder truss carries other trusses on hangers and lands on an interior wall or post. It is identifiable on the truss layout drawing, or in the attic as a doubled, tripled or deeper truss with hangers on its face.

D_roof roof and ceiling dead load · L_r roof live load by tributary area · A_trib roof area tributary to this support, about half of what a girder bearing at both ends collects

the point load is the roof load per square foot times the share of roof the girder hands to this support.

Table 3 shows how the reaction scales with the roof area collected and with the roof covering.

2 · Which walls are structural

Bottom line. Whether a wall is structural is decided by what bears on it and whether it is counted as bracing, and the two answers are independent.

Classification asks three independent questions

Informs D1

The test is functional, not visual: a wall is gravity-bearing if members above deliver their reactions to its top plate, and it is part of the lateral system if it is sheathed, anchored and counted as bracing. The answers are independent, so a wall can be both, gravity-only, lateral-only or neither (Figure 3).

A truss roof enlarges the lateral-only category: it removes roof load from interior walls without removing those walls from the bracing. An attached garage adds another case. Where living space sits over the garage, the garage ceiling is second-floor structure over a long span, and the wall lines around the garage carry concentrated lateral demand because the vehicle door consumes most of one of them.

Evidence ranks from the permit drawings to field signs

Informs D1

• Original permit set. The truss layout drawing shows girder trusses directly; the framing plan shows joist direction and span; the shear wall schedule names braced panels, nailing and hold-downs.
• Attic inspection. Truss type, girder locations, hanger hardware and any field modification. It is the only way to confirm that no member has been cut since construction.
• Joist direction on the second floor, which decides what each ground-floor wall carries.
• Stacking. Bearing walls stack, and a wall over a beam or a thickened slab is strong circumstantial evidence.
• Weak signals. A double top plate, 2×6 framing, or blocking over the wall raise suspicion and conclude nothing, since many partitions share them.

The lateral question has its own evidence (Part 5).

3 · Beams and headers: carrying load across an opening

Bottom line. Required strength grows with the square of the span and stiffness with the cube of depth; in residential spans deflection often decides the depth, and a girder truss overhead can double the requirement for the same opening.

A framed opening routes load through the header, jacks and kings

The header spans the opening and delivers its end reactions to jack studs, which run from its underside to the bottom plate. King studs run full height beside the jacks and brace them. Cripples above the header and below a sill carry little gravity load but keep sheathing nailing continuous, which matters where the wall is a shear panel (Figure 4).

Strength scales with depth squared and stiffness with depth cubed

b width · d depth · S section modulus (strength) · I moment of inertia (stiffness) · w line load · L span · E modulus of elasticity

bending capacity rises with the square of depth and stiffness with its cube, while moment rises with the square of span and deflection with its fourth power.

Depth is therefore a stronger lever than adding plies (Figure 5). The same relationship explains why a header goes on edge: a 2×6 on edge is 13.4 times as stiff as laid flat, and a 2×4 5.4 times; the ratio is (d/b)².

Deflection limits protect finishes, not safety

CRC Table R301.7 limits floor members to L/360 under live load; L/240 under total load is the companion check from CBC Table 1604.3 and common practice. These are serviceability limits calibrated to what gypsum, plaster and tile tolerate before cracking. A beam can pass bending and shear and still sag enough to bind doors above it, so deflection often sets the depth for residential spans.

NDS strength values carry a load-duration factor (C_D = 1.0 for floor live load, 1.25 for roof live load). It applies to strength only, never to deflection. Where floor live load dominates, using 1.25 would overstate bending capacity by 25%, so the reference case uses 1.0.

Reference case: a 12 ft opening in an interior bearing wall

Informs D2

A 12 ft segment is removed from a ground-floor interior bearing wall with floor joists spanning 13 ft on each side (tributary width 13 ft) and an 8 ft wall above. Design span is 12.5 ft. Case A has typical trusses overhead; Case B adds a girder truss landing at midspan.

Case A needs S ≥ 66 in³. A 3½ × 11⅞ in LVL provides 82 in³ (ratio 1.25) with live-load deflection at 70% of L/360. A doubled 2×12 of No. 2 Douglas fir-larch, at its lower allowable bending stress of 900 psi, would need 191 in³ and provides 63: sawn lumber carries this line load only to about 7 ft.

Case B adds a 4,000 lb point load. Required S rises to about 129 in³, 2.0 times Case A, and the lightest LVL that passes is 3½ × 16 in (ratio 1.16). The end reaction grows from 4,600 to 6,600 lb (Figure 6).

Three results hold beyond these numbers. A 12 ft opening under a floor is past the prescriptive header tables in either case, so the member is designed. A 16 in beam cannot sit flush in a 2×10 or 2×12 floor, so Case B forces the flush-or-dropped question. And jack studs consume wall length at each end, which is often length the lateral system was using.

Required section modulus grows with the square of the span

Informs D2

Table 4 and Figure 7 apply the reference line load across clear spans from 4 to 16 ft.

Added floor dead load can move the member up a size and the house off the prescriptive path

Informs D2 D5

A 1½ in gypsum-concrete topping for a radiant floor adds 14.4 psf, 141% of the bare floor dead load. In the reference case it raises w from 733 to 920 plf, and the 11⅞ in LVL reaches a strength ratio of 0.99. That margin is inside the uncertainty of the inputs, so the lightest member that passes with margin is 3½ × 14 in. The topping also changes the permit route: in SDC D0–D2 the prescriptive path assumes floor dead loads of no more than 10 psf, and 24.6 psf exceeds it (Part 5). A floated acoustic floor draws on the same budget (Soundproofing · Floor build-ups and dead load; HVAC · Radiant delivery by floor).

Beam materials compared

Informs D2

Table 5 compares the common beam materials.

Beam position: flush, dropped, or span shortened by a post

Informs D2

Material and position are separate choices (Figure 8). A flush beam keeps the ceiling plane continuous, which a radiant ceiling and clean linear lighting need, but its depth cannot exceed the floor depth and every joist hangs in a hanger. A dropped beam has no depth limit and the joists bear on top of it, and its soffit can carry ducts and pipes. Retaining a post at midspan halves the span, which divides the moment by four and deflection by sixteen and often returns the member to sawn lumber. The post then carries the largest reaction (wL/2 for two simple spans, about 0.63·wL if the beam is continuous) and needs its own path to soil; a retained wall stub can also keep a braced panel in place.

4 · Reactions: getting the end loads to the soil

Bottom line. Each beam end delivers a concentrated load into members sized for a uniform one; the reaction is resolved only when a continuous path reaches soil with an adequate check at each transfer.

Bearing across the grain sets the number of jack studs

Informs D3

R end reaction · F_c⊥ compression perpendicular to grain, 625 psi for a Douglas fir-larch plate

the bearing area under each end must be large enough that the plate below is not crushed across its grain.

Case A needs 7.3 in² of bearing, two jack studs; Case B needs 10.5 in², three. The bottom plate, loaded across its grain, governs bearing; a tall or unbraced post or stud pack is also checked as a column.

On a slab, soil bearing sets the footing size

Interior wallsExterior walls

Informs D3

In a slab house the original interior bearing line usually sits on a continuous thickened footing. A beam end that lands on a remaining wall segment over that footing is checked against it; a new pad is needed where a reaction lands off it, as at a post or a moved support. The foundation plan shows which applies.

A typical 4 in interior slab of this era has neither the thickness nor the reinforcement to spread a multi-kip point load over several square feet. The slab is cut locally and a thickened, reinforced pad is poured. Concrete bearing passes easily (Case A: 436 psi under two jacks against roughly 1,100 psi allowed); soil bearing sets the size.

q_allow allowable soil bearing; 1,500 psf is the lowest presumptive value in CRC Table R401.4.1, used where no soils data exist

the pad must spread the reaction over enough soil that the soil pressure stays below what it can carry.

Table 6 and Figure 9 give the pad size across reactions and soil bearing values.

Two properties follow. Cost and disruption scale with the number of pads, since each is interior concrete demolition. And a pad occupies the same volume as under-slab drains and slab-embedded radiant tubing, so the pad layout and the service layout constrain each other.

On a framed floor, a reaction needs a stacked path

Informs D3

CRC R502.4 requires bearing partitions perpendicular to joists to sit within the joist depth of a support below, and partitions parallel to joists to bear on a beam, doubled joist or wall. A multi-kip point load at the third point of a joist is outside every prescriptive table. Landing on a floor is not a load path; the path continues through a post, a doubled joist or beam, a wall or post directly below, and a footing (Figure 10).

5 · Lateral: resisting earthquake and wind

Bottom line. A beam on posts resists almost no racking, so removing or shortening a braced panel is a lateral problem with its own solutions; whether the prescriptive path survives depends on the bracing length left on each line and on the layout as a whole.

The house resists racking as a box

Roof and floor sheathing act as horizontal diaphragms that collect inertial force and deliver it to vertical shear walls, which carry it to the foundation. An unsheathed stud wall has almost no racking resistance because its nailed joints behave as pins. Sheathing nailed at its edges turns the wall into a shear panel (Figure 11). In prescriptive language these are braced wall panels on braced wall lines; in engineered design, shear walls.

Shear capacity scales with panel length; uplift scales inversely

Informs D4

v unit shear (lb/ft) · V shear on the panel · b panel length · h panel height · T uplift at the tension end, before dead-load restoring moment

shortening a panel puts more force on each foot of it and pulls harder on its end post.

Table 7 shows the uplift for one story shear as the panel narrows.

Prescriptive bracing counts only panels at or above a minimum length, about 4 ft for a wood structural panel on an 8 ft wall, with narrower alternates such as the portal frame. In the shared reference case, widening a 6 ft opening to 10 ft in a 15 ft segment leaves 5 ft of wall, about 2.5 ft each side: below the standard minimum, so the line needs alternate panels, length elsewhere, or engineering (Windows & Doors · Lateral).

Seismic demand scales with building weight, roof included

Informs D5

Seismic base shear scales with building weight, V = C_s·W. The tile roof that reaches interior walls only through girder trusses raises the seismic weight of the whole roof level: 18.7 against 9.7 psf, 9 lb more per square foot of roof. In SDC D0–D2 the prescriptive path also assumes limits on average dead load: about 15 psf for roof and ceiling (25 psf with increased bracing), 10 psf for floors, 15 psf for exterior and 10 psf for interior walls. A tile roof sits in the adjusted band; the bare floor is at its 10 psf limit within uncertainty; a radiant topping (24.6 psf) or a second gypsum layer on both faces of interior walls (+4.4 psf, Soundproofing · Mass law) takes that element past its limit and the affected design off the prescriptive path.

Braced wall line spacing and irregularities are properties of the layout

Informs D5

In Seismic Design Categories D0–D2, braced wall lines are spaced at most 25 ft apart in each direction. Spacing up to 35 ft is allowed in two cases: between two adjacent lines to accommodate a single room of not more than 900 sf, or where the required bracing length is increased by the spacing adjustment factor in the bracing tables. Removing an interior line can double the spacing at once (Figure 12).

CRC R301.2.2.6 also lists structural irregularities that close the prescriptive path for the affected portion in SDC D0–D2: braced panels offset out of plane from the panels below; a floor or roof diaphragm edge not supported by a braced wall line; panels offset in plane without support; floor or roof openings wider than the lesser of 12 ft or half the dimension; floor levels offset vertically; and braced wall lines not perpendicular to each other. Removing an interior line can leave a diaphragm edge unsupported, and second-floor bracing that stood over the removed line loses its support.

Existing braced panels are identified by sheathing, nailing and anchorage

Informs D1

Braced panels in a house of this era carry plywood or OSB on at least one face beneath the finish, edge nailing at 6 in or tighter, hold-down hardware at panel ends, and anchor bolts or straps at the bottom plate; a small inspection opening at a candidate panel end shows the sheathing and the hold-down. Where the original drawings include a shear wall schedule, the lateral system was engineered, and changing it is an engineering task rather than a prescriptive one. On stucco houses the original design may also have credited the stucco itself as Portland cement plaster bracing under rules that have since tightened.

Lost bracing is restored by mechanisms other than the beam

Informs D4

Table 8 compares the mechanisms that restore lateral capacity.

Diaphragm re-nailing (to redistribute force to lines with spare capacity) and a new interior braced wall line where the layout allows one are further options.

6 · Movement and alteration limits

Bottom line. Trusses can move seasonally and cannot be cut, and sawn members can be notched and bored only within set limits; together these bound where partitions attach and where services run.

Truss bottom chords can rise in winter and settle in summer

Interior wallsExterior walls

The top chords sit in the cold, damp attic and the bottom chord in the warm, dry insulation layer. Differential moisture shrinkage can arch the bottom chord upward, commonly ¼ to ½ in at midspan where it occurs, less in mild climates, and the movement reverses each season (Figure 13).

A partition rigidly fastened to the chord is lifted with it, opening a crack at the ceiling junction, or, if the partition resists, pushes load into a member never designed to receive it. Partition heads therefore connect to trusses through slip clips that give lateral restraint and allow vertical movement, with the ceiling finish detailed to float over the joint. The resulting moving gap is an air path and a sound path (Soundproofing · The partition-head gap) and a finish detail.

No truss member is cut without an engineered design

Informs D5

CRC R802.10.4 prohibits cutting, notching, drilling or otherwise altering truss members without a design by a registered professional. Each member is sized for a force distribution set by the whole truss, and a cut member cannot be restored by scabbing on a piece. Services in the attic pass through the open webs or below the bottom chord. Added attic load (storage, equipment) is also an alteration of the truss design.

Notching and boring limits bound where services can run

Table 9 and Figure 14 give the limits and the reason for each.

7 · Changing the layout

Bottom line. Removing a wall severs its load path until the permanent member is in, and adding a wall brings its own load, durability and fire checks.

Temporary shoring recreates the load path while it is open

Between removing a bearing wall and setting the permanent beam, the load path is severed and shoring recreates it. This guide covers the concept, not the procedure:

• Shoring carries what the wall carried, computed as in the reference case, usually split between two shoring lines, each taking about half the tributary load plus construction load.
• Shoring needs its own path. A shore standing mid-span on a joist relocates the problem. On a slab, a sole plate spreading a temporary load is usually adequate; this differs from the permanent concentrated reaction of Part 4.
• The aim is holding elevation, not only strength. Settlement during the open condition is recorded permanently in the finishes above.
• Lateral stability during the open condition. Where the removed wall was also a braced panel, the lateral system is deficient until it is restored, so duration is a structural variable.
• A shore carries nothing until it is in contact. Any gap closes only after the structure deflects into it.

Added partitions have their own checks

• Second-floor partitions add dead load to a floor sized for 40 psf live and about 10 psf dead. A bearing partition is placed per CRC R502.4; a non-bearing partition parallel to the joists usually lands on a doubled joist or blocking, and a perpendicular one distributes better.
• Partitions on a slab sit on a preservative-treated or naturally durable bottom plate (CRC R317.1) with corrosion-resistant fasteners (R317.3).
• Partition heads under trusses connect through slip clips (Part 6).
• Non-bearing is not unregulated. Fire-blocking at ceiling and floor lines and in concealed spaces (CRC R302.11), and rated construction where a wall encloses the garage or a stair.
• Framing type is also an acoustic choice. Staggered studs, double studs and cavity depth change sound isolation and wall thickness; that selection is in Soundproofing · Partition assemblies. This guide decides only which walls are structurally free to be rebuilt.

8 · Code, permits and the engineer threshold

Bottom line. The prescriptive CRC path covers conventional framing; any portion that leaves it, by span, point load, bracing, weight or irregularity, is designed by a licensed engineer or architect.

Which code applies

The 2025 California Building Standards Code took effect on 1 January 2026 and applies to permit applications filed on or after that date. The California Residential Code (Part 2.5) derives from the 2024 IRC and governs one- and two-family dwellings; the California Building Code (Part 2) takes over for anything that leaves the prescriptive path, such as engineered lateral design, structural steel and special inspection. AB 130 (2025) bars changes to state residential building standards, and new local amendments, from 1 October 2025 to 1 June 2031, apart from emergency and wildfire measures; local amendments in effect on 30 September 2025 stand. This cycle is likely to remain current through most remodels started now.

Provisions a framing change engages, and why each exists

Table 10 lists the provisions a framing change engages.

California departures from the model code come from seismicity

• Irregularity screening (R301.2.2.6) has no practical counterpart in low-seismic regions; observed earthquake damage drove it.
• Bracing methods are restricted in SDC D0–D2: let-in bracing is not permitted, and gypsum board and Portland cement plaster bracing carry significant limits. This bears on stucco walls that may have been credited as bracing when built.
• A heavy roof raises the required bracing through an adjustment factor in the bracing tables.
• Connections are specified closely (plate washers, hold-down anchorage, edge nailing), because the 1994 Northridge earthquake showed connections rather than members failing.
• Post-installed anchors for hold-downs need a current evaluation report covering cracked concrete and seismic load, and usually special inspection under CBC Chapter 17.

The engineer threshold tracks the prescriptive boundary

Informs D5

California Business and Professions Code §6737.1 exempts single-family wood-frame dwellings of not more than two stories and basement from the requirement that a licensed engineer prepare the plans, provided the structure substantially complies with conventional framing requirements. Where any portion deviates, the building official requires plans and calculations for that portion by a licensed engineer or architect. "Conventional framing" is read as the CRC prescriptive path, so the threshold follows it, subject to the building official's interpretation (Figure 15).

Table 11 lists the common cases.

Permit documents and inspection

• A building permit is required to remove, add or reframe a wall and to create or alter an opening.
• Engineered portions carry signed calculations and drawings; local submittal requirements (number of sets, wet signatures, electronic filing) are set by each building division.
• A frequent plan-check rejection is calculations that do not match the drawings: a beam sized in one and drawn differently in the other, or a wall shown removed and not addressed. It is a document-control error, detectable by comparing the two sets.
• Framing inspection takes place with the structure exposed, before insulation and drywall; hold-downs, nailing, plate washers and straps are checked then.

Where it goes wrong

1. The beam is sized and the reaction is not. A 4.6–6.6 kip reaction onto a wall that stops at the floor, or onto an unmodified slab (Part 4).
2. Asking only "is it load-bearing?" A wall can fail the lateral question while passing every gravity test, and a beam does not restore bracing (Part 2, Part 5).
3. Missing a girder truss. The same opening needs about 2 times the section modulus under one (Part 3).
4. Assuming a removed braced panel can be replaced by the beam, or that more weight (a topping, double drywall) leaves the prescriptive path intact (Part 5).
5. Cutting a truss member for a duct, a light or attic storage (Part 6).
6. Fastening a partition head rigidly to a truss chord, which cracks the ceiling joint each winter (Part 6).
7. Sizing sawn lumber with LVL stresses. Allowable bending stress differs by almost a factor of three; a doubled 2×12 reaches about 7 ft at the reference load, not 12 (Part 3).
8. Connection errors found at inspection: panel edge nailing at 12 in where 6 or 4 was specified; pneumatic nails over-driven through the sheathing face; multi-ply beams nailed so the plies act separately; a top plate cut past half its width without the strap (Part 6).
9. Anchorage errors: cut washers where plate washers are required; the wrong hold-down or fasteners, which voids its listed capacity; adhesive anchors without an evaluation report or special inspection (Part 8).
10. A header installed flat, or LVL laminations horizontal; a beam spliced over the opening (Part 3).
11. Fire-blocking or garage separation not restored at reframed walls and ceilings (Part 8).
12. Calculations that do not match the drawings at plan check (Part 8).

Reference

Glossary

Braced wall line

A line along which the CRC requires a set amount of bracing; lines are spaced at most 25 ft apart in SDC D0–D2.

Braced wall panel

A wall segment that qualifies as bracing under CRC R602.10; the prescriptive counterpart of a shear wall.

Cripple stud

A short stud above a header or below a sill.

Diaphragm

A roof or floor plane that collects lateral force and delivers it to shear walls.

Girder truss

A doubled, tripled or deeper truss carrying other trusses on hangers, delivering their combined reaction as a point load.

Hold-down

Hardware anchoring a shear wall end post to the foundation against uplift.

Jack stud (trimmer)

A stud from the underside of a header to the bottom plate, carrying the header reaction.

King stud

A full-height stud beside an opening that braces the jack.

Load-duration factor, C_D

NDS adjustment to strength for load duration; never applied to deflection.

Portal frame

A prescriptive detail with a strapped header over narrow sheathed segments.

SDC

Seismic Design Category; D0, D1 and D2 in the CRC prescriptive range.

SDPWS

AWC Special Design Provisions for Wind and Seismic, the standard for engineered wood shear walls.

Structural irregularity

A configuration listed in CRC R301.2.2.6 that closes the prescriptive path in SDC D0–D2.

Tributary width

The width of floor or roof whose load a member receives.

Truss uplift

Seasonal upward arching of a truss bottom chord from differential moisture between chords.

WSP

Wood structural panel (plywood or OSB) bracing.

Formula sheet

Section properties

Table 12 lists the section properties used above.

Figure color legend

Red: deficient, or fails the stated criterionAmber: marginal or unresolvedGreen: meets the criterionGray: existing or baselineTeal: neutral quantity, force, reference line or annotation; never a grade

Framing members are drawn in tan and concrete in light gray as materials, not grades.

Code points to confirm

Values that rest on secondary sources or on section numbers that may have moved in the 2025 edition:

• Braced wall line spacing and both 35 ft provisions: section and table numbers in the adopted CRC (R602.10.1.3 in recent IRC editions)
• Prescriptive weight limits (R301.2.2.2) and minimum braced panel lengths
• CRC Table R602.10.4 limits on gypsum board and Portland cement plaster bracing in SDC D0–D2
• The roof dead-load adjustment factor in the seismic bracing tables
• CRC R301.2.2.1.2 reclassification of SDC E to D2
• Stud notching and boring percentages (R602.6) and the joist hole limits (R502.8) in the adopted edition
• Design values: LVL F_b 2,600 psi, F_v 285 psi, E 2.0×10⁶ psi and the depth-factor exponent are typical for 2.0E product and are confirmed against the product evaluation report; DF-L No. 2 F_b 900 psi, F_c⊥ 625 psi, E 1.6×10⁶ psi

Sources

• 2025 California Residential Code (Title 24 Part 2.5), Chapters 3, 4, 5, 6 and 8: R301.2.2, R301.5–R301.7, R302.6, R302.11, R317.1, R403.1.6, R502.4, R502.8, R602.3, R602.6–R602.11, R802.10.4.
• ICC, CodeNotes: Cutting, Drilling and Notching (IRC) — joist notch limits and the R602.6.1 top-plate tie (0.054 in × 1½ in, eight 10d nails each side, 6 in past the opening).
• California Business and Professions Code §§5537, 6737.1, as summarized in city "who may prepare plans" guidance (Contra Costa County, City of Sacramento).
• California Building Standards Commission, Information Bulletin 25-03 (AB 130).
• APA, Wall Bracing for High Seismic (IRC weight limits, braced wall line spacing).
• AWC, Special Design Provisions for Wind and Seismic (SDPWS) — shear wall aspect ratio limits; AWC NDS for Wood Construction — load-duration factor.
• Companion guides: Soundproofing, Windows & Exterior Doors (set v2); Insulation and HVAC (set v2).

Set v2 draft 1, 2026-10-23: rewritten to spec set v2 from the v1 guide (archived), with sawn-lumber stresses, the girder reaction to one support, and the weight limits corrected after review; values from one script. 2026-10-23: Insulation and HVAC references now link to their set v2 guides.

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