# Structural Feasibility Review — Backyard Office

September 9, 2026. This review supersedes the earlier structural report and wood-portal notes. It is a research-backed assessment of a schematic visualization, not a stamped design, structural calculation package, permit determination, or authorization to build.

Model-version notice, September 20: the live preview now places the nominal
48″ × 24″ upper side window on the LEFT/tree-facing wall, not the right.
Its opening and schematic framing moved together. References below to the
right upper window describe the September 9 model; the same unresolved
stacked-opening checks now apply on the left. This notice is not a new
structural assessment, and the later raised-site support concept is unreviewed.

## Bottom line

Keep the wood-only direction as an option to investigate, but do not treat doubled headers as a complete solution. The revised model now separates the headers' gravity supports from the unresolved lateral design, corrects obvious framing collisions, and shows where engineering is still needed. **No exact standard wood lateral-system assembly has been verified for the six-foot stacked opening, narrow returns, wall height, and raised floor.** This is not evidence that an engineered wood solution is impossible.

The preferred next step is a focused feasibility consultation with a California-licensed structural engineer: can a wood shear-wall/diaphragm design preserve this facade, and if not, what is the smallest necessary architectural change? Do not buy the headers, order the openings, or frame this wall from the viewer.

## What changed in the model

| Correction | Why it matters | Visible consequence |
| --- | --- | --- |
| Separate two-stud trimmer packs for the upper and lower front headers | Removes the fictitious lower-header pocket inside a supposedly solid proprietary panel; gives each gravity header an identifiable support path | Openings retain their positions; X-ray changes |
| Transparent lateral-design zones instead of selected-looking solid panels, hold-downs and anchor counts | Does not imply a product or connection has been verified | X-ray communicates unresolved work |
| Upper header now modeled 7 ft overall, lower 6 ft 6 in overall, each with 3 in conceptual end bearing | Coordinates member ends with the separate trimmer packs | No finished facade change |
| Side-window stud, trimmer and blocking conflicts removed | No modeled timber passes through the three side glazing openings | X-ray changes only |
| Roof rafters moved inside the roof envelope | Corrects rafters previously protruding below the modeled roof assembly | Roof assembly deepens from 6 to 9 in; underside drops 3 in |
| Front sole plate interrupted at door threshold | Removes a continuous framing plate across the doorway | Door appearance unchanged |

The 12 × 10 ft footprint, 14 ft 4 in modeled grade-to-high-roof height, 1:12 slope, slider position, and window geometry are retained. The fascia is 3 in deeper and the upper-level ceiling is lower. These are geometric corrections, not proof that the assemblies meet structural, energy, insulation, roofing, or waterproofing requirements.

## The front wall: what the new research establishes

- **Tall wood panels exist.** Current ICC-ES ESR-2652, reissued April 2026, lists tall 18 in Simpson WSWH panels and permits specified top trimming; an approximately eleven-foot panel is not inherently an unavailable product size ([ICC-ES ESR-2652, Table 1](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)). Height availability alone does not verify capacity, connections, or this installation.
- **The standard garage portal is not a match.** ESR-2652 specifies a garage-portal header clear span of 8 ft to 18 ft 6 in; this design has a 6 ft clear opening, irrespective of overall beam length ([ICC-ES ESR-2652, §3.2.1.3](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)). Enhanced portal action is limited to specified shorter panel configurations, while other models use standard-application behavior; the limits must not be misrepresented as a ban on all tall WSWH panels ([ICC-ES ESR-2652, §4.1.2](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)).
- **The previous lower-header/panel intersection was unsupported.** Simpson restricts trimming to the top and field drilling to published locations, and no evaluated midheight side pocket for the modeled lower header was verified in the reviewed installation evidence ([Simpson standard/balloon installation](https://www.strongtie.com/products/lateral-systems/strong-wall-shearwalls/high-strength-wood-shearwall/standard-and-balloon), [ICC-ES ESR-2652, §4.2.1](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)). The revised independent gravity posts eliminate that visual conflict, but they also consume wall width that a final shear design must account for.
- **A doubled beam is not a lateral system.** Where portal action is used, beam end moments, connections, wall behavior and foundation resistance are part of the design; a gravity-only LVL capacity table cannot establish those checks ([Simpson garage-portal design](https://www.strongtie.com/products/lateral-systems/strong-wall-shearwalls/high-strength-wood-shearwall/garage-portal), [ICC-ES ESR-2652, §§4.1.2, 4.2.4](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)).
- **Raised-floor wood-panel installations can be possible, but not with generic bolts.** ESR-2652 describes specific extended anchors, compression nuts, solid blocking, shear-transfer components and foundation requirements for wood-floor applications ([ICC-ES ESR-2652, §§3.1, 4.2.5 and Figure 4](https://icc-es.org/wp-content/uploads/report-directory/ESR-2652.pdf)). Avoiding a fabricated steel frame does not eliminate engineered steel connectors and anchorage.
- **Common prescriptive portal figures still do not fit the modeled height.** The actual 2025 CRC PFH and CS-PF figures show 10 ft portal and 12 ft total wall limits, which are not satisfied by the present upper-header/top-of-wall arrangement ([2025 CRC PFH figure](https://codes.iccsafe.org/bundles/document/new_document_images/4554/FigR602.10.6.2.jpg), [2025 CRC CS-PF figure](https://codes.iccsafe.org/bundles/document/new_document_images/4554/FigR602.10.6.4.jpg)). The correct comparison is to wall and header datums, not the 14 ft 4 in grade-to-roof height.

The modeled front wall top is 12 ft 5¾ in above finished floor, the upper-header top is 12 ft 1⅞ in, and only **⅞ in nominally remains below the double top plates**. That is a coordination warning, not usable tolerance guaranteed to a builder. Selected window rough openings, shim/flashing space, deflection allowance, rafter bearings, and final roof build-up could force changes to the header, window, or wall.

## Gravity framing still needs actual calculations

The LVL members remain unverified placeholders. Weyerhaeuser's current TJ-9000 guide distinguishes uniform-load capacities, concentrated loads, reactions, bearing and multi-ply connection requirements; its span is center-to-center of bearing, not overall member length ([Weyerhaeuser TJ-9000](https://www.weyerhaeuser.com/application/files/7917/8525/8572/TJ-9000_Specifiers_Guide_for_Trus_Joist_Beams_Headers_and_Columns.pdf)). The guide's nonsnow roof tables include deflection criteria that must be coordinated separately with glazing tolerances, so the previous simple “header passes” conclusion is withdrawn ([TJ-9000, pp.20–21](https://www.weyerhaeuser.com/application/files/7917/8525/8572/TJ-9000_Specifiers_Guide_for_Trus_Joist_Beams_Headers_and_Columns.pdf)).

The right upper-window trimmers now stop at the lower-window framing rather than continuing through the glazing. Their reactions therefore land on the lower header and require a concentrated-load check. The upper-floor edge beam, ledger, side-wall post packs, floor transfer blocking, roof bearing seats, uplift connections, diaphragm sheathing, and foundation reactions also remain uncalculated.

A drawn 3 in bearing seat is not verified simply because it exceeds a published minimum; required bearing depends on reaction, member width, material and support capacity ([TJ-9000, p.26](https://www.weyerhaeuser.com/application/files/7917/8525/8572/TJ-9000_Specifiers_Guide_for_Trus_Joist_Beams_Headers_and_Columns.pdf)). Likewise, plywood sheathing and fastening must be designed as part of the full lateral load path rather than assumed from the X-ray's stick framing ([2025 CRC R301](https://codes.iccsafe.org/content/CARC2025P2/chapter-3-building-planning)).

## Upper deck: correct the earlier blanket conclusions

The physical deck footprint is **68.62 sq ft**, not 99 sq ft; the containing room is 99 sq ft. Its gross ratio is 69.31%, but gross model footprint must not be confused with code-counted sleeping-loft area.

- **Mezzanine:** actual 2025 CRC R314 requires 7 ft clear above and below, normally limits area to one-third, and includes a qualifying sprinklered-dwelling one-half exception; the modeled low deck is not an ordinary compliant mezzanine simply because it is called a loft ([2025 CRC R314](https://codes.iccsafe.org/content/CARC2025P2/chapter-3-building-planning)).
- **Sleeping loft:** R315 applies to dwelling or sleeping units, has an area limit below 70 sq ft, and includes a conditional two-thirds-room exception for a specified sprinklered arrangement; its applicability to this accessory office/play deck has not been established ([2025 CRC R315](https://codes.iccsafe.org/content/CARC2025P2/chapter-3-building-planning)). R315.3 excludes adjacent sloped-ceiling areas below 3 ft from sleeping-loft floor area, so comparing the gross 68.62 sq ft footprint directly with 66 sq ft does **not**, by itself, prove failure of that conditional exception ([2025 CRC R315.3–R315.4](https://codes.iccsafe.org/content/CARC2025P2/chapter-3-building-planning)).
- **Access and use:** the modeled ladder is approximately 88.6° from horizontal, whereas the R315 ladder provision specifies 70–80°; use classification, clearances, permanent egress, handholds, landings and guards remain unresolved ([2025 CRC R315.5](https://codes.iccsafe.org/content/CARC2025P2/chapter-3-building-planning)).
- **Tiny-house provisions:** Orinda adopted Appendix BB, but BB applies to tiny houses used as single dwelling units, not automatically to a small office; its reduced loft guard rules cannot simply be imported into this design ([Orinda ordinance](https://mcclibraryfunctions.azurewebsites.us/api/ordinanceDownload/16541/1404112/pdf), [2025 CRC Appendix BB](https://codes.iccsafe.org/content/CARC2025P2/appendix-bb-tiny-houses)).

The deeper roof leaves only about 2 ft 10¾ in to 3 ft 8¾ in at the exterior wall-line datums above the upper-floor finish, before ceiling finishes. Actual code-counted area must use the final interior ceiling geometry and the applicable code interpretation. Neither “safe kids' loft” nor “definitely a second story” is an appropriate final classification from this visualization alone.

## Jurisdiction and a focused engineer brief

The 2025 California code cycle took effect January 1, 2026, and Orinda identifies Contra Costa County as its contracted building-permit authority; Orinda planning approval is separate from a building permit ([California BSC](https://www.dgs.ca.gov/bsc/codes), [Orinda Building Permits](https://www.cityoforinda.gov/432/Building-Permits)). Confirm the permit-application date, adopted local amendments, and whether residential-accessory or other occupancy provisions apply before selecting the code path ([2025 CRC scope](https://codes.iccsafe.org/content/CARC2025P2/chapter-1-administration), [Orinda ordinance](https://mcclibraryfunctions.azurewebsites.us/api/ordinanceDownload/16541/1404112/pdf)).

Ask the engineer and building official to resolve these items before further architectural refinement:

1. Intended upper-deck use and whether that use can be permitted with acceptable access, guards and headroom.
2. A wood-only lateral feasibility scheme, including actual usable return widths after header posts, all four walls, roof/floor diaphragms, torsion, uplift and load transfer.
3. Front header/window/roof fit using selected products and required tolerances.
4. Member grades, load assumptions, concentrated reactions, bearing and multi-ply fastening.
5. Foundation and raised-floor anchorage based on site soil, seismic, wind and gravity demands.

The geometry tests now verify a more internally consistent model. They do not verify any structural capacity, and the current drawing should remain labeled **concept only: engineering and permit review pending**.