# Shared upstairs geometry

[3D view](../../index.html#/existing-ground-floor/3d) · [JSON master](geometry.json)

One fixed, approximate upstairs shell shared by all three ground-floor layouts. It appears only in 3D: **Show upstairs** starts unchecked and reveals the walls, windows, main roof, rear-extension hip and the owner half of the chimney. The garage roof stays visible independently of this checkbox. The choice follows the existing shared 3D display preferences. The full geometry always casts shadows, including when hidden.

Sources: SRC-001 south/north elevations (page 4 / 1916 PL 004) and east elevation (page 5 / 1916 PL 005), calibrated with their 5 m graphic bars. First/second-floor plans on page 3 cross-check footprint, returns and openings; west elevation confirms the party gable and shared chimney. [Original drawings](../../index.html#/originals) and [source register](../../sources/INDEX.md). Source PDF is unchanged.

Drawing X/Y and ground-floor height datum match the existing baseline. The first-floor shell starts at 2470 mm; approximate wall tops are 5140 mm at the front projecting room and 5332 mm at the recessed/east/rear walls, front eaves about 5235 mm over the projecting bedroom and 5592 mm over the recessed bedroom, ridge 8140 mm and highest chimney pot 9680 mm. Window positions and heights are rounded from the elevations. The large front upstairs window is 3220 mm wide with three principal panels matching downstairs G001, retaining the south elevation's approximately 1345 mm height. Ground-floor elevation openings are ignored; current ground-floor masters supply those windows.

Owner authorises approximate geometry that remains shared between designs and requests that the checkbox reveal upstairs and roofs. Frame sizes, thicknesses, chimney footprint/pots, rooflight and roof junctions are illustrative. The front roof is cut back around the recessed bedroom with a constant 150 mm horizontal overhang on both front walls; its continuous sloping plane puts the recessed edge higher. East/rear eaves follow that higher edge. Roof and elevation/plan junction discrepancies are reconciled approximately. The existing rear-extension roof has a three-sided hip and a lowered porch eave, with approximate 2810 mm main eaves and 4090 mm ridge. The garage has an always-visible flat 2470–2670 mm slab with 100 mm overhang. Rear-roof gable infill reaches the 2470 mm ground-floor wall tops, closing the former 340 mm gap above O; the junction remains illustrative. Its diagonal edges have a shallow 120 mm fascia, compared with the 340 mm eaves fascia elsewhere on this roof. These existing roofs appear on every layout. Both OPT layouts also extend the east-facing low-roof plane forward over the proposed infill. **Hip side-extension roof** switches between a full lean-to and a front hip matching the other low-roof hips. The old front gable/verge is omitted at the continuous junction for the OPT layouts. Pitch and heights derive from the existing roof (1280 mm rise over 2417 mm run, approximately 27.9°); 150 mm front overhang and exterior wall-to-roof infill remain illustrative. The equal-pitch hip begins at drawing Y=5235 mm, reaching the Y=3203 mm front roof edge; its high abutment is about 3886 mm. Both roof modes cast shadows even when upstairs is hidden. Settings and shared roof parameters do not alter ground-floor masters or kitchen drafts. There are no upstairs internal partitions, furniture, stairs or finishes. Flat ground-floor ceilings cast shadows unless replaced by the optional vaulted linings in Walkthrough. The chimney stack, cap and all three pots are clipped at the X=0 party boundary. Next door is always invisible but casts shadows as a reflection of the selected house across X=0, including its rear roof and the other chimney half. This owner-requested approximation does not infer a mirrored garage. Other obstructions are omitted; this remains an approximate sunlight study, not a survey or construction model.

Only **Walkthrough** offers **Vault existing rear extension** in all three layouts and **Vault side kitchen roof** in the two OPTs. Both start off. The side vault starts at AC’s kitchen face (Y=4991.0207 mm); the toilet remains flat. C001 and C002 retain their measured low ceilings. Opened flat-ceiling areas are replaced with sloping, shadow-casting linings and perimeter closures. Five independent roof-window controls cover P, Q/S/T, U and two side positions. In **3D**, enable a window and adjust its X/Y sliders independently of vaulting; the overview never builds vaulted ceilings. In **Walkthrough**, enable the relevant vault to view and position the shared windows from inside. Positions are constrained to the roof face and vaulted room with 100 mm clearance; two windows cannot overlap. If the first side window leaves insufficient room, the second reports that it cannot be placed until the first is moved or switched off. Roof settings persist across layouts, both modes and reloads. Changes rebuild the affected scene and refresh sunlight/shadow maps; glazing transmits direct sunlight through real holes in the roof and lining, with lined reveals. Exterior roof visibility still follows Show upstairs in 3D.

The owner reports 5-inch (127 mm) wooden beams. The preview assumes these represent rafter depth and uses **280 mm total roof-surface-to-lining thickness, perpendicular to the slope**, allowing for covering/battens, rafters with insulation between them and additional insulation/lining underneath. The general approach follows [Celotex’s between-and-under-rafter guidance](https://celotex.co.uk/assets/between-and-under-rafters_application-datasheet_nov18.pdf); the total is an illustrative modelling allowance, not a measured build-up or thermal/structural specification. Outer roof heights remain as previously inferred. Windows assume 780 × 980 mm overall along the slope with approximately 40 mm frames; no product, rafter spacing, trimming or installation feasibility is established. The two side windows fit the default positions in both roof modes. Hip-front space above the kitchen is too shallow for these assumed windows, so side placements stay on the main slope. Ground-floor masters and kitchen draft identities are unchanged.

Wall/stack references AH–AN are reserved in the shared wall registry, omitted from 3D labels. This shared shell does not alter ground-floor geometry or kitchen draft hashes and is not a separate OPT design.

Regenerate the shared application after editing this JSON:

    python3 -B scripts/plan_navigation.py