# Lift-in-Place Cellular Concrete Roof Panel — Lens 1 Spec (v1)

Basis: Virtuoso "Studio and One-Bedroom Expansion" prelim set (2021, not for construction), scaled off the 5' bar. Ken's answers, 6 Sep 2026. Hand estimates only — for the model and for the PE conversation, not for construction.

## 1. Project facts (stated)

| Item | Value |
|---|---|
| Location | Jamaica — hurricane wind region, no snow |
| Bearing walls | 3D-printed concrete walls |
| Roof membrane | Spray-applied (Eco Finish industrial coating) |
| Footprint (studio, scaled) | ~25' wide (grid 1–2) × ~21' deep (grid A–B) |
| Stud direction | Span the 21' dimension (A to B) |
| Studs | 6" CFS, gauge to be proposed |
| Channel | 1-1/2" cold-rolled channel run horizontally *under* the stud bottom flanges, screwed up into the studs; punchouts left open for concrete flow and conduit |
| Reinforcement | Basalt mesh sandwiched between stud bottom flange and channel (spec TBD) |
| Layer stack (form up) | 2" concrete cover → 1-1/2" channel + mesh → 6" stud cavity → 2" cap = **11.5" total** |
| Ground pour | 6.5" (2" cover + 1.5" channel zone + 3" into the stud) |
| Top pour (on roof) | 5" (remaining 3" of cavity + 2" cap), slight slope to drain |
| Midspan bearing | **Yes** — printed interior wall or beam near grid 3; studs span ~10.5' each side |
| Cellular concrete | 30–40 pcf |
| Panels | One panel per roof if possible, two if not; cast-in pick points |
| Cure before pick | 7 days |
| Engineering | PE to be engaged later (Ken has one in mind) |

## 2. Loads (hand estimate, 35 pcf)

| Load | psf |
|---|---|
| Cellular concrete, 11.5" @ 35 pcf | 34 |
| Steel (studs, track, CRC, inserts) | 4 |
| Membrane / misc | 1 |
| **Dead** | **~39** |
| Roof live (min) | 20 |
| Slope build-up if 1/8"/ft over 21' (extra ~2.6" at the high edge, avg 1.3") | +4 avg |
| **Total gravity for sizing** | **~60–65** |

Wind: hurricane-region flat roof. Net uplift at corners/edges routinely exceeds 0.6 × dead even at 34 psf dead. Anchorage to the printed walls is a design item, not a detail — see §5.

## 3. Span — the governing issue

At 16" o.c., 21' clear span, ~60 psf:
- Moment ≈ 53 kip-in per stud. A 600S162-68 (14 ga, 50 ksi) is roughly 42–45 kip-in allowable → **over**.
- Deflection ≈ 4.2" single stud → **~L/65**. Limit for a concrete-topped roof is L/240 or tighter (≈1.05").
- The cellular concrete does not help: at 30–40 pcf it is ~200–500 psi with negligible stiffness. Steel carries everything; concrete is fill, insulation (~R-1.5/in → ~R-17 total), and ceiling.

**A 6" CFS stud cannot clear-span 21' under this roof.** Three ways out:

| Option | What changes | Stud proposal |
|---|---|---|
| **A. Midspan bearing** (preferred if the printed wall layout allows) | Add a printed interior bearing wall or a steel beam at ~10.5' (near grid 3 / the bath–kitchen wall line) | 600S162-54 @ 16" works with margin (≈L/400); use **600S162-68 @ 16"** for screw pull-out and hurricane robustness |
| B. Deeper joists, keep the concept | Stud depth 10" | ~1000S200-97 @ 16" clears 21' (≈L/290); panel gets ~4" thicker and ~12 psf heavier |
| C. Keep 6", double/box and tighten spacing | 12" o.c., boxed pairs | Still marginal on deflection; not recommended |

Option A keeps the 6" system exactly as Ken described. The animation should model A as the default with B as a config switch.

## 4. Panel at pick (Option A, one panel)

| Item | Value |
|---|---|
| Panel plan size | ~25' × 21' (525 sf) plus edge forms |
| Concrete at pick | 6.5" @ 35 pcf ≈ 19 psf |
| Steel | ~4 psf |
| **Pick weight** | **~12,000 lb** (+ lifting frame) |
| Crane | Mid-size hydraulic (40–60 t class depending on reach); cast adjacent to the building |
| Pick points | 8 cast-in inserts on stud lines, 2 rows at ~0.2L from each end, spreader frame so all legs are vertical |
| Cracking risk | 7-day cellular concrete in a 2" layer under a flexing steel frame. Basalt mesh helps; the real control is a stiff spreader frame and keeping frame deflection under ~L/360 during the pick. PE to check |
| Two panels | 12.5' × 21' each ≈ 6,000 lb — fallback if crane access is tight; joint runs parallel to studs at grid 3 |

## 5. Interfaces to detail

- **Wall top:** cast a bond beam on the printed wall with embedded plates or anchor bolts. Panel bears on a continuous track; weld or bolt track to embeds. Uplift straps/anchors at each stud line at edges and corners.
- **Edge of panel:** closure track or angle so the top pour doesn't run over the wall; the spray membrane turns down over it.
- **Ceiling:** 2" cellular concrete under the studs is the finished ceiling (one skim coat max). Mesh should sit ~1" from the bottom face for crack control.
- **Top pour:** 2" minimum cap over studs; build slope in the cap (1/16–1/8"/ft) toward scuppers or a drain edge. Second mesh layer in the cap if the PE wants it.
- **Penetrations:** sleeves for plumbing vents and electrical set in the form before the ground pour.

## 6. Open items for Ken / the PE

1. Channel-to-stud screw pattern and spacing of channel rows (the channel now carries the 2" ceiling layer and the mesh; the PE will want to see the fastener count).
2. Exact position of the midspan bearing line relative to the interior wall layout.
3. Basalt mesh spec (grid, weight, layers).
4. Design wind speed / exposure the PE will use (Jamaica NBC adopts ASCE 7-style loads).
5. Cellular concrete supplier mix (density, 7-day and 28-day strength).