# LDD-16 · Exterior Lighting Infrastructure

> **Status:** 🟢 LOCKED.

## One-line intent

Lighting is infrastructure — not add-on. No future trenching ever required.

## Why this matters

Trenching after landscaping is in is roughly 8x more expensive than trenching before. Designing an underground conduit network during construction is one of the highest-ROI moves available for any custom build.

## Locked decisions

**Core principle**

- Lighting is infrastructure, designed during construction, never retrofitted via trenching later.

**System**

- Underground conduit network with central hub
- 1" branch conduit
- 1.5–2" trunk conduit
- Pull strings + tracer wire included in every run

**Install phases**

1. Rough-in (before slab + before landscape work)
2. Structure (during build)
3. Landscape (lighting fixtures installed after grading finalized)

## Open items / requires engineer review

- **Conduit hub location** — likely adjacent to main electrical panel in laundry/ops core. Confirm.
- **Number of branches and target fixture locations** — even at "infrastructure-only" rough-in, you have to know where the conduit terminates. List target fixture locations now.
- **Voltage strategy** — 12V or 24V landscape low-voltage? Or 120V line-voltage for downlight/security? Probably mixed: 120V for security floods and key driveway, 24V for landscape and accent.
- **Fixture spec** at install-time — fixture style integration with the matte-dark exterior and the disciplined interior lighting framework (LDD-08).
- **Photocell + scene control integration** — exterior lighting on the same Lutron/Crestron system as interior?
- **Future feature accommodation** — fountain, pool, sauna pad, EV pad, garden lighting, holiday lighting circuit. All should have stub-outs.

## Cross-references

- → [LDD-08 lighting framework](08-lighting-framework.md) — exterior on same scene control system.
- → [LDD-09 electrical](09-electrical.md) — branch from main panel in laundry/ops core.

## Cost drivers

- **Underground conduit network** (rough-in only): conduit + trenching during construction phase = $4–12K depending on lineal feet and trench access.
- **Pull strings + tracer wire**: $0.3–1K total — cheap insurance.
- **Stub-outs at future fixture locations**: $50–150 each, set them now.
- **Junction boxes + transformers** at hub: $1–4K.

**Likely-case rollup: $5–18K rough-in only**, separate from fixture spend. Fixtures + control add $8–25K at install time. Total $15–40K when complete, depending on density.

## Air-gap concerns

1. **"Underground" + "PEMB foundation" interaction.** Trenches for landscape lighting conduit can't undermine the building footings. Coordinate with structural before any trench is dug.
2. **No mention of landscape design itself.** Without a landscape plan, you're stubbing conduit toward "approximately where lighting will go." Better: get even a sketch landscape plan before rough-in so stub-outs are precise.
3. **Solar PV interaction.** If solar is roof-mounted, that's fine. If solar might be ground-mounted (more efficient at this site if rural), the exterior conduit hub needs PV-conduit capacity too.
4. **EV charging stubs at exterior pads.** If there's any future plan for an exterior charging pedestal (e.g., near guest parking), trench for it now.
5. **Generator location coordination.** If generator is exterior-pad mounted, the gas line + conduit must run from this hub area.

## Diagram

(no dedicated SVG — exterior conduit follows site plan, not yet defined.)

## Status

🟢 **Green — get this in the ground during rough-in.** Highest-ROI infrastructure move.