# LDD-18 · Interior Material Language

> **Status:** 🟢 LOCKED.

## One-line intent

Industrial structure + warm touch — exposed steel and structure where the hand doesn't go; wood and softened stone where it does.

## Why this matters

Material language is the project's single emotional decision. Industrial-only feels cold. Warm-only feels suburban. The hybrid strategy is harder to pull off but pays back in lived experience every day.

## Locked decisions

**Core idea**

Industrial structure + warm touch.

**Elements**

| Surface category | Material treatment |
|---|---|
| Exposed | Steel, structure (PEMB columns, beams, exposed conduits, ducts) |
| Touch | Wood, softened stone (handrails, sills, counter edges, door hardware) |

**Edge rule**

- 1/4" to 3/8" radius **everywhere** there's a touchable edge (counter, handrail, door return, cabinetry, threshold)

**Railing**

- Steel + wood cap

## Open items / requires engineer review

- **Specific wood species** — white oak vs walnut vs Douglas fir? Each has cost, color, and grain implications.
- **Stone selection** — what's the "softened stone"? Honed limestone? Soapstone? Quartzite with rounded edges? The language is vague.
- **Steel finish** — raw hot-rolled (warm, evolves with time), clear coat (preserves color), powder coat (uniform, can match matte-dark exterior), patina (engineered rust)?
- **Floor flooring connection** — per [LDD-24](24-flooring.md), gym is urethane, living is SPC LVP, workshop/garage/mech is polished concrete. Material language continuity from floor to wall is unspecified.
- **Cabinet face material** — wood matches casework everywhere, or two-tone (warm wood for upper, dark metal for lower)?
- **Door material + finish** — LDD-19 calls for solid-core 84" doors at $50–150 — that's a paint-grade door. Where do the wood-feel doors go?

## Cross-references

- → [LDD-19 doors + stairs](19-doors-stairs.md) — material continuity.
- → [LDD-24 flooring](24-flooring.md) — floor material allocation by zone.
- → [LDD-12 ceilings](12-exposed-ceilings.md) — exposed structure as ceiling.
- → [LDD-20 social counter](20-social-counter.md) — counter materials are the highest-touch surface.

## Cost drivers

- **Wood cap rail + wood touch points** (handrails, sills, hardware): $4–9K depending on species + total LF.
- **Stone selections** (counters, hearth if any, possible accent walls): $8–25K depending on extent.
- **Steel finishing** (hot-rolled vs powder coat for exposed structure visible inside): $4–10K incremental over raw steel.
- **Edge radius execution** (1/4–3/8" everywhere): mostly labor; budget +5–10% on millwork line.

**Likely-case rollup: $20–55K interior material premium above paint-grade baseline**, distributed across finish line items.

## Air-gap concerns

1. **"Softened stone" undefined.** Pick a specific stone now. The word "softened" implies honed/leathered finish, not polished. Make it explicit and source samples.
2. **Edge radius rule is easy to violate.** Cabinet shops default to sharp 90° edges; they cost less. Specify 1/4" minimum radius in the cabinet spec and inspect at install.
3. **Steel oxidation over time.** Raw hot-rolled steel in a humid interior will rust. Clear coat or wax it. If exposed steel in a kitchen or bathroom, plan for re-waxing as part of ownership.
4. **Floor-to-wall material language transitions** at zone boundaries. From living wing SPC LVP to mech room polished concrete, what's the wall material? Continuous drywall? Wood wainscot? Industrial steel liner? Decide per zone.
5. **Sound character.** Wood + softened stone + drywall absorb mid-frequency sound; steel + concrete + IMP reflect it. The mix should be tuned for each room's acoustic intent. The hybrid material strategy implicitly does this — just verify, especially in the gym (mostly reflective) and the living/breakfast zone (needs some absorption).

## Diagram

(no dedicated SVG — material language is qualitative.)

## Status

🟢 **Green — language is coherent.** Specific selections (wood species, stone, steel finish) are detail-design tasks.