Chapter 29 Key Takeaways: Flooring Systems
The Subfloor Is the Foundation of Everything
No finish floor outperforms its substrate. Before installing any flooring:
- Flatness: 3/16 inch in 10 feet for most flooring; 1/8 inch in 10 feet for tile; 1/16 inch in 24 inches for large-format tile
- Stiffness: L/360 deflection limit for tile; bouncy floors tile poorly and squeak
- Moisture: Wood subfloor at 6–9% moisture content; concrete slabs tested with calcium chloride (ASTM F1869)
Fixing high spots = belt sanding or grinding. Fixing low spots = self-leveling compound. Fixing loose panels = drywall screws at 6–8-inch spacing into joists.
Hardwood: The Long Game
| Factor | Solid Hardwood | Engineered Hardwood |
|---|---|---|
| Where | Above grade only | Above, on-grade, and some below-grade |
| Radiant heat | Not compatible | Compatible (most products) |
| Refinishing | Many times (3/4-inch wears slowly) | Limited by wear layer thickness (2–6mm) |
| Installed cost | $7–$15/sq ft | $9–$18/sq ft |
Refinishing: The signature advantage of hardwood. Surface finish worn? Sand to bare wood, apply new finish. Can restore 100-year-old floors to like-new condition.
LVP: What You're Really Buying
The most important specification: wear layer thickness in mil.
| Wear Layer | Appropriate Use |
|---|---|
| 6–8 mil | Low-traffic or short-term only |
| 12 mil | Normal residential living rooms, bedrooms |
| 20 mil | High-traffic areas, pets, children, kitchens |
| 28+ mil | Commercial or very high residential traffic |
SPC core = denser, better for radiant heat, slightly less comfortable. WPC core = foamed, warmer/quieter underfoot, slightly less stable.
Critical limitation: Temperature expansion. LVP requires proper expansion gaps (1/4–3/8 inch at all walls). Inadequate gaps + large temperature swings = buckling.
Genuine advantages: Waterproof, pet/child-friendly, DIY-installable, works below grade where hardwood cannot.
Tile: Substrate and System
Tile cracks when the substrate flexes. Prevention: 1. Verify L/360 floor stiffness 2. Install cement board (1/2-inch) or uncoupling membrane (DITRA) over wood framing 3. Use the correct thinset and notch size for your tile format 4. Large-format tile (over 15 inches) requires back-buttering and leveling clips
Grout: Seal sanded grout after curing. Reseal annually in traffic areas. Epoxy grout is more expensive but far more stain-resistant in kitchens and bathrooms.
Carpet: The Pad Is Half the Floor
Carpet fiber durability: Nylon > Triexta > Polyester > Olefin for resilience under traffic.
Pad quality matters as much as carpet quality. Minimum: 7/16 inch, 6 lb density for standard residential use. Thin pad accelerates carpet deterioration.
Pet odor in carpet cannot be reliably eliminated with cleaning. Full replacement (carpet, pad, and subfloor treatment) is the correct approach when odor has penetrated to the pad or subfloor.
Squeak Causes and Fixes
| Cause | Fix From Above | Fix From Below |
|---|---|---|
| Subfloor-to-joist gap | 2-inch screws into joist | Shims + construction adhesive |
| Loose subfloor panel | Screw panel into joist at 6" spacing | — |
| Carpet-covered subfloor | Counter-Snap or snap-off screws | Squeak-Ender bracket system |
| Hardwood plank rubbing | Graphite lubricant between boards | — |
| Structural (joist splice) | Does not fix cause — address structure | Sister joist, re-level bearing |
First step always: Find the exact source. Walking the floor while a helper watches from below is the fastest diagnostic.
Transitions and Details
- T-molding: Same-height floors in adjacent rooms
- Reducer: Different-height floors at doorways
- End cap: Hard floor terminating at a wall or carpet edge
- Stair nose: Floor edge at top of stair or step-down
Floating floor sequence: Install floor first (with expansion gap) → install baseboard last, fastened to wall only, not through the floor.
Door clearance: New floor thickness raises the floor. Trim door bottoms before installing so they swing freely with 3/4-inch clearance above the new floor.
Cost Reference
| Flooring Type | Installed Cost Range |
|---|---|
| Solid hardwood (mid-grade) | $7–$12/sq ft |
| Engineered hardwood (mid-grade) | $9–$18/sq ft |
| Hardwood refinishing | $3–$6/sq ft |
| Ceramic/porcelain tile | $8–$18/sq ft including substrate |
| LVP (20 mil, installed) | $5–$9/sq ft |
| Carpet (mid-grade, installed with pad) | $5–$8/sq ft |
| Subfloor preparation | $1–$3/sq ft depending on conditions |