🚿 FL Shower Pan & Waterproofing Guide
Liner selection, slope calculator, ANSI 118.10 compliance & HVHZ requirements.
Liner System Comparison
PVC Liner (30 mil) — STANDARD: Most common in FL new construction; compatible with clamping ring drains; folds corners (requires no-crease technique); $0.50–1.20/sq ft material; life 20–30 years in FL.
PVC Liner (40 mil) — UPGRADED: Preferred for large showers (>36 sq ft); better puncture resistance; code required for steam showers; $1.00–2.00/sq ft; life 30–40 years.
CPE Liner (40 mil) — ALTERNATIVE: Chlorinated polyethylene, better chemical resistance; does NOT bond to mortar bed like PVC; preferred by some FL inspectors for low-VOC projects; $1.50–2.50/sq ft; life 25–35 years.
Hot Mop (4-ply felt) — TRADITIONAL: Applied hot at job site, no seams; requires licensed waterproofing contractor; common in South FL commercial; 72-hr cure before tile; $150–300 installed (pro only); life 15–25 years.
Bonded Membrane (Schluter KERDI) — BEST: Direct-bond to substrate, no mortar bed required; ANSI 118.10 compliant; compatible with large-format tile directly; requires Schluter-branded drain; $2.50–5.00/sq ft; life 30–50 years.
Tile-Ready Foam (WEDI / Kerdi-Board) — PREMIUM: Pre-sloped foam panels, no mortar bed pour; built-in waterproofing; fast install (1 day vs 3+); ANSI 118.10, best for FL concrete slabs; $5.00–12.00/sq ft system; life = lifetime of tile.
Liquid-Applied Membrane (Mapei AquaDefense / RedGard) — HVHZ: Brushed or rolled, 2–3 coats; used over cement board; NOT for mortar bed; FL HVHZ R7017 requires breathable WRB on exterior walls; $1.00–3.00/sq ft; life 20–30 years.
Shower Floor Slope & Mortar Bed Guide
Code minimum slope: 1/4" per foot from all walls to drain; standard 3/8" per foot; steep 1/2" per foot. On a standard 42x60 inch shower (3.5 ft width), at 1/4" per foot the total drop from corner to center is ~1.75 inches minimum.
Dry-Pack Mix Ratio (FL Standard): 5 parts clean sand : 1 part Portland cement (Type I or II); water just enough to hold shape (sandcastle consistency). Do NOT use pre-mixed mortar or thin-set for mortar bed.
Min Mortar Bed Thickness (ANSI A108.01): At drain 3/4" minimum over liner; at curb/walls 1-1/4" minimum; reinforcement (15 lb felt or metal lath) when bed exceeds 1-1/4".
Cure Time Before Tile (FL Heat & Humidity): Dry-pack bed 24–72 hours (minimum 24 hrs before walking on); tile minimum 24 hrs after bed achieves 75% strength. Do NOT let mortar bed dry too fast — cover with plastic in direct FL sun.
Curb Height Requirements (FL): Standard shower curb 2" minimum above finished floor (FBC R307.2); ADA/barrier-free max 1/2" curb (ADA 2010 §608.7); steam shower 9" minimum; HVHZ (Miami-Dade/Broward) verify with local AHJ — some coastal areas require 3" min for water intrusion protection.
FL Waterproofing Code Requirements
ANSI 118.10 — Bonded Waterproof Membranes: Membrane must achieve 7-day water absorption ≤ 0.2%; elongation ≥ 50% at break (critical for FL thermal expansion cycles); adhesive shear strength ≥ 50 psi after water immersion. Products meeting it: Schluter KERDI, Mapei AquaDefense, Laticrete Hydro Ban, RedGard, USG Durock Tile Membrane. ANSI A118.12 (electrically conductive mortars) required for heated shower floors. TCNA Handbook Method B-422 references bonded membrane over cement board.
FBC R307.2 / IPC 417.5: All shower receptors shall be waterproof; liner (PVC/CPE) shall extend at least 3 inches above the top of the rough curb; liner turned up and secured at studs before cement board; liner test: fill with water to 2" below top of rough curb for 24 hours — zero leakage (FBC R307.2.1).
Inspection Requirements (FBC): Pre-pour inspection required before mortar bed pour (liner, drain, liner dam); rough plumbing inspection for drain rough-in; some FL counties require flood test inspection by an inspector, not just contractor self-certification.
HVHZ (High Velocity Hurricane Zone) Requirements
Applies to Miami-Dade and Broward Counties (and portions of Palm Beach).
- FL Product Approval required for all waterproofing membranes in HVHZ exterior applications.
- Interior shower waterproofing: standard ANSI 118.10 products acceptable in HVHZ.
- Exterior shower / pool bath walls: must comply with FBC R7017 — weather-resistant barrier (WRB) required behind tile on exterior walls.
- HVHZ: all cement board fasteners must be corrosion-resistant (304 SS minimum for shower interiors).
- Miami-Dade Product Control: search productcontrol.miamidade.gov for approved membranes.
Steam Shower (HVHZ): Vapor barrier required on all walls AND ceiling; ceiling slope ≥ 1/2" per foot toward wall to prevent steam condensate drip; generator must be FL Product-Approved; outdoor units need 140 mph wind rating.
Pre-Pour Inspection Checklist
- Liner laid flat — no folds or bunching at corners (corner fold in one direction; never fold liner on itself).
- Liner extends ≥ 3" above top of rough curb all around (FBC R307.2).
- Liner secured to studs at correct height (no staples below waterline).
- Drain clamping ring bolts finger-tight — liner seated; weep holes clear before mortar pour.
- Flood test complete — 2" water held for 24 hours, zero drop (FBC R307.2.1).
- Drain body level and at correct rough-in height (account for mortar bed + tile + setting bed; drain collar finishes flush with tile).
- Cement board installed over liner (not under) on walls; board bottom should NOT sit in mortar bed.
- All cement board seams taped with alkali-resistant mesh + thinset before membrane.
- Inspector notified for pre-pour sign-off where required (Miami-Dade, Broward, Palm Beach, Hillsborough).
- Mortar bed mix verified (5:1 sand:Portland, dry-pack consistency).