Water Containment vs. Accessibility

Shower curbs (thresholds) prevent water from escaping the shower. Curbless showers eliminate the barrier for accessibility—but require more careful slope planning.

Both can be code-compliant and waterproof when done correctly.

Traditional Shower Curbs

Minimum Height

6 inches is standard, but can vary by local code and door type.

  • Too low → water escapes
  • Too high → difficult to step over (especially for elderly or mobility-impaired)

Construction Methods

Pre-formed foam curbs:

  • Lightweight, easy to cut
  • Waterproofing wraps over top

Mortar bed curbs:

  • Built-in-place using metal lath + mortar
  • Fully customizable height/width

Curb-forming systems:

  • Plastic/metal forms filled with mortar
  • Integrated with waterproofing membrane

Critical Details

✅ Waterproofing must wrap over the curb (top and both sides)
✅ Tile overhang: Front edge must be waterproofed and sloped to drain
✅ Corners: Inside corners reinforced with fabric or pre-formed corners
✅ Height verification: Measure from shower pan, not subfloor

Curbless (Zero-Entry) Showers

Code Requirements (NJ/IRC)

  • Bathroom floor must slope toward drain (or install trench drain)
  • Waterproofing extends beyond shower area (to prevent water migration)
  • Minimum 30” x 30” clear floor space inside shower

Structural Considerations

Curbless showers often require:

  • Recessed subfloor (to accommodate slope + tile thickness)
  • Structural modification (cutting joists, adding support)
  • Permit and inspection (structural changes require approval)

Drainage Strategies

Linear drain:

  • Rectangular drain channel
  • Allows single-plane slope
  • Popular for curbless designs

Center point drain:

  • Requires four-way slope
  • More complex to build curbless

Trench/channel drain:

  • Outside shower area
  • Collects water from bathroom floor

Waterproofing Requirements

Waterproofing must extend:

  • Entire shower area (obviously)
  • At least 9” beyond curb line (TCNA recommendation)
  • Full bathroom floor (if using trench drain strategy)

Hybrid Approach: Low-Profile Curbs

2-3 inch curbs provide:

  • Easier step-over than 6” curbs
  • Water containment (with proper slope + door seal)
  • Less structural modification than full curbless

Not technically “curbless,” but achieves similar accessibility goals with less risk.

Common Failures

❌ Curb too low (water escapes)
❌ Waterproofing doesn’t wrap over curb top
❌ Curbless shower without adequate slope
❌ No extended waterproofing beyond shower area
❌ Structural modification without permit