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Threshold Transitions at Sloped Slabs and Accessible Entrances

Threshold transitions at accessible entrances and sloped slabs require a balance between waterproofing, thermal control, and code compliance. This article outlines detailing strategies that meet ADA, IBC, and energy performance standards while preventing air and water leakage.

Design Considerations

Accessible thresholds must not exceed 1/2” vertical rise and require beveled transitions over 1/4” in height per ADA and ICC A117.1. These conditions pose challenges for integrating pan flashing, continuous insulation, and air barrier continuity—especially when combined with sloped or depressed slab edges.

Detailing Strategies

  • Use pre-formed ADA-compliant threshold pans with back dams and upturned legs
  • Extend liquid waterproofing onto slab depressions and integrate with flashing membranes
  • Install flexible sill sealant at the interior-to-exterior transition and under door frames
  • Use sloped foam wedges or tapered transition plates to preserve slope while supporting finishes

Code and Envelope Compliance

Combine ADA clearances with IBC energy code insulation requirements by applying rigid foam around depressions and fully taping all joints. Ensure that any exposed metal at the threshold is thermally broken or insulated with gaskets or sealant barriers. Coordinate detailing with door manufacturers and architectural drawings to prevent field conflicts.

Inspection and QA/QC

  • Confirm slope and tolerance of finished threshold with laser level or gauge
  • Check sealant coverage and expansion foam continuity at the sill
  • Photograph membrane application under threshold prior to door setting
  • Perform water spray or hose testing at accessible doors per ASTM E1105 where applicable

Include QA notes and mockup drawings in submittal packages for project team review prior to fabrication or sitework.

Disclosure: As an Amazon Associate, EnvelopeIQ earns from qualifying purchases

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