PDB Automatic Door Bottom

The gap between the bottom of a door and the floor or threshold is one of the largest sources of sound leaks. The most effective way to seal this opening is with an Automatic Door Bottom (PDB), available in both Mortised (PDB Mortised) and Surface-Mounted (PDB Surface) styles.

The term “automatic” refers to how the door seal automatically lowers when the door closes and lifts when the door opens. A metal plunger on one end of the seal contacts the door jamb, triggering the mechanism to move the rubber insert up or down. This prevents the seal from dragging on the floor, ensuring smooth door operation, longer seal life, and consistent acoustic performance.

What sets IsoStore’s automatic door bottom seals apart is their uniform sealing pressure and dual-rubber design. The double rubber insert creates a 3/8" dead air space, which significantly improves sound isolation and energy efficiency compared to single-rubber or foam-based seals.

IsoStore offers two styles of PDB door bottoms:

• PDB Mortised: Fully recessed for a clean, concealed appearance
• PDB Surface: Semi-mortised or surface-mounted for easier installation

Both styles deliver the same high level of soundproofing performance and durability, differing only in installation method and appearance.

Each Automatic Door Bottom (PDB) includes all required fasteners and complete manufacturer installation instructions. Below is a quick overview of how to install each style.

PDB Mortised

The PDB Mortised model installs inside the bottom edge of the door, providing a clean, hidden appearance. When installed, the seal is completely concealed from view on both sides, with only 1/4" to 3/8" of rubber extending below the door when engaged.

This model is secured using small mounting screws that attach the automatic seal directly into the bottom of the door slab, ensuring a tight, permanent fit. The mortised design offers the most discreet installation while maintaining excellent soundproofing and air-sealing performance.

PDB Surface

The PDB Surface model installs directly onto the face of the door slab, positioned between the door stops. For a cleaner look, it can also be semi-mortised, recessed slightly into the bottom of the door so one side sits flush with the surface.

When installed, the seal remains visible from one side of the door, with the rubber drop ranging from 1/4" x 3/8". This version uses three heavy-duty screws to secure the unit firmly to the door.

Both models deliver the same automatic sealing performance, protecting against sound leakage, drafts, and light penetration while maintaining smooth door operation.

ADB Mortised Fitting Guide

ADB Surface Fitting Guide

• PDB Mortised Fitting Guide
• PDB Surface Fitting Guide
• PDB Mortised Product Specs
• PDB Surface Product Specs