Internal Door Construction - Hollowcore

Hollowcore doors are commonly used as internal doors in residential and commercial properties due to their affordability, lightweight design, and ease of installation. They are constructed using a hollow or semi-hollow core sandwiched between two thin outer panels, typically made from materials like MDF (medium-density fiberboard), HDF (high-density fiberboard), or plywood. Here's an in-depth look at the construction of a hollowcore internal door:

---

1. Hollowcore Door Composition

The construction of a hollowcore internal door involves several key elements, which combine to make the door lightweight, affordable, and easy to install. Here's a breakdown of the components:

a. Outer Skin (Face Panels)

The outer surface or face panels of the hollowcore door are the visible parts of the door and are typically made from:

• MDF (Medium-Density Fiberboard): This is a common material for face panels due to its smooth surface, which is ideal for painting or laminating. It is less prone to warping or splitting than natural wood.

• HDF (High-Density Fiberboard): Similar to MDF but denser and stronger. HDF is used for higher-quality hollowcore doors to provide better resistance to dents and damage.

• Plywood: Another option for the outer layer, plywood consists of thin layers of wood veneer glued together. It offers better resistance to impact than MDF or HDF but is often more expensive.

The thickness of the outer panels is usually around 3 to 6 mm, depending on the door's intended use and the level of durability required.

b. Core (Internal Structure)

The core of a hollowcore door is where it differs from solid core or solid wood doors. The internal structure consists of a honeycomb or cellular pattern that fills the hollow space between the outer skins. This core provides basic structural support while keeping the door lightweight.

Common types of hollowcore structures include:

• Honeycomb Cardboard Core: A honeycomb-shaped cardboard lattice is often used as the core material in hollowcore internal doors. This pattern is lightweight and cost-effective, providing sufficient internal support to prevent the door from collapsing. The honeycomb structure adds rigidity while still keeping the door relatively lightweight.

• Wooden or Plastic Stiffeners: Some hollowcore doors use narrow strips of wood or plastic (vertical or horizontal) to create a lightweight support grid inside the door. These stiffeners increase stability and help prevent bowing or warping.

The internal space between these structures remains largely empty, which is why the door is classified as hollowcore.

c. Stiles and Rails (Frame)

The stiles and rails are solid components that form the perimeter frame of the door. These are the parts that give the door its basic shape and ensure that it can be properly mounted with hinges. They are usually made from:

• Solid wood (often softwood like pine)

• Engineered wood (such as MDF or plywood)

• Stiles: These are the vertical components located along the sides of the door. They provide a solid structure for mounting hinges and the lockset.

• Rails: These are the horizontal components located at the top and bottom of the door. They provide structural integrity and support for the overall door frame.

The stiles and rails are glued to the outer face panels and are critical for the door's stability and handling.

d. Lock Block

In hollowcore doors, a lock block is often integrated into the structure. This is a solid piece of wood or engineered wood placed inside the door where the lock and handle will be installed. The lock block provides a solid anchoring point for the lockset and handle hardware, as the rest of the hollow structure wouldn’t be strong enough to securely hold these components.

The lock block is typically located on one side of the door (the side where the handle will be), and its position is usually marked on the door by the manufacturer.