Prices, Promotions, styles, and availability may vary. Our local stores do not honor online pricing. Prices and availability of products and services are subject to change without notice. Errors will be corrected where discovered, and Lowe's reserves the right to revoke any stated offer and to correct any errors, inaccuracies or omissions including after an order has been submitted.

Exterior Doors vs. Interior Doors: What’s the Difference?

Lowe's Editorial Team

By Lowe's Editorial Team
Published June 28, 2024

When looking for new doors, it’s important to know about the difference between exterior and interior doors and the materials manufacturers use to make them. Exterior doors must withstand the weather and provide security. Interior doors are both decorative and functional.

What Are Interior Doors

Interior doors separate rooms and close off spaces such as closets. They also provide privacy for people in different rooms. The most common materials of interior doors are solid wood, fiberglass, MDF (medium-density fiberboard) and glass. They can block sound between rooms and help regulate indoor temperatures.

What Are Exterior Doors

Exterior doors lead to the outdoors. They are essential for security and weatherproofing. For this reason, they are built with strong and durable materials such as solid wood and metal. Exterior doors are usually thicker than interior doors and require high-quality hardware and locks to make them secure.

Types of Doors

Before buying a new door, consider how you want to install it. There are two types of installations for both exterior and interior doors.

Prehung Door

A prehung door combines a frame and door in a single unit. Prehung doors are preassembled and easy to install. They are perfect for adding to new homes and fixing damaged frames. This type of door has hardware, hinges and a precut knob hole as well as a frame. Prehung doors take less time to install than slab doors.

Slab Door

A slab door is just the door itself without hinges, knobs or a frame. This type of door is a good choice when you want greater design flexibility. If you choose a slab door, you’ll need to buy a metal strike plate, shims, mortises, hinges and a doorknob. However, some slab doors also come predrilled for door knobs and hinges. They’re a lighter, more affordable option than prehung doors.

Exterior Doors vs. Interior Doors: Key Differences

Standard Sizes

Standard widths for interior doors are 24, 28, 30, 32 and 36 inches. They must be at least 80 inches high.

The standard size for an exterior or front door is 36 inches wide by 80 inches high. But the dimensions can vary from 30 to 42 inches wide and from 80 to 96 inches high.

Materials

The main difference between exterior and interior doors is material. Interior doors are protected from the weather, so they are made of less durable material. Exterior doors are sturdier to provide security and protection against the weather.

Materials for Interior Doors

  • Molded Composite: This affordable option looks and feels like real wood. The color doesn’t fade or need painting, so this material requires minimal maintenance.
  • Wood: Woods vary in color, weight and durability. Hardwoods include knotty alder and oak. Softwoods include pine.
  • Engineered Wood: Options such as medium-density fiberboard (MDF) and hardboard are durable and long-lasting.
  • PVC: This material is durable, water-resistant and fire-resistant. It comes in a range of colors to suit different interior designs.

Materials for Exterior Doors

  • Steel: Manufacturers use this material to make doors with tight-fitting frames and energy-efficient core insulation. Steel doors often feature double- or triple-panel insulating glass to reduce heat transfer. With good weather stripping, steel will not shrink, swell or warp much. It needs very little maintenance in harsh weather.
  • Fiberglass: This high-quality composite is easy to install. It can withstand harsh climates. Fiberglass doors last longer than wood or steel ones and won’t shrink, warp, split or crack
  • Wood: Wood materials range from solid wood like high-quality fir or walnut. Higher-end models feature intricate designs and thick panels that withstand weather fluctuations.
  • Wrought Iron: Wrought iron doors are durable and secure. They are heavy, so they tend to be pricier and more difficult to install than other types of doors. Wrought iron doors are available in various designs. You can customize them with different types of glass and hardware, such as handles and locks.

Core Type

Interior doors can have hollow cores. This lightweight, affordable design is easy to install and popular with many homeowners. This type of door works well for bedrooms, bathrooms and closets. However, hollow core doors are not good at blocking sound and are not very fire-resistant.

Exterior doors typically have solid cores that withstand the weather and protect your home’s interior spaces. These doors are usually made of wood or have woodgrain finishes. They contain layers of steel or metal for better temperature control and security.

Insulation

Exterior doors with solid cores keep your home insulated and help you save energy. Their design withstands harsh weather conditions, extreme temperatures, drafts and storms. Solid core doors help keep your home comfortable and prevent it from getting too hot or cold. Exterior insulated steel doors are usually filled with insulating materials like foam or mineral wool, which also help tackle extreme weather conditions.

Interior doors don’t offer the same level of insulation because they often have hollow cores. But some types of interior doors can help reduce drafts between the rooms in your home.