What Is a Slab Door?

In the parlance of the construction industry, a slab door is a standalone door without a frame or door jamb. Learn more about slab doors and how they can fit your next home improvement project.

What are slab doors?

Slab doors are door panels that come detached from a door frame. They can function as both interior doors and exterior entry doors. Some come with pre-drilled mortises for hardware like door hinges, door latches, and faceplates. Others come as solid wood slabs and the installer must chisel out their own mortises.

Slab doors can be built from a variety of materials.

  • Solid wood doors. Solid wood slab doors offer a classic look for both interior and exterior applications. Solid wood doors offer insulation from the weather and noise, though some more modern options are better at blocking the outside. Solid wood is the most common option historically, and most vintage doors are solid.
  • Hollow core doors. These are a lightweight and low-cost option for interior doors, particularly for closet doors. They will not do much in the way of insulating temperature or absorbing the sound, but if that is not a consideration, hollow core doors can be a great budget option.
  • Solid core doors. Solid core slab doors are made from composite wood or other materials, which include MDF, particle board, plywood, glass fibers, and even foam. They can come finished with a solid wood veneer that makes them look quite similar to a solid wood door. When it comes to temperature insulation and sound absorption, solid core slab doors excel. Their dense, multi-layer construction traps heat and sound better than solid wood or hollow core options. 
  • Metal doors. Metal doors are typically made of an aluminum/steel composite. Although they are heavy and a bit impersonal, they make excellent exterior doors and work especially well as security doors.
  • Fiberglass doors. Fiberglass is a sturdy wood alternative that is comparatively lightweight and has impressive insulating properties. Fiberglass slab doors tend to be more expensive than their wood counterparts, so people often install them as an exterior entry door and then use some version of a wood door for their interior door needs. Today’s fiberglass doors can be made with wood textures that looks similar to real wood.

How to install slab doors

Installing standalone slab doors requires more time and skill than installing a prehung door, so only take this on if you have prior carpentry experience. Here is a step-by-step guide to hanging a slab door.

  1. Assemble your tools. To hang a slab door, you will need the actual door slab, doorknob, face plate, strike plate, and hinges. You will also need the following tools: hammer, nails, power drill with various bits, wood chisel, pry bar, speed square, spring clamps, and a pencil.
  2. Match your new slab door to the one you are replacing. The fastest way to create mortises on your new slab door is to copy the configuration of the door you are replacing. Remove the doorknob in your old door and place the two doors side-by-side on the floor with their hinge sides pointing upward. If you like, you can clamp them together using spring clamps. This will keep them in place.
  3. Use the speed square to mark your mortise cuttings. Take your speed square and pencil and copy the exact location and dimensions of your old door’s hinges onto the hinges of the new slab door. Measure from the top and bottom of the new door to make sure your markings are in the exact spot they need to be.
  4. Use the chisel to cut out the proper space mortise. Make sure you use a sharp, high-quality chisel to do the most precise work possible. Make the mortise area as flat and smooth as possible.
  5. Screw in the hinges. Using your power drill, remove the hinges from your old door and install them into your new door. To be on the safe side, you may want to drill pilot holes before moving on to the screws themselves. It is crucial that the hinges are flush with the side surface of the door. If they stick out too much, you will need to deepen your mortise. If they are too recessed, you will need to shim your mortise with either cardboard or a very thin strip of plywood. Once you’ve gotten your hinges completely flush, you’re ready to move on to the next step.
  6. Hang the door. Place the slab door inside the doorframe. Use the pry bar to raise the door to the exact level of the existing drill holes on the door frame. When you have it perfectly lined up, drill the hinges into the existing holes. You must do this exactly right, or you’ll accidentally enlarge the door jamb’s drill holes and make the door unstable.
  7. Install your remaining hardware. Once your door is hung, you can add remaining hardware like a doorknob and strike plate. Save this step for last because it’s a lot easier to tweak the positioning of a strike plate than the position of a hanging door.

Advantages of using slab doors

When installing new doors in your home or office, you will choose between standalone slab doors and prehung doors that already come attached to a frame. There are several reasons to opt for the slab door option.

  • Lower retail cost. A slab door is cheaper than a prehung unit, so you will pay less at your local hardware store. When pricing home repairs, however, you must factor in the cost of labor. If you need to hire someone to install your door for you, you will likely pay more money to install a slab door over a prehung door. If you plan to install the door yourself, you can save money overall.
  • Greater array of options. It is relatively easy to find standalone slab doors made from a variety of materials and in a variety of styles. From solid wood doors to solid core doors to hollow core doors to fiberglass and metal doors, you should encounter little difficulty in sourcing what you need. You will also also have a greater choice of aesthetic designs.
  • Slab doors typically fit more easily into existing door openings. Prehung doors come with their own door frame, and those frames don’t always cooperate with existing door openings. Slab doors are much easier to shape to the size of your existing frame or door opening.

Disadvantages of using slab doors

While slab doors offer flexibility and initial cost savings, they also come with a unique set of drawbacks.

  • Harder to install than prehung doors. A DIY carpenter may have an easier time installing a prehung door than a slab door. You don’t need to line up a prehung door to the exact perfect spot on a door frame. 
  • May be more expensive when you factor in labor. Slab doors cost less than prehung doors, but what about the cost of installation? If you’re paying someone else to install a door for you, they will likely need more time to hang a slab door than to install a prehung door—particularly if they have to build a whole new door frame.
  • Harder to achieve a weatherproof seal. Some contractors prefer the prehung option when it comes to exterior entry doors. This is because such prehung units might arrive with an airtight seal and plenty of waterproofing. When you install your own slab door, you have to handle those elements yourself, and it may be hard to get the seams quite as tight as they do at the factory.

MT Copeland offers video-based online classes that give you a foundation in construction fundamentals with real-world applications, like how house framing works. Classes include professionally produced videos taught by practicing craftspeople, and supplementary downloads like quizzes, blueprints, and other materials to help you master the skills.

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