What's the Difference Between a Pre-Hung Door and a Slab Door?

When installing a door, you may wonder what is the difference between a prehung door and a slab door, and when you might use one door over the other. Let's look at the definitions first.

What is a Pre-Hung Door?

A pre-hung door is, as the name implies, a door that is already hanging in its own frame. It's a fully self-contained unit. Even before installation, it's theoretically possible to open and close the door within its own frame (it's not advisable, though, as you might torque the frame and damage it). The main parts of a pre-hung door are: door slab, hinges, and frame.

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What is a Slab Door?

A slab door is what we normally think of when we think of doors: just a rectangular slab of wood, composite, or steel. It has no hinges or hardware. It's up to the remodeler to attach it to the door frame via hinges.

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Which is Cheaper--a Pre-Hung Door or a Slab Door?

All factors being equal, a slab door is cheaper simply because it consists of less materials. Also, given the weight of the pre-hung door, it costs more to ship the pre-hung door and thus the cost is passed onto the consumer.

When Would I Use Prehung Door?

Some factors that may influence your decision to install a prehung door:

• When there is no existing door frame.
• When the existing door frame is so damaged or warped as to make it impossible to hang a slab door.
• When doing new construction or extensive remodeling. If the door frame is open and exposed, you may find it easier to install a prehung door than a slab door.
• When installing an exterior door. Prehung doors come weathertight off the shelf: you don't need to do anything to make them tight-fitting. Unless you are a real pro, it's extremely difficult to install a tight-fitting exterior slab door.

When Would I Use Slab Door?

Some factors that may influence your decision to install a slab door:

• When cost is a factor.
• When you want to install an antique or otherwise unique door in an existing place.
• If you find it difficult to handle the weight and bulkiness of a prehung door (slab doors, though still cumbersome, are lighter than a prehung door unit).
• When installing an interior door. It doesn't matter if interior slab doors are weathertight.

What are the Downsides of Installing a Prehung Door?

Prehung doors are extremely heavy and hard to manage. You may be able to manage a prehung interior door because their door slabs are made of light material and are often hollow inside. Prehung exterior doors need at least two strong people to manage. Also, prehung doors aren't as easy to install as they seem. Yes, you don't have to worry about exacting task of hanging the slab to the doorframe, but you still have the exacting task of fitting the prehung unit into the wall. The prehung units need shimming. If not done right, shimming can completely ruin the way the slab fits into the frame and the way it swings. After you've installed the prehung door unit, you still need to finish all of the work around it: drywall, painting, molding, siding (if an exterior door).

How About Downsides of Installing a Slab Door?

Slab door installation requires a steady hand, a good eye, and lots of practice. You'll probably be fine if you're doing a one-for-one installation. That is, if the door you are installing is exactly the same size and has the same configurations (screw holes for the hinges, door knob sizing and positioning, etc.) as the door you are removing. Any variation in door size and configurations, and it will be difficult, if not impossible, to make it hang right.

Can You Summarize the Prehung Doors vs. Slab Doors Argument?

Sure. If your house is torn-up from restoration work or you're constructing a new space, you'll be installing a prehung door. If you're got a good doorframe in place and aren't keen on tearing out drywall, install a slab door. No method is really easier than the other, and each has its own special worries.