You can often fit a new door slab into an old frame as long as the frame’s in decent shape. The frame needs to be solid, square, and free of warping or rot. The new door has to match the old one in width, height, and thickness, and the hinge and knob placements need to line up or be adjusted carefully. However, if your frame is damaged, swapping just the door won’t cut it. In that case, replacing the entire unit would be the best move for a smooth, secure installation.

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A slab door is a standalone door without a frame or hardware. A prehung door is a complete set that includes the door, frame, hinges, and sometimes the doorknob and lockset.

In most cases, a prehung door is the better and easier option to install, especially for DIY projects or exterior applications, as they often come pre-weatherproofed. They require fewer tools and less experience to install properly. Although prehung doors are heavier and have a higher upfront cost, the investment is often worthwhile for a complete upgrade that includes a new frame.

A slab door may be a better choice if you are on a tight budget, have a custom-sized wall opening, or only need to replace the door while keeping the existing frame. While the initial cost is lower, you will need to purchase all the hardware separately and do more DIY work to hang it, which may not result in significant time or money savings.

Most of the time, the direction your door swings does matter. Your door’s swing is also called its handing, and it determines how your door opens. The layout of your home probably only gives your door enough room to hang and swing in one direction. On the other hand, it might not matter if your door can open freely in either direction without inconveniencing you and your household.