Pre-hung vs slab doors

The short answer

A slab is just the door. It gets fitted to your existing frame, and new hinge mortises and a hole for the handle are cut to match. A pre-hung door comes already hung in its own frame with hinges attached, and the whole unit replaces the old frame.

If your existing frame is solid, square and a style you want to keep, a slab can be the cleaner, cheaper job. If the frame is damaged, out of square, or you are changing the door size, go pre-hung.

When a slab makes sense

• The jamb is in good shape with no splits or rot.
• The door currently closes evenly with a consistent gap around it.
• You want to keep the existing casing and paint.
• The new door is the same size and swing as the old one.

Fitting a slab is more precise work than it looks. The new door has to be planed to the opening, and the hinges and latch have to land exactly where the old ones did. Done well, it is invisible. Done badly, the door rubs, the latch misses, and you end up with filled mortises showing through the paint.

When to go pre-hung

• The frame is cracked, rotted, or has been patched before.
• The door rubs or the gap is wedge shaped, which usually means the frame is out of square.
• You are changing size, swing or style.
• You are replacing the casing anyway, for example during a trim upgrade.
• It is an exterior door. Exterior doors should almost always be replaced as a complete pre-hung unit so the sill, weatherstrip and frame seal together.

A pre-hung door means the old casing comes off and the frame comes out, so it is a natural time to upgrade casing throughout the house.

Before you order

Measure the existing door, not the opening, and note which way it swings. Check whether your walls are standard thickness, because older homes and exterior walls can need a wider jamb. If in doubt, have the installer measure first. A door that comes home the wrong size or swing is the most common delay we see.