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Short Summary
Main recommendation: Install a prehung interior door by leveling and squaring the frame with shims placed from two different directions, then securing the jamb with screws, so the door is square, level, flush, and has an even gap. The video also stresses leaving room under the door for future flooring, such as 5/8-inch plywood plus tile, to meet the basic flooring requirement for Tarion warranty coverage in Ontario.
Key Points
- Check the rough opening first: a prehung door frame is generally about 2 inches wider than the door size (e.g., a 24-inch door in a 26-inch opening), with the frame checked for level.
- Plan for the finished floor before installing: add 5/8-inch plywood (about 1 1/8 inches total with the tile) and set a matching shim so the door clears the finished floor.
- Shim in opposing directions to avoid twisting the frame; using shims from only one side can warp the jamb and prevent the door from working properly.
- Finish the fit with precision: framers get close, but the finishing carpenter must dial in consistent gaps of about 1/8 inch around the door.
- Secure the jamb only after it is checked, and keep shims in place while driving screws so the jamb does not spin.
Details Worth Noting
- Concrete instructions:
- Use a level to check the frame before installing the door.
- Lift the door and jamb until roughly flush with the frame, then pack shims underneath to carry the door's weight; this allows one person to work alone.
- Place shims behind the jamb on the hinge side and make that side perfectly level.
- Insert shims from two directions behind the door so spacing stays even and the frame does not twist.
- Put a screw where the door stop will later be installed, since the stop covers it.
- Repeat the shimming and leveling at each hinge up the side of the door.
- Check the level across shims above and below each hinge.
- Hold the shims while driving each screw; shim again if the gap does not close.
- Open the door to drive the screw at each corner, then at the middle, working top to bottom and checking the gap each time.
- When adding shims, make them slightly tighter than the last spot, since the screw will compress them and widen the gap by about 1/32 inch.
- If the framing is twisted, use shims from the same direction on that side to keep the jamb square.
- Finish by installing the door stop on the inside with a brad nailer, doing the trim work, and cutting the shims flush by scoring and breaking them off.
- The presenter notes the door is about 1 1/2 inches thick and the jamb material is half-inch, giving some play for an out-of-square opening.
- Framing is typically within 3/8 to 1/2 inch of level or square; the finish carpenter is expected to correct this.
- The video specifies 5/8-inch plywood as the minimum flooring underlayment under tile to meet Tarion requirements in Ontario; do not install less.
Bottom Line
A prehung door can be installed reliably by a single person by using shims from both directions and checking square, level, and flush at every step, with flooring height accounted for beforehand.
