Installing a pre-hung door in your house should be straightforward provided you have the appropriate tools. Make sure you have a set of wood shims and #8 finishing nails on hand for this step.
Shims help ensure the frame fits into its larger opening perfectly and fill any gaps. Use a level to check alignment of head jamb against wall before placing shims at hinge side of head jamb for better fit.
Measure the Door
Before ordering your new door, it is essential that you accurately measure its space. This will ensure it fits as promised and looks aesthetically pleasing in your home.
Begin by taking measurements of the rough opening for a door casing replacement using interior trim, taking width and height measurements before using a level to check that there is even spacing between wall and header framing (also referred to as reveal).
Your frame should be of uniform size so that it allows you to purchase a prehung door that will fit seamlessly without needing to shim it. A too-big frame could cause the door to rub against its top when open or closed, necessitating further research before purchasing new doors. Inswing or outswing? Deciding is often difficult but takes the form of additional research before buying any door.
Remove the Old Door
When replacing a door, it’s often easiest and cheapest to also change out its jamb (the frame that connects it to the wall and door). This DIY project should be doable by most home improvement enthusiasts.
Start by uninstalling your existing door and checking to make sure its jamb is square if required.
To select an ideal door size, remove all trim and measure across three locations of the rough opening studs – center, left and right) until achieving the smallest measurement. Note this measurement.
As well, measure the rough opening studs from three locations (center, top and bottom), noting the lowest measurement. Use these measurements to purchase a prehung door that fits snuggly into the jamb; be sure to round off measurements to the nearest inch so as to order an ideal door that is 1/4″ smaller on both height and width than these measurements – this will reduce any trimming you or your builder will have to perform post installation.
Align the Door
Your aim should be to mount the door so it will swing freely and perfectly level, perhaps by adding shims on either side of its hinges.
To determine the appropriate size for a new door, start by taking steps to unwrap all casing surrounding its frame. This will expose any rough opening or framing in the wall and you can use a tape measure to take measurements from each stud location; select the measurement with the lowest measurement as your width of choice for your new door.
Check that both the king stud and trimmer studs are level with the walls and close any gaps between trimmer studs and wall by using 8d nails and caulk, then using shims to raise trimmer stud on hinge side to align it with drywall, using level jambs on either side to ensure they’re flush with each side of drywall.
Install the Door
Once you have determined the appropriate size, temporarily place the new door and jamb unit into its opening. Shim the header (top) of the door jamb in two equal places until an even margin, or “reveal”, exists between its frame and each stud on each side – known as reveal.
Your house dictates how the door should open; for this, decide between left-handed (LH inswing) or right-handed (RH outswing) swing direction. To find the most comfortable swing, put your nose against one of the hinge pins; this should show which way will be used when opening and closing it.
If you want to speed up this process, consider using a patented tool called the EZ-Hang, which reduces shim requirements and can make hanging interior doors five times faster. It works at any stage of construction; its seven bracket design provides fast and precise alignment for fast door hanging.