Prehung interior doors, are an easy way to replace the existing door in your home. Buying just a door and hoping to hang it on existing hinges is quite a task that requires some tedious work. In this article we will discuss how to hang trim on prehung interior doors. Whether you are installing French doors, solid wood into your doors, or six panel interior doors as long as they are all prehung the process is still the same.

First you must remove your old door. Start by removing the trim on both sides of the door jam. Using a hammer and pry bar, gently pry the trim from the drywall and the door jam, be extremely careful not to put holes in drywall. If you’re planning to reuse the door trim after you take it off, you must also be careful not to break it while removing it.

Many prehung doors will come with door trim. The door trim will usually be cut to the correct height and width needed. If it does not come with door trim, you will need to take measurements to cut your trim to the correct size.

Measuring and installing door trim:

To measure the left and right sides of your door trim, you will take a tape measure and measure from the bottom of the door jam to 1/8 inch past the header of the door jam. To measure your top trim piece, measure at the top of the door jam from the left to the right for the inside measurement. After you have the inside measurement, at 1/4 inch and that will be the inside measurement for your top door trim. Remember you are cutting your door trim pieces at 45° angles.

After you have measured and cut your door trim pieces, use a 18gauge nail gun and shoot the left side trim onto the door jam on the same side that the door is hung on. Make sure the bottom of the trim is flush with the bottom of the door jam, then make sure that you leave a 1/8 inch reveal from the inside of the door jam to where the trim starts.

Now install your top trim piece making sure it is flush and lined up evenly with the first piece that you installed. It is important to make sure that you leave an 8 inch reveal on your top trim as well so that your door looks symmetrical after it is hung.

Finally you’re ready to install your last piece of trim. Set it into place and once again using your 18gauge no gun zealots to the door jam and its proper location. You will not paying the door trim on both sides until the door has been properly installed.