How to fit an internal door: Easy Guide

How to fit an internal door

If you want to replace an old door, fitting an interior door isn’t as difficult as it might seem. If you have the confidence to use tools such as a saw and chisel then this is a DIY project you can likely take on yourself. The key to a quick and simple door installation is accuracy. Here's how to hang an internal door:

Tools you will need 

  • Tape measure

  • Sharp pencil

  • Hand saw

  • Clamps

  • Sandpaper or a hand saw 

  • 25 mm (1") Chisel

  • Hammer or wooden mallet

  • Drill (wired or cordless)

  • Drill bit

  • Workbench

  • Wooden wedges

  • Internal door

  • 2-3 suitable door hinges

  • Screws

  • Hammer & nails 


Measuring for a new door

If you have a frame with no door, measure the inside of the frame, the height and the width of the inside of the frame - The height is measured at two points (left and right) and the width is measured in three points (top, middle and bottom). Use the largest of both sizes to determine what size door is required, round up, not down.

graphic of door width and height

Measure existing door(s)

Measure any existing doors in place so you can have them as accurate references when ordering new ones. Note that installing new hinges requires removing any existing hinges, so this is important!

Choosing the right door

You’ll need to choose the right door for your requirements. If you’re unsure of which door is right for you then use your measurements to check out our range of doors by size for inspiration.

Our Selection of internal doors by size

  • A2040 x 826mm  (80.25" x  32.5")
  • 2040 x 726mm  (80.25" x  28.5")
  • 2040 x 626mm (80.25" x 24.6")
  • 2040 x 526mm (80.25" x 20.7")
  • 2040 x 526mm  (80.25" x  20.7")
  • 78" x 18"   (1981 x 457mm)
  • 78" x 21"   (1981 x 533mm)
  • 78" x 27"   (1981 x  686mm)
  • 2100 x 920mm  (82.75" x 36.25")
  • 78" x 33"   (1981 x 838mm)


Don’t see a size here that suits? Ask our experts on Live Chat and they will be able to assist you. Or take your measurements to one of our branches (Reading, Belfast, Newtownabbey) and tell them you need an internal door for your space, and share your measurements with one of our team they’ll be happy to help.


How to fit your new internal door


Step 1: First, check any instructions that may come with your new door to see if there are any special requirements. Next you’ll need to remove the old door from its frame. To do this simply knock out the hinge pin from your hinges and then lift the old door out of the frame. You may need the help of a second person for this. If the hinge pin is tight and hard to remove, gently knock it out using a hammer and a nail with a flattened tip. 


Top tip: Make sure you have removed any nails that are sticking out of the frame and sand down any splinters or sharp edges.

Step 2: Stand the new door up in the doorway to check whether it needs trimming. If it does, use a pencil to mark the top of the door opening onto the new door.

Step 3: Secure the door to your workbench with clamps. Cut off the excess wood from the bottom of the door. To do this, the tools you’ll need are hand saw, clamps, circular saw and sandpaper.

Step 4: After you have measured and trimmed the height of your new door, transfer the width measurement of your doorframe onto the door. Using a tape measure and pencil, mark up on the door and then use a planer to remove the excess from the width. Once the excess is removed, sand the edges of the door. 

Step 5: Using a wedge, mark the hinges. Place the door on the doorframe and use the wedges to support it. On the door pencil mark the locations of the bottom, middle, and top hinges. Following the mark points you previously drew on the door, the next step is to mark the hinge positions on to the side of the door. Additionally, you need to specify the hinge's depth.

Step 6: Chisel around the outline of the hinge – the tools you’ll need to do this is a drill, drill bits, chisel, hammer and screwdriver.

Top Tip: To prevent splitting, cut at 5 mm intervals. To eliminate extra material use the chisel flat down.

Mark the holes after grabbing the hinges. Once the holes have been marked, drill the pilot holes, and attach all of the hinges to the door. 

Step 7: While holding the door to the doorframe using the wedge supports or with assistance (if you have a helping hand) screw the middle bolt into each hinge.

If it fits then add the remaining screws. 

Next steps and finishing touches

Now that your new door is in place you may want to carry out finishing touches such as painting the door or making cut-outs for handles or latches.  We hope that you have found this guide helpful and that it has given you the confidence to fit your own door. Good luck!