ARTICLE

How to fit internal doors

Hanging a door in a door frame sounds like it should be a simple task. But uneven floors, warped frames and century-old houses can make it rather more complex. It’ll certainly test the skills of the rookie DIYer so you might decide it’s a job for the pros. If so expect to pay approx £30-50 per door. Feeling confident? Excellent! Read on, in our guide How to fit internal doors.

How to fit internal doors

How to fit internal doors

You will need:

  • Sharp pencil
  • Tape measure
  • Screwdriver
  • Mallet
  • Chisels (18mm / 3/4” or 25mm / 1” and 10mm / 3/8”)
  • Combination square
  • Saw
  • Plane
  • Cordless drill
  • Wood drill bit set
  • Sandpaper


  • What fire regulations should I be aware of?
  • How do I know which way to hang the door?
  • How do I realign a frame that is out of kilter?
  • How much gap should there be at the top, bottom and sides of the door?
  • How do I fit the hinges on the door
  • How do I fit the hinges on the frame?
  • What do I do if my door sticks once it’s fitted?

    Time to complete job: Set aside a day per door
    Approximate budget: Expect to pay from £35 per door. The better the timber the costlier the door.

    Before you start
  • Doors are heavy and cumbersome. Work with a friend!
  • Always wear goggles and a face mask when planing or cutting wood
  • This is a job for a confident DIYer. Seek professional help if at all unsure

    Should I buy solid or hollow doors?
    Hollow doors are cheaper doors. Typically constructed using a hardboard or plywood skin, with a honeycomb interior of cardboard, they’re lighter and more easily damaged than solid doors.

    The choice is yours: solid doors have a better 'feel' to them and are essential if going for a natural wood finish.

    If you are painting your doors then hollow doors will do the job nearly as well. Make sure you buy the correct size door as well. They tend to come in standard sizes, so buy a door the same size as the existing one, in height, width and thickness.

    What fire regulations should I be aware of?
    If your door leads into an adjoining garage, or if it opens into the loft room you’ll need to adhere to building regs and install a fire resistant door. These are constructed with a heavy core and are thicker than standard interior doors, and are designed to give between 30 and 60 minutes of fire resistance.

    When fitting a fire resistant door you’ll need a hardwood, one-piece, rebated frame and an automatic door closer. You are better off getting a professional to fit a fire door, to ensure it meets all regulations.
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    Which way should an internal door open?
    Doors usually open into the room, particularly if coming from a hallway. Do bear in mind the position of the light switch - avoid hanging an internal door so the switch is behind it when opened. It avoids lots of fumbling in the dark!

    How do I know which way to hang the door?
    A hollow core door will have a block inside to accommodate handles and locks and there will usually be writing on the top of the door to indicate which way up it should be hung. If you’re still unsure which way is up, the bottom horizontal rail will be taller than the top horizontal rail, if it has them.
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    How do I tell if my door frame is in alignment or if it’s moved over the years?
    Before you go trimming your new door down to size it’s important to check that your door frame is plumb, so that your door will look spot on, and so it's easier to fit. There’s an easy way to do this: simply hang a plumbline from the two upper corners of the frame, then measure at the bottom how much the door frame has moved out of square.

    How do I realign a frame that’s out of kilter?
    You’ll need to remove the existing architrave and insert thin wooden shims (packing) between the frame and wall so the frame sides are plumb.
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    How do I cut the door to size?
    • Hold the new door in the doorframe to see if it needs adjusting, and mark any areas of the edge of the door that need trimming.
    • If you’re replacing an old door that fitted well, it will make an ideal template. Simply lay it on top of the new door and with a pencil mark where to plane or cut the waste material off the door, so it fits in the frame with a 2 to 3mm gap all the way around. You should only need to remove a very small amount of timber, if you have bought the right size door.
    • Always take an equal amount of wood from both the top and the bottom of the door so it’s still balanced. Take care when cutting down hollow doors as they have thin battens forming the door edges - if you cut too much off, then you will expose the hollow centre of the door.
    • Use a panel saw if you need to take more than 6mm off the height of the new door, then sand it smooth. If you need to trim off less than 6mm, use a hand or power plane.

    How much gap should there be at the top, bottom and sides of the door?
    • If your door frame sits square there should be a 2mm gap between each door edge and frame, just enough for a 2 pence piece to fit in.
    • If you have carpet allow 5-10mm at the bottom of the door. If you have a particularly dense pile carpet allow an extra few millimetres.
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    What sort of hinges do I need? And how many?
    The most common type of hinge for hanging internal doors is the classic butt hinge, which opens like a book and has between 3-5 screw holes on each side. If your door is a very heavy timber one, then you’ll need three butt hinges, for everything else two will do.

    How do I fit the hinges on the door?
    • As you are replacing a door, then put the properly-sized door into the frame, and then mark off the existing hinge positions on the side of the door from the frame.
    • If you are putting the door in a new frame, make a mark six inches from the top and the bottom of the door – these marks represent the top of the hinge at the top of the door and the bottom of the hinge at the bottom of the door.
    • Open a hinge and place it on the edge of the door in line with one of the marks you have just made, with the pivot of the hinge on the opening face of the door. Draw around it with a pencil and repeat the process where the other hinge is going to go.
    • Now you want to make shallow recesses so that the hinges sit flush with the door edge, but don’t try to knock the recess out in one go – take small pieces out using a chisel and mallet and check regularly that you’re not going too deep into the door.
    • Now that each hinge flap is sitting in its mortise, mark the screw positions with a pencil and drill pilot holes. Screw the hinges on to the door.
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    And how do I fit the hinges on the frame?
    • If you are replacing a door in the old frame, then your hinges should match up with the recesses in the frame, so good ahead and screw them in place.
    • If it’s a new frame, place the door up against the frame using one or more wedges to lift the the door off the floor. Mark the corresponding hinge marks on the door frame.
    • Set the door aside and carefully cut mortises in the door frame just as you did with the door itself. Once cut, hold the door against the frame to double check placement.
    • Mark pilot holes on the frame with a pencil and drill through as you did for the door.
    • Using only one screw in each hinge, and with the door in the open position, screw the top hinge into the frame, and then the bottom hinge and check that the door opens and closes easily. If it does then pat yourself on the back (after you’ve fixed the rest of the screws).
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    What do I do if my door sticks once it’s fitted?
    Mark where the door is hitting the door frame as it closes, and plane a little off these areas. If the door is binding - that is when closed it pushes itself open again - it could be your hinges are cut a little deep in the frame, so loosen the hinges and pack them out with thin wooden shims, until your door fits and closes perfectly.