Before fitting an external door, you must first decide whether you are going to replace the door slab only, or if you are going to replace both the door and frame as this will affect whether you require permission from Building Control.

If you are replacing both the door and the frame, you are required to either:

  • Employ a registered installer who will notify the local authority on your behalf. They will issue you with a certificate on completion, which can be used as proof of compliance.


  • Submit a building notice or full plans application and pay a fee to Building Control for inspection of the work you have carried out. 

It is often easier to purchase a doorset, which comes already hung in the frame, particularly where the existing frame isn't square. This can reduce installation problems and the time taken to fit the door.


Measure the door opening or the existing door if it's a good fit, to ensure you get the right size door. Measure at three points horizontally and vertically taking the largest measurement to determine the correct width and height door to buy.

Different doors allow different amounts of trimming so if you can't buy the exact size, make sure you check the amount you can trim so that you can achieve the perfect fit.


Hold the new door in the frame to see if it needs adjustment. A well fitted door should have a 2mm gap on either side and at the top. The gap at the bottom will depend on the thickness of your flooring/carpet.

Plane the door as required, using an electric plane will help you get an even finish, and sand for a smooth finish.


If you would like to add a letter plate, measure where you would like it to sit and cut out the hole. Remember, any cutting made to the door will require protecting with an appropriate base sealer, you can then fit the letter plate.

We also recommend fitting a weather bar/rain deflector to further protect the door.


  • Check new hinges fit the old ones in the frame. If not, mark on where new ones will sit and chisel away the extra wood.
  • At least three hinges will be required for an external door.
  • Screw each hinge in place with one (centre) screw. The hinge knuckle should stick out from the frame edge.
  • Prop the door in the door frame using wedges to ensure correct gap at the bottom.
  • Mark where the top and bottom of the hinges sit on the door.


  • Unscrew hinges and lay them on the edge of the door, lining up with the pencil marks. Draw around the hinge.
  • Chisel out the middle to the same depth as hinge flap.
  • Check hinge fits flush and fix with one (centre) screw per hinge.


Support the door on wedges and fix hinge flaps to the door frame. Ensure the door opens and closes smoothly and finish fixing with all screws.


There are several different locks available on the market including mortice locks, rim locks or multipoint locking systems. Whichever one you choose, follow the manufacturer's instructions on how to fit.


For advice on how to finish your products, always refer to the fitting and finishing installations provided. You can find further guidance here. 

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