How to trim a new door to size

  Shop for external doors from XL Joinery  

Many doors are manufactured so they can be trimmed a little for a perfect fit. However, there is usually a limit to how much can be removed because trimming a door too much can compromise its integrity. Remove equal amounts from opposite sides to ensure the door maintains a uniform look, especially if it is a panel or panel effect door. And, whenever you trim a door you will be exposing untreated edges which will need to sealed.


For information on trimming and finishing Wonkee Donkee XL Joinery doors see:  Tips on fitting internal doors from Wonkee Donkee XL Joinery  and Tips on fitting external doors from Wonkee Donkee XL Joinery

      Wonkee Donkee says "Fire doors often have different rules regarding trimming to ensure they keep their specified fire rating. Always check manufacturer’s instructions regarding individual doors."  

Before you begin 


The first thing you need to do is check the door can be trimmed, and if so by how much, as all doors are different. You should always choose a door which is as close as possible to the size you need and only needs to be trimmed slightly. 


For more information see: How to measure for a new door slab


Make sure you are working in a clean and dry area where there is room to have the door secured on its edge, or lying on a flat steady surface which it can be clamped to. It's best to use an appropriate workbench or some saw horses to hold the door in place. Check the edge of the door you plan to trim and remove any nails or pins, or door hardware, which could damage your cutting tool. 


If you are removing more than 6 mm from any side then you might need to use a guided circular saw or panel saw, in which case you must follow the manufacturer's instructions on the saw. This guide looks at how to trim a door with a woodworking hand plane. You could use a power planer if you have one.


Step 1- Mark where to trim to

Measure and mark on the door where you'll need to trim. Make sure you mark accurately, using a straight edge or similar tool as a guide, along the length of the edge you need to trim. Always double check measurements before you make any cuts.


Step 2 - Plane edge

  Plane the edge of the door to make sure it is an exact fit  

Carefully plane the edge of the door to the line you have marked out. It's best to set the plane to remove only thin slivers with each stroke, so you remove small bits at a time. This reduces the risk of trimming too much off. Make small strokes, moving from the end into the centre of the edge, and then work similarly from the other end.

      Wonkee Donkee says "Don’t plane too much from the door. It’s easy to plane off bits but  you can’t stick them back on!"  

Step 3 - Finish edge

  Sand the edge of a door to make it smooth, ready for painting  

Check the edge you've planed is straight and level with a straightedge. Finally, smooth the edge by sanding if necessary. Make sure you finish the edge you have exposed with the same product you've used on the rest of the door and apply as many coats as necessary. This will ensure the door is fully sealed and ready to be fitted.

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