How To Trim An Internal Door To Size

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So, you’ve got your door primed, painted and ready to fit in the frame. Hang on, though – first you’ve got to check if it fits! On occasion it won’t, but that’s definitely no reason to panic. This week at Savoy Timber, we’ve got some handy pointers on how to measure and trim your door down to size. It’s simpler than you think!

What You’ll Need To Trim An Internal Door


Happily, you won’t need a ton of stuff in order to get yourself properly prepared for this task. Apart from the workbench, most of it comprises items you’ll be able to pull out of the nearest drawer. It includes:

  1. A pencil
  2. A 2 pence piece
  3. Tape measure
  4. A hand wood plane (or a powered one)
  5. Hard-point hand saw
  6. A decent-sized workbench
  7. Small wooden wedges

Measuring Your New Internal Door To Size

Before you get started on the fun stuff, first you need to measure your door to make sure it fits. Remember on this one – slow and steady wins the race! If you’re ever unsure of anything, always double check. It’s notoriously harder to stick all the wood chippings back on if you end up making a mistake.

Using The Old Door

You can cheat a bit here – if you’ve got the old door to hand and it fit the frame perfectly, you can use it as a guide to measure up your new one. Just lay the new one on top of the old one (or vice versa – depending on which one of them is bigger), and use a pencil to mark off any excess wood for cutting.

Using The Frame

On the other hand, if you’ve not got the old door to hand, you’ll have to use the frame to measure the new door. It’s easiest to have another pair of hands for this – one for each side of the door. Hold the door up against its frame and use the pencil to draw a line down the mechanism side to mark where you’ll make the cut.

A few key things to remember during this process:

  • The door needs to have a gap under it – unless you’re not that keen on opening it (ever).
  • There needs to be a gap of at least 2mm around the top and sides of the door, to give it room to swing open. (This is where your 2p piece comes in; to measure the gap.)
  • Draw lines on both sides of the door, so that you can reduce both sides equally. This helps keep the symmetry of the design, so that all your panels on the finished door don’t seem to skew to one side.

Trimming Your Internal Door Down To Size

The sides of the door usually shouldn’t need a whole lot of wood removing, and it’s a reasonably simple job – as long as you’ve got a steady hand!

Use a hand plane (or a power plane) to shave off equal amounts from each side, using the pencil lines you marked earlier. At Savoy Timber we’d advise working inwards from the outer edge of the door, so that you don’t split the end grain. Keep checking the fit as you go, and don’t be afraid to hold it up to the frame to see how you’re getting on. It might sound like a pain, but remember you only get one shot at this – unless you want to buy a whole new door, that is. If it’s worth doing right, it’s worth doing slowly!

Finally, use sandpaper to smooth down the rough edges, for the smoothest possible finish, and that’s all there is to it! Your door has officially been trimmed down to size. Now all that’s left is to hang it. If you’re comfortable with doing that yourself, top notch, but if you’re not there’s no need to worry. Keep an eye on the blog – very soon we’ll have a dedicated article that runs you through the best way to hang your internal door in its frame.

If you can’t wait that long, you can always pop into one of our stores in Blackpool, Wigan or Preston, where our staff members will be only too happy to give you a few pointers. While you’re there, feel free to check out our full range of doors, in case you’ve got another frame that needs filling!

Don’t forget to follow us on Twitter: @SavoyTimber