The age-old question of ‘can you trim a door?’ can’t be answered simply unfortunately! Different manufacturers and suppliers specify the maximum trimming tolerance of their products and this can vary greatly. Especially when you take fire doors into consideration. Internal doors and external doors from the same manufacturer may also have differing trim tolerances. We recommend, if you’re going to trim a door, that you consult or employee a carpenter as it can be fiddly and it could result in a costly mistake!

Table of contents:

  1. Can you trim internal doors?
  2. Can you trim fire doors?
  3. Can you trim external doors?
  4. What options do I have aside from trimming a door?

Can you trim internal doors?

Most internal doors manufacturers advise different trimming tolerances so as a standard and to be on the safe side we advise that you don’t trim more than 5mm per side. This is with the exception of LPD, which only allow 3mm on each side. It’s worth noting that if you’re needing to trim a lot off of a door then you probably have the wrong size and may be able to buy exactly what you need. If you do need to trim to 6 or 7mm, contact us with your chosen brand and we’ll help you find out if this is okay. Trimming over a manufacturer’s tolerance will void any warranties.

The construction of door will impact how much you can trim too as, with hollow core doors for example, you will eventually cut into the void and render the door unusable. Similarly there are design elements to think about. Trimming the amount you need to trim might mean that a design feature is taken away. In the image to the right, if you trimmed too much you’d impact the look of the doors.

Can you trim fire doors?

It’s recommended that fire doors aren’t trimmed at all as you’ll be using the door in a way that it wasn’t tested for. Doors are tested rigorously to their exact dimensions, with smoke seals and with all the recommended hardware. So there could be a possibility that if the door is trimmed, it won’t offer 30 minutes of fire protection. If you’re installing fire doors optionally throughout your home then chances are as this won’t affect performance that much, they’ll still give occupants time to evacuate the building. If the fire doors are a legal requirement then you could be breaking the law by installing sub-standard fire doors.

Instead of purchasing a fire door and trimming it, why not opt for a fire door blank? These are essentially pieces of wood that are plain and simple but designed to be cut to any size you need. If you have odd size doors or non-standard door dimensions this is a really easy work-around. Plus fire door blanks are considerably less expensive than complete fire doors. Bare in mind you will still need fire-rated hardware and seals too!

Can you trim external doors?

External doors can be trimmed dependent again on manufacturer recommendations. XL Joinery external doors can be trimmed by up to 10mm on each side whereas LPD external doors can only be trimmed by 3mm on each side. It’s worth checking with us on 01752 422 501 when you have your chosen brand, or when you know you’re going to need to trim from a standard door size, this way we may be able to recommend the best brand for you to choose.

Don’t forget that when trimming external doors the edges must be finished to keep the doors weatherproof and to comply with manufacturer’s warranties and guarantees.

What can I do instead of trimming doors?

Door blanks, both fire rated and non-fire rated, are manufactured to be cut to any size as they are essentially one large piece of unfinished material. They’re not particularly stylish as there are no panels, moulds or glazing. However, they could be a viable option if your home or property has odd size doors that you don’t wish to get custom made. Another benefit of door blanks is they’re extremely cheap. So even if you have regular size doors, you could opt for these to keep your costs down.

Contact us on 01752 422 501 for door trimming tolerance specification or for advice on what your best option would be. 

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