Can Internal Doors be Cut to Size? And other Frequently Asked Questions

When it comes to doors, both internal and external, we’ve a considerable body of expertise to draw upon. And we put that expertise to good use, answering customer questions about all things door-related. What better way to answer those questions than with the help of an FAQ?

The most common question we receive is about whether internal doors can be cut to size. But there are scores of others, too. If you’ve got a question, then read on: we’re going to address six of them here, and the chances that yours may feature here are high.

Can Internal Doors be Cut to Size?

Can you cut an interior door? Of course!

Sometimes, it might be necessary to adjust the size of an internal door. If the frame is too small for a standard size one, the opening is awkwardly-shaped, or you’ve got a thick carpet to contend with, then trimming your internal door might be the best option.

In the case of most timber doors, this is easily done. You’ll only need to take a little bit from the bottom or sides in order to allow the door to swing freely. You will, however, need to sand the door to an even surface and re-finish it so that it looks consistent.

Before you break out the power-sander, however, it’s worth checking the manufacturer’s guidelines on tolerance. Around the edge of a composite door is a layer of solid timber – but if you go beyond the recommended tolerance, you risk eating into the core of the door. Unless you’ve opted for a solid-wood door, this will ruin the look of the door.

In most cases, the maximum permitted tolerance is just a few millimetres. If you find that you need to go beyond that, then the better option is usually to invest in a different door. For this reason, it’s worth measuring several times before you make a purchase.

For more information on cutting internal doors, here's a handy guide: Internal Door Sizing

Can an Internal Door Open Outwards?

For the most part, you’ll want your internal doors to open away from you as you walk through the house. So, doors which lead from hallways into other rooms should open into those rooms. This prevents the hallway from becoming impassable when doors are open. It’ll also prevent you from inadvertently smacking a passer-by as you move from a bedroom or bathroom into a corridor.

As a rule, rooms which then open into other rooms should follow the same logic – so if you’re moving from a hallway into a room and then into another room, you should be pushing every door along the way.

Which way should an internal door open?

Of course, in some cases you might not want to do this. Outward-opening doors can preserve space on the other side of the door, which is a requirement for cupboards and other cosy spaces (which is why smaller bi-fold doors are a good option in such cases.) And if there’s a flight of stairs leading up on the other side of the door, having it open inward might well be impossible. Other exceptions occur when you’re moving from a garage into the home – which, for security purposes, counts as an external door.

It’s up to you which way you have your door open. You might find that an outward-opening door suits a certain part of your property better than an inward-opening one. In this case, there’s no reason not to make the change.

If you’ve already got your door installed, then changing its direction will usually prove difficult, as it’ll necessitate a new frame. But arguably more important than inwards and outwards is left-or-right opening. If you decide to change this, then you’ll need to move things like light switches to the other side of the door – which means significant upheaval.

Can I Use an Internal Door Externally?

There is no law of the universe saying that you can’t install an interior door in an exterior location. With that said, using interior doors outside is extremely inadvisable for several reasons.

Firstly, interior doors are not as robust as exterior ones. Their edges are more easily accessible, and they’re less durable: a sufficiently determined intruder could feasibly put a boot through an internal door, where an external one would put up more of a fight. Your exterior doors serve an important security function – that’s why they’re built differently to internal ones. For this reason, installing an interior door externally will often invalidate your home insurance.

Secondly, interior doors aren’t anywhere near as good at excluding draughts and retaining heat. Cold breezes can easily slip around the edges, costing you a significant amount in energy bills. The energy lost by a door (or window) in a given timeframe can be described by its ‘u’ value. Building regulations stipulate that this be kept at 1.8 or lower for new installations – which means internal doors don’t qualify.

Finally, internal doors aren’t built to withstand the harsh changes in temperature and moisture that they’ll be exposed to outdoors. Just imagine the furniture in your lounge being exposed to sleet, snow and blazing heat. After a year or so (or sooner) it probably wouldn’t be doing too well!

Can I Fit an Internal Door?

Internal doors are pretty straightforward to install. You don’t need any special training, or any particular tools. And, given that the internet is so full of advice and instruction on the subject (including this very website!), DIY installers have never had it so good. Unless you’re installing the door frame as well, we’d say the average person can install a door in an afternoon. Just be sure that you know exactly what you’re doing, and that you have all of your tools ready (as well as a volunteer enlisted) before you get started.

If you're DIY-savy and want to install your own door, take a look at our guide on How to Fit an Internal Door.

With that said, for some of us it’s worth getting in professional help. You might not have the time to commit to the task – or the patience. What’s more, let’s face it, some of us just aren’t cut out for this sort of work, and beginners are more prone to making mistakes than seasoned installers. If you’re worried about getting it done yourself, then it’s generally worth the peace of mind of investing in having the installation done for you.

Here's a great Youtube tutorial from Silverline Tools on how to remove an old door and install a new door

Can You Mix Interior Door Styles?

Most homeowners decide to go for matching (or, close-to-matching) doors throughout their interior. But some choose instead to mix-and-match. This might be done because of financial pressures – replacing a couple of doors is not as expensive as replacing every single one in the house. On the other hand, you might simply prefer a bit of variety!

Now, style is, almost by definition, subjective. What one person considers the height of good taste; another might find not at all to their liking. This applies to choosing internal doors, and to matching them up.

We therefore can’t offer any hard-and-fast answers about what’s going to work and what won’t. Your doors are, after all, going to be installed into your property – and so your opinion is what counts. If you want natural-finish solid-wood doors downstairs and brilliant-white composite ones upstairs, then who are we to stand in the way?

We can, however, give you a few things to bear in mind when mixing door styles (and making bold stylistic decisions in the home in general).

The first is that style is vulnerable to change over time. A risk that pays off one year might date quickly. The second is that your personal taste might not match that of the housing market: if you plan on selling your home, you’ll generally find that a cohesive approach is more reliable when it comes to impressing prospective buyers.

This applies in particular to period homes where a specific style is required. If you have a beautiful Tudor cottage, then it makes sense to install appropriate doors throughout (however great you might think a contemporary aluminium door looks!).

When Should I replace an Interior Door?

When to replace an interior door is another question to which there’s a wide range of answers. If you haven’t started looking at your existing doors with a degree of disdain, then you might want to stick with them a while longer. But if you’ve already started to consider a replacement, why not simply get it over with? A new set of interior doors will help you to feel more comfortable in your own home – particularly if you’re still using the set you bought when you moved in.

A quality set of internal doors should last for a decade or more. But you might decide on a change well before things start to look shabby. There are certain signs which might indicate that a door is past its best. If it’s started to slam shut of its own accord, or drag against the carpet, then you might take it as a sign of things to come. While such problems can (and should) be fixed by tightening a few screws and lubricating a few hinges, there comes a point where it makes more sense to replace.

In Conclusion

We’ve run through just a few of the questions we’re often asked – but if you have another one, then be sure to get in touch. Our team are friendly and knowledgeable, and ready to help!