Why and When Do Wooden Doors Swell? (Here’s How to Fix it)

Wooden doors are regarded by many as the best doors possible for residential homes of all kinds. There are plenty of wood species and stains available to match any aesthetic while not sacrificing performance in different regions, and wooden doors can be designed in practically any manner you can imagine. 

However, despite most door-worthy woods having properties that make them resistant to damage of various kinds, every wood door can still swell under the right conditions. That can become a minor annoyance, or it can outright ruin your door if it’s too much of a problem. 

Today, we want to go over when wooden doors swell, why wooden doors swell, and how you can fix a swollen wooden door to avoid getting a replacement. 

Let’s get started. 

What is Door Swelling? 

As the term suggests, swelling in a wooden door is when it begins to puff out slightly. This is caused by moisture that we’ll talk more about soon, but the effects of it can vary dramatically. 

You’ve probably noticed on a hot summer day that your home’s doors become a little creaky at night. This is caused by the door expanding, usually just from heat and humidity, and then contracting when it gets cooler after dusk or the humidity level drops. The changes made by temperature-based swelling and contracting are tiny and more or less just an annoyance when they make your door creak for a while. This is because the very tiny size changes in your door can affect how hardware is set in both the door and the frame, creating a less-than-perfect fit. 

Why is Your Door Swelling? 

Wooden doors aren’t just doomed to swell every time the weather changes or it gets a bit humid. There’s a specific reason your door is swelling, and it’s fairly easy to correct. 

Now, you know that your door swells because moisture gets inside of it. This expands the wood, and while you usually can’t tell unless the swelling is ridiculously out of control, you can tell when your once quiet door is suddenly squeaking and creaking as its extra mass forces it to move differently on its hinges. 

Your door swells like that because it’s not properly protected against moisture. This can be a problem with the door from the manufacturer, the door might have aged without being properly cared for, or if you did any work on your door without properly finishing it, that can cause a problem, too. 

In short, losing the protective finish, which is usually a sealant, tends to cause this issue the most. 

However, you must also consider the type of wood used. Certain woods, such as teak, are resilient to moisture and water in general. So, if you have a door made from something like teak, you’d really have to neglect your door’s maintenance, or you’d have to have a shoddy door from the beginning to experience any abnormal levels of swelling. 

On the other hand, there are some woods, particularly the ones used for cheap wooden doors, that aren’t as resilient to moisture, and they will swell fairly frequently. Coincidentally, they’re also the doors that tend to experience the most extreme results from swelling. 

When Do Wooden Doors Swell? 

Door swelling typically doesn’t happen all the time. That should only be the case if you’re in an area that is exceptionally humid, or your doors are otherwise constantly exposed to excessive moisture. Even if your door isn’t properly sealed, you shouldn’t experience non stop swelling in most situations. 

As such, most people will only have to deal with front door swelling during extremely humid summer months. This is when there tends to be far more moisture in the air than normal, and improperly protected doors will likely experience a decent amount of swelling until the climate balances back out. 

However, people who live along the coasts or in other humid climates will likely experience door swelling most of the year. There is simply far too much moisture in the air all the time, and unprotected doors can’t take it. To make things worse, people in coastal areas also have to consider the impact of salt. Swelling might not be your only worry when your doors start creaking. 

Finally, any time there is a lot of flooding or another extreme source of water such as a hurricane or prolonged downpour in warm weather, swelling is practically guaranteed. Especially if your home becomes flooded and the door more or less sits in water for a while. Unfortunately, swelling probably won’t be your biggest concern in such a situation. 

Is Door Swelling Bad? 

So, door swelling will happen to practically everyone at some point, even if your doors are reasonably protected. Is it a big deal, though? Will you need to go door shopping every time it’s particularly humid and your door doesn’t resist it perfectly? 

Obviously, swelling won’t instantly ruin a door. It happens so often that, if it were immediately a major concern, the door manufacturing industry would be absolutely booming with constant repeat customers. 

Just because it’s not a huge issue the second it happens doesn’t mean it can just be ignored, though. There are a few serious consequences to letting your door swell, even if it’s just a little bit, consistently. 

First, keep in mind that swelling occurs because moisture gets in your door to an excessive degree. Your door is made of wood, and when wood gets wet, it rots. This isn’t a major concern right away, and that’s especially true if you have a door that is naturally rot-resistant like a teak door, but if left unchecked for a long period, all that excess moisture can cause irreparable damage to your door. Once rot sets in, your only option is to get a new door. 

You also have to worry about cracks. Any time wood dries, especially if it dries too quickly, it can crack. Modern wooden doors are made to exceptional quality standards if you buy them from a reputable wooden door manufacturer. Those high-quality doors are highly unlikely to crack, but given enough constant swelling and drying, small cracks can work their way through the grain. 

On less expensive doors, this is an even bigger problem. Once a crack forms, even if it’s a small one, the effects of swelling and moisture will be compounded. 

Warping is another major concern. It’s not too common, but if a door swells too much and unevenly, and then it dries quickly, it can warp. Warping is when a door, or any piece of wood, twists, and skews, it happens, mostly to exterior doors, because of moisture exposure most of the time. This creates a bunch of problems. If it’s a small warp, you might find that it’s hard to engage the lock because it has become slightly unaligned. There is usually enough “give” in the wood for you to still shut it effectively, though. 

If it’s a serious warp, not only will you have problems shutting it, but it might damage the door’s hardware or the connection points on the frame, and it won’t seal properly, allowing cool air and a breeze in during the winter months, and letting your air-conditioned air escape during the summer months. A very slight warp is not ideal, but you can get by with it. Once a warp becomes serious, you basically need a new door. Luckily, it is almost always preventable with the instructions we give you to prevent swelling later on. 

Finally, it can damage the hardware on your door and door frame. The hardware attached to your door is likely brass or stainless steel. So, rusting from moisture exposure isn’t likely. However, when a door swells, it becomes heavier, and it becomes proportioned differently than when it’s dry. This can slightly shift the screws and other bits attached to your door and the frame. 

When the door dries out, and the swelling subsides, that hardware can get slightly shifted again. This is not a huge deal if your door only swells once or twice. That is unlikely to create any real problems. However, if your door is frequently swelling and shrinking, it can work screws loose, pull them away from the framing, and generally cause some frustrating problems. This takes a while to become noticeable unless your door swells dramatically and then shrinks quickly, but it will become noticeable and have consequences if it is left unchecked. 

How to Fix Door Swelling 

As we’ve pointed out, door swelling, and everything that can eventually stem from it, occurs because moisture is allowed to get into the door. That typically happens because of one of three reasons. 

1. Manufacturer Error: If the manufacturer did not apply a water-resistant finish, your door will likely swell from day one. It’s common practice among door manufacturers to apply a protective finish of some sort. So, this won’t be an issue unless you buy a particularly cheap door. 
2. User Error: If you have sanded down your door and re-stained it, but you didn’t make sure the stain was water-resistant or apply a water-resistant coating, you are unfortunately the cause of the door swelling; you removed the protective coating. 
3. Aging and Neglect: As a door experiences normal wear and tear, most types of protective finishes will get worn out. If this happens, and you’re not staying on top of your door maintenance, the door can experience swelling even if it technically has a protective finish. 

As you can see, everything here has to do with the finish. As such, the way to fix door swelling is to refinish it. 

Here’s a step-by-step guide to doing that. 

1: Inspect: 

First, you need to inspect the door to see if any damage has occurred due to the swelling. While it’s on the hinges, you’ll want to check the hinges and watch as the door opens and closes slightly. If they’ve worked their way loose, that is something you’ll have to correct. Now, take the door off its hinges, and inspect the ends for noticeable cracks. Small hairline cracks are fine, but major splits indicate the need for a replacement. Finally, lay the door on flat ground, and make sure it hasn’t warped. With the door knob and locks removed, it should lay flat. 

2: Sand: 

You’ll need to sand the door before you can start refinishing it. Unless there are major blemishes, a light sanding is enough. Start with a medium-grit paper to remove the previous finish, and then work your way up in stages to a fine grit to put a nice polish on it. If there are major blemishes, start out with very coarse sandpaper to work through those blemishes before moving up to finer papers. 

Make sure you sand the entire door but try to remove as little material as possible. A handheld sander will make this step a breeze, but make sure you take your time, or you can easily add huge blemishes or remove too much material.

3: Stain and Seal:

This step will vary depending on the stain or paint you choose. Some are naturally water resistant, and that will mitigate the need for a secondary sealant such as varnish. However, if your preferred stain doesn’t repel water, you’ll want to invest in varnish to coat the door without covering up the stain. Most paints designed for residential home use are water repellant, but they cover up the wood’s grain and are not ideal for high-end doors with tons of natural beauty. 

Whether you’re staining or painting, apply the product of your choice in a thin, even layer with a standard paintbrush. Allow that layer to dry, and then add at least one more coat. 

If you’re using a stain that does not protect the wood from moisture, apply a coat of varnish in the same manner. 

4: Install

Once the final coat has dried, it’s time to reinstall the door. Start by getting the door reattached to the hinges. If your hinges were loose at the frame earlier, take this time to tighten them. 

Once your door is back on the hinges, reinstall the knob and locks the same way they were when you removed them. 

Now, you don’t have to worry about why and when wooden doors swell. Just make sure you stay on top of maintaining the door.