A Step-By-Step Guide To Door Swelling Prevention And Repair

Are you a sufferer of swollen exterior doors that stick, squeak, or just plainly refuse to close properly? Well you’re not the only one. Swollen exterior doors are a common problem that many homeowners face today. In this essential guide, we’re going to dive into why doors tend to swell and, most importantly, how you can avoid your doors from ever swelling in the first place and how to fix your doors when they do swell.

Why Do Exterior Doors Tend To Swell?

Wood is a hygroscopic material, which means that it absorbs, and releases,  moisture from the surrounding air. When the humidity in your door’s environment is high, it will absorb moisture and swell. When the humidity is low, your door will release moisture and shrink. Humidity coupled with exposure to rain and direct sunlight may cause wooden doors to expand and shrink unevenly, which will cause issues. These situations can also cause your door to warp which we cover in our blog, How To Fix & Prevent Warped Wooden Doors.

How To Fix Your Swollen Door

• Check Your Hinges & Threshold

Before we start taking your door off and going to work, we should examine your door hinges and door threshold. Ensure that your door isn’t getting stuck due to loose or broken hinges. If your door hinges are loose, tighten them and if they are damaged beyond repair, replace them. Your door’s threshold needs to be properly installed and level with the floor, if this is not the case we suggest reinstalling the threshold if it is in good condition, otherwise you may need to replace it.

• Inspect The Damage

If both your hinges and threshold are in working order and your door is still getting stuck or won’t close properly, the first thing you should do is examine the door for any signs of damage. If the door is damaged, you may see signs of warping, cracking and splitting, swelling, or water damage. For a repair guide for warped doors, take a look at our blog, How To Fix & Prevent Warped Wooden Doors.

If you find that your door is in fact swollen, you need to evaluate how severe the swelling is and where the swelling has taken place. When a door is slightly swollen in, for example, the bottom of the door, a simple sanding might suffice (only up until step 3 of this guide). However, when the swelling is across the entirety of your door, you may need to do some more extensive repairs (follow this entire guide). In extreme cases where your door is severely swollen to the point of compromised structural  integrity, you may have to replace the door.

• Remove And Initial Sand

The next step, after you have found that your door is in fact swollen, is to take it off the hinges for sanding. Don’t forget your safety glasses and facemask, work in a well ventilated and well lit area. Sand the door with a coarse grit in order to remove any finish or paint that might trap moisture within the door. After the paint or finish is removed from the door you may move on to the next step.

If, however, you’ve evaluated the swelling to be minor and localised, you may sand the swollen area. Ensure that you feather the edges so that it blends into the rest of the door surface. Once the swollen area of the door is levelled, you may move to a finer and finer grain paper to sand the entire door until you’re left with a smooth surface. Even with these minor swelling cases, we recommend you still dry the door before applying a finish or paint (skip step 5 in other words).

• Dry Out The Door

In order to dry out your door properly, you need to leave it in a controlled environment (garage or a workshop of some kind) with a dehumidifier. When drying out your door you need to be patient, because in order to avoid additional stress or warping on your door, it needs to dry out gradually. Depending on the wood your door is made of, the amount of water within the door and how well you sanded it, drying can take from a day or two to a few weeks. For an exact estimate we recommend contacting a professional.

To ensure your swollen door dries properly without over-drying, regular monitoring is essential. Begin by checking the door’s fit in its frame. If it starts to close smoothly without sticking, this is a good indicator that the swelling is reducing. Additionally, use a moisture metre for a more accurate reading of the wood's moisture levels (A stable reading over several days typically signifies that the door has sufficiently dried). Visual inspection is also a viable technique; look for any remaining signs of dampness or discolouration. For a more tactile approach, the door should also feel dry and return to a lighter weight when dried adequately. It's important when in doubt, or when working on a particularly valuable door, to seek advice from a woodworking professional who can provide guidance tailored to your specific situation and ensure the best care for your door.

• Final Sanding

After the door has dried sufficiently, especially if the swelling was not minor or localised, you must do a final sand of your door. Start sanding the door with a coarse sandpaper, gradually moving to finer and finer grits while periodically checking the fit of the door - put it back on the hinges every now and then to see how well it fits. It is crucial in this step to sand away any remaining swelling or unevenness on the door’s surface that may have remained after the door has been dried properly. Stop when the surface of the door is even and smooth. If, however, you find yourself sanding away an excessive amount of wood to get to the desired fit or surface finish, then your door may be beyond repair and may need replacing.

• Apply Stain And Sealant

After drying and sanding, you need to apply a finish to your door. Remember to ensure that you are completely satisfied with how your door fits as well as how it opens and closes before you start applying your finish. Apply your stain or sealant in even thin coats, allowing each coat to dry properly before adding the next one. How many layers you should apply depends on the finish you’re using. Check the instructions on the product you’re using or contact a professional to find out how many coats you should apply to your door for adequate protection. Remember to reapply your chosen finish as time goes on to further the longevity of your door.

• Reinstall

Finally, after all the above steps have been completed properly, rehang your door in its frame and check whether it opens and closes properly. Keep in mind that this should not be the first time you test how your door fits - you should be sure to test it before applying your finish (before step 6).

How Can You Avoid Swelling In Your Doors?

To prevent swelling in your exterior doors, it's important to focus on moisture management. Start by finding any sources of water exposure, such as rain or high indoor humidity, and address these issues directly. Using a waterproof sealer (applied regularly as time goes on) or getting a storm door/screen are two viable options for addressing these water sources. Remember to keep an eye on your door in order to identify any signs of wear. You should address any surface damage to your door as soon as possible to avoid moisture from seeping into any imperfections in your door’s finish or seal.

If you notice fluctuations in your door’s size with changing seasons, it's usually a clear sign of indoor humidity issues. Placing a dehumidifier in the largest room of your house, or in a central location that affects multiple areas, may help stabilise the humidity levels. A high-capacity dehumidifier not only protects your wooden doors from swelling but also creates a healthier living environment by reducing the risk of mould, bacteria, and viruses that thrive in humid environments. Regularly maintaining your doors with these preventative measures will help you protect your doors from damage such as warping and swelling.

In sum, managing swollen exterior doors boils down to regular maintenance and proactive measures. Frequently sealing your doors with a waterproof sealer and monitoring indoor humidity with a dehumidifier are effective measures you can take to prevent swelling. Additionally, addressing any signs of wear or damage ASAP will help ensure that your doors stay in pristine condition for as long as possible. By following steps in this guide, you can maintain the functionality and appearance of your doors. Please feel free to check out our other blogs on wooden doors for more tips and guides.