Why Do Door Jambs Have Grooves in Them?

Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.

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Door jambs are made of different materials, including wood, fiberglass, vinyl, and aluminum. For many homes, the common material is wood. In such cases, you may notice some have grooves on one side.

Door jambs have grooves in them to help prevent the wood from cupping. They also serve a secondary function to help your door jamb sit on uneven door frame openings.

As you go through this article, you’ll find out the difference between a door jamb and a door frame, the explanation behind those grooves, and their function. We’ll also look at other ways to prevent cupping and warping of door frame components.

What Are the Grooves on My Door Jamb?

Many door jambs are made of wood. It’s usually wooden jambs that have grooves on one side.

The grooves on your door jamb are intentionally-made spaces, sometimes called “relief cuts.” They mostly provide stress relief on the door jamb, which can prevent cupping (where the wood’s edges curve upwards). They help keep the wood straight and flat against changes in moisture or temperature.

If your door frame cups or warps, the gaps between the door and the frame may become uneven. You may not be able to close your door properly. In some extreme cases, the wood can also split.

The grooves also help the door jamb sit correctly on an interior wall that might not be completely flat.

Door Jamb Grooves in Relation to the Frame

Door jambs are a part of the door frame, which is composed of all of the following components:

Door jambs: These are the two vertical parts of your door frame that secure to the wall.
Header/head jamb: This is the horizontal part at the top of the door frame. The door jambs are attached to this part of the frame.
Sill: This is the bottom part of the door frame that is bolted to the floor. It provides support and seals the gap between the door and the floor, but it’s usually only found on exterior doors.
Door casing: This is the portion that surrounds the outside of your door frame. Also called door trim or molding, it covers and helps seal any gaps between the door frame and the interior wall.

Door jamb grooves are generally found on the back side of the door jambs where they secure to the wall. The grooves make the door jambs slightly less stiff, which helps them fit to the wall more firmly. They also give you space to add an adhesive if necessary.

Often, these grooves are found on all types of moldings, including the door’s header and casing.

Once the jambs are secured to the wall and the door casing is installed, the grooves are completely hidden.

Tips To Prevent Your Door Frame From Warping

Wood warps when there’s a change in its moisture content. It can bulge when it absorbs too much water and cracks when it dries out. To prevent deformation, you need to treat your wood. Here are some ways to help waterproof wood:

Treat your door and doorframe. You can use linseed or tung oil. These door oils can nourish and treat the wood down to the fibers inside, making the wood more resistant to water. The FurnitureClinic Wood Boiled Linseed Oil from Amazon.com is an excellent wood sealer and can also be used as furniture polish.
Seal the wood with lacquer, polyurethane, or varnish. You can buy several types of wood treatment from Amazon.com, such as the Minwax Clear Lacquer, the Minwax Helmsman Spar Urethane Aerosol, or the Minwax Polycrylic Protective Wood Finish. All of these products are easy to use, dry quickly, and require little additional work.
Apply a coat of paint. They can also provide some additional water resistance to your door frame.
Choose appropriate materials and treatments. They should be suitable for interior or exterior doors.
Apply an extra coat of waterproofing. Add these to the bottom of your door frame and door. These parts are more exposed to moisture and other liquids that may spill on the floor.
React quickly to signs of deformation. When you notice some warping or cupping, quick action will make it easier to solve the problem rather than waiting for it to get worse.
Apply treatment to a bare door. Remember to first take off any door hardware, like locksets, doorknobs, and handles.
Apply treatment before installation. If you can, apply any waterproofing to your door frame before installing it on the wall.

How To Fix a Warped Door Frame

We can do what we can to treat the wood of our doors and door frames, but sometimes, some warping and deformation can still happen. Here’s what you can do to fix a warped door frame:

Remove the door casing. Using a putty knife, carefully remove the trim or molding around your door frame.
Tap the door frame to bring it tighter to the wall. Open the door and use a rubber mallet to tap the door frame and push the wood tighter to the wall.
Test out opening and closing your door. Do so throughout this process so you can see which parts of your door frame need more adjustment.
Adjust the spacing between the door and the jamb as needed. If portions of your door still rub against the frame, you may need to use a planer to scrape some excess wood from your frame to make more space. The gap between the edges of your door and your frame should be about a dime’s width.
Apply wedge-shaped shims if needed. Wedge them into the gap between the door frame and the wall where the frame doesn’t look even. Trim the edges of any shims that may be sticking out.
Reattach the molding or trim to the sides of the door frame. This covers up the gap between the frame and the wall.

Choosing Door Frame Materials

When you’re choosing the wood for your door jamb, these qualities make them less susceptible to warping:

Kiln-dried wood: Drying wood in a kiln takes out the moisture quicker, making it less susceptible to warping, unlike air-dried wood.
Pre-treated wood: Applying treatments like oils, polyurethane, lacquer, or varnish can be a bit tricky. You can buy door frames made of wood that are already treated, so you don’t have to worry about doing it yourself.
Other door frame materials: PVC, vinyl, aluminum, and other engineered materials don’t warp, cup, or deform because they don’t absorb or hold moisture. You may decide to choose a door and doorframe made of these materials instead.

Conclusion

When buying wooden door frames, you’ll notice that many of them have grooves or relief cuts. These grooves are sometimes present for several reasons, but they mostly help prevent the wood from cupping or becoming deformed due to absorbing or losing moisture.

In addition to using grooved door jambs, there are other ways you can prevent the door frame from warping. For example, you can treat wood to waterproof it and make it more resistant. You can also choose alternative door and door frame materials that don’t warp or cup.