It’s a real shim when your door isn’t perfectly plumb
Whether you’re installing a new door in your home or fixing a sagging door or one that isn’t opening and closing smoothly, door shims are going to become your new best friend. Shims are super affordable but have a massive impact on how your doors fit into your wall opening and function. In this guide, we’ll discuss how to shim a door the right way to get you installing doors like a professional in no time at all.
Shimming a door is a pretty straightforward job, but you do need to make sure you have the right kinds of shims before you get started. For most residential applications, you can use wood or plastic shims, which you can pick up for just a few dollars online or at your local home improvement store.
If you’re shimming a fire-rated door—you might have one leading into your boiler room or your garage, especially if you have solar batteries or an oil tank in there—then you should opt for metal shims, which are non-combustible.
If you’re removing a door and installing a new one in your home, you should first get the new door frame centered in your rough wall opening using shims.
Start by getting the door roughly centered in your opening with the door closed. Depending on how your wall opening is framed, you should have anywhere from 1/4 of an inch to 1 inch of space on all sides of the door frame. Once your door is in place, insert shims loosely around the edges to hold it there.
Always use shims in pairs. It might be tempting to push a single shim into a gap, but since shims are angled, doing so will cause warping in your door frame over time. Instead, use two shims facing in opposite directions to create a perfectly flat but adjustable spacing. Aim for shims behind each door hinge and at the bottom and top of each stile. You can add more to the top and middle of the lock stile for additional stability, but it’s not necessary.
Hold your level up against your hinges with the door closed. If they’re perfectly level, you can move on to the next step. In most cases, the door won’t be perfectly level, so you’ll need to make adjustments. This is especially true if you’re using this guide to fix a sagging door.
Where you make adjustments will depend on how your door is sitting in the wall opening. Make adjustments on the hinge side only, if possible.
If the top of your door on the hinge side is too far toward the wall framing, lightly hammer in the shims behind your top hinge.
If the bottom of your door on the hinge side is too far toward the wall framing, lightly hammer in the shims behind your bottom hinge.
Once you’ve made adjustments, check again to make sure the door is plumb.
Now that your door is plumb, you can adjust the shims on the hinge side of the door to get the spacing right and tighten the door inside the wall opening. Start with the top shim, and don’t hammer in the shims so much that your door shifts. Try to get the spacing on your hinge side about equal to the spacing on the opposite side.
Start at the top hinge, then work down the hinges, and finally tighten the shims at the top and bottom of the door.
Follow the same process on the lock side, and try to get equal spacing on both sides of the door. Again, don’t hammer your shims too far, or you’ll risk pushing your door frame out of alignment.
Start at the top of the lock side and work your way down.
If you placed shims above your header, gently hammer those in to snug up the shims. Driving them in too much will cause the header to bow downward, and it could cause issues with the door’s functionality.
Finally, drive screws or finish nails through the door frame, through the shims, and into the framing around it to secure the door in place. You should at least add nails or screws through the shims behind each hinge and on the top and bottom set of shims on the lock side of the door.
For a more professional and finished appearance, cover the screw or nail heads with wood filler and paint over it. You can also counter-sink your screws to hide the heads better.
Shimming a door is a fairly inexpensive DIY project. You only have to pay for the shims themselves, which cost anywhere from $1.50 to $10 per pack. If this is something you do regularly, you can get over 200 shims for $25. If you’re crafty and have a jig, you can even make your own shims for free from scrap lumber, bringing the overall cost down to literally nothing.
Shimming a door is a simple process that you can most likely handle on your own. The same is true if you’re installing a new prehung door or fixing an existing door that has shifted or warped over time.
Buying the shims and doing the work yourself will likely cost you between $5 and $10, whereas you’d spend an average of $100 if you hired a door installer near you to do the shimming professionally. That means an average savings of around $90 on the cost of a door installation, and the process is relatively straightforward.
However, if you don’t have the time to shim your door or you’ve tried to do the work but can’t seem to get your door centered, plumb, and level, you can always call in an expert for help.
Dan Simms contributed to this piece.
If you have an uneven door, the best way to level it or make it plumb is to use shims between the frame of the prehung door and the wall opening around it. Rough wall openings for doors usually leave substantial space for shimming so that you can make these adjustments. Start by shimming the hinge side of the door to center the prehung door, and then shim the lock side. Once it’s centered, hammer in the shims and continue checking that it’s plumb to get it to sit snugly in the wall opening and perfectly plumb and level.
You don’t need to shim both sides of a door, but it’s always a good idea. Wall framing is rarely perfectly plumb, and shims let you make minor adjustments to get your door perfectly level and plumb. This will ensure the door swings open and closes smoothly. You can also use shims on both sides of the door you’re installing or adjusting to center it in the wall opening.
You put shims between the three-sided frame to which the door hinges are attached and the framing of the rough wall opening. Using shims like this will center your door in the wall opening and allows you to make small adjustments to get your door plumb and level for smooth operation. Your shims and the gap they fill will be covered when you install door trim, so don’t worry too much about the appearance.
You should shim both sides of a door because it helps reduce the chances that the frame will warp. It can also help ensure that the door is hung evenly and level. If you are hanging the door by yourself, you may need to remove the slab to lighten the weight, making it easier to support the frame while shimming both sides. If you have two people, the process will be easier and faster whether or not you leave the slab in place.
