If you’ve ever installed drywall only to discover that the finished wall looks slightly wavy, bowed, or uneven, the drywall itself might not be the problem. Often, the real culprit is the framing underneath it.
Wood studs and ceiling joists aren’t always perfectly straight or aligned. This is especially common in older homes, but even new lumber can bow, twist, shrink, or sit slightly out of alignment. When drywall is fastened directly over those inconsistencies, it tends to follow them.
That’s where drywall shims come in.
Drywall shims are inexpensive, simple, and easy to overlook, but they can make a noticeable difference in how flat and professional a finished drywall surface looks. They’re placed between the framing and drywall to compensate for low spots, uneven studs, and other small differences in the framing.
In this guide, we’ll look at what drywall shims are, what they’re made from, when you need them, how to install them, and when you should use something else instead.
Affiliate disclosure: This post may contain Amazon affiliate links. As an Amazon Associate, I may earn from qualifying purchases at no additional cost to you.
What Are Drywall Shims?
Drywall shims are thin strips of material installed over wall studs or ceiling joists to create a flatter, more even surface for attaching drywall.
Think of them as tiny spacers.
If one stud sits 1/8 inch farther back than the studs surrounding it, attaching drywall directly to the framing can cause the sheet to dip inward at that location. Adding a shim to the recessed stud brings its face forward so that it lines up more closely with the surrounding framing.
Once the drywall is installed, the shim remains hidden behind it.
Drywall shims are commonly long, narrow strips made from dense cardboard or fiberboard. They’re intentionally thin because they’re designed for relatively small adjustments.
If you’re looking to check out your options for drywall shims, check out this selection on Amazon.
One shim might be enough to correct a minor discrepancy. For a slightly larger difference, multiple shims can sometimes be stacked.
Although drywall shims aren’t complicated, they solve an important problem: drywall needs a reasonably flat framing surface if you want the finished wall to look flat.
What Do Drywall Shims Look Like?
Drywall shims don’t look like the little wedge-shaped wooden shims you might have used while installing a door or cabinet.
Instead, they’re generally:
- Long
- Narrow
- Flat
- Uniform in thickness
- Made from dense cardboard or fiberboard
Their shape allows a shim to sit along the face of a stud or joist, providing continuous support behind the drywall.
You’ll find drywall shims sold in bundles because it’s common to need quite a few when correcting an entire wall.
Amazon product suggestion:
- Seajan 100 Drywall Shims Cardboard Wallet Shim Use to Butt Joints and Level Baseboards and Flush Out Bullnose Corner Adaptors Straighten Uneven Wall Studs or Joists (45 x 1-1/2 x 1/16 Inch)
- Strait-Flex Drywall Shims for Leveling – Fix Framing Irregularities, Butt Joints, Door Jambs and More – Easy-Dispense Compressed Cardboard Strips – 100 pcs 1-1/2” x 45” x 1/16”
- 80 Piece Solid Plastic Shims for Leveling, Flat Drywall Shims for Leveling, 3/64, 5/64, 1/8, 5/32 Inch (Black)
Why Would You Need Drywall Shims?
Walls might look perfectly straight before drywall goes up, but framing can have surprisingly small variations.
Wood is a natural material. It can warp, twist, bow, shrink, or crown. Framing can also simply be installed slightly out of alignment.
Those differences might seem insignificant when you’re looking at bare studs. Once a large, relatively flat sheet of drywall is attached to them, however, inconsistencies can become much easier to see.
Drywall shims can help correct problems such as:
- A stud that sits slightly behind adjacent studs
- Uneven wall framing
- Uneven ceiling joists
- Small transitions between old and new framing
- Remodeling situations where surfaces don’t quite line up
- Slight differences in framing depth
- Low areas that could cause drywall to bow inward
Essentially, you’re creating a more consistent plane before installing the drywall.
How Drywall Shims Help Create Flatter Walls
Imagine three wall studs sitting next to each other.
The first and third studs are perfectly aligned, but the middle stud sits 1/8 inch farther back.
If you screw drywall across all three studs, the sheet may pull inward toward that middle stud as the screws are tightened. Instead of remaining perfectly flat, the drywall can develop a subtle dip.
Now place a 1/8-inch shim over the middle stud.
The shim brings that mounting surface forward so that it’s closer to the same plane as the other two studs. The drywall now has a more even surface to rest against.
This is why checking framing before hanging drywall can save you considerable frustration later.
Joint compound can hide seams and minor surface imperfections, but it isn’t the ideal solution for correcting significantly uneven framing underneath an entire sheet.
Where Are Drywall Shims Used?
Drywall shims can be used on both walls and ceilings wherever drywall needs additional support or minor adjustment.
Uneven Wall Studs
This is probably the most straightforward application.
Run a long straightedge across several studs. If one sits noticeably farther back than the others, a shim can help bring it forward.
If you’re installing drywall as part of a soundproofing project, getting the framing as even as possible is also an important part of preparing the wall. Check out my beginner’s guide to soundproofing your room with drywall for more tips on using drywall to help reduce noise.
Ceiling Joists
Ceiling framing can also be uneven.
Because light travels across ceilings at shallow angles, imperfections can sometimes become particularly noticeable after painting. Correcting low framing areas before installing the ceiling drywall can help create a smoother finished appearance.
Working overhead presents additional challenges, so make sure any shimming method is secure before hanging the panels.
Remodeling Projects
Older houses rarely give DIYers perfectly straight framing.
Once old wall coverings are removed, you might discover studs that vary considerably from one another. You may also be trying to make new framing line up with an existing wall.
Shims provide a simple way to make small corrections without rebuilding an entire wall.
Transitions Between Materials
Shims can also be helpful when drywall needs to meet another surface but the two aren’t quite at the same depth.
Building out the framing slightly can help create a cleaner transition.
Drywall Shims vs. Wood Shims
Although both products are called shims, they aren’t necessarily interchangeable.
Traditional wood shims are usually wedge-shaped. They’re commonly used for jobs such as leveling cabinets and setting door or window frames.
Check out the Wood shims, 420 Count Bulk Contractor case, 100% kiln Dried Pine Wood shims 8″ Long.
Drywall shims, on the other hand, are typically long, flat strips with a consistent thickness.
That uniform thickness is useful when you need to bring the face of a stud forward evenly along a larger portion of its length.
A wedge shim could create a high point behind the drywall if used incorrectly. A flat drywall shim distributes the adjustment over a larger area.
For broad framing corrections behind drywall, purpose-made drywall shims are generally much easier to work with.
Drywall Shims vs. Furring Strips
You may also hear about furring strips when researching uneven walls.
The basic principle is similar: both can create a new mounting surface for drywall. The difference is largely the scale of the correction.
Drywall shims are thin and work well for small adjustments.
Furring strips are typically thicker pieces of wood or other material and can be more appropriate when an entire wall needs to be built out by a substantial amount.
For example, if one recessed stud needs a tiny adjustment, a drywall shim may be all you need. If you’re trying to bring an entire wall forward substantially, a furring system may make more sense.
How Thick Are Drywall Shims?
The exact thickness varies by manufacturer, so always check the specifications of the shims you’re buying.
Many drywall shims are roughly around 1/16 to 1/8 inch thick, making them suitable for fine adjustments.
One of their useful characteristics is that they can often be layered.
Suppose one shim doesn’t bring a recessed stud out far enough. Depending on the application and manufacturer’s instructions, another shim can be added.
The important thing is not simply counting shims. You’re trying to bring the framing into a consistent plane.
That means you should continually check your progress with a straightedge or level.
How to Check a Wall Before Installing Drywall
Shimming works much better when you identify problems before you’ve started hanging sheets.
Place a long level or straightedge across several studs.
Look for gaps between the straightedge and the faces of the studs. You can also gently rock the straightedge to identify studs that project farther out than their neighbors.
Mark problem areas with a carpenter’s pencil.
It helps to check several places vertically because a stud may be aligned near the floor but bowed farther up the wall.
For larger projects, a laser level can also help establish a consistent reference plane.
You’re looking for two basic problems:
Low spots can potentially be brought forward with shims.
High spots require a different approach because adding material obviously won’t make a projecting stud move backward.
How to Install Drywall Shims
Installing drywall shims is relatively straightforward, although the exact method depends on your framing and the shim manufacturer’s instructions.
1. Inspect the Framing
Before installing anything, examine the studs.
Look for bowed, twisted, damaged, or badly positioned lumber. Shims are useful for small corrections; they aren’t a substitute for repairing serious framing problems.
2. Find the Low Areas
Place a straightedge or long level across multiple studs. I recommend something semi-professional like the OEMTOOLS Straight Edge 24″, Machinist Tool.
Mark the recessed areas that need to be brought forward.
3. Determine How Much Adjustment You Need
Place a shim against the low stud and check the wall again.
You may need one shim or several layers to achieve the proper depth.
Avoid automatically stacking several shims. Add only as much thickness as necessary.
4. Attach the Shims
Secure the shims to the framing so they stay in position while you’re hanging drywall.
Depending on the shim and application, this may be done with staples or another appropriate fastener.
The shim should sit flat against the framing rather than buckle or fold.
5. Check the Wall Again
Don’t skip this part.
Run your straightedge across the framing again after installing the shims.
You might discover that you need another layer—or that you’ve added too much.
6. Install the Drywall
Once you’re satisfied with the framing plane, hang your drywall normally.
Use drywall screws of an appropriate length to account for the drywall thickness, shim material, and required penetration into the framing.
Follow applicable building requirements and the drywall/fastener manufacturer’s recommendations for your particular installation.
Can You Stack Drywall Shims?
Yes, drywall shims can commonly be layered when a single shim doesn’t provide enough correction.
That’s one reason thin shims are so convenient.
Rather than having one thick spacer, you can gradually build up the low area.
However, stacking has practical limits.
If you find yourself building a substantial stack of shims across a large portion of the wall, stop and determine why the framing is so far out of alignment.
You might be dealing with a bowed wall, incorrectly installed framing, structural movement, or a situation better handled with furring strips or framing repairs.
Shims are best viewed as a fine-adjustment tool rather than a solution to major framing problems.
Can You Make Your Own Drywall Shims?
Technically, you can use other suitable materials to create spacing behind drywall, and experienced builders sometimes fabricate their own solutions.
For most DIY drywall projects, however, purpose-made shims have one big advantage: consistent thickness.
Consistency makes adjustments predictable.
If you’re trying to correct a difference of only a fraction of an inch, randomly cut pieces of cardboard or scrap material can make the job more difficult rather than easier.
Commercial drywall shims are inexpensive, uniform, and designed specifically for this type of work.
Are Cardboard Drywall Shims Strong Enough?
Seeing a cardboard-like shim behind a heavy sheet of drywall might initially seem strange.
But drywall shims aren’t intended to function like structural framing.
Their purpose is to fill a small space between the framing and drywall while providing a consistent mounting plane. The screws still need to properly engage the framing underneath.
This distinction is important.
You aren’t replacing the stud with cardboard. You’re adding a thin spacer over the stud.
Always choose a product designed for drywall installation and follow its manufacturer’s specifications.
What Happens If You Don’t Shim Uneven Studs?
Sometimes, nothing particularly noticeable happens.
Framing doesn’t need microscopic precision for every drywall project, and drywall systems can accommodate small imperfections.
But more substantial irregularities can result in:
- Wavy-looking walls
- Visible dips
- Bulges
- Uneven seams
- More difficult finishing
- Poor transitions between surfaces
- Shadows that emphasize imperfections
Lighting can make these issues considerably more obvious.
A wall might look fine during installation but reveal waves after it’s painted and sunlight or artificial lighting hits it from the side.
That’s why spending a little extra time checking the framing can pay off later.
When Shouldn’t You Use Drywall Shims?
Drywall shims aren’t a universal fix.
You shouldn’t rely on them to cover up serious framing problems, structural damage, moisture damage, or major wall movement.
Similarly, if one stud projects significantly farther forward than everything surrounding it, adding shims to every other stud isn’t automatically the best solution.
The high stud itself may need to be addressed.
Large discrepancies might require:
- Replacing damaged or severely warped framing
- Correcting framing installation
- Planing an appropriate high spot where permitted
- Sistering framing members
- Installing furring strips
- Consulting a professional about possible structural problems
The goal isn’t to use as many shims as possible. The goal is to provide the drywall with a stable, reasonably flat mounting surface.
Are Drywall Shims Worth Using?
For such a simple product, drywall shims can solve an annoyingly visible problem.
They’re inexpensive, don’t require specialized skills, and can make hanging drywall over imperfect framing considerably easier.
They’re especially worth keeping around if you’re:
- Renovating an older home
- Repairing an existing wall
- Finishing a basement
- Drywalling an attic
- Working with visibly uneven framing
- Trying to match new drywall to an existing surface
Even if you don’t ultimately need them, checking the framing before hanging drywall is still worthwhile.
Frequently Asked Questions About Drywall Shims
What are drywall shims used for?
Drywall shims are used to build out recessed or uneven framing before drywall is installed. They help create a flatter mounting surface for drywall sheets.
Do drywall shims go behind drywall?
Yes. Drywall shims are attached to the framing and sit between the stud or joist and the drywall panel. Once the drywall is installed, you won’t see them.
Can you use drywall shims on ceilings?
Yes. Shims can be used to compensate for minor differences in ceiling framing as well as wall framing. Make sure the shims are securely installed and that the entire drywall installation follows appropriate fastening requirements.
Can you stack drywall shims?
Generally, yes. Thin drywall shims can be layered to create the required thickness. However, a large discrepancy may indicate that another repair method is more appropriate.
Are drywall shims necessary?
Not for every drywall job. If your framing provides a sufficiently flat mounting plane, you may not need any. They’re useful when individual framing members sit behind the desired plane or when small depth adjustments are necessary.
Can drywall shims fix bowed studs?
They can help compensate for certain low areas created by bowed or uneven framing. However, severely bowed, twisted, or damaged studs may need to be corrected or replaced rather than simply shimmed.
Can I use regular cardboard instead of drywall shims?
Purpose-made drywall shims are preferable because they provide a known, consistent thickness and are manufactured for this application. Random cardboard may vary considerably in thickness and performance.
How do I know where drywall shims are needed?
Place a long straightedge or level across multiple studs or joists before hanging drywall. Gaps can reveal framing members that sit behind the desired plane.
Final Thoughts: Small Shims Can Make a Big Difference
Drywall shims aren’t exactly the most exciting item in the toolbox, but sometimes the simplest accessories prevent the most frustrating problems.
If you’re wondering what drywall shims are, remember that their job is straightforward: they’re thin strips placed between drywall and framing to compensate for small inconsistencies and help create a flatter mounting surface.
Before hanging your next sheet of drywall, take a few minutes to run a long straightedge across the studs. If you discover a recessed stud or an uneven section of framing, fixing it now can be much easier than trying to disguise a wavy wall with joint compound later.
A small pack of drywall shims, a straightedge, and a little patience can go a surprisingly long way toward getting that smooth, professional-looking wall you’re after.