How to Use Drywall Shims - Kitchen Cabinets

Drywall shims, also known as plasterboard shims, are thin, tapered wood or plastic wedges used to fill small gaps between drywall sheets during installation. Using drywall shims correctly is an essential skill for professional drywall finishers and DIYers alike. Proper shimming creates seamless drywall surfaces ready for finishing and decoration.

In this comprehensive guide, we will cover everything you need to know about how to use drywall shims for flawless drywall installation and finishing results.

Selecting the Right Drywall Shims

There are a few types of shims to choose from when shimming drywall:

Wood Shims

Made from thin sheets of laminated wood veneer.
Available in tapered and reverse-tapered styles.
Tapered shims are thicker at one end and taper down. Useful for filling gaps that are wider at one side.
Reverse tapered shims are thicker in the middle and taper at both ends. Helpful for filling uniform gaps.
Typically come in 4”, 6”, 8” and 12” lengths.
Very inexpensive.
Absorb glue and paint well.

Plastic Shims

Manufactured from plastic polymers like PVC.
Reusable and highly durable.
Resist warping, rotting, and splitting.
Offered in tapered and double-tapered designs.
Range from 2” up to 12” in length.
Cost more than wood shims.
Do not bond well with adhesive or paint. Must be removed after drywall finishing.

Metal Foil Shim

Ultra-thin sheets of aluminum foil.
Used to shim very narrow gaps under 1/8” wide.
The foil is flexible and can be folded and layered for custom thickness.
Foil shims should not be used alone. Back them with wood or plastic shims.

When selecting shims, choose lengths that are slightly shorter than the gaps you need to fill. Opt for wood shims for most drywall shimming applications. Use plastic shims when durability and reuse are preferred. Metal foil shims work well for very thin gaps.

Proper Drywall Gap Shimming Techniques

Shimming drywall correctly is critical for smooth wall and ceiling surfaces. Follow these best practices when shimming gaps between drywall sheets:

1. Prepare the Gap

Carefully cut back the drywall paper lining the gap using a utility knife. This exposes the gypsum core.
Vacuum or sweep out any dust or debris in the crack.
Widen the gap slightly if less than 1/8” wide. This ensures the shims have surface to grip.

2. Test Fit the Shims

Select shims about 1/8” to 1/4” less than the gap width when inserted.
Avoid using multiple thin shims. Thicker single shims create more gluing surface.
Double cut shims can fill large gaps. Score partially through the middle to bend forked ends into the gap.
Verify shims fit without force and do not split when inserted.

3. Apply Drywall Adhesive

Use an adhesive designed for drywall installation like all-purpose joint compound.
Apply adhesive into the gap and coat shim surfaces.
Avoid getting adhesive on exposed drywall paper or finished side of wall.

4. Insert the Shims

Place shims gently into the gap without bending or damaging them.
Ensure shims sit squarely in the opening. Align the taper direction to fill properly.
Use a putty knife to fully seat shims and remove any excess adhesive squeeze-out.

5. Allow Adhesive to Cure

Let adhesive dry and cure thoroughly according to manufacturer directions.
Hardened adhesive locks shims firmly in place before finishing processes.
Do not disturb or apply pressure to shims while adhesive is wet.

Properly shimming drywall requires precision, care, and patience for flawless concealed results. Follow detailed steps to fill gaps correctly.

Shimming Drywall Butt Joints

One of the most common places to use drywall shims is at butt joints where two drywall sheets meet end-to-end. Uneven studs, warped drywall, and misaligned sheets often create gaps at butt joints. Careful shimming produces smooth, continuous surfaces at butt joints for seamless finishing.

Selecting Shims for Butt Joints

Choose tapered or double-tapered wood or plastic shims to fill vertical butt joint gaps:

Optimal shim thickness matches the gap width.
Use longer 6”, 8”, or 12” shims to span the joint evenly.
Reverse tapered shims work well for uniform gaps.
Double tapered plastic shims flex easily into uneven gaps.

Shimming Technique for Butt Joints

Follow these steps to correctly shim drywall butt joints:

Fully expose the joint gap by cutting back lining paper using a utility knife.
Vacuum loose debris and dust from the gap.
Pre-fit shims and confirm they seat fully into the gap without bending.
Generously coat shims and joint opening with adhesive like joint compound.
Insert shims evenly into gap, aligning the taper direction to fill space.
Firmly seat shims into adhesive using a putty knife. Scrape away any squeeze-out.
Allow adhesive to fully cure before finishing over the shimmed joint.
Feather and finish over the joint with joint compound for a smooth finish.

Shimming butt joints properly prevents uneven surfaces and visible seams after finishing drywall.

Shimming Drywall Corner Gaps

Inside and outside drywall corners often open up during installation. Corner gaps look especially unsightly and require shimming for proper finishing. Use extra care when shimming corner joints:

Selecting Corner Shims

Tapered wood or plastic shims work best for corner gaps.
Opt for the shortest shims that adequately span the gap to increase strength.
Thicker shims provide more gluing surface and support at corners.
Flexible plastic shims allow easier insertion into tight corner joints.

Shimming Technique for Corners

Follow these pointers for clean, strong corner shimming:

Fully remove paper lining from the corner gap to expose gypsum core.
Lightly widen the gap width if very tight. Shims need minimum 1/8” to grip.
Test fit shims and confirm they seat completely into the corner.
Apply adhesive generously into the gap and onto shim surfaces.
Carefully insert shims at 45 degree angles to seat firmly into adhesive.
Use a putty knife to fully embed shims while removing excess adhesive.
Let adhesive fully cure before finishing over shims.
Feather joint compound from shims for seamless corner appearance.

Proper corner shimming minimizes cracks and uneven areas at drywall corners.

How to Shim Electrical Boxes

Recessed electrical boxes in drywall often result in unsightly gaps and cracks around their perimeter. Carefully shimming gaps around boxes produces smooth, continuous drywall surfaces surrounding electrical fixtures.

Helpful Tips for Electrical Box Shimming

Use tapered or double-tapered wood shims cut to length for best support.
Shim the top and side gaps in priority order for optimal appearance.
Plastic shims allow adjustment after insertion around tightly-fitted boxes.
Layer shims when necessary to build out to the wall surface evenly.
Coat shims and inside gap edges generously with adhesive before insertion.
Fully seat shims behind boxes using a putty knife. Avoid bending thin shims.
Let adhesive fully cure before handling or running wires to the box.
Fill any remaining discrepancies with joint compound when finishing the drywall.

Proper shimming provides flush, consistent drywall seams around recessed electrical fixture boxes.

Pitfalls to Avoid When Shimming Drywall

While an essential process for flawless drywall results, shimming does require careful techniques. Avoid these common shimming mistakes:

Using warped, cracked, or undersized shims that don’t fit the gap.
Failing to fully seat shims evenly into the adhesive.
Applying too little adhesive so shims fall out later.
Bending or damaging shims when forcing them into gaps.
Disturbing uncured shims and adhesive causing gaps or cracking.
Leaving adhesive residue or shim paper exposed for a poor finish.
Shim overruns hardening and interfering with smooth finishing.
Failing to shim gaps at all and merely filling with joint compound.

Careful selection of quality shims along with precision and patience prevents shimming errors.

Tips for Achieving Great Shimmed Drywall Results

Follow these proven tips for mastering the art of drywall shimming:

Take time to properly expose and prepare all gaps before shimming. Rushed preparation causes problems.
Buy quality shims designed for long-term holding power and smooth finished appearance.
Work methodically and meticulously when test fitting, gluing, and placing shims for consistent results.
Allow adhesives to fully cure before disturbing or working around shims.
Apply painter’s tape along joints after shimming to prevent finishing materials from contacting shims.
Smoothly feather finish layers over shims to conceal their locations and create seamless drywall.
Fill any lingering discrepancies after shim removal with thin coats of joint compound.

Expert shimming makes achieving perfectly smooth drywall finishes much easier.

Drywall Shim Removal Tips

In some cases, shims must be taken out after installation to prevent finishing problems:

Plastic shims should always be removed since they repel paint and joint compound.
Protruding shims may need selective removal prior to finishing to prevent lumps.
Take care when prying shims from cured adhesive to avoid cracking joints. Use shim scrapers designed for removal.
Remove any shims not tightly adhered so they don’t become dislodged later.
Vacuum adhesive remnants out of gaps after taking shims out.
Fill gaps where shims were removed with successive thin coats of joint compound until flush.
Avoid removing too many shims which compromises support at joints.

With practice, shims can be selectively extracted to ensure flawless finished drywall surfaces.

Frequently Asked Questions About Drywall Shims

What are drywall shims made of?

Drywall shims are typically constructed from wood, plastic, or thin aluminum. Wood veneer is the most common shim material, followed by plastic polymers like PVC. Very thin foil shims are pure aluminum.

How thick should drywall shims be?

Aim for drywall shim thickness about 1/8” to 1/4” less than the gap width. Shims taper thinner at one end to wedge into openings when gently tapped. Avoid multiple thin shims which lack gluing surface.

Do drywall shims get removed?

It depends. Wood shims can be left permanently installed after drywall finishing since they bond well with joint compound. Plastic shims should always be removed since they resist paint and finishing materials. Protruding shims may also require selective removal.

Should you glue drywall shims?

Yes, drywall shims should always be glued into place for stability and crack resistance. Joint compound, construction adhesive, and drywall glue all work to adhere shims into gaps. Apply adhesive to both the shim and gap surfaces for optimal strength.

How long do drywall shims take to dry?

Adhesive drying times vary by product used. Most standard drywall adhesives fully harden within 8 to 24 hours. Always follow manufacturer recommended cure times before finishing over shims. Test shim adhesion to ensure they are secure.

Can you use wood putty instead of drywall shims?

Wood putty alone is not recommended since it lacks the strength and stability of shims. Use putty only for very minor cracks or filling gaps after shim removal. Putty shrinks and cracks easily at joints compared to quality shims.

What can be used instead of drywall shims?

In a pinch, veneer wood scraps, playing cards, paint stir sticks, wooden paint brush handles, ice pop sticks, tongue depressors, or laminated business cards can work as improvised shims. None grip as securely long-term as purpose-made wood, plastic or metal shims.

Why are my drywall shims falling out?

Shims become dislodged due to inadequate adhesive, trying to use too many thin shims, or disturbing joints before adhesive fully cures. Ensure adequate adhesive is used on both shim and gap surfaces. Allow adhesive to fully harden for at least 24 hours before stressing joints.

Can I use drywall shims on plaster walls?

Yes, the shimming process for plaster walls is quite similar. The keys are fully exposing the gap, pre-fitting the shims, generously applying adhesive, and avoiding disturbance until cured. Wood, plastic, or metal shims all work on shimming vintage plaster walls.

With proper materials, careful technique, and practice, shimming drywall gaps becomes fast and frustration-free. Take time to master the nuances of quality shimming for flawless professional drywall results. We hope these detailed tips equip you to expertly fill annoying drywall gaps using shims. Let us know if you have any other drywall shimming questions!

Conclusion

Drywall shims play an indispensable role in achieving perfectly smooth and continuous gypsum board surfaces. When gaps appear between panels or around penetrations, carefully shimming them prevents unsightly flaws. By understanding shim types, materials, applications, gluing techniques, curing times, and removal methods you can flawlessly fill drywall gaps for superior finished results.

With the proper selection of tapered wood, plastic, or metal shims along with precision, patience, and practice, drywall shimming can be mastered easily. Avoid oversights like poor shim adhesion, disturbance before curing, and improper pre-fitting. Follow the recommendations in this guide for expert-level shimming on your next drywall project. Happy shimming!