Woodworking shims are thin, tapered pieces of material used to fill gaps, level surfaces, or adjust alignment in woodworking and construction projects. Whether you're installing cabinets, hanging doors, or leveling furniture, shims are essential for achieving a professional finish. This guide covers everything you need to know about selecting and using shims effectively.
Types of Woodworking Shims: Wood vs. Plastic vs. Composite
Shims come in three main materials: wood, plastic, and composite. Wood shims are traditional, made from cedar or pine, and are easy to trim with a utility knife. However, they can split or compress over time. Plastic shims are durable, waterproof, and resistant to compression, making them ideal for high-moisture areas like bathrooms. Composite shims combine wood fibers and resin, offering a balance of strength and workability. For most woodworking projects, plastic shims are recommended because they don't absorb moisture and maintain their shape.
How to Choose the Right Shims for Your Project
When selecting shims, consider the gap size, load-bearing requirements, and environment. For light-duty tasks like leveling furniture, standard wood shims work fine. For heavy loads like kitchen cabinets or door frames, use plastic or composite shims rated for higher weight. Check the taper: a gradual taper (e.g., 1/8 inch per foot) provides finer adjustment. Avoid shims with visible cracks or warping. For outdoor projects, always use plastic or treated wood shims to prevent rot.
Step-by-Step Guide to Using Shims
1. Identify the gap: Use a level to find where the surface is uneven. 2. Insert the shim: Slide the thin end into the gap, tapping gently with a hammer until snug. 3. Check alignment: Recheck with a level and adjust by inserting or removing shims. 4. Trim excess: Score the shim with a utility knife and snap off the protruding part. 5. Secure: Apply adhesive or fasteners to hold the shim in place if needed. Avoid over-tightening, which can cause the shim to shift.
Common Mistakes and How to Avoid Them
Mistake #1: Using too many shims stacked together. This can create instability. Use one or two shims per gap, pairing them thin-end to thin-end for a snug fit. Mistake #2: Not trimming shims flush. Leave about 1/8 inch protruding to prevent future movement. Mistake #3: Using wood shims in damp areas. They can swell and cause damage. Opt for plastic shims instead. Mistake #4: Forgetting to pre-drill when fastening through shims. This prevents splitting. Always test fit before final installation.
Real-World Buying Advice
For a standard homeowner, a pack of 50 plastic shims (assorted sizes) covers most needs. Look for shims with a non-slip surface or textured finish for better grip. If you're a hobbyist, consider a shim kit with multiple thicknesses. Avoid bargain-bin shims that are brittle or poorly tapered. Brands like EZ Shim and Mack's are reliable. Check reviews for real-world feedback on durability. Remember, the cost difference between cheap and quality shims is minimal, but the performance difference is significant.
Frequently Asked Questions
Can I reuse shims? Generally no, as they can compress or break. Use new shims for each project.
What size shims do I need? Standard shims are about 1/8 inch thick at the thick end and 1/32 inch at the thin end. For larger gaps, use longer shims or stack two.
Are plastic shims better than wood? For most applications, yes, because they resist moisture and compression. Wood shims are fine for dry indoor use.
How do I cut shims? Use a sharp utility knife and score along the desired line, then snap. For precise cuts, use a chisel or saw.
Choosing the right woodworking shims and using them correctly ensures your projects are level, stable, and professional. Focus on material, taper, and load capacity. Avoid common mistakes like over-stacking or using the wrong material for the environment. With these tips, you'll achieve perfect alignment every time.