6 Best door frame shims for precise installation

A plumb, square, and level door frame is the difference between a high-end finish and a callback for a sticking door. While framing studs are rarely perfectly straight, professional shimming bridges that gap between the rough opening and the finished jamb. Selecting the right shim material and design can significantly speed up installation while ensuring the door operates smoothly for years. The following guide breaks down the best options to help achieve that precision fit on every project.

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Nelson Cedar Shims: The Industry Standard Staple

Cedar shims remain the go-to choice for traditionalists because they compress slightly under pressure, creating a high-friction fit that won’t easily slide out. They are cost-effective, readily available in bulk, and offer excellent structural stability once fastened.

Because wood naturally absorbs moisture and expands, these shims are ideal for interior installations where climate control is consistent. However, always check for dry-rot or inconsistent thicknesses in low-quality bundles, as warped cedar can throw off the reveal of a high-end door.

For heavy, solid-core doors, cedar provides a solid “crush-resistant” base that won’t deform over time. Snap them easily with a utility knife to hide excess material behind the casing once the door is hung.

EZ-Shim: Best for Fast Foolproof Adjustments

EZ-Shims utilize a unique interlocking, stepped design that allows for precise, incremental adjustments without the slippage common with tapered wood wedges. They are manufactured from durable polymers, ensuring they won’t rot or compress over time.

These are particularly effective when working alone, as the serrated edges lock together, preventing the shim from backing out while the door is being hung. They are thin, making them perfect for tight gaps where a standard cedar shim would be too thick to slide into place.

Save these for situations requiring extreme accuracy, such as installing expensive hardwood frames where you cannot risk damaging the jamb with excessive hammer force. The cost per unit is higher than wood, so reserve them for critical hinge-side adjustments.

Wobble Wedges: Top Pick for Versatility on Site

Wobble Wedges are essentially heavy-duty, flexible polymer shims designed to handle leveling tasks that go far beyond standard door frames. Their ribbed surface provides incredible grip, preventing them from sliding on slick subfloors or metal framing.

Contractors often prefer these when dealing with uneven floors where a door must be shimmed specifically to allow for carpet or tile clearance. They are stackable and interlock firmly, providing a stable foundation for the door frame’s bottom plates.

Because they are made of high-impact plastic, they won’t swell if the floor is mopped or exposed to seasonal humidity. They are an essential item to keep in a tool bag for quick, unpredictable site adjustments where standard wood shims just won’t cut it.

Bigfoot Door Shim: The Ultimate Pre-Hung Door Jig

The Bigfoot Door Shim is not just a wedge; it is a specialized leveling tool designed specifically to support the bottom of a pre-hung door. It cradles the frame base, ensuring the threshold is level before any nails are driven.

This tool is invaluable when installing exterior doors on concrete slabs or uneven sub-flooring. By creating a solid platform, it eliminates the “teeter-totter” effect often encountered when trying to balance a heavy exterior unit on small, individual shims.

Using a jig like this drastically reduces the time spent on repetitive adjustments. It is a high-utility investment for anyone tackling multiple door installations where consistency across the entire project is the priority.

Go-Ez Shims: Best for Bulk Buy for Production Work

Go-Ez shims are designed for speed and efficiency, often featuring a design that allows for rapid snapping to the exact depth needed. They are a staple for high-volume residential framing crews who need a reliable, low-cost solution that doesn’t waste time on the job site.

These shims are consistent in their thickness, which removes the guesswork involved with sorting through messy cedar bundles. They are engineered to be thin and stackable, allowing for fine-tuned precision without the thickness variance found in natural wood.

If a project involves dozens of doors in a single build, the time saved by using a consistent, uniform product like this adds up to significant labor savings. Buy them in bulk to keep costs down and ensure the entire crew is using a standardized method for door installation.

Trim-Tex Plastic Shims: Best for Wet Locations

Trim-Tex shims are built for harsh environments where wood would eventually fail. They are completely impervious to water, making them the superior choice for exterior door frames or bathrooms where moisture is a constant concern.

They are available in various color-coded thicknesses, which helps in identifying how much “gap” has been filled during the install. This color-coding prevents accidental over-shimming, which is a common cause of bowed door jambs.

When installing a heavy exterior door in a humid climate, wood shims can rot behind the casing, leading to sagging and air leaks. Switching to high-grade plastic ensures the structural integrity of the frame remains intact for the life of the building.

Wood vs. Plastic Shims: Which Material Is Best?

Wood shims offer a natural, high-friction surface that stays exactly where you put it, but they are subject to moisture expansion. They are the best choice for interior walls where you want a material that behaves similarly to the surrounding lumber.

Plastic shims provide unmatched stability in wet areas and consistent, predictable sizing. However, they can be more slippery than wood, often requiring a slightly higher degree of care to ensure they don’t migrate during the fastening process.

The best approach is to match the material to the climate zone. If you are working on an exterior wall with heavy thermal bridging, choose plastic to avoid moisture-related movement that could break the seal of your spray foam or weatherstripping.

How to Properly Shim a Door Frame to be Plumb

1. Start at the Hinge Side: Always plumb the hinge-side jamb first. Use a long level, placing it against the jamb, and add shims behind each hinge location until the jamb is perfectly vertical.
2. Secure the Hinges: Drive screws through the hinges and into the shimmed areas to lock the frame in place.
3. Set the Strike Side: Once the hinge side is set, place the strike-side jamb to ensure a uniform gap (reveal) between the door and the frame. Use pairs of opposing shims—sliding one against another to create a perfectly parallel surface.
4. Final Check: Confirm the door swings freely without binding or “springing” open on its own.

Common Shimming Mistakes and How to Avoid Them

• Over-shimming: Applying too much pressure with shims can bow the jamb, causing the door to bind in the center. Use just enough to bridge the gap; the frame should remain perfectly flat.
• Skipping the Hinge Points: Shims must be placed directly behind every hinge. If you miss a hinge, the weight of the door will eventually pull the jamb out of plumb.
• Failure to Secure: Always drive finish nails or screws through the shims. A shim held in place by friction alone will eventually loosen due to the vibration of the door slamming.

Essential Tools for a Perfect Door Installation

A professional install requires more than just shims and a hammer. Keep these tools on hand for a stress-free process:

• 6-foot Level: A short level won’t catch the full vertical plane of a door frame; longer is always better.
• Shim Saw/Utility Knife: For clean, flush trimming of shims once the door is secure.
• Impact Driver: For driving high-quality shims-screws that hold the frame firmly to the studs.
• Spacers: Small plastic shims or strips of cardboard used to hold a perfect, even reveal around the door while you work.

The secret to a long-lasting door installation is patience during the shimming phase, as even the best door will perform poorly if the frame is out of square. By choosing the right material for your environment and taking the time to set each hinge point correctly, you eliminate the risk of future headaches. Treat the shimming process as the structural foundation of the frame, and the rest of the finish work will fall right into place.