Tile Shims: How to Use Them and the Results You Get

Even the best thinset cannot fully rescue a tile job on an uneven surface, and that is where a humble helper earns its keep. Tile shims are thin wedges and spacers that let you fine-tune the height and pitch of individual tiles so the finished surface sits flat, level, and free of the ridges known as lippage. Whether you are tiling a slightly wavy floor or a wall that drifts out of plumb, shims give you the small adjustments thinset alone cannot. This guide explains the types, how to use them, results, and pitfalls.

What Tile Shims Do

Shims solve two related problems: leveling and alignment. When a substrate has minor high and low spots, adjacent tiles can end up with one edge sitting proud of its neighbor, creating a lippage ridge you can feel with a bare foot and see under raking light. Shims and wedges let you nudge a tile up or hold it in position while the mortar sets, so all the edges finish flush. They also help maintain consistent slope on shower floors and keep large tiles from sagging before the thinset cures.

Types of Tile Shims and Leveling Aids

Several tools fall under the shim umbrella:

• Tapered plastic wedges: Thin, angled shims slid under or beside a tile to raise a low edge a precise amount.
• Tile leveling clips and wedges: A two-part system where a clip sits under the tile edge and a reusable wedge cinches adjacent tiles flush; snapped off after curing.
• Horseshoe spacers: Stackable U-shaped shims that set both grout-joint width and slight height differences.
• Composite and wood shims: Thin tapered strips for gross adjustments under a mortar bed or a wobbly substrate.

The clip-and-wedge leveling systems are the most popular for large-format tile because they hold neighboring tiles at the same height while everything cures.

When You Actually Need Shims

Shims are not always necessary. On a genuinely flat, well-prepped substrate with small tile, careful troweling and spacers may be enough. You need shims or a leveling system when you are working with large-format tile that shows every ripple, an uneven or slightly out-of-flat subfloor you could not fully correct, a floor that must hold a precise slope to a drain, or a wall that has waves you must tile over. The bigger the tile and the more visible the surface, the more valuable leveling aids become.

How to Use Tile Shims Step by Step

Using a clip-and-wedge leveling system follows a clear sequence:

• Comb and set the thinset. Trowel mortar and back-butter large tiles for full coverage; shims correct height, not poor bonding.
• Place the clips. Slide leveling clips under the edges of each tile at regular intervals along the joints.
• Set the adjacent tile. Butt the next tile against the clips so they straddle the joint.
• Insert and tighten the wedges. Push a wedge into each clip and press until the tile faces sit perfectly flush with each other.
• Check with a straightedge. Lay a level across the tiles and adjust before the mortar skins over.
• Let it cure, then break the clips. After the thinset sets, tap the clips sideways along the grout line to snap them below the surface, then grout normally.

For simple tapered wedges, slide them under the low edge, tap gently to lift the tile, check with a level, and trim any protruding shim before grouting.

The Results You Can Expect

Done well, shims and leveling systems produce a surface with virtually no lippage, uniform grout joints, and a professional, hand-glides-across-it flatness that is especially noticeable with large tiles and polished finishes. On shower floors they help hold a consistent pitch so water drains cleanly. The improvement is most dramatic under raking light, where an unshimmed job reveals every ridge and a shimmed job reads as a smooth, continuous plane.

What Tile Shims Cost

Leveling aids are inexpensive relative to their benefit:

• Bag of tapered plastic wedges: $5 to $12.
• Box of 100 to 250 leveling clips: $15 to $35.
• Reusable leveling wedges (pack): $10 to $25.
• Complete clip-and-wedge starter kit with pliers: $30 to $60.

Clips are consumable, since they snap off and are discarded, while the wedges and setting pliers are reusable across many projects, keeping the per-job cost low.

Common Mistakes to Avoid

The biggest error is treating shims as a fix for bad mortar coverage or a badly out-of-flat floor. Shims correct small height differences; they cannot bridge large voids or compensate for a substrate that should have been leveled first. Do not overtighten wedges, which can squeeze thinset out and starve the bond. Remove or trim any shim that would protrude into the grout joint, and always snap leveling clips off below the tile surface so no plastic shows. Finally, work in the mortar’s open time so you can still adjust before it sets.

Shims vs. Fixing the Substrate

It is worth being clear about where shims end and substrate work begins, because confusing the two leads to failed floors. Leveling clips and wedges are precision tools for the small, tile-to-tile height differences that remain after good preparation; they are not a way to tile over a genuinely wavy or bouncy floor. If a straightedge reveals dips deeper than about 3/16 inch over 10 feet, the fix is a self-leveling compound or floor patch, not a fistful of wedges. Likewise, a springy subfloor that deflects under foot needs stiffening, an added layer of plywood or a proper joist assessment, before any tile goes down, because leveling clips cannot stop a moving floor from cracking tile and grout. Think of it as a hierarchy: correct the structure first, flatten the surface second, and use shims last for final fine-tuning.

Tips for Beginners Using Leveling Systems

If it is your first time with a clip-and-wedge system, a few habits smooth the learning curve:

• Buy the right clip thickness for your tile; clips are sized to a range of tile thicknesses, and the wrong size will not seat properly.
• Place clips at consistent intervals, typically every 8 to 12 inches along each joint and near corners where lippage shows most.
• Do not overtighten, which squeezes out mortar and can crack thin tile; snug and flush is the goal.
• Work within the mortar’s open time, setting and leveling a manageable section before the thinset skins over.
• Snap clips along the grout line, never across it, so they break cleanly below the surface without chipping a tile edge.

With a little practice, the system becomes second nature and pays for itself in a flatter, more professional-looking floor.

Where Shims Matter Most

Some situations make leveling aids nearly essential rather than optional. Large-format and rectified tiles show even the tiniest height difference between neighbors, so a clip-and-wedge system is the difference between a smooth plane and a ridged one. Polished and glossy tiles reflect light in a way that exaggerates lippage, making leveling doubly important. Wall installations benefit too, since gravity pulls freshly set tiles downward and shims hold them in position until the mortar grabs. And on shower floors, tapered shims help you hold a precise slope to the drain so water sheets off cleanly instead of pooling. In each of these cases, the small cost of clips and wedges buys a visibly more professional result.

Getting Flat, Professional Results

For the price of a bag of plastic parts, tile shims and leveling systems turn a good tile job into a great one, eliminating the lippage and uneven grout lines that betray amateur work. They shine most with large-format and polished tile and on any surface you could not get perfectly flat. Set your thinset properly, use clips and wedges to hold neighboring tiles flush while everything cures, then snap them off and grout. The result is a surface you can run your hand across without catching a single edge, exactly the finish a quality tile floor deserves.