How to Fix a Wobbly Toilet

Why a Wobbly Toilet Is More Than an Annoyance

A toilet that rocks or shifts when you sit on it isn't just uncomfortable — it's doing real damage every time it moves. The toilet is sealed to the drain flange with a wax ring, and that wax ring is what keeps sewer gas out and water in. Every wobble compresses and deforms the seal a little more. Eventually it fails, and you get a slow leak you can't see — water seeping under the toilet base, soaking into the subfloor, and rotting the wood from below.

In Oakland and Macomb County, where many homes have bathrooms on the second floor, a failed wax seal can send water through the ceiling below before you ever notice a puddle. The fix is straightforward: level the toilet, shim it, snug the bolts, and seal the base. It takes about 30 minutes and a few dollars in materials.

Step 1: Check What You're Working With

Before you start shimming, you need to understand why the toilet is wobbling. Grab a torpedo level and set it across the top of the toilet bowl, side to side and front to back. Watch the bubble — it'll tell you which side is low and roughly how far off level the toilet sits. Your toilet doesn't need to be perfectly level to work fine, but the level tells you which side needs to come up and gives you a plan of attack for where to place shims.

Here's the important part: if this toilet has been wobbly for a long time — months or years — be cautious. Every time it rocked, it stressed the wax ring. Before you shim and tighten, you need to confirm the seal is still good. Look for water stains or discoloration around the base, check the ceiling below the bathroom for water marks, and smell for sewer gas. If you see any signs of a failed seal, the toilet needs to come up so the wax ring can be replaced before you resecure it. Shimming over a broken seal just hides the problem.

If the toilet was recently installed or you're confident the seal is intact, move on to securing it.

Step 2: Loosen the Mounting Bolts

The toilet is held to the floor flange by two mounting bolts (sometimes called closet bolts), one on each side of the base. They're usually covered by small plastic caps. Pop the caps off — they either snap off, twist off, or pry off with a flathead screwdriver.

Loosen both bolts slightly. You don't need to remove them — just back them off enough to give the toilet a little room to shift when you slide shims underneath. A quarter to a half turn is usually plenty. If the bolts spin without loosening, hold the bolt head with pliers while you turn the nut.

Step 3: Shim the Base

Pick up a pack of soft toilet shims — they're sold as "wobble wedges" or similar names at any hardware store. Look for the soft, flexible type with ridged teeth on the surface. The teeth grip the floor better than smooth shims, and if you need to stack two together to fill a larger gap, the ridges lock them to each other so they don't slide out.

Using what your level told you, start on the side that needs to come up the most. Slide shims in from the outside edge of the toilet base, pushing them in until you feel friction. Don't hammer them — just press firmly. Place about four shims per side, spacing them around the base. Then do the other side.

Go back and recheck your level. Sometimes pressing a shim in on one side loosens one on the other. Make small adjustments until the toilet feels stable and doesn't rock in any direction. The goal isn't laser-level perfection — it's eliminating the wobble and getting a solid, stable seat on the floor.

Step 4: Trim the Shims and Tighten the Bolts

Once you're happy with the fit, mark each shim with a marker where it meets the outside edge of the toilet base. Then remove and trim them one at a time — pull one shim, cut it, and push it back in before moving to the next. Doing them one at a time keeps the toilet in position while you work.

A pair of side cutters (diagonal cutting pliers) works better than a utility knife for trimming shims. Two quick snips and the excess is off cleanly. Recess each shim slightly under the edge of the base so it's not visible. You can use the leftover cut piece to push the trimmed shim snugly into place.

With all shims trimmed and seated, tighten the mounting bolts on both sides. Snug them firmly — you want the toilet locked down — but don't crank on them. Porcelain cracks under too much bolt pressure, and that turns a simple fix into a toilet replacement. Alternate a quarter turn on each side so the toilet draws down evenly. When it feels solid and doesn't move, stop. Snap the bolt caps back on.

Step 5: Seal the Base with Silicone

With the toilet stable and the shims hidden, run a bead of 100% silicone caulk around the base where it meets the floor. White silicone matches most toilets. Lay a thin, even bead — you'll spread it with your finger, pressing the silicone slightly up under the edge of the base for a clean look.

Smooth the bead with a wet finger, wiping excess onto a damp paper towel as you go. Take your time here — a clean caulk line makes a big visual difference.

One critical detail: leave a two- to three-inch gap at the back of the toilet. Do not seal the base all the way around. If the wax ring ever fails in the future, you want water to leak out onto the bathroom floor where you'll see it — not get trapped under a sealed base and silently soak into the subfloor for months. The gap at the back is your early warning system.

When to Call a Professional

Shimming and caulking is a solid DIY fix when the wobble is caused by an uneven floor. But there are situations where the problem runs deeper:

If the toilet flange is broken, corroded, or sitting below the finished floor, no amount of shimming will create a reliable seal. The flange needs to be repaired or replaced, and depending on the situation that can mean cutting into the drain pipe. If the subfloor around the toilet feels soft or spongy when you press on it, water damage has already set in — the subfloor may need to be cut out and replaced before the toilet goes back down. If the mounting bolts spin freely and won't tighten, the flange slots are stripped and the flange needs to be replaced or reinforced with a repair ring.

At The Toilet Guys, we handle wobbly toilet fixes every week. If it's a simple shim-and-secure, we'll take care of it for $100. If the flange or subfloor needs work, we'll diagnose the full scope, explain what's needed, and give you a clear price before we start. Toilet replacements start at $499 installed, and every installation includes a new wax ring, new supply line, and our wobble-free guarantee.