How to Shim a Toilet? A Step-By-Step Guide

Do you feel nervous when the toilet rocks in the middle of your dirty work? We can’t blame you because a wobbly toilet is a real pleasure killer.

But here’s the trick — you can place shims under the toilet bowl to stabilize it. It solves more than one problem in your bathroom, so let’s see how to do that.

How to Shim a Toilet?

Shimming a toilet is a six-step process that you can complete single-handedly. Here’s how it works:

Step 1: Check the Toilet for Gaps

The first job to do is to check the gaps between your rocking toilet and the floor. Dirt or dust may accumulate around the base, so clean it up before you start the inspection. 

A good cleaning job reveals even the smallest holes under the bowl.

After that, you can begin looking for uneven parts of the bathroom floor and gaps dividing it from the porcelain base. Pay attention to the gaps’ height and width — you might need multiple shims for that area. 

Remember that gaps may appear all around the base. Go the full circle to inspect the entire toilet bowl.

Step 2: Insert the Shims

When you identify the gaps, it’s time to place the shims under the toilet. You can use small handmade wood shims, but plastic and rubber items are also available for purchasing.

The good thing is that shims are very affordable, turning your work into a cheap DIY project. Depending on the gap dimensions, you’ll need one or two pieces to level out all the divisions between your floor and tank. You can insert the shims like this:

• Place one shim on the floor, with its sharp edge facing the toilet base gap
• Push the shim with your fingers, so it can enter and fill the gap
• When you can’t press the shim further, use a small hammer to give it the extra push — it will seal the gap entirely

The same process applies to all gaps under the bowl. When you insert all shims, make sure that the toilet is stable — there should be no wobbling anymore. 

Step 3: Trim the Shims

Your toilet is now safe and stable, but the work does not end here. On the contrary, you still have to cover the shims and make the bathroom throne aesthetically pleasing.

The main way to do that is to trim the shims. Most shims are longer than needed, so the back of each piece will remain visible. It’s a part that doesn’t fit into the gap — cut it using the utility knife.

However, be careful not to damage the floor. The knife may scratch the surface, especially if you have a vinyl floor. Another useful tip is to follow the toilet bowl’s shape — cut with the right angle to make the shims nearly invisible.

The goal is to level the shim with the surface of the toilet bowl. This way, your toilet will look better, and you’ll have a perfectly shimmed bowl.

Step 4: Test Your Toilet

You can now test your toilet to see how it works. The first task is to check whether it wobbles — push it gently with your hand and see if it moves. It shouldn’t budge, but you have to make sure by checking it from all sides and angles.

The second task is to test the toilet for possible leaks. You don’t want to see your toilet leaking at the base, so remember to flush it a few times. Your toilet shouldn’t leak after installing and trimming the shims. 

Step 5: Caulk the Toilet Base

The work is not over yet because you can still notice the shims under the toilet. Although they fill the gaps and fit in tightly, there is a notable difference between the average shim and the porcelain surface of the toilet bowl.

In such circumstances, caulking the toilet base is mandatory if you want to cover the crime scene. But how do you caulk around the toilet? Follow these steps:

• Clean the toilet base as well as the floor around it
• Apply masking tape around the bowl to prevent caulk from spilling on the floor
• Buy a 100% silicone caulk tube and put it in the caulk gun
• Target all shims one by one and pull the trigger — the gun will fill uneven surfaces with caulk
• Use your thumb to press fresh caulk — this helps you to align it with the toilet much more precisely
• Now you can detach the masking tape from the floor

Step 6: Let It Dry

It’s always a good idea to let the caulk dry overnight. Your toilet is already safe with all those shims, but caulk needs time to dry and stiffen. That’s why it’s best to caulk around the toilet in the evening — you can let it rest for at least eight hours overnight.

Basic Types of Shims

There are multiple types of shims, but they all serve the same purpose. Some people improvise by inserting handmade wooden shims or even old coins, but we recommend using professional tools.

The best types of shims are the ones with ridges or ribbed designs. Shims can vary in size and shape, but we usually focus on two options.

Plastic toilet shims come in different colors and shapes. They offer a cheap way to level uneven surfaces, and they are easy to insert. The pro of installing plastic shims is durability — plastic elements support heavyweight toilets with ease.

However, plastic shims sometimes crack due to continuous temperature fluctuations in the bathroom. If your bathroom is cold, but you often use air conditioning to heat it, plastic shims may crack over time.

Rubber toilet shims are another option for leveling uneven toilet bowls. Like plastic, rubber pieces are durable and support heavy toilets. The only difference is that you may have to insert multiple rubber shims because they bend under pressure.

However, the benefit of using rubber shims is that they rarely ever break or fall apart. The flexibility of rubber makes these shims extremely reliable.

What to Do With a Wobbly Toilet?

If your toilet suddenly starts wobbling, it’s unlikely that the floor is uneven. On the contrary, this mostly indicated a problem with a toilet flange and its wax ring.

The toilet flange represents the metal or plastic ring — it is the entrance to the outlet drain, so you can find it under the bowl. The toilet flange has a wax ring on the top, a protective layer that stabilizes the toilet.

Sometimes you’ll find out that the toilet flange is damaged, so you’ll need a flange repair kit to fix the wax seal problem before inserting toilet shims.

We explained how to do that in our post about a wobbly toilet. 

Why It’s Bad to Let Your Toilet Wobble?

The reason why you shouldn’t ignore a wobbling toilet is that it can permanently damage the floor.

Even if your floor seems sturdy enough, deep dents and scratches may appear over time as the toilet moves back and forth. One hit from a toilet is enough to ruin your floor’s surface, so you have to take action as soon as possible.

Besides that, wobbling can also prompt bacteria growth under the toilet. Bacteria thrive in moist environments, especially if moisture collects underneath the bowl and stays there for too long.

A rocking toilet will also allow human waste to escape after flushing, so you’ll feel that disgusting poop and urine smell.

Should You Caulk Around the Toilet After Shimming?

Yes, you should caulk around the toilet after shimming. It’s a useful post-shimming tactic for several reasons.

Firstly, caulking makes the toilet look better after installing toilet shims. The type of toilet shims is irrelevant — tile caulk hides plastic toilet shims and rubber elements just the same. 

Secondly, caulk helps your white toilet remain perfectly neat and clean. The surface of the bowl becomes smooth, so you can clean the whole structure with ease. Caulk also stabilizes the bowl, not allowing it to become a rocking toilet.

If you are afraid of leaks, you don’t have to caulk around the entire toilet base. It’s possible to leave the back of the base open. That way, you will still hide the shims, but you also allow water to go out and warn you about possible damages.

The Bottom Line

So how to shim a toilet? You know the answer by now — check your toilet for gaps, insert the shims, trim them, and caulk around the bowl. 

It eliminates your rocking toilet issue and improves the overall appearance of the bathroom. The best thing is that shimming a toilet is very easy and you can do it on your own. So what the heck are you waiting for?

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