How to Shim a Toilet on an Uneven Floor?

You often feel that your toilet is not stable and is rocking to either the left or right side when you are using it, which can be due to the loose fixing or the uneven floor of the bathroom.

How to Shim a Toilet on an Uneven Floor? You can shim a toilet on an uneven floor by cleaning the area around it, searching the gaps, inserting and trimming the shims, and then finishing for the final look. Plastic, rubber, and wood shims are used for leveling the toilet base on uneven floors.

You can fix the problem using small plastic or rubber wedges under the toilet where the floor is uneven and make it stable to avoid any inconvenience while sitting on the toilet seat.

How can you shim a toilet on an uneven floor?

You need a few tools to shim a toilet on an irregular floor without any difficulty if the toilet is installed in an unbalanced place. 

You need shims, gloves, a caulking gun, hammer, knife, or blade, and masking tape for this task.

Clean the surface

Ensure that the surface is clean where the commode is installed and that there is no water leakage around it.

Fix the leakage before starting the process of shimming because it can cause problems in the future. 

You can wipe the water splashes or standing water on the floor with a dry cloth or vacuum the area.

Use a sponge and a light-duty detergent to clean the area under the toilet if you notice any mold and mildew growth because of the moisture. 

It is better to wear gloves to keep your hands germ-free and safe. You can use a brush or a mope to remove the grime of dirt or dust from the floor that can look nasty to the overall appearance of the toilet area.

Search the gaps

The next step is to search for the gaps and holes under the toilet that cause the rocking and wobbling of the seat.

You can check the location where the floor is uneven and the fixture is not balanced on it, such as it may be uplifted from one side than the other.

This gap between its base and floor determines the size and thickness of the shims required. Therefore, you may need more than one shim to place under the base to balance the level.

It requires a careful inspection from all sides because the floor can have rough surface.

However, you can slide it under the toilet to see how far it goes if the gap is small and you can not notice it easily.

Insert the shims

You can now insert the shims into the gaps and holes you have identified by positioning it in such a way that the sharp side is under the gap, and the thick side is outside of the toilet.

Depending on the space between the floor and the bowl base, you can insert more than one shim.

Push it with your hands to insert it properly into the gap, and use a hammer to fix it into the hole to avoid wobbling.

Repeat the process with all the gaps around the commode and test the stability by sitting on the toilet. Finally, check the gaps and shims’ location again if it still wobbles from its place.

Trimming of shims

The obtrusive ends of the shims look unattractive and affect the aesthetic appearance of your bathroom.

The next step is to carefully cut the projecting sides with a sharp knife or blade to avoid any damage and scratches on the floor.

Cut them from the edges so that the sides are not visible, and you need special attention while cutting them if you have vinyl floor covering because the risk of getting scratches on them is more than the tile floor.


Caulking around the base and the gaps is essential to give a finished appearance and make the shims invisible.

It will also prevent the water from entering the gaps and accumulating dust and mold around the corners.

Wear hand gloves and take a caulk gun filled with 100% silicone caulk to fix the shims at their place. You can cover the base and the floor with masking tape to prevent them from the extra caulk. 

It is better to apply the caulk only around the gaps because the water will accumulate under the base if there is any leakage under the bowl. Fill the gaps with caulk with your fingers, so the surface looks smooth and even. 

What types of shims are used for a toilet on an uneven floor?

You can use different types of shims to fix the rocking of the toilet on an irregular surface, depending on the size and length of the gap between the base and the floor.

Plastic shims

Plastic shims are made of composite plastic and are available in soft and hard plastic, depending on the requirement of the gaps and the floor.

They are more durable than wood wedges because they resist water absorption and do not warp over time.

They are slippery when you stack them over each other to fill the gaps because they are difficult to glue with an adhesive, especially in high-traffic areas and movements, such as rattling pipes.

Nylon shim is also a type of plastic wedge made of nylon and provides more stability to the wobbling toilet. It has a ribbed-like outer surface that can stack over each other and not slip from its place.

Flexible plastic shims are a great alternative to rubber wedges because they provide flexibility and a strong grip on the surface to avoid rocking the seat. 

Rubber shims

They are affordable and provide enhanced durability than other wedges because they can survive the temperature change around them, unlike plastic shims, which can get cracked with the fluctuating temperature around them.

They are flexible and versatile and can easily be stacked over each other with glue if the gaps are big and require more than one shim to fill the gap and holes.

They do not cause floor scratches as you can easily cut the protruding edges without any damage to the floor, and they are easy to install.

Wood shims

Wood shims provide great support between the uneven bathroom floor and base because they are sturdy pieces of wood that can stabilize the commode’s wobbling or any other appliances.

However, moisture and water leakage under the toilet plumbing can cause the rooting of wood, which affects the durability of the shim.

They can provide stability and support to the plumbing fixture and stack together without slipping.

Water-resistant hardwood wedges are a good option for the bathroom plumbing fixtures, such as bathtub, sink, and vanity to balance them.

Why would you shim a toilet on an uneven floor?

A wobbling toilet seems uncomfortable every time you use it, especially if you have a bathroom under the stairs and in a garage where the surface is not even and smooth.

It is better to fix the problem as soon as possible because it can cause the toilet to damage if you leave it to wobble over a long period.

Also, it can cost less money and more convenience to shim it than replacing the commode or leveling the bathroom floor.

You have to face embarrassment when a guest wants to use the toilet and it is wobbling.

Moreover, there are chances of young kids falling from their seats to get stable and sit comfortably on the commode.

Mold and bacteria can grow because of the standing water on the uneven floor under the toilet, which looks unhygienic and nasty for the bathroom environment.

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