How To Fill Gap Between Vanity And Wall (7 Solutions)


In ideal situations, the bathroom vanity would always be flush with the wall. However, situations are not always ideal, and between your vanity and the wall could be an unsightly gap. 

There are various ways to fix this, though, depending on where the gap is located and its size. 

Smaller gaps can be filled with caulk or covered with a backer rod or filler strips, whether they are at the back of the vanity or to the side. Tiling a side wall can also help mask a narrow space. A thick backsplash, shelving, or a side cabinet can mask wider gaps. 

7 Ways To Fix Gap Between Vanity And Wall

Filling a gap between the vanity’s countertop and the wall isn’t complicated; you just have to find the best solution based on the gap size. 

Check out the methods below to fill small to large gaps.

1. Fill The Gap With Caulk 

Small gaps between the vanity and wall – smaller than ¼ of an inch in size – are incredibly common.

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They typically happen due to walls that are not perfectly straight, and could be more visible if the wall behind the vanity is painted instead of tiled.

These gaps may not bother you from an aesthetic standpoint. However, splashes and spills could leak through, soaking the vanity’s back and leading to rot and mildew. 

Stagnant water trapped between the wall and vanity could also be the source of a foul smell in the bathroom. 

The easiest way to fix this issue is with caulk. 

How To Caulk The Gap Between Vanity And Wall

  1. Gather the necessary materials. For this project, you need: silicone caulk, a caulking gun, mineral spirit or degreaser, rags, and latex gloves.
  2. Thoroughly clean the vanity edge that should adhere to the wall, as well as the wall behind or next to the vanity. Wipe with mineral spirit or degreaser to remove all oil or grease traces. If using a degreaser, rinse thoroughly with clean water and let the surface dry out.
  3. Load the caulk tube into the caulking gun. Put on the gloves 
  4. Holding the tip of the caulk tube at a 45-degree angle, apply a thin bead of caulk. Start from one side and keep applying until you reach the other side. 
  5. Smooth the caulk with your gloved finger, pushing it into the gap. This operation ensures a better grip of the silicone to the surface and removes excess caulk. Let the caulk cure as instructed. 
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2. Install A Backer Rod 

Gaps up to ½ of an inch in size are often the result of sinks or vanities that require more space – maybe for the proper placement of a P-trap or other plumbing requirements.

These gaps may be too large to fill with caulk, but backer rods could save the day. 

Backer rods are foam tubes available in various lengths and thicknesses. Once installed, you can add a layer of sealant on top to achieve an aesthetically-pleasing finish. 

Installing Backer Rods Between Vanity And Wall

  1. Measure the gap between the wall and vanity with a ruler and write down the number. Use it to buy a backer rod of the appropriate diameter. 
  2. Measure the length of the gap and cut the backer rod to size.
  3. Push the backer rod into the gap – it should go about ¼ of an inch lower than the vanity edge. 
  4. Fill the gap between the vanity edge and the backer rod with a waterproof sealant, such as white or colored silicone caulk. 
  5. Let the sealant cure as instructed before using the sink.

3. Use Vanity Filler Strips 

Vanity filler strips can be used instead of backer rods to fill gaps larger than a quart of an inch but not larger than half of an inch to an inch. 

These strips are typically self-adhesive and are easy to fold in the middle so that you can install them perfectly flush with the wall and vanity top. 

Degrease the surface and let it dry completely before starting, or the strip might not adhere. 

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Peel a portion of the paper covering the adhesive side and stick it in such a way that it adheres to both the vanity countertop and wall.

Work your way from the starting point to the other side of the vanity by peeling off a small section and sticking the tape in place before moving to the next section. 

Continue until the entire gap is covered.

Use a trowel or another tool to press the filler strip to the vanity edge and wall; then, you’re done.

4. Install A Thick Backsplash

Gaps up to half an inch or slightly wider are also easy to mask with a thick backsplash. This solution is often the most aesthetic, especially if the gap is between the vanity counter and the back wall. 

Backsplashes typically have a thickness of up to ½ of an inch. Adding up the adhesive thickness, the backer board could cover a gap of up to 0.75 inches.

A backer board could be an ideal solution if you love the sought-after look of painted walls in the bathroom but don’t want to worry about splashes ruining your walls or leaking behind the vanity. 

The video below details how to install the backsplash: 

5. Tile A Side Wall

If yours is a side wall and a backsplash wouldn’t look finished, you can still fix the gap with tiles. In this case, however, it might be best to tile the entire surface – or create a pattern to follow.

For instance, you don’t have to tile the wall from floor to ceiling. You could only tile half of three-quarters of it. Continue tiling the wall behind the vanity at the same height for an aesthetically pleasing result. 

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Alternatively, leave the wall behind the vanity bare (exposed brick or painted only) and tile the entire side wall from floor to ceiling. 

6. Add Shelving

Side gaps can also be filled with shelving if you aim to achieve both aesthetically pleasing and functional results. 

If the gap is wider than an inch but not wide enough to accommodate a freestanding shelf unit, you can adapt an over-the-toilet shelf type to place it over the vanity. The shelf’s side panels will fit into the gap perfectly. 

For gaps wider than two inches, you can have the shelving unit built to size so that it covers every inch of empty space. 

7. Add A Side Cabinet 

Tall bathroom cabinets are a functional feature, and they can cover a wider gap between the vanity and the side wall. 

Standard dimensions start at six inches wide. Some brands manufacture slim-line cabinets that can be narrower (around four inches in width), but they are more difficult to come by.

However, you don’t have to buy a ready-made cabinet. A carpenter could build one that perfectly adapts to your space. While this solution is more expensive, it is usually affordable if you opt for mid-range materials such as laminated MDF instead of hardwood. 

To prevent water from seeping between the vanity and cabinet, seal the edge with silicone caulk or a caulking strip.


The gap between the bathroom vanity and the side or back wall can be unsightly, and it can create the right environment for bacteria to thrive. 

Filling it isn’t hard, though. Small gaps are easy to fill with silicone caulk, cover with a caulk or filler strip, or fill with a backer rod and top with sealant. 

Wider gaps can be masked with a thick backsplash or filled with tiles. Side shelving or a slim cabinet can help you get rid of wider gaps.