How To Fill Gap Between A Bookcase And Wall [Step By Step Guide]

Have you noticed a gap between your wall and your bookcase? Are you looking for ways to fix this gap? If you do, we are here to help you out. Well, we've researched the steps for filling gaps between a bookcase and the wall to come up with an easy guide for you!

If you notice gaps between your bookcase and the wall, you want to:

  1. Clean the area to be filled
  2. Put a backer rod in the gap
  3. Tape off the surface around the gap
  4. Put caulk into the gap
  5. Level the caulk using a putty knife
  6. Leave the caulk to dry
  7. Refill with caulk if needed
  8. Repaint the caulked gap

We will detail these steps throughout the post. We'll provide you with the proper materials during the discussion. You'll find more about filling gaps in the sections ahead. With that said, let's dive right in!

3d-illustration-modern-interior-loft-style, How To Fill Gap Between A Bookcase And Wall [Step By Step Guide]

Fixing The Gap Between Your Bookcase And The Wall

The gap between your wall and the bookcase is unappealing and ruins the appearance of your space. You don't have to worry about gaps, though. It's pretty easy to fix.

It is important to note that the steps illustrated here apply to wood walls, drywalls, and wooden bookshelves. These steps can be used for gaps between the bookcase, the wall, and other significant gaps.

For this project, you'll need a cutter, putty knife, backer rod, carpenter's tape, caulking gun, caulk, and paint.

1. Clean The Area

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Before doing anything, make sure that you dust off the area. Caulk may not adhere to the surface if there is dirt.

2. Put A Backer Rod At The Gap

A backer rod is a foam rod of different lengths used to control the amount of sealant and caulk applied. It acts as a stopper to prevent excessive use. Backer rods are made to resist most solvents, so it is ideal for filling gaps.

The backer rod is a vital piece when repairing wide gaps with caulk. Without it, the caulk will turn wiggly once dried. The rod also levels uneven depths within the gaps.

Additionally, there will be more shrinkage without it. So, it is crucial to add backer rods before applying caulk into the gap. Insert the backer rod into the gap.

There are different sizes, so choose appropriately for your need. It should snugly fit into the gap fairly.

If it doesn't, the gap may be too narrow. The rod should be fitted uniformly, else it'll shrink at different rates, and you won't get a flat surface.

Note that although small gaps can be filled with caulk directly, holes larger than 1/4 inch should be supported by backer rods.

Click here to see this backer rod on Amazon.

3. Tape Off The Surface Around The Gap

You need to tape off the surface around the gap to protect it. This also ensures that no caulk will get to other areas where it shouldn't be. Stick carpenter's tape at the edges on each gap side as necessary.

Click here to see this tape on Amazon.

4. Put Caulk Into The Gap

There are different colors and types of caulks. If you are working on wood surfaces, use a latex type. This type is paintable; hence, you won't have trouble hiding the caulk later. You can choose a caulk color to match your wall.

Load the caulk into the caulking gun.  Cut the tip of the caulk tube. Cutting it straight instead of angled is recommended for more freedom during application.

Ensure that the cut is slightly smaller than the gap so that it'll not overflow when you apply.

Before applying, ensure you have a clean rug to wipe off your putty knife and the excess caulk. Place the tip of the tube into the beginning of the gap.

Squeeze the caulk gun trigger for the caulk to flow. Do this while moving until you finish the rest of the area. Remember that the key to having a smooth finish is the uniform application of caulk.

See this caulk on Amazon

5. Level The Caulk Using A Putty Knife


Take note that it is okay to overflow the gap with caulk slightly. The purpose of the putty knife is to smoothen the excess caulk.

Right after the caulk application, glide the putty knife slowly down the caulked area. You want to keep the square edge of the putty knife against the wall to leave a clean edge.

You should see a thin buildup on the tape after you've done this step. If the buildup is thick, you have to redo it. Wipe off the excess caulk with your putty before continuing.

See this putty knife on Amazon.

During the process, you may accidentally pull the caulk out of the gap, especially if you wipe it. Don't worry; fill it up again.

6. Leave The Caulk To Dry

Different caulks have different drying times.  

Sometimes, you have to leave it for a couple of days to see if it'll shrink before you proceed to the next step. If it needs another coat, leave the tape in the meantime so you don't have to redo it.

You should have a flat surface once the caulk has dried.

7. Refill With Caulk If Needed


If you see that the surface is not flat and the caulk has shrunk, you have to do a second coating. Otherwise, you are good to go. You can remove the carpenter's tape at this point.

Remove traces of caulk at the spots where they shouldn't be with a scraper, and you're ready for the final step.

8. Repaint The Caulked Gap

Finally, it's time for painting. Take note that other types of caulk are not paintable, so make sure you use one if you intend to paint it. Before applying paint, coat the dried caulk with a very thin layer of fresh caulk. This will act as a bond to the paint.

This final step is optional if you have picked a caulk that matches your wall color; you don't need to paint the caulk.

There you have it, the simple steps in filling the gap between your bookcase and wall.

What Causes Gaps Between The Wall And A Bookcase?


Your wall may have shifted, which resulted in gaps between the wall and the bookcase. This can happen over time. A gap can also be a result of poor construction and bookcase installation.

Whatever the reason, small gaps are acceptable. However, if you notice the gaps are continuously becoming large, consult a professional. This may be a sign of serious structural issues.

Is Silicone Caulk Better Than Latex Caulk?


Pure silicone caulk is durable and best for moisture-prone areas such as the bathroom. It acts as a sealant by protecting joints from water. However, it cannot be painted.

It is also more expensive than the latex type. For cleaning excess silicone caulk, use mineral spirits.

On the other hand, if you need to paint over a caulk, use a latex caulk. This is less expensive and ideal for filling small gaps in wood or drywall. Clean-up is a breeze for this type. You just have to wipe off the excess or use soap and water.

Choosing between these two types depends on where you'll use them.

Final Thoughts


Filling gaps between a bookcase and a wall is not a daunting task. Just have the right tools and apply the right methods to get the job done.

Take note that caulking seals the gaps easily, but you need to use a back rod to keep the application even. A back rod also serves as a bridge and supports the caulk when filling large gaps. Also, using the right caulk is essential for the success of this project.

Finally, now that you are equipped with the proper knowledge, you'd be able to pull off your DIY project confidently.

While we have your attention, check out these related posts:

6 Best Wood Fillers For Large Gaps

3 Best Paints For Bookshelves

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