DIY Built Ins with Ikea Billy Bookcases

A step-by-step on how to make DIY Built Ins with Ikea Billy Bookcases. Learn how to make Ikea Billy Bookcases look like custom built-ins.

I am going to be 100% honest and say this was the hardest DIY I have completed so far. Mainly because I did it all by myself. I think this project would be much easier if you had a helping hand along the way. I was in such a hurry to get this done I didn’t want to wait on someone to come to my rescue and help so keep this in mind if you plan this project on your own.

To say that I was happy with the way it turned out would be an understatement….I am thrilled! I was very pleased with the look I got for the price. I was able to achieve this for under $200, which is a win in my book! I am going to share with you exactly how I achieved this built-in look with these Ikea bookcases, but if you’re looking for more tutorials on how to get this look check out this post on Lauren’s site Blesser House to see another way to get the built-in look with these Billy bookcases. I got a lot of my ideas from her post.

So here we go, everything you need to know on how to get the built-in look with these prefab bookcases.

This post contains affiliate links for your convenience.  For more information, see my full disclosures here. 

DIY Built-ins

How to Make DIY Built ins with Ikea Bookcases

Step 1: Measure

The first thing I did was measure. The only information you really need to get this project started is to know how big of a space you’re working with so you know how much of the materials you need. After completing my measurements I ended using the size of my floating desk to base all my other measurements on. I wanted bit larger of a floating desk to fit my iMac so I ended up going with the floating desk that was 16″ deep and 40″.  So after setting my floating desk size I was then able to figure out how much I needed for the other materials. I will list what sizes I got in all the materials throughout the post.

Step 2: Put Together the Bookcases

This was so simple. It took me about 45 min to put together both of these bookcases. I think I am becoming a pro at this Ikea furniture! After I got the bookcases put together I placed them where I wanted them to go spaced 40″ apart to account for the floating desk.

I was a bit worried that I would have to make some cuts into my current baseboards and molding to make the bookcases fit flush against the walls, but it ended up fitting pretty snug. The bookcases have a cutout already in the back to go over baseboards and they fit mine pretty closely. Since I was ok with the small gap between the wall and the bookcases I didn’t end up making any cuts. I then made sure to secure the bookcases to the wall using the L-brackets that came with the bookcases. Before I secured the bookcases to the wall I put up my floating desk to make sure I had my measurements right before I secured them to the wall.

Step 3: Attach the Floating Desk

I wanted to complete this step next because with doing this myself I felt with the desk attached it would make it easier to work with the top. This was by far the hardest part of the whole process for me. Since I was on my own I ended up using one of the shelves to hold up the other end of the desk while I screwed in the other side. This took me a good hour or so to get it right!

I lined up the desk to be even with where one my shelves would go to make it seem more fluid and then took wood screws and screwed it into a 1×3. I used 1x3s on the sides and front of the desk to give it that floating look. Then I screwed the plywood panel to the top of the 1x3s and finished it off with another 1×3 on the front.

Step 4: Attach Your Supports

The next step is to attach your braces or supports for your top MDF panels. In order to have something to nail the MDF boards to I needed to place 2x4s on the top of the bookcases. I laid two long 2x4s on the front and back of the bookcase as well as a couple on the sides to attach my side panels too. I screwed these 2x4s into the top of the bookcase sides so the screws wouldn’t come through the top.

This was a fairly simple step and after doing this they already felt more sturdy and secure. I ended up needing to cut a few more of these 2x4s down to add to the front supports because after I started attaching my MDF panels I had a small section where I had nothing to attach it to. At that point it was a little harder to add to it so I recommend having a brace that goes all the way along the front to start with. With my floating desk being 40″ it ended up making the whole piece 103″ long after adding in the width of the bookcases.

Step 5: Add Your MDF Panels

I knew that I would need 103″ long in MDF boards for the front as well as 11″ for each side panel. I had Home Depot cut these down for me since I didn’t have a table saw handy. I had them cut all the pieces the be 9″ high and had them cut enough to equal 103″ on the front and 11″ on each side. I also had them cut a 40″ by 11″ to cover the underside of the new top between the two bookcases.

After I had all of my pieces cut I then brought out my nail gun and started nailing the MDF boards to the 2×4 braces behind them. I also made sure to stack up a few extra 2x4s behind where the MDF pieces met. I only had to do this once since I only had one break in my MDF panels on the front. Since the panels didn’t come in 103″ long I had to piece together two on the front. Adding this extra brace behind the two pieces helped keep it together.

Step 6: Add Your Molding & Baseboards

This is the part where I started to feel like I was coming into the homestretch with this project! All the heavy lifting was done. In order to give the built-in that finished look I wanted to add some molding and baseboards. I got Home Depot to cut my molding and trim down to manageable pieces and then cut my corner pieces at a 45 degree angle with my miter saw. This is a hard step if you have never cut 45 degree angle pieces before. There are a ton of great YouTube videos to help you out. I was lucky enough to have my dad show me how to do this a couple of years ago and once you get the hang of it, it’s not that intimidating. Make sure to get a bit of extra molding and baseboards in case you mess up. After I had all of my pieces cut I then brought out my handy nail gun again and started nailing it to the MDF panels for the molding and to the bottom of the bookcases for the baseboards.

After I had all the trim up it was starting to come together and look like it was really made as one piece. It definitely didn’t look like two prefab bookcases anymore!

Excuse all of my shots including the chandelier. No matter what my angle was I couldn’t get a good full shot without getting the chandelier in the shot.

After the baseboards were attached it really started to have that “built-in” feel!

Step 7: Spackle & Caulk

You can decide if you want to spackle throughout the process or wait until the end. I waited until the end and made sure to spackle up any of the nail and screw holes. I also didn’t like the predrilled holes for the shelves, so in order to give the bookcases a more finished feel I filled in the holes I wasn’t using with some nail filler. After it was dry I then went over it with a sanding sponge to smooth it down. I didn’t end up painting over holes because after the sanding it looked great without it.

Then I went a little crazy with the caulk! I didn’t want to see a single crack and wanted it to truly look like it was seem-less! I caulked every crack I could find. If you are needing a few tips on caulking, check out this post of mine on painting baseboards for a few pointers!

Make sure not to forget the area where your new baseboards meet the bookcases…

Step 8: Paint

Your final step to complete that built-in look is to paint! After all of your caulk and spackling is completed you will want to paint your molding, baseboards, and MDF panels to match the rest of the bookcase. I took one of the Ikea bookcase shelves to my local Sherwin Williams and had them perfectly match that Ikea white. I got the paint in semi-gloss since it is what you would normally paint your trim and baseboards with for your home. I gave it two coats of paint, and may decide to give it another! Check out my Beginner’s Guide to Painting post for some great painting tips!

I was extremely pleased at how this turned out. There are a few imperfections, but they’re probably only noticeable by me! A few paint touch-ups and some styling and this piece is going to really make my home office feel complete!

Now all I have to do is get everything put into place and I will have a home office makeover reveal coming your way next week. I can’t wait to show you the final reveal. In the mean-time be sure to go here and check out the other fabulous guest participants for this One Room Challenge. If you’re needing some room makeover inspiration you will find it here for sure!

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This post contained affiliate links. For more information, see my disclosures here.