Make Built-In Cabinets, step by step

There is no better kind of storage than built-in storage, especially when you can integrate it with the architecture of a space. So when we wrapped up our attic into a bonus room, we were excited to make use of the recessed niche around the window. Today we are going to show you how we designed and installed built-in cabinets using stock cabinets. Spoiler: it is in fact an Ikea hack!

Built-In Cabinets With Floating Shelves In Window Niche

This post covers the wall-to-wall, built-in cabinets, but you can also read about how we built the Hands-on floating shelves too. The two features work together to make a functional feature wall, but it is a bit much to cover in one walkthrough!

Step 1: Plan Your Built-Ins

Because this recessed portion of the room was only 17″ deep, we knew we hoped to add some built-in storage.

At first, that recessed space felt like a curveball to symmetry fanatics like us – it is off-center in the room, it is only 17″ deep, and it has not one, but two, sloped ceilings. But it was in fact its narrow depth that triggered the idea for some sort of built-in. Plus we knew this big blank slate of a room would certainly benefit from some brought in storage and height / interest on that wall.

Wide angle panoramic photo of an empty bonus room with tan walls, wood floor, windows, and niche nook

We had lately used Ikea’s kitchen planner to plan our laundry room cabinets and had a strong experience. So we tried out a few cabinet configurations for this space, and Photoshopped some rough shelf ideas onto them.

Ikea Kitchen Planner Ideas For Bonus Room Built-In Cabinets

We ultimately chose on four standard 30″ tall base cabinets across the bottom with one 20″ drawer base centered under the window. The proportions felt right and we liked the “window seat” effect it created in the middle. Once we finalized this design in Ikea’s planning tool, it automatically generated a shopping cart we could check out with.

Step 2: Assemble Your Ikea Cabinets

The first step was assembling all of our cabinets boxes. I will not bore you with those details, but we do have tons of tricks & pointers for installing Ikea kitchen cabinets. No need to put on the doors or drawers yet.

Room with sloped ceiling and Ikea cabinet boxes being built, with a girl's doll using one as a window seat

This is also a good time to double-check your plan and make sure it is shaping up the way you expected.

Step 3: Build Cabinet Bases

The standard Ikea legs were too high for the window, so we had to build our own bases. We used a combination of stacked 2×4″ and 1×4″ boards to get the exact right height (see photo below). These bases are not in fact to hold up the cabinets, though. They are mostly to give you something to attached your toe kick or baseboard too at the end. But we did like having them under the cabinets simply in case. You know, in case some kids decides to stand on these or something.

Step 4: Attach Cabinets To The Wall

Ikea uses a rail system to hang cabinets on the walls. You attach the metal rail to the wall, and then the cabinets hang from it using metal clips. The Ikea instructions will show you exactly how to get the right height for your rail. Simply be sure to use a stud finder and a level to hang your rail securely in place.

detail of how Ikea Sektion cabinets attach to metal wall rail using screw and washer

You can also see that before we hung the metal rail, we screwed a 2×4″ into the wall studs behind it. This gave our 12″ cabinets a little bit of extra depth to better fit the 17″ deep space.

Step 5: Add Filler Pieces

With each cabinet hung on the rail (but not locked in yet) we worked on adding filler pieces between each cabinet box. This will assist them look like one built-in unit. Because of the size of our space (and because the window is slightly off-center) we ended up with some larger-than-normal gaps to fill. You can also use pieces of pre-primed wood or purchase Ikea’s filler pieces. Cut them to size on a table saw and then clamp them in place. We screwed them together with small screws through each side of the cabinet.

how to add filler pieces to Ikea cabinets using clamps and screws

We also had to add a filler piece on either side of the window, since otherwise you’d see the metal rail contraption. Luckily the girl at Ikea saw our plan and suggested we buy two extra filler pieces, so we were all set.

white cabinet filler pieces used to cover exposed side of Ikea cabinet installation

You might think you are done here, but you in fact have a second layer of filler pieces to add still!

Step 6: Add More Filler Pieces

Those filler pieces between the boxes we simply brought in were flush with the cabinet boxes, but not the cabinet doors. So they alone would not give us the final, custom look we hoped.

filler piece between two white Ikea Sektion cabinets with Bodbyn doors creating recessed spot between doors and drawers

Now we needed to add a second layer of wood to mimic the cabinet doors. This part can be a little tricky depending on the style of your doors. These BODBYN doors from Ikea have a slight bevel on the edge, so we in fact used a sander to give a similar effect to the edge of our cabinet doors.

Filler panels brought in to Ikea Bodbyn Sektion cabinet drawers bases

We glued these pieces in place, although we could’ve nailed them in and filled the holes afterward. We painted everything Soft Wood by Valspar at Ace after finding on Pinterest that it is a close match to the Ikea white used on these particular doors.

Step 7: Add Toekick or Baseboard

It is hard to see in these photos because our cabinets are relatively low to the ground (blame the low window). But we brought in baseboard under the cabinets, using those 2×4″ from Step #3 as our surface to nail into. We had to rip the baseboard a bit narrow on our table saw, but you should not need to do that if yours are a standard height.

Step 8: Add Counters

We considered doing wood counters (as you saw in our photoshopped renderings), but we chose keeping everything white would be best We picked up some wood project panels at Lowe’s that would be deep and wide sufficient to fully cover each section of cabinets, primed them, and then painted them Soft Wool to match.

Wood project panels from Lowe's being primed and painted white using a small foam roller for use as countertops

Once they were fully dry, we screwed them in place from the inside the top of each cabinet. We’d suggest letting them cure for a few days before placing anything heavy on them.

Step 9: Add Cabinet Hardware (Optional)

The last step was adding matching pulls to each door and drawer. You can see our walkthrough for installing cabinet hardware for a video on how to do this.

Built In Cabinets Under Window With Floating Shelves In Playroom

With our built-in cabinet fully complete, we turned our attention to the Hands-on floating shelves and call this pleasant wrapped up!

You can read all about how we wrapped up off the rest of this space, including all of the before & after photos of our new bonus room.

More Built-In Cabinet Projects

We have done similar cabinet built-in projects in several spaces, so if you’d get more ideas and inspiration, be sure to check out some of the posts below: