There’s no storage solution quite as satisfying as built-ins, especially when they become part of a room’s architecture. When we finished our attic into a bonus room, the recessed niche around the window felt like the perfect place to add built-in cabinets. In this post we’ll walk through how we designed and installed a wall-to-wall built-in using stock cabinets — spoiler: it’s an Ikea hack.
This article focuses on the built-in cabinets. We also built DIY floating shelves to pair with them and you can read about that separately. Together they create a functional and attractive feature wall that adds storage, height, and interest to the room.
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Step 1: Plan Your Built-Ins
The recessed niche in our bonus room was only 17″ deep, so built-ins were an obvious solution. At first the niche felt like a challenge: it’s off-center, shallow, and framed by two sloped ceilings. But its narrow depth actually made a built-in the perfect choice. We wanted storage that would also bring visual interest and height to that wall.
We used Ikea’s kitchen planner to try different cabinet layouts, then added rough shelf ideas to visualize proportions. After testing options we settled on four standard 30″ tall base cabinets across the bottom with a 20″ drawer base centered under the window. That arrangement gave a balanced “window seat” effect and fit the niche nicely. Once the plan was finalized in the planner, it produced a shopping list we could use for purchase and assembly.
Step 2: Assemble Your Ikea Cabinets
The first construction step was assembling all the cabinet boxes. We followed standard assembly methods and left doors and drawer fronts off for now. This is a good stage to double-check that the layout matches your plan and that everything aligns before you install.
If you’re new to Ikea cabinet installs, there are plenty of tips and tricks to streamline the process. Taking time now to confirm fit will save work later.
Step 3: Build Cabinet Bases
Standard Ikea legs were too tall for our low window, so we built custom bases to achieve the right height. We stacked 2×4 and 1×4 boards to get the precise elevation. These bases mainly provide a nailing surface for the toe kick or baseboard later, though it’s also reassuring to have some support under the cabinets.
Step 4: Attach Cabinets To The Wall
Ikea’s Sektion system uses a metal rail to hang cabinets. The rail is attached to the wall and the cabinets clip onto it. Follow the manufacturer’s guidance for rail height and attachment, and be sure to locate studs and use a level so the rail is secure and perfectly straight.
We also screwed a 2×4 into the studs behind the rail to add a bit of depth, which helped our 12″ cabinets fit the 17″ recess better.
Step 5: Add Filler Pieces
With each cabinet hung (but not fully locked), we added filler strips between boxes so the installation read as one continuous built-in. Because our window sits slightly off-center we had wider gaps to fill than usual. You can use pre-primed wood or Ikea filler panels cut to size. Clamp them in place and screw through into the cabinet sides to hold them securely.
We also installed fillers beside the window to hide the metal rail. A store associate recommended buying a couple of extra filler pieces, which made finishing that edge straightforward.
Step 6: Add More Filler Pieces
The initial filler strips were flush with the cabinet box edges but sat behind the cabinet doors. To achieve a finished, custom look we added a second layer that matched the door profile. Depending on your door style, you may need to shape or sand the edges to mimic the factory bevel or detail.
We glued these panels in place, though you can also tack them with nails and fill holes later. After installation we primed and painted everything to achieve a seamless match; we used a paint color called Soft Wool that closely matches the Ikea white of our doors.
Step 7: Add Toekick or Baseboard
We installed a toe kick (baseboard) under the cabinets, nailing into the 2×4 base we built earlier. Because our cabinets sit low due to the window, we ripped the baseboard slightly narrower to fit; in most standard installations this extra step won’t be necessary.
Step 8: Add Counters
We considered wood countertops but decided to keep the built-in all white for a cohesive look. We bought wood project panels sized to cover each cabinet section, primed and painted them to match, and then secured them from inside the top of each cabinet. Allow the tops to cure for a few days before placing heavy items on them.
Step 9: Add Cabinet Hardware (Optional)
The final touch was installing matching pulls on each door and drawer. Hardware is optional, but it completes the look and makes the cabinets easier to use. Once hardware was installed we stepped back and finished the rest of the niche with floating shelves to complete the built-in feature.
With cabinets, counters, and hardware in place we completed the look by installing the floating shelves above the window, creating a polished and practical feature wall.
For a full view of the room transformation, see the before and after photos of our finished bonus room.
More Built-In Cabinet Projects
We’ve completed similar built-in projects in other rooms. For more inspiration, consider projects that adapt stock cabinets into custom solutions; they’re a great way to achieve a built-in look without custom millwork.
- Ikea Besta Hack Into Built-In Cabinets
- Built-In Bookshelves Using Stock Cabinets
- Turning Dressers Into Bookshelf Bases
- Built-In Dresser from a Stock Dresser
- How to Make Wardrobes Look Built-In
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