Built-in storage is hard to beat, especially when it’s integrated into a room’s architecture. After we finished our attic and turned it into a bonus room, we wanted to make the most of the recessed niche around the window. In this post we’ll walk through how we designed and installed built-in cabinets using stock Ikea cabinets — yes, this is an Ikea hack — and the practical steps we followed to get a custom, built-in look without custom cabinetry prices.
This article focuses on the wall-to-wall built-in cabinets. We also added DIY floating shelves to the niche, which complement the cabinets; you can read about the shelves in a separate tutorial since the combined project is fairly detailed.
Table of Contents
Step 1: Plan Your Built-Ins
The recessed window area in our bonus room is only 17″ deep, which at first seemed like a design challenge. The niche is slightly off-center and has two sloped ceilings, but its narrow depth actually made it a great candidate for low-profile built-ins. Adding cabinets would bring storage and visual interest to an otherwise blank wall while keeping the room feeling open.
We used Ikea’s kitchen planner to try various cabinet layouts. After testing a few configurations and mock-ups, we settled on four standard 30″ tall base cabinets across the run with a centered 20″ drawer base below the window. The layout creates a cozy “window seat” feel while providing balanced storage. Once our plan was finalized in Ikea’s tool, it generated a parts list and shopping cart that made ordering straightforward.
Step 2: Assemble Your Ikea Cabinets
Start by assembling the cabinet boxes on the floor. You don’t need to attach doors or drawer fronts yet — leaving them off makes alignment and filler work easier. If you’re new to installing Ikea cabinets, there are many helpful tips and tricks available to speed up assembly and improve fit.
Take this time to double-check your measurements and layout before permanently installing anything. Minor adjustments now will save effort later.
Step 3: Build Cabinet Bases
We needed a lower profile than Ikea’s adjustable legs, so we built custom bases from stacked 2x4s and 1x4s to get the precise height we wanted for the window seat. These bases primarily give you a place to attach the toe kick or baseboard at the end, and also add a bit of reinforcement under the cabinets. They don’t have to be complicated — just level and securely anchored to the floor.
Step 4: Attach Cabinets To The Wall
Ikea’s rail-hang system makes mounting cabinets straightforward: attach the metal rail to the studs, then hook each cabinet onto the rail with the supplied clips. Use a reliable stud finder and a long level to ensure the rail is perfectly positioned. We also screwed a 2×4 to the studs before mounting the rail to give the shallow 12″ deep cabinet boxes a bit more backing and to better fit our 17″ deep recess.
Step 5: Add Filler Pieces
Once the cabinets are hung (but not yet fully secured together), add filler strips between the boxes so they read as one seamless built-in unit. Because our window is off-center and the niche is an odd width, we needed larger filler pieces than usual. You can use Ikea’s fillers or cut pre-primed lumber to size on a table saw. Clamp the fillers in place and screw them to the cabinet sides so everything aligns.
We also installed fillers beside the window to hide the metal rail. A quick trip to Ikea and a helpful associate made sure we had the right-sized filler pieces for those spots.
Note: these initial fillers sit flush with the cabinet boxes, but not with the door faces. There’s a final layer to add that will complete the custom look.
Step 6: Add More Filler Pieces
To create a finished, built-in appearance you need a second layer of filler that aligns with the cabinet doors. These secondary panels bridge the gap between the cabinet box filler and the door edges so everything reads as one continuous surface. Depending on your door style, you may need to shape or bevel the edges so the filler matches. For our BODBYN doors, we sanded the edges slightly to mimic the door profile before attaching the panels.
We glued these panels in place, though nailing and filling is also an option. Once the fillers were installed we primed and painted everything the same shade — Soft Wool by Valspar — which closely matched the Ikea door finish and made the whole run feel custom and cohesive.
Step 7: Add Toekick or Baseboard
We installed baseboard under the cabinets to create a finished toe-kick. Because our cabinets sit lower to match the window height, we ripped the baseboard narrower on a table saw to fit. Attach the toe-kick to the 2×4 supports from Step 3 so it’s secure and seamless with the surrounding trim.
Step 8: Add Counters
We opted for painted wood counters to keep the whole built-in bright and consistent. We purchased wide wood project panels at Lowe’s that covered each cabinet run, primed them, and painted them the same Soft Wool color. After the paint cured, we fastened the tops from inside the cabinets. Allow a few days for the paint to fully cure before placing heavy items on the surface.
Step 9: Add Cabinet Hardware (Optional)
Adding matching pulls to doors and drawers is optional but completes the look. Choose hardware that coordinates with your room’s style and install it carefully for even spacing. If you prefer a minimalist look, you can skip pulls and use push-to-open hardware instead.
With the cabinets complete we finished the niche with DIY floating shelves to echo the built-in look and added styling to the wall. The final result feels custom, adds useful storage, and makes the room feel more finished.
If you want to see the full transformation, we documented the entire bonus room remodel with before-and-after photos in our project post.
More Built-In Cabinet Projects
We’ve used similar techniques to create built-in storage in other rooms. For more ideas and inspiration, look through our other projects that transform stock cabinets into custom-looking built-ins.
- Ikea Besta Hack Into Built-In Cabinets
- Built-In Bookshelves Using Stock Cabinets
- Turning Ikea Dressers Into Bookshelf Bases
- Built-In Dresser Out Of An Ikea Malm
- How to Make Ikea Pax Wardrobes Look Built-In
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