A step-by-step tutorial to build professional-looking built-in bookshelves using IKEA Billy bookcase sections for efficient vertical storage.
If there were a medal for assembling IKEA bookcases, we’d be standing on the podium — we went full DIY and turned Billy units into custom built-ins!
Built-in bookshelves are a perfect weekend project when you need more storage, want to personalize a living room or playroom, or aim to add visual and practical value to your home. Using pre-made bookcase sections saves time and lowers the skill barrier while delivering a high-end result.
Benefits of Using IKEA Billy Bookcases for Built-Ins
Beginner Friendly
If you’re new to home improvement, this is an excellent first built-in project. The challenging parts of cabinet construction are done for you — you’re mainly aligning, anchoring, and trimming for a seamless, built-in appearance.
Cost Efficiency
Standard-height Billy bookcases at IKEA were priced around $89 each at the time of the original project. For the convenience and finished look you get, that price is hard to beat compared with building full custom cabinetry from scratch.
Customizable Options
Billy bookcases offer many accessories and door styles, such as Oxberg doors, so you can tailor the look and function of your built-ins to suit a playroom, living room, office, or closet.
For our playroom/media room makeover, we needed a lot of storage. Built-ins are an ideal solution for kids’ spaces because they add vertical storage for toys, craft supplies, and games while keeping the room tidy and stylish. Hiring a contractor for custom built-ins was outside our budget, so we adapted IKEA units to create built-ins ourselves.
DIY IKEA Billy Bookcase Built-In Ideas
Update: Years after completing this project, we’ve reused these methods for multiple built-in projects. The approach is reliable and adaptable to different rooms and layouts.
Examples and Variations
You can adapt the same Billy bookcase built-in approach for:
- Home office built-ins with glass doors
- Floor-to-ceiling walls of storage in a playroom
- Half-height bookcase built-ins to suit seating or wainscot height
- Closet built-ins using stacked or modified units
Built-ins work beautifully in living rooms, bedrooms, home offices, playrooms, recreation rooms, closets, and dining rooms — essentially any space that benefits from organized vertical storage. They look custom and high-end but can be achieved affordably with these IKEA units and a bit of trim work.
Measuring for DIY Built-In Shelves
Accurate measurements determine how many bookcases you’ll need. Our playroom wall was 214″ wide, so we planned the number and width of Billy units to leave about 4–5 inches of space on either side for trim and anchor boards.
Billy bookcases come in common widths such as 31.5″ and 15.75″ (round up when planning). Divide your wall width by the unit width to estimate how many bookcases you can fit, and allow at least 4″ at each end for attachment blocking and trim.
How to Make DIY Built-In Bookshelves
Supplies
The exact quantities and sizes depend on your wall measurements. Below are the items we used for our installation:
- Multiple 32″ x 80″ and 32″ x 42″ Billy bookcases (as needed for your wall)
- Bookcase height extenders if you need additional height
- One or more 16″ x 42″ Billy bookcase for smaller sections
- Oxberg-style cabinet doors (optional, for lower cabinet storage)
- 2×4 stud boards for blocking and mounting
- 1×6, 1×4, and 1×2 pine boards for face trim and headers
- Interior baseboard molding to match your trim height
- Circular saw, jigsaw, and power drill
- 1.5″ finishing nails and 1.5″ wood screws
- Wood shims, finishing wood glue, and a square tool
- Tape measure, pencil, hammer, and trim caulk
- Semigloss paint matched to IKEA white (we used a close match)
Assembling IKEA Bookcase Sections
We assembled the Billy units following IKEA instructions, then positioned the bookcases centered on the wall so there was approximately 4″ of space on both ends. After settling on the layout, we anchored each bookcase to the wall using the included hardware.
Next came the carpentry that transforms bookcases into built-ins: adding blocking, face boards, headers, and trim to make the units look integrated with the wall.
Step-by-Step Build Process
- Make the sides appear flush to the wall
Where we had a half-wall, we built a box from 2x4s mounted to the wall to fill the gap and create a surface the bookcase could sit against. This blocking creates a solid backing to attach trim and face boards.
- Secure the bookcase to the box
We cut pre-primed 1×6 face boards to fit between the bookcase and wall and nailed them to the 2×4 box. The bookcase was also nailed to that board for a secure connection.
- Notch the board for existing baseboard
Using a jigsaw, we notched the 1×6 where needed to accommodate the existing baseboard. Precision is helpful, but small gaps can be corrected with caulk later.
- Make the box flush and trim it
We added another 1×6 across the top of the 2×4 box to bring it flush with the bookcase and secured everything with finishing nails.
- Hide gaps with a face board
On the opposite side, we attached a 2×4 directly to the wall, added a 1×6 face board on top, and glued and nailed it to make the bookcase appear built into the wall. We also ran nails through the sides of the bookcase into the face board for extra strength.
- Secure bookcases to boards and to each other
Use wood screws at the base of each bookcase to anchor them to the face boards and then screw adjacent bookcases together so they act as a single, solid unit.
- Build and attach a header
To close the gap between the top of the bookcases and the ceiling, we constructed a header from a 1×4 with a 1×2 face piece screwed to its top. This header was secured to the outside top of the bookcases with finishing nails.
- Optional: add traditional molding
We applied front molding to the header to echo the Craftsman trim elsewhere in the room. You can instead use crown molding; that option requires a miter saw for the angled cuts.
- Optional: install doors on lower cabinets
If you want concealed storage, attach cabinet doors (such as Oxberg) to the lower bookcase sections before installing baseboard. Test door clearance before final trimming.
- Attach baseboard and shim gaps
Install baseboard along the bottom of the built-in. If doors were installed, you may need to trim a small amount from the baseboard so doors close freely. Use shims where necessary to level the units and fill larger gaps.
- Caulk, fill, and paint
Caulk all seams and gaps to create a seamless built-in appearance. Fill nail holes as desired. Once dry, paint the face boards, caulk lines, and trim with a semigloss paint that matches the bookcase finish for a unified look.
Finished Built-In Shelving
The result is a wall of durable, usable storage with lower cabinets for toys and supplies and open shelving above for books and decor. The built-ins are solid, functional, and dramatically improved the room’s storage capacity and visual appeal.
We still had a few small finishing touches—such as painting the stairway side and touching up caulk—but overall the installation was a success and moved our playroom project forward in a big way.
If you need reliable, budget-friendly built-ins but don’t want to build cabinets from raw lumber, retrofitting IKEA Billy bookcases with blocking and trim is an excellent beginner-to-intermediate solution that delivers a custom look without the custom price.
Storage for days — and a finished wall that looks like permanent built-ins.
Frequently Asked Questions
What paint color matches IKEA white shelves and furniture?
How do you run power cords and cables through built-ins to make an entertainment center?
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