Steps I took to build the BILLY built-in bookshelves
1. I started out by framing out the two walls that flanked either side of the bookshelves using 2×4’s. I wanted these to act like walls framing in the built-in BILLY bookshelves, thus I needed the walls deep enough to recess the BILLY’s in about 1 1/2 inches from the finished front.
2. After the framing was complete, I assembled the IKEA BILLY bookshelves for a rough fit. It is absolutely essential that everything fits snug. At this stage, you can still easily make changes.
3. Next is to secure the BILLY bookshelves to each other. Use screws of the right length, so it won’t poke through the other side of the BILLY unit.
Once all of the BILLY bookshelves are joined, go ahead and secure them to the framed walls with 2 1/2″ screws.
4. It is time to start closing in the framed walls. I used MDF for this project because I wanted them to look like trimmed out walls and not just a drywall wall. Remember to check for plumb-ness.
Then, fill any of the joints and nail holes with drywall putty. Let it dry, and then give everything a good sanding.
5. Prime all of the MDF and then paint.
6. Now is time to install the finishing trim. For my project, I went with an inside quarter round along the top. This covers the joint between the drywall bulkhead and MDF, as well as the small gap above the built-in bookshelves.
For the bottom, I used the same baseboards as the rest of the basement (standard 1×4″ MDF baseboards). Again, this helps provide continuity to the entire space, tying the built-in BILLY’s with the rest of the renovation.
Fill the gaps and nail holes with drywall mud, give it a light sand, and then finish off the new trim with a final coat of paint.