ᐅ How can I prevent sagging and bending in BILLY bookshelf shelves?

Minmaximo9 schrieb:

If I install a center support, what is the best way to mount it? Should I screw it directly into the shelf or attach it from underneath?

Great questions! I recommend screwing the center support from underneath the shelf. This way, the screws are not visible from above and the surface remains smooth. It’s best to use flat-head screws so nothing sticks out and damages your books.

Minmaximo9 schrieb:

Is there a specific size or type of wood that works best?

A solid hardwood strip at least 18 x 30 mm (0.7 x 1.2 inches) is more than sufficient. The important thing is that it is stable and straight. Alternatively, you can also use aluminum profiles, which are lightweight and very strong.

Minmaximo9 schrieb:

Would it be possible to add extra support legs under the shelves?

Support legs are technically possible but more complex. Since the shelves typically sag in the middle, it’s usually better to combine a center support with reinforced side panels. If you use support legs, you need to raise the shelf, which can be tricky visually and requires precise measurements.

Minmaximo9 schrieb:

How critical are the side panels of the shelf really?

The stability of the side panels is crucial! Flexible sides cause the shelf to behave like a hammock. Reinforced sides provide a firm resting surface for the shelf and distribute the load better. If the sides wobble, you should definitely secure them or reinforce them with brackets.

In addition to the central brace: use multi-strip battens or a sturdy batten that you secure both to the floor and connect to the back panel. This will also prevent lateral sagging.

Regarding the support legs: if you are planning for a very heavy load, an avoidable effort would be to add an additional vertical brace in the middle of the shelving. However, this must be firmly anchored, ideally to the floor and to the top shelf.

As for the side walls: a slightly flexible side wall is normal, but it must not sag. Secure loose sides properly, otherwise too much point load will be applied to the shelves.

Thank you, that helps me a lot!
Last question for today: Does anyone have suitable dimensions for the middle support beam that can be installed directly under the 80cm (31.5 inches) wide shelves without complicated drilling? I would like to keep it as simple as possible and avoid making significant changes to the shelf structure.

This is great, so many tips coming together here! 🙂

Regarding the dimensions: For Billy shelves that are 80 cm (32 inches) wide, a central support beam around 80 cm (32 inches) long and 2–3 cm (0.8–1.2 inches) high is usually recommended. A thickness of 2–3 cm (0.8–1.2 inches) is ideal, providing enough stability.

Minmaximo9 schrieb:

I would like to do this as simply as possible myself without changing the shelving structure too much

The best way is to fix it from underneath using angle brackets that you can easily unscrew later. Gluing is less secure; screws are always better!

Give it a try—you’ll see a noticeable improvement in load-bearing capacity 🙂

Install the center brace so that it is positioned exactly in the middle, with a length matching the base (80cm (31.5 inches)) and a thickness of about 2-3cm (0.8-1.2 inches). Attach it from underneath; no holes are needed on the top.

JORGERON schrieb:

Install the middle brace so that it sits exactly in the center, with a length matching the base (80 cm (31.5 inches)) and a thickness of about 2-3 cm (0.8-1.2 inches).

Exactly. If you also attach window or support strips to the back side, this further increases stability.

A good idea is to connect the middle brace to the shelf base with a bracket and a rear strip, creating a strong load distribution.