Tips to make bookshelf stronger?

Hi All,

Long time reader first time poster. Have gotten into some woodworking lately as a result of some extra time thanks to covid in Melbourne. I've decided to make a bookshelf (photos attached), however I feel it is just not sturdy enough. I have used 12mm marine ply and pocket holes with glue to join all the parts but it still does not feel anywhere near strong and sturdy enough.

What else can I do/add to increase this part of the shelfs strength? Any help will do or advice on modifications even accepted.

Thanks for you help 🙏

It looks like you re opting for an open back design.

This means the whole shebang is liable to fold over on itself as there is no cross bracing included in the design.
To stop the folding and add some support to teh shelves adding a ply back will make a difference.

If you want to retain the open look nI would at a minimum add full length pieces/strips of 19x50 mm under the top and each shelf right across the back of the whole unit. Also add one to the top of the lowest shelf or base. Being at the back you won't see these but they will strengthen the

To stiffen it up further I'd also add a base to get that lowest shelf off the floor otherwise shelf will collect a lot of dirt.

As bob mentioned its going to need bracing of some description.

Thanks guys, appreciate the feedback.

I think I'll go with some bracing along the back as suggested and use it as a lip so items won't fall down the back.

I'll also be adding a 900 high base to the bottom serving as a closed bookshelf. Fingers crossed it turns out alright.

Welcome to the Forum, Alex.

In my view, 12mm plywood is far too thin and far too flexible to use for bookshelf construction. Suggest that you cut your losses and start again.

My darling is an academic and I have made her heaps of bookshelves. Her books seem to breed endlessly!

The first bookshelves that I made were copied after some really cheap units in a discount store and made from 19 x 200 mm radiata pine, shelves about 1200mm long. These worked well for a while, then the shelves slowluy sagged and twisted an tipped some books onto the floor.

Next set from 19 x 150 mm eastern white pine, 900 mm wide, plywood backed with the shelves screwed to the plywood on 150mm centres. Worked a little longer than previously, then the front edge of the shelves sagged and mould developed in the books (the plywood stops air flow).

Then I read somewhere:

1. Stiffness increases with the density of the timber, and
2. Stiffness increases with the square of the thickness.

Analysis: Use denser timber and the stiffness goes up a little; Make shelves thicker and the stiffness goes up a lot.

My final iteration of bookshelves use 32mm celery top pine and shelf lengths up to 1500mm have not sagged after 35+ years. The thicker pine also looks good and I have assembled then using dry dovetails so that they can be easily disassembled and transported.

Attachment 478762 Attachment 478763

:whs:

12mm ply and pocket screws are entirely inadequate for a bookshelf. Bracing might stop it wobbling around when it's empty, but load it up and there's a not-insignificant chance it could collapse.

agree with other posters...

Pocket holes will not be sufficient to support the load of books, plus given that its plywood you've used you run the risk of the plys separating. If OTH its entirely decorative then you could get away with it if you're only using it to display ornaments etc.

If you're keen on not starting over but i'd add some "dividers" to support the weight of each of the shelves and take as much off the strain of the pocket holes.

Also +1 to adding a backing board, best thing you can do is route a dado into the back to accept the backing board or nail a backing board to the entire back of the bookcase. Would recommend adding glue for extra strength.

I agree with what others have said.

Even a basic book shelf from Ikea uses 18-19mm shelves and its rigidity comes from the 3mm board nailed to the back.

12mm is definitely not strong enough. Luckily you might not need to start over again if you double up and put another 12mm board sitting on top of the fixed shelves.