shelves in chimney alcove

[Sollie]

I want to put some shelves in the alcove that is 120 x 24 cm to hold a small stereo and speakers, some fairly heavy box files and books.
I have laid two pieces of 12mm mdf I had already here on top of each other on 1x1 battens screw to the wall so supported on 3 sides and it bowed with stereo on it.

My question is what materials should I use and what size battens? I used the online sagulator and found the quote for 24 mm mdf said it would not bow but it did.

Should I be using 18mm ply ?

Also I want to make it look as neat as possible, how can I cover the edges of the ply?
thanks in advance

 

[Roger928]

The 12mm mdf would need to be glued to add strength.

If you pack laminates on top of each other ( like an old car spring) they will usually deflect but when glued they become much stronger.
Edges of ply can be veneered or solid wood fixed on.

 

[rsgaz]

Should I be using 18mm ply ?

Also I want to make it look as neat as possible, how can I cover the edges of the ply?

Solid wood is stronger than plywood for shelves and less prone to sagging. In plywood, half of the grain is going in the wrong direction. A nice solid wood shelf would also already have a nice edge.

 

[foxhole]

18mm mdf should be ok, unless glued securely 2 pieces of 12mm do not have the same properties a 24mm mdf.
You could have secured the 12mm top and bottom of the baton with a baton across the front edged with 12mm mdf, this would give a very strong shelf [glued and screwed.] And would appear to be a floating shelf.

 

[cwhaley]

I did this recently in my house. I screwed battons the walls and chimney breast, fixed another batten along the front to make a frame. I then put 16mm MDF (ply would also work nicely) on top, 4mm ply on the bottom and a finishing strip along the front.

They then look like floating alcove shelves and can take a a good bit of weight. In fact, one of mine houses two speakers, an EQ, an amp. and a tuner.

I've attached some pictures of them - I haven't finished decorating so please ignore the mess!

 

[Nilly]

The alcove shelves which a local cabinet maker did for us are made of 2 x sheets of 18mm ply fully bonded together, giving a chunky looking 32mm thick shelf.

The bottom piece of this sandwich is smaller than the top by the width of the battens which are screwed into the wall along each side and the back, so when the shelf is located onto the battens, the battens disappear giving the appearance of a floating shelf. A bit of filler on the underside hides the line where you might see it on the higher shelves. A profiled strip along the front hides the ply edge.

The alcoves are at least 1.2m wide and the shelves have had books on them without any sagging after 2 years.