Worried about drooping

[Paul920]

I'm fitting some shelves into alcoves either side of a chimney breast. The span is 850mm and they will be 330mm deep, sitting on little metal pegs so their height position can be adjusted. They will take books, lotsa books.

But I don't know what to make them out of. I don't think even 25mm MDF will do it and so was considering 18mm blockboard. Do you think that will work and if so then do I need a strip of wood along the front to provide a smooth finish? The units are to be painted. Thanks for any advice.

 

[Deluks]

Double up some 18mm ply and add a timber strip to finish the front edge. Cant you fit a bracket at the back to halve the span, or a batten on back wall?


This will help you decide.

http://www.woodbin.com/calcs/sagulator.htm

 

[Paul920]

The sagulator is a good tip thanks. Doesn't have blockboard unfortunately, but I think b/board is even more rigid than ply so at 18mm should do the trick.