I'm pricing and researching supplies for built-ins in my living room. The plan is cabinets on the bottom, a cubby for a TV and staggered shelves for several hundred HEAVY books above that. My instinct is to build the whole thing out of 3/4" birch ply, but I'm also looking at pre-built wall cabinets for the base to possibly save myself some hassle.
This leads to a number of questions about material choice and structural design. For instance, could a couple IKEA wall cabinets be the base for a structure that will hold a thousand pounds? Two thousand pounds? (I'm aware the floor has to support this as well – I'm on a slab.)
So, based on materials, joints, and structure, how can I estimate how much a piece of furniture can hold? How much weight can a box-frame support? At what span will a shelf of material X fail? Are there tables or online resources available for this sort of thing?
Best Answer
There are a number of online calculators related to the problem in the answers & comments to an earlier question about building shelves:
References included:
All of these were to calculate sag -- wood and metals are going to sag before they collapse in most cases. The exception would be when fasteners tear out the side of wood (eg, an anchor comes free from the wall), and sometimes, there isn't a whole lot of time between sag & fail (I had a bookshelf bow, pull free from the shelf supports, and then cascade as it took out all of the other shelves below it).
Concrete will fail explosively (sudden collapse with little to no warning, which is why reinforced concrete specifically has less than the optimal amount of steel in it, so the steel goes first), but that's not normally used for shelves.