Reprinted from my e-mail response on the directors' listserve, to a query about straight, 4 legged wooden chairs, which is what we have in my library:
Here is what I learned the hard way about sturdiness of straight 4 legged wooden chairs. You MUST have stretchers between the legs, or the legs will split. Stretchers are the horizontal dowels between the legs. The lower down they are, the stronger the protection. And, it's better to have them front and back, if you can, but if you can only have them in one position, have them on the front.I learned this because our chairs began to split on the front legs within a week or two of the library opening in the summer -- that's with very light use. I assumed that people were tipping the chairs back and coming down hard while sitting in them. I was wrong! This kind of leg splitting is classic for the leg torque that comes from that side twist as the chair is moved sideways while the person sits without lifting their weight out of the seat. I discovered this by calling a chair specialist at Purdue University. But later found that the man's work was also included in an American Libraries Technical Report on library chairs.
The reason the stretcher is so key is that the biggest stress on a chair is not being banged down or sat upon. The biggest stress comes when somebody sits down and decides to scootch the chair just a bit to one side or the other, to "center" themselves a bit. That is when the chair legs will be torqued and splintered. And most of the stress is on the front legs, not the back leg when this scootch happens, most of the time.
Arms on the chair will add a lot of strength to the chair, too. Armless chairs are much more prone to breakage, whatever the design. But you have to be sure the arms will fit under your tables. Measure it carefully.
Sit in the chair and see if you can get students and a variety of staff to try them out. Be sure the carved seat is comfortable. Sharply defined edges on the seat are gonna be BAD on the behinds for your students. The amount of lumbar support from the back of the chair matters, too. Remember how long law students end up sitting in the library!
And be sure they put good glides on the chair feet no matter what kind of chairs you get. That will save a lot of wear on your floor, carpet & chairs.
And Last! A warranty is not worth a damn if the company is not going to stand behind it. We had a warranty on the chairs we ordered and it still was pretty much worthless. The company wanted to quarrel about whether the chair breakage was due to misuse. They can get out of their warranty any time if they want to... If you can, get the company to give you several library references. They can supply all the offices in the world. Libraries are a whole different ballgame!
Most architects and furniture specialists do not know how different the requirements are for library furniture. The standards for regular office furniture will simply not stand up to the rigors of library use. Don't let the architects or designers order standard office furniture for the public spaces in your library! That's what happened in my library and we have paid for it. It's penny wise and pound foolish. I could not get the university central administration to listen, and we had to retro-fit the wooden chairs with stretchers that first summer and add better glides, just to keep the whole set of chairs from collapsing.
The supplier of the wooden chairs did not honor the warranty. They claimed that the breakage was due to mis-use of the chair. We ended up negotiating a settlement where all the participants -- the designer, the supplier, the vendor, the individual sales rep, and the law school, all chipped in part of the cost. It wasn't worth it to the university to sue the company to force them to honor the contract, but we will certainly never do business with that furniture supplier again. So much for warranties.
One more thing that I did not anticipate: bluejeans' grommets are scratching the heck out of the wooden seats. All the wooden chairs' seats are quite scarred. We need to schedule some regular maintenance on the wooden chairs as well as carrels, tables and the window sills close to lines of carrels where students have been placing coffee cups!