Yes, they do exist, and you can get these from mattress manufacturers. The essence of a split box spring or foundation is to enable you to navigate through spaces that a standard size wouldn’t do. When making an order, be sure to request for the two-piece box spring as this will work with the split mattress. Retailers can provide the same. However, you would require to wait a few days as they make the order and deliver the item. In some cases, the waiting time can be up to weeks. A box spring will measure thirty by eighty inches. It will work for a total length of eighty inches, and an entire width of sixty. Some people opt to cut their queen box springs to accommodate the splits. While this may work, you should consider that in doing so, you could damage the structure. What’s more, this could void the warranty of the box spring and that of the mattress in place. The split box springs or foundations are quite durable as they feature lots of wood and steel. Thus, they are safe for use. They should set you back about fifty to two hundred dollars, depending on the manufacturer.