A sofa bed is a piece of modular furniture that can be set up to act as a couch, or as a bed. The sofa bed frame usually collapses in on itself and stows within the frame of the couch, though other sofa bed frame types are integrated parts of the couch frame. The frame itself will collapse to turn the sofa itself into a bed rather than storing a separate mattress within the sofa. Choosing the best one starts with determining your budget, aesthetic desires, and functional needs.
Most fold-out sofa bed frame models that stow within the sofa itself are queen size mattresses, which are suitable for two adults. Fold-down couches can be either queen size or full size, slightly smaller than a queen. Determine who is most likely to use the sofa bed at any given time and consider their needs. Children generally need less sleeping space than adults, so if adults will be using the unit most often, it is best to go bigger. Fold-out sofa bed frame units tend to be larger, but the mattress itself can be quite thin and uncomfortable. If comfort is a prime concern, consider other options, such as a futon.
Futon frames feature one large, overstuffed cushion or mattress that will act as the surface of the couch as well as the bed. The sofa bed frame will simply fold down flat to allow the cushion to fold out flat as well. The advantage to this design is the thickness of the cushion, which can be more comfortable than the thinner mattresses found in fold-out sofas. Futon mattresses can be somewhat lumpy and unsupportive, however, so after more than one night of sleeping on it, guests may get uncomfortable.
Of course, you will need to measure the room in which the sofa bed frame will be placed before committing to any purchase, as this may dictate how large or small or a unit you will need. While sofa bed units can be pushed up against a wall, a futon will generally need to be pulled away from a wall when it is used as a bed because the back of the sofa frame will fold down. The fold-out sofa can stay in one place because the bed frame will be pulled outward from within it. Consider this when choosing which design will work best for your room.