WHAT YOU NEED TO KNOW BEFORE YOU BUY
Forget about springs. Think about what happens to the springs when you fold up the sofa bed. Only the poorest quality sofabed mattresses are made from springs. The only practical material is urethane foam.
Foam comes in two types: standard, and memory foam. Memory foam is good for regular beds, but not for sofabeds. The last thing you want is anything that conforms to the bar. Standard foam quality is measured by foam density. High density foams have smaller pores and it requires a little more material to make up the “spaces” between the pores. Consequently, the better mattresses weigh a little more than the others. Of course the more the mattress weighs, the more urethane goes into it, and the more it costs.
The very best sofa bed mattresses are made from 2.5 lbs per cubic foot density foam. Mattresses made from 1.8 lbs per cubic foot density foam are also considered good. Anything less is low quality, which will deform over time, and will not give a good nights sleep.
Thickness is also a very important factor. The “rise” is the height of the sofabed, ( not including seat cushions). All sofa beds fold up into three layers. Therefore the “rise” is something over three times the mattress thickness. Manufacturers of sofa beds us mechanisms in two rises; 12″ and 15″. This means that a sofabed with a 4″ thick mattress will have a rise of something over 12 inches, and will make a comfortable sofa. If the mattress is 5 inches thick, the rise will be something over 15 inches. A 15″ rise makes a much less comfortable sofa, but a more comfortable bed. What this means to us is that if your sofa bed frame is designed for a 4″ thick mattress, that is what you must buy. If your sofabed is designed to accommodate a 5″ thick mattress, you have a choice. The 4″ will work well, and cost much less, but the 5″ will give you a better mattress. If you can fit a 5″, you should spend the extra dollars. Whatever you do, don’t try to put a 5″ mattress in a 4″ frame. It will crush the mattress. Also, over time, it will also ruin the frame by slowly elongating the rivet holes and wearing the rivets. It will also be a killer to fold up the bed.
Surprisingly, there is no standard sizes in sofabeds. There are a few sizes which are considered “common.” They are: 54 x 72 & 60 x72. Nevertheless, most sofa beds are not that exact size. Here in the USA, there are only two mattress companies which make up any size sleeper sofa mattress for the same price as the common sizes. Both of them make mattresses of the 2.5 lbs per cubic foot density which I recommend.
Unfortunately, neither one makes both thick nesses.
Replacement sofa bed mattress company uses 4″ foam.
sofa bed mattress company uses 5″ foam.