Things You'll Need
Using a traditional mattress with a futon frame is a simple process. The main problem with using a regular mattress is that the futon will not be able to fold into sofa size. With a regular twin mattress, the futon must always remain as a bed. The futon may also need some additional support to support the weight of the mattress and box spring, if you use one. After choosing a box spring and mattress, converting the bed will take less than one hour.
Inspect the frame of your futon. Check the distance between the slats and the material the futon is made from. Both metal and wood frames will work with regular mattresses, but some futon frames may not have the ability to carry the weight of a full-sized mattress every day. Check this by sitting on the frame alone. If it sags under your weight, the futon will not support the mattress. Expand the futon from a sofa to bed position.
Add extra support to the frame if necessary. Remove the old mattress. The slats should be about 6 inches apart from each other to provide the necessary support for a box spring and mattress. If the slats are too far apart, rest wooden planks on the frame between the slats for additional support. Cut the slats so they fit onto the frame without sticking out too much. Don't worry about screwing them to the frame. The weight of the mattress will hold them in place.
Check to see if a box spring is necessary for the installation of the mattress. A box spring provides additional support and also helps remove potential bumps from the mattress caused by the frame. It is possible to feel the slats of the futon through the mattress in some cases, which will be eliminated if you use a box spring. Choose a box spring if you prefer firmer support while you sleep.
Place the box spring on the bed. Place a dust ruffle over the box spring to hide it and the futon frame from view.
Place the mattress over the box spring. Place additional padding over the mattress if desired. Cover the bed with sheets and blankets.
Purchase a mattress that provides the level of comfort and support that you want. Many people have good results with a mattress that contains interior springs and has a memory foam exterior.