A normal sofa Frame height finishes about 30-32″ from the ground. Loose back pillows will finish 3-4″ above the back rail. This helps provide head/neck support without pushing you forward. Small variations to the frame height aren’t an issue, however larger changes can be. A very short frame height won’t provide sufficient support. An overly tall frame however could push you forward in the seat instead of allowing you to recline back properly.