For a start, there definitely exists a possibility for increasing the build area of your printer. Before we go into the steps to do so, it would be prudent to mention that, larger prints can be made by fusing smaller parts together and it is not essential to increase the build area for this sole reason. I am sure, you would want to do this out of curiosity. The steps we would be mentioning here, are generic in nature, you would have to extrapolate them to your printer.
(a) Decide on how large do you want the print area to be. Because this would translate into acquiring equally large build plate.
(b) Next step would be to increase the dimensions of your X, Y and Z axes of your printer depending on your chosen build area and the chosen height. This would entail, looking out for belts, rails and support framework to hold everything in place so that the printer would not wobble or have excessive vibrations.
(c) Once you have successfully put together the physical components required to move the extruder in a defined 3D space next step would be to let the electronics in the 3D printer know that you have expanded the build area, starting from finding the compatibility of your board for such expansion along with compatibility of on board drives. The firmware has to be tweaked according to the customizations you have adopted.
(d) Theoretically assuming that you have completed all these steps, next big thing that needs to be done would be to calibrate your printer for accuracy and precision which would be another post in itself.
Each one of these steps have to be attempted individually and according to the make of your printer.