A frame for the playhouse can be designed out of 2-by-4-inch boards. The best method is to start by nailing the boards together to form a square which will serve as the floor of the playhouse. The next step is to create the walls. Walls are built by using 2-by-4-inch boards to create a rectangle the proper height and length of each playhouse wall. Additional boards should be placed vertically roughly one foot apart within this rectangle to add stability to the walls. When adding a window, cut pieces of the boards to create a square frame within the wall in the desired location of the window. The door of the playhouse needs to be framed in the same way. Once all of the walls have been built, they should be nailed to the floor. The playhouse should be beginning to take shape at this point. You will be able to locate the door and windows in this skeleton frame.
A flat roof can be created out of a single sheet of plywood, or a peaked roof can be built with a little more effort. In order to build a peaked roof, attach a board extending straight up to the center of the front and back wall. The length of these support boards will determine the height of the roof's peak. Create a ridge beam by attaching another board to the end of each support board. This ridge beam will span the length of the playhouse from front to back. Now nail two boards to each end of the ridge beam and extend them diagonally to the nearest top corner of the playhouse walls. This is the basic frame of the roof. Attach several more boards extending from the front and back walls to the diagonal boards to improve the stability of the roof. Then nail boards extending from the ridge beam to the top of the playhouse walls. These boards should be spaced about one foot apart, and their purpose is to support the roof of the playhouse.
Once the skeleton frame of the playhouse is completed, plywood should be applied to the outside of the frame in order to create the walls and roof. Cut one piece of plywood at a time and attach it to the playhouse before cutting the next piece to avoid confusion. Remember to mark the locations of windows and doors on the plywood and cut them out with a jigsaw before attaching them with nails to the frame. Doors and windows can be cut out of plywood as well and attached to the shell of the playhouse with hinges. Remember to sand any rough edges with sandpaper to avoid splinters.