Create a blueprint of the exact sizes and measurements of the clubhouse. Use a tape measure to make all measurements. Choose a space in the back yard where the clubhouse will go. The area you choose should be an area for kids only. Measure the site carefully to be sure you have enough space.
Purchase six panels of plywood. The six pieces will be the four sides, the roof and floor of the clubhouse. The height of the clubhouse should be a little bit taller than the height of the child you're building it for.
Mark any spaces that will be the door or windows and cut them out.
Nail the four walls together. To ensure that the walls are properly bonded together, use wood glue to secure the edges of the clubhouse to reinforce the hold of the nails.
Attach the floor and ceiling of the clubhouse. Nail them together and secure the hold with wood glue. Before applying any glue and nails, ensure that the pieces of wood are properly lined up. To make the roof a little fancier, you can build a pitched top. Do this by leaning two pieces of plywood against each other on top of the clubhouse in an inverted V-shape.
Paint the outside of the clubhouse. Let the children select the color and let them help with the painting.
Furnish the clubhouse. Use paintings, child-sized furniture and other toys. Make a sign such as "Billy's Clubhouse" or "Suzie's Playhouse."